Workbook EduKit PA Project kit Process automation. With CD-ROM. Festo Didactic EN

Transcription

1 Workbook EduKit PA Project kit Process automation With CD-ROM Festo Didactic EN

2 Use for intended purpose This system and the workbook have been developed and produced exclusively for training and further education in the field of process automation and technology. The respective training companies and/or trainers must ensure that all trainees observe the safety precautions which are described in the accompanying manuals. Festo Didactic hereby excludes any and all liability for damages suffered by trainees, the training company and/or any third parties, which occur during use of the system in situations which serve any purpose other than training and/or vocational education, unless such damages have been caused by Festo Didactic due to malicious intent or gross negligence. Order no Revision level: 04/2009 Authors: Bernhard Schellmann, Hans Kaufmann Editors: Jürgen Helmich, Klaus Kronberger Graphic design: Doris Schwarzenberger Layout: 05/2009 Festo Didactic GmbH & Co. KG, Denkendorf, 2009 Internet: Adiro Automatisierungstechnik GmbH, Esslingen, 2009 Internet: The reproduction, distribution and utilisation of this document, as well as the communication of its contents to others without explicit authorisation, is prohibited. Offenders will be held liable for compensation of damages. All rights reserved, in particular the right to file patent, utility model and registered design applications.

3 Table of contents Introduction 9 Training content 5 Learning objectives 6 References to German school syllabi and vocations 6 Obligations of the trainees 11 Risks associated with the modular production system 11 Guarantee and liability 11 Use for intended purpose 12 Safety precautions 12 Transport 14 Unpacking 14 Scope of delivery 14 Visual inspection 14 Maintenance 15 Updates 15 Part A Plant construction 1. Process description A-3 2. Planning A-9 3. Installation A Commissioning A Marketing and sales A Evaluation of learning objectives for plant construction A-55 Part B Practice-based learning: manual measurement, open-loop and closed-loop control 1. Manual measurement B-3 2. Manual open-loop control B Manual closed-loop control B Evaluation of learning objectives for manual measuring, open-loop and closed-loop control B-47 Festo Didactic GmbH & Co. KG 3

4 Table of contents Part C Practice-based learning: automated measurement, open-loop and closed-loop control 1. Basic principles C-3 2. Automated measurement C Automated open-loop control C Automated closed-loop control C Evaluation of learning objectives for automated measurement, open-loop and closed-loop control C-59 Part D1 Plant construction with solutions 1. Process description D Planning D Installation D Commissioning D Marketing and sales D Evaluation of learning objectives for plant construction D1-55 Part D2 Practice-based learning: manual measurement, open-loop and closed-loop control with solutions 1. Manual measurement D Manual control D Manual control D Evaluation of learning objectives for manual measurement, open-loop and closed-loop control D2-47 Part D3 Practice-based learning: automated measurement, open-loop and closed-loop control with solutions 1. Basic principles D Automated measurement D Automated open-loop control D Automated closed-loop control D Evaluation of learning objectives for automated measurement, open-loop and closed-loop control D Festo Didactic GmbH & Co. KG

5 Introduction Festo Didactic s process automation and technology learning system is aimed at various educational backgrounds and vocational requirements. The systems and stations included with the modular production system for process automation (MPS PA) facilitate training and vocational education which is based on real-life company situations. The hardware comprises industrial components specifically prepared for this purpose. The process automation project kit provides you with a suitable, practical system with which you can convey key competencies including: Social Technical Procedural In addition, teamwork, willingness to cooperate and organisational skills are also part of the training. The learning modules focus on realistic project phases. These include: Planning Installation Wiring Commissioning Operation Open-loop control technology Closed-loop control technology Maintenance Troubleshooting Training content The following subject areas are covered: Mechanical Mechanical layout of a system Process engineering Read and prepare flowcharts and documentation Piping connections for process engineering components System analysis Electrical engineering Create electrical circuit diagrams Correct wiring of electrical components Sensor technology Correct use of sensors Measurement of non-electrical, process engineering and control technology quantities Commissioning Initial commissioning of a process system Initial commissioning of a controlled system Festo Didactic GmbH & Co. KG 5

6 Introduction Open-loop control technology Controlling actuators Relay circuits Closed-loop control technology Fundamentals of closed-loop control technology Expansion of measuring chains into closed-loop control circuits Analysis of regulated systems Use of regulators Troubleshooting Systematic troubleshooting of a process system Inspection, maintenance and servicing of process systems Learning objectives Become familiar with the setup and the mode of operation of the fill-level system. Read and expand flow diagrams. Read and expand simple electrical circuit diagrams. Become familiar with the setup and mode of operation of a pressure gauge. Become familiar with the setup and mode of operation of a pump. Become familiar with the setup and mode of operation of a flow sensor. Record and analyse characteristic curves. Become familiar with the terms open-loop control and closed-loop control. Become familiar with the concepts of discontinuous control (2-step control) and continuous control. Become familiar with the essential work steps in the field of plant construction, from planning to operation. References to German school syllabi and vocations Type of school Planning, engineering, assembly, marketing Commissioning, production system Open-loop control technology Closed-loop control technology Secondary schools, 10 th grade SU 2 SU 2 Vocational secondary schools, 9 th grade Vocational secondary schools, 10 th grade SU 2, 4 SU 2, 4 SU 2, 4 SU 4 SU 1 SU 1 SU 2 SU 2 SU = syllabus unit 6 Festo Didactic GmbH & Co. KG

7 Introduction Vocations according to learning content Planning, engineering, assembly, marketing Commissioning, production system Control technology Regulation technology System engineer LC 7 LC 8, 9 LC 10, 11 LC 10, 11 System technician, sanitary, heating and air-conditioning LC 5, 6 LC 7 LC 10 LC 10 Chemical laboratory technician LC 12 LC 12 Chemical technician LC 4 LC 4, 5 LC 8 LC 5, 8 Electronics technician LC 6 LC 3 LC 7 Electronics technician for automation Qualified personnel for water supply technology LC 10 LC 10 LC 6, 7 LC 10 LC 4, 13 LC 4 LC 4, 14 LC 4, 14 Precision mechanic LC 8, 16a LC 8, 16a Industry mechanic LC 6 LC 13 Mechatronics technician LC 10 LC 9 LC 4, 7 LC 7 Pharmaceuticals technician LC 7 LC 7 Process technician for glass technology LC 9 LC 13 LC = learning content Teachware, EduKit PA process automation project kit including evaluation of learning objectives Festo Didactic GmbH & Co. KG 7

8 Introduction Hardware flow chart, EduKit PA process automation project kit 8 Festo Didactic GmbH & Co. KG

9 Introduction Sample room layout Festo Didactic GmbH & Co. KG 9

10 Introduction Classification into groups within the product range Important note The fundamental prerequisites for the safe use and trouble-free operation of the EduKit PA project kit include knowledge of basic safety precautions and safety regulations. This workbook includes the most important instructions for the safe use of the EduKit PA project kit. In particular, the safety precautions must be adhered to by all persons working with the EduKit PA project kit. Furthermore, all pertinent rules and regulations for the prevention of accidents, which are applicable at the respective location of use, must be adhered to. 10 Festo Didactic GmbH & Co. KG

11 Introduction Obligations of the operating company The operating company undertakes to allow only those persons to work with the EduKit PA project kit who: are familiar with the basic regulations regarding work safety and accident prevention and have been instructed in the use of the EduKit PA project kit, and have read and understood the section concerning safety and the safety precautions. In the event that the EduKit PA project kit is not monitored by the operating company itself, an appropriate person must be designated who, on the basis of his technical qualifications, is capable of evaluating the functionality of the station as well as the dangers which result therefrom, for himself and all trainees. All staff should be tested at regular intervals on their safety-awareness at work. Obligations of the trainees All persons who have been entrusted to work with the EduKit PA project kit undertake to complete the following steps before beginning work: Read the section on safety and the safety precautions in this manual Familiarise themselves with basic regulations regarding work safety and accident prevention Familiarise themselves with the specific dangers associated with compressed air, without which the equipment would not be feasible, and accordingly ensure their own safety Disconnect the station from mains power when cleaning work or inspections are requested by the person in charge. Risks associated with the modular production system The EduKit PA project kit is laid out in accordance with the latest state-of-the-art technology as well as recognised safety rules. Nevertheless, life and limb of the user and third parties may be at risk and the machine or other property may be damaged during its use. The EduKit PA project kit may only be used: For its intended purpose When its safety functions are in perfect order Faults which may impair safety must be eliminated immediately! Guarantee and liability Our general terms and conditions of sale and delivery always apply. These are made available to the operating company no later than upon conclusion of the sales contract. Guarantee and liability claims resulting from personal injury and/or property damage are excluded if they can be traced back to one or more of the following causes: Use of EduKit PA project kit for other than its intended purpose Incorrect assembly, commissioning and/or operation of EduKit PA project kit Festo Didactic GmbH & Co. KG 11

12 Introduction Use of the EduKit PA project kit with defective safety equipment or with incorrectly attached or nonfunctioning safety and protective equipment Non-compliance with instructions included in the manual with regard to transport, storage, assembly, commissioning, operation, maintenance and setup of the EduKit PA project kit Inadequate monitoring of system components which are subject to wear Improperly executed repairs Disasters resulting from the influence of foreign bodies and acts of God Festo Didactic hereby excludes any and all liability for damages suffered by trainees, the training company and/or any third parties, which occur during use of the system in situations which serve any purpose other than training and/or vocational education, unless such damages have been caused by Festo Didactic due to malicious intent or gross negligence. Use for intended purpose This station has been developed and manufactured exclusively for training and vocational education in the fields of automation and technology. The respective training companies and/or trainers must ensure that all trainees observe the safety precautions which are described in the accompanying manuals. Use for intended purpose also encompasses: Compliance with all instructions included in the manual Completion of inspection and maintenance tasks Safety precautions General Trainees should only work at the station under the supervision of a trainer. Observe specifications included in the data sheets for the individual components and in particular all safety instructions! Teachers and trainers must be capable of assessing the experiments they supervise or execute with electrical energy, as well as any potential danger using their knowledge and training (e.g. with regard to their own specialty, regulations and standards). Electrical Electrical connections must only be established and interrupted in the absence of voltage! Use low-voltage only (max. 24 V DC). Correct polarity must be assured when connecting certain electrical components, especially sensors. These components may be destroyed in the event of polarity reversal or short-circuiting. Electrical components are pre-wired at the factory, and are mounted onto an H-rail for direct attachment to the rectangular profile. Alternatively, they can be shipped unwired as a kit. In either case, wiring work must only be carried out by qualified personnel. 12 Festo Didactic GmbH & Co. KG

13 Introduction Do not pour water over any electrical components. If water is inadvertently poured over electrical components, switch supply power off immediately. The entire system must be inspected for possible damage by a teacher or trainer in this case. Avoid overloading the digital outputs with excessive current. Maximum current consumption of the actuators used must be determined before they are connected. Pneumatics Set system pressure to a value between 3 and 6 bar to operate the 2-way ball valve with a pneumatic semi-rotary actuator. Do not exceed the maximum permissible pressure of 800 kpa (8 bar). Do not activate compressed air until all of the tubing connections have been completed and secured. Do not disconnect tubing while under pressure. Mechanical Mount all of the components onto the profile plate. Make sure that piping and screw connections are carefully secured. Process engineering Always fill the lower tank in the voltage-free state! Switch the 24 V DC supply power off and disconnect the power supply unit from the power supply (230 V DC). Use potable tap water (recommended), which ensures long-term, maintenance-free operation of the system. The maximum permissible operating temperature of +65 C for the tank must not be exceeded. The maximum permissible operating pressure of 0.5 bar for the liquid in the tubing may not be exceeded. The pump must not be allowed to run dry. The pump must not be used with seawater, contaminated liquids or viscous media. Empty the liquid from the system by opening the drain valve after completing the experiments or before changing the piping layout. Inspect the liquid and replace it at least once a week if contaminated. Clean the system as required, but in any case at least once a week. Do not use aggressive cleaning materials or scouring agents. The liquid ages if the system is left at a standstill for a lengthy period of time. Always empty the tanks and the piping before leaving the system at a standstill for a long period of time. No liquids must be allowed to remain in the system for long periods of time, because this may result in the growth of bacteria such as the so-called legionellae. Festo Didactic GmbH & Co. KG 13

14 Introduction Technical data, system Max. operating pressure in piping Power supply for the station Profile plate Station height: with one tank with two tanks 50 kpa (0.5 bar) 24 V DC / 4.5 A 350 x 200 mm 670 mm 1090 mm Inside dimensions of the Systainer 490 x 360 x 272 mm (H x W x D) Volumetric flow rate of the pumps Clean water tank Flexible piping system 0 to 6 l/min. Max. 3 litres DN15 ( 15 mm) Transport The EduKit PA project kit is shipped in a Systainer. The freight forwarder and Festo Didactic must be notified without delay of any damage that occurred in transit. Unpacking Carefully remove the filler material from the Systainer when unpacking the project kit. When unpacking the project kit, make sure that none of the parts are damaged. Examine the station for possible damage after unpacking. The freight forwarder and Festo Didactic must be notified of any damage without delay. Scope of delivery Check delivered items against the packing slip and your purchase order. Festo Didactic must be notified of any deviations without delay. Visual inspection Each time the system is started up, it must first be inspected visually. Perform the following inspections before starting the EduKit PA project kit: Inspect electrical connections and wiring. Check piping, pipe connectors and pneumatic components, including tubing for correct fitting, leakproof sealing and condition. Check mechanical and pneumatic components for visible defects (cracks, loose connections etc.). Eliminate any damages discovered during inspection before starting the station! All regulations and instructions must be adhered to in order to ensure correct operation of the EduKit PA project kit. 14 Festo Didactic GmbH & Co. KG

15 Introduction Maintenance The EduKit PA project kit is largely maintenance free. The following steps should be carried out at regular intervals: Clean the entire project kit with a soft, lint-free cloth and check components for freedom of movement. Inspect liquid for contamination! The liquid may age if the project kit is left unused for any length of time. The system should be drained completely if it is not used for a long period of time. Updates Current information on and supplements to the technical documentation for the EduKit PA project kit are available on the Internet at Festo Didactic GmbH & Co. KG 15

16 Introduction 16 Festo Didactic GmbH & Co. KG

17 Part A Plant construction 1. Process description A Technical reference A Economic reference: market research A-6 2. Planning A Project management A Work order, requirements specification A Sequence planning and scheduling, project structure plan, performance specification A Purchasing materials and goods A Standards, regulations, data sheets A Risk assessment A Mechanical engineering A Sketches and technical drawings A PI flow diagram A Parts list, mechanical A Assembly plan, mechanical A Quotation and cost calculation A Test report A Electrical engineering A Electrical circuit diagram A Parts list, electrical A Assembly plan, electrical A Cost calculation A Test report A Installation A Work safety A Preassembly, mechanical A Pre-wiring, electrical A Final assembly with component labelling A Commissioning A Mechanical testing, report A Electrical testing, report A Overall commissioning A System analysis: evaluation of test reports A Shipping and product approvals, performance description A-50 Festo Didactic GmbH & Co. KG A-1

18 Introduction 5. Marketing and sales A Quotations A Product presentation A Documentation A Intellectual property rights A Evaluation of learning objectives for plant construction A-55 A-2 Festo Didactic GmbH & Co. KG

19 1. Process description 1.1 Technical reference Information The subject of plant construction will be examined in greater detail on the following pages. Although plant construction encompasses several individual disciplines, they can be seen as a whole. Learners will be introduced to the most important aspects of plant construction using a consistent method based on practical examples. The knowledge acquired also provides them with an overview of the interaction which takes place between a variety of professions, such as electrical engineering, mechanical engineering and process engineering. The overall concept of the MPS-PA project kit is also intended to support the vocational orientation of pupils and trainees and to encourage young people to pursue technical careers. General learning objectives Participants are familiarised with the following topics: Project management Process engineering Mechanical and electrical engineering Creating flow diagrams and simple circuit diagrams Analysing results Mechanical and electrical assembly and wiring Commissioning with test report Marketing and sales Festo Didactic GmbH & Co. KG A-3

20 1. Process description Information Changing and maintaining fill levels are common daily tasks. These processes usually take place in the background or within areas of a machine or system that is not immediately visible. Nevertheless, monitoring process quantities such as fill level, pressure and flow rate offers a great deal of potential. Economy, improved quality and more safety for personnel and machinery are only a few of the aims which can be achieved by consistent process monitoring. Below are a few examples of applications in which these factors play a role. Pressure monitoring Example: galvanising plant The acid bath at a galvanising plant is continuously recirculated and filtered. A filter in the piping system ensures that contamination and particles are removed. During operation, the contamination is deposited on the filter and resistance within the piping system increases. As a result, pressure upstream of the filter rises. Pressure is monitored via a sensor. When a specified pressure is exceeded, the filter must be cleaned or replaced. A-4 Festo Didactic GmbH & Co. KG

21 1. Process description Flow monitoring Example: water meter A household water meter continuously measures the occupants water consumption by measuring the flow rate in the fresh water supply line. The consumer relies on a uniformly accurate read-out of actually consumed quantities. The water utilities are also dependent on the accuracy of the water meter. Deviation results in a loss for one party and an erroneous gain for the other. Fill level monitoring Example: water tower In order to ensure a constant supply of drinking water, ground, spring or lake water is pumped into water towers where it s stored before being distributed to cities and communities. The fill levels in these towers should be kept as constant as possible, although varying amounts of water are withdrawn by households. Water flows from the water towers via distributors into the storage tanks of domestic household water systems. From there it is accessed directly via a water tap or it s stored again, for example in toilet tanks. Festo Didactic GmbH & Co. KG A-5

22 1. Process description Further examples of pressure, flow and fill level monitoring: Pressure must be held constant in water jet cutting systems, even in the event of fluctuating water demand. A certain amount of water must be added in order to achieve the desired consistency in a cement mixing system. The volumetric flow rate is time-controlled and flows constantly. Cooling lubricant is pumped into a tank at the machine in order to ensure an uninterrupted supply to machine tools. Cooling lubricant is withdrawn continually during the machining process. The fill level is continuously monitored. Pumps deliver cooling water from car radiators to car engines in order to prevent them from overheating. A storage container compensates for volumetric fluctuation due to thermal expansion and loss. Liquids are pumped from one tank to the next for storage in filling systems. When a given quantity of liquid is withdrawn, for example, the fill level has to be evened out. Fountains are operated with the help of a pump and a storage tank. 1.2 Economic reference: market research Information There are approximately 14,500 water catchment systems in Germany. More than 60% of drinking water is ground water; the rest comes from rivers, lakes, bank filtrate and springs. For example, the supply of water for Baden-Württemberg is assured by a joint management authority consisting of communities, cities and water utilities, namely Bodensee-Wasserversorgung (Lake Constance water supply). Roughly four million people are supplied with water from Lake Constance, which is pumped from a depth of 60 metres near the town of Sipplingen. Approximately 130 million m 3 of water are transported through a piping network that is 1700 kilometres long and includes roughly 30 tanks used for intermediate storage. The largest water tank, with a capacity of 100,000 m 3, is located in Baden- Württemberg s capital city, Stuttgart. Task Find out about water supply in your city or area. Determine the course of the water before it arrives at all the households. A-6 Festo Didactic GmbH & Co. KG

23 1. Process description Information The fill-level system simulates the supply of water from the withdrawal of raw water, for example from a spring, to the filling of a water tower with the help of a pump up to consumption by households. Two tanks are available for this project, one of which represents the elevated water tower, and the other the household s domestic water tank. The water has to be pumped into the water tower by means of an impeller pump. Volumetric flow rates, pressures and fill levels need to be recorded at the system. Variable valve settings and electrical voltages are used in order to do this. Festo Didactic GmbH & Co. KG A-7

24 1. Process description A-8 Festo Didactic GmbH & Co. KG

25 2. Planning 2.1 Project management Work order, requirements specification Information The system is shipped as individual components and must be set up on-site, both mechanically and electrically. Various experiments should be carried out, documented and assessed after the system has been fully set up and tested. The following services, work sequences and documents are specified in the work order to this end by the customer: Mechanical design Documentation (text and images) Develop and create circuit diagrams Generate parts lists/list of components Develop an assembly plan Plan and carry out wiring and connection of electrical components Determine material costs Prepare a presentation on the subject of water supply Create an approval checklist and report Design and implement a graphic evaluation Calculate, record and evaluate time required for activities Create data sheets for recording measured values System commissioning Measured value acquisition as an experiment Process calculations and technical questions Create technical drawings Produce components if necessary Festo Didactic GmbH & Co. KG A-9

26 2. Planning Sequence planning and scheduling, project structure plan, performance specification Information First of all, in the planning the various tasks, as listed on the work order and the requirements specification, must be organised and divided in the order in which they will be carried out. The requirements specification is prepared by the customer and includes all the services to be rendered. The supplier creates the performance specification on the basis of the stipulations set forth in the requirements specification. In it, the supplier records the services to be rendered, the activities to be carried out, important dates for presentations and meetings etc., deadlines for partial and full performance of the obligations and a project structure plan. The project plan lists the respective activities arranged according to sets of tasks in the form of a flow chart. These sets are subsequently arranged interdependently in chronological order. This schedule is called the project sequence plan. The activity lists indicates the planned duration of each step before the next one can be started. Task The performance specification should be put together during the concept phase (see worksheet for shipment of a completed and functional fill-level system with two tanks). The performance specification is enhanced during the planning phase. Complete the performance specification worksheet (concept phase). Create a project structure plan and use it to develop your project sequence plan with the required procedures in tabular format with a rough time estimate. Use the list of services to be rendered from the work order for orientation. Assemble a project team for the various tasks. Use the performance specification to describe the objectives of the project, the people involved, the quality requirements with regard to setup and functionality of the system, general conditions, deadlines, milestones and the scope of documentation. A-10 Festo Didactic GmbH & Co. KG

27 2. Planning Performance specification Project name/designation: Order no. Customer: Project employees: Project no. Schedule: Intermediate deadlines: Assembly deadlines: Completion deadline: Terms and conditions of payment: o Advance payment: o According to payment schedule: Concept phase Description of the product Description of the range of applications Description of the function Formulation of the problem/requirements Done Technical data Costs and target prices Planning phase Preliminary calculation of manufacturing costs Personnel and material costs Project costs Festo Didactic GmbH & Co. KG A-11

28 2. Planning Item Step designation Duration in days Preceding activity Team members Project sequence plan A-12 Festo Didactic GmbH & Co. KG

29 2. Planning Purchasing materials and goods Information Two important aspects of the planning phase include the procurement of materials and goods. These steps should be planned carefully and in detail. The timely completion of a project may depend on this in some cases. The first step of purchasing materials and goods involves finding a suitable supplier. A suitable supplier can be selected using the Internet, as well as visits to, and meetings with, potential suppliers. As a rule, the following steps are completed after selecting a supplier: Issue an RFQ: At this point, product specifications need to be clarified and prices, lead-times and terms and conditions of payment and delivery have to be negotiated. Issue a purchase order: It s important to include the correct information on the purchase order. This includes a precise product designation, the quantity, the price and the delivery date, as well as terms and conditions of shipping and payment. Dispatch the order confirmation: The supplier sends you an order confirmation after he has received your purchase order. All the points which were agreed upon before the order was placed should be reviewed at this time. Important points include the product designation, the price, the quantity, lead-time and terms and conditions of payment. The goods arrive: Goods are usually received by the good inwards department, where the shipment is inspected for damage and/or defects. If any defects are detected, they must be recorded and documented. The resulting documents must then be submitted to the liable party, i.e. the manufacturer or the supplier. The invoice arrives: Before the invoice amount is finally paid, the prices on the invoice are compared with the prices on the purchase order in order to rule out any possible errors. The order is closed once the invoice amount has been paid. Carry out final costing: The purchasing costs are used for final costing. This step is helpful to estimate future projects. Festo Didactic GmbH & Co. KG A-13

30 2. Planning Standards, regulations, data sheets Information A process engineering system consists of numerous components from various manufacturers. The components must comply with uniform quality standards. These standards are specified in accordance with DIN and EN, as well as ISO, VDE and VDI. The following standards are taken into consideration and the following data sheets are required to plan and design the fill-level system in accordance with current knowledge as of 2008: DIN standard for graphical symbols and flow diagrams for process plants DIN 19227, parts 1 and 2 standard for the graphic representation of process, measurement and control technology symbols DIN EN standards for graphical symbols and identifying letters for mechanical components DIN EN standards for graphical symbols and identifying letters for electrical components DIN ISO standards for graphical symbols and identifying letters for pneumatic components Data sheets for piping, stopcocks and the impeller pump DIN EN 60617, DIN EN standards for graphical symbols and identifying letters... DIN ISO 1219, DIN EN standards for engineering drawings of pneumatic components and function charts The standards and stipulations set forth by DIN and VDE as well as the safety precautions for working with electrical current and voltage, must be observed for all electrical work. Technical information about the components is included in the data sheets on CD-ROM. Electrical components The respective devices are designated in the electrical circuit diagrams in accordance with DIN EN Type of equipment Actuators (servo drive, actuating coil, electrical motor, linear motor) Diodes Auxiliary relays Terminals, terminal blocks, terminal strips Capacitors Circuit breakers, isolating switches Power transistors Indicators (mechanical, optical, acoustic) Relays Identifying letter M R K X C Q Q P K Tubes, semiconductors Contactors (for load) Sensors in general, position switches, proximity switches, proximity sensors etc. Fuses Q B F A-14 Festo Didactic GmbH & Co. KG

31 2. Planning M RRE/7. 7 2K M2 10 XMA2 1 XA2 O0 24VA 2A4 A1(START) / ADNGA Motor Ansteuerung Motor control - (GND) A2 (ANL) R- 4 3 R+ A D A D Brücke umst ecken für: Digital/Analog Ansteuerung use bridge to choose digital/analog control 0VA 0VA /24VB 24VA_EXT XMA2 9 XA2 24VA NI V42 V0 T UO Anlaufstrombegrenzer current limiter 2A (bk) M 2K1 2 O1 2K VA M3 3 O2 + 2K VA 2M4 4 5 O3 O M5 0VA 0VA 6 O5 0VA 7 O6 0VA 2PA_ BUSY BN BU 8 O7 + 0VA 24VB/6.0 24VA FED BK 0VA 0VB/6.0 24V 2M1 0V 24VA 0VA 2X4 7. 6/ 10C2 XA2 0VA XMA2 11 0VA_EXT 4.9/0VB Example of an electrical circuit diagram MPS PA mixing station, outputs Festo Didactic GmbH & Co. KG A-15

32 2. Planning Pneumatic components Pneumatic components are designated in circuit diagrams in accordance with DIN ISO All the components included in any given circuit have the same primary identifying number. Letters are assigned depending on each respective type of component. Consecutive numbers are assigned if several components of the same type are included within a single circuit. Pressure lines are designated with a P and are numbered separately. Actuators: 1A1, 2A1, 2A2... Valves: 1V1, 1V2, 1V3, 2V1, 2V2, 3V1... Sensors: 1B1, 1B2... Signal input: 1S1, 1S2... Accessories: 0Z1, 0Z2, 1Z1... Pressure lines: P1, P2... Identifiers for pneumatic components also include a system number ( ) which appears to the left of the circuit number, the component identifier and the component number. A-16 Festo Didactic GmbH & Co. KG

33 2. Planning V103 V102 8B1_ 6B1_ 12 1M M4 3 max. 2bar 1-1V2 1V1 IST P U 1B1 BN BK 1 BU RU 4 _1B9 2 WH RI 1-3A1 3 _1B V1 1-2V2 1-2V3 1-1A1 4 2 SOLL 3 1 E P PROP_V 1-1V V A V1 1M V2 1-4V3 I 4 1-3V M5 1-3V2 1-3V3 Example of a pneumatic circuit diagram MPS PA filtering station Festo Didactic GmbH & Co. KG A-17

34 2. Planning Process engineering components Components are designated in the PI flow diagram in accordance with EN ISO and DIN V206 V205 V204 LS+ 201 LS- 202 B201 LA+ 210 LS- 203 B202 LA+ 211 LS- 204 B203 LA+ 212 FI 202 FIC 201 P201 LS+ 205 LS- 206 B204 LA+ 213 V207 V208 V201 V202 V203 P202 M V210 V209 X201 V211 X202 M Example of a PI flow diagram MPS PA mixing station A-18 Festo Didactic GmbH & Co. KG

35 2. Planning EN ISO standard The layout and function of a process engineering system are described in a piping and instrument flow diagram (abbreviated PI flow diagram). Apparatus or machinery System section or machine if not assigned to one of the following groups Container, tank, hopper, silo Chemical reactor Steam generator, gas generator, oven Filtration device, liquid filter, sieve, separator Gear unit Lifting unit, conveying unit, transfer unit Column Electrical motor Pump Stirrer, stirring container with stirrer, mixer, kneader Centrifuge Dryer Compressor, vacuum pump, fan Heat exchanger Feed and separating equipment, other devices Actuator unit, other than electrical motor Crusher Identifying letter A B C D F G H K M P R S T V W X Y Z Identification of process engineering components DIN standard In addition to system components, process, measurement and control points are also included in PI flow diagrams. The process related functions of the measured quantities are described by means of process, measurement and control points per DIN The identifier should indicate the measured quantity or another input quantity, how it s processed, its direction of control action and its specified location. A process, measurement and control point consists of a circle and is designated with an identifying letter (A to Z). The identifying letters are entered in the top part of the circle and numbering is entered in the bottom part. The order of the identifying letters is as per the table, Process, measurement and control identifying letters per DIN Example L I C Lic First letter Supplementary letter First subsequent letter Fill level Display Automatic control Festo Didactic GmbH & Co. KG A-19

36 2. Planning The identifying procedure for process, measurement and control points is freely selectable. Consecutive numbering is advisable because each process, measurement and control identifier may only be used once, even if there are several measuring points with the same measured quantity. Further information can be found in DIN 19227, part 1. Process, measurement and control identifying letters per DIN Letter A B C Measured quantity or other input quantity, actuator First letter Supplementary letter Processing Subsequent letter Sequence: O, I, R, C, S, Z, A Error message Automatic control D Density Difference E Electrical quantities Sensor function F Flow, throughput Ratio G Distance, length, position H Manual entry, manual intervention Upper limit value (high) I Display J Sensing of measuring points K Time L Level (also separation layer) Lower limit (low) M Moisture N O Visible sign, yes-no statement P Pressure Q Material characteristics, quality Integral, sum R Radiometric quantities Recording S Speed, frequency Switching, sequence control, logic control T Temperature Measuring transducer function U Combined quantities Combined actuator function V Viscosity Actuator function W X Weight, mass Other quantities Y Z Calculation function Emergency intervention, protection by means of triggering, safety device, safety relevant message + Upper limit value / Intermediate value Lower limit value A-20 Festo Didactic GmbH & Co. KG

37 2. Planning Task Familiarise yourself with the standards and data sheets. Which information do the above mentioned standards and data sheets provide you with? Create a summary of the most important characteristics for each standard and the components used Risk assessment Information An important aspect of the planning phase is the risk assessment. All machinery and equipment manufacturers are required to carry out a risk assessment for their machines and equipment. This is a legal requirement and is stipulated in the EC machine directive. The directive states: The manufacturer of machinery or his authorised representative must ensure that a risk assessment is carried out in order to determine the health and safety requirements which apply to the machinery. The machinery must then be designed and constructed taking into account the results of the risk assessment. Below is an example of what a risk assessment might look like. Festo Didactic GmbH & Co. KG A-21

38 2. Planning 2.2 Mechanical engineering Sketches and technical drawings Task The scale of the overall drawing of the fill-level system is 1:5. Add the most important assembly dimensions to the drawings so that it can be used later to set up the system. Topview A-22 Festo Didactic GmbH & Co. KG

39 2. Planning Front view Festo Didactic GmbH & Co. KG A-23

40 2. Planning Side view, right A-24 Festo Didactic GmbH & Co. KG

41 2. Planning The rectangular profiles to which the tanks are attached are joined with retaining plates. Manually sketch out the hole pattern for the retaining plates for M5 socket head screws. The retainer for the impeller pump has to be made. Calculate the length of the sheet metal. a, b, c... Lengths of bending sections n number of bends v compensation value; v = 3 mm for a sheet metal thickness of 1 mm and a bending radius of 4 mm L = a + b + c n v Festo Didactic GmbH & Co. KG A-25

42 2. Planning PI flow diagram Information The piping and instrument flow diagram (PI flow diagram) depicts the technical equipment included in a system with the help of graphical symbols which are connected using lines. The graphical symbols represent the system components and the lines identify lengths of pipe, as well as electrical functions and signals for process measurement and control. The designation V101 from the PI flow diagram is a process designation. Process related tasks are described in a process, measurement and control plan using graphical symbols, i.e. process, measurement and control points. The identifier should indicate the measured quantity or another input quantity, how it s processed, its control action and its specified location. A process, measurement and control point consists of a round, oval or hexagonal symbol and is assigned an identifying letter (A to Z). The identifying letters are entered in the top part of the symbol and a number is entered in the bottom part. The order of the letters is specified in the table entitled Identifying letters for process, measurement and control technology per DIN Task Fill in the missing designations. Create a PI flow diagram for the system using the components from the table. Components list Identification Graphical symbol Meaning of the graphical symbol B101 V102 Stopcock FI 101 PI103 Pressure measuring point with display P101 A-26 Festo Didactic GmbH & Co. KG

43 2. Planning PI flow diagram PI flow diagram, EduKit PA project kit Festo Didactic GmbH & Co. KG A-27

44 2. Planning Parts list, mechanical Task The components and their required quantities can be determined from the overall drawing and the PI flow diagram for the purpose of creating a parts list. The part numbers are included in the data sheets and the Festo Didactic product catalogue. Using this information, create a parts list for the basic mechanical setup of EduKit PA without electrical components. A-28 Festo Didactic GmbH & Co. KG

45 2. Planning Item Quantity Name Part number Assembly plan, mechanical Information In order to keep assembly of the system as simple as possible, components are grouped into subassemblies. Task Create an assembly plan for the basic setup of the fill-level system using the table on the next page. Write out a set of procedures, indicating how you would assemble the system. Sub-assemblies are numbered consecutively with the designations B1, B2 and so forth. (The Times column refers to a task in a later chapter and can be disregarded for this exercise.) Festo Didactic GmbH & Co. KG A-29

46 2. Planning Subassembly Item Work step Tool Work step carried out Times Assembly plan, mechanical A-30 Festo Didactic GmbH & Co. KG

47 2. Planning Quotation and cost calculation Information A fill-level system is required in another department within your company for training purposes. First of all, you ll produce a complete basic setup in the form of a prototype in the training department. The fill-level system will then be sold to the respective department. Determine an estimated sales price in the form of a simple cost calculation. Electrical and mechanical components should be listed separately. Use the following quotation as a basis for your calculation: Item Quantity Designation Unit price Amount 1 1 Basic mechanical components kit with aluminium profiles, including all accessories Tank, MPS-PA-B tank, round Pump, Flow meter, Pressure gauge m Pipe, Push-in connector, T-distributor, Push-in bracket, Stopcock, Blanking plug, Net price Quotation (sample prices are not the same as actual prices!) Task Calculate the costs for the fully assembled mechanical portion of the system. Costs are calculated separately for the mechanical and electrical parts while the cost calculation for the electrical components will be completed later (see 2.3.4). The prices of the components can be taken from the above quotation. Manufacturing wages and overheads, as well as administrative and sales costs can be based on figures provided by the appropriate people in your company, researched on the Internet or estimated for the purposes of a rough calculation. Make a rough estimate of the time required for assembly in order to determine labour costs. Use local hourly rates for this. Festo Didactic GmbH & Co. KG A-31

48 2. Planning Term Explanation Pieces, hours Amount Total Material costs (1) Material overhead costs (2) Procurement costs for materials, components Purchasing costs, warehousing costs, bookkeeping 5% of (1) Gross material costs (3) Total of (1) + (2) Manufacturing wages (4) Manufacturing overhead costs (5) Wage costs allocated to the product Depreciation, social security costs, training costs, auxiliary materials, tools, premises, payroll accounting Manufacturing costs (6) Total of (4) + (5) Special manufacturing costs (7) Production, fixtures, outsourced processing (e.g. hardening) Production costs (8) Total of (3) + (6) + (7) Administration and sales (9) Administration, taxes, advertising costs 15% of (8) Cost of sales (10) Total of (8) + (9) Profit (11)... % of (10) Net sales price Sales price without value added tax Total of (10) + (11) Gross sales price Sales price with value added tax Simple cost calculation for mechanical assembly Task When you buy components, a difference is made between net and gross prices. What s the difference? Calculate the gross sales price for the above example. What s meant by overheads? A-32 Festo Didactic GmbH & Co. KG

49 2. Planning What s meant by manufacturing costs? Test report Information Once mechanical assembly has been completed, the fill-level system and all its components must be inspected and approved (i.e. screw connections in the pipe fittings, straightness and parallelism of the piping, tank mounting, profiles and the impeller pump). In actual practice, test reports are used to document the functionality and the condition of the system. Test report requirements are specified either by the customer or by currently valid standards. Task Create a test and approval report with a word processing program which has space for the following entries: - Test points are numbered consecutively in a tabular report and the numbers are added to the picture below. - The list includes columns for each item number, the test point designation, a tick mark for approval and comments. - Space is provided at the end of the test report for the name of the inspector and the date. - The comments column must provide adequate space for the entry of any defects detected during inspection. Festo Didactic GmbH & Co. KG A-33

50 2. Planning Mechanical assembly without electrical actuation A-34 Festo Didactic GmbH & Co. KG

51 2. Planning 2.3 Electrical engineering Electrical circuit diagram Information The impeller pump is turned on and off using a detented switch in the basic setup. The pump s on/off status is displayed by an indicator light. The impeller pump is supplied with 24 V DC power via a power supply unit. Task Create an electrical circuit diagram for the system and identify all the components. All the system s electrical components must be designated in accordance with DIN EN Circuit diagram Festo Didactic GmbH & Co. KG A-35

52 2. Planning Parts list, electrical Information The parts list for the electrical components must be planned. The item numbers for the various components are shown in the following figure. Task Complete a part list for the entire electrical assembly. The part numbers can be taken from the data sheets and the Festo Didactic product catalogue. Put a tick mark in the column Components for basic setup for each component required for this task. Which additional consumables will be required? Estimate the amount. A-36 Festo Didactic GmbH & Co. KG

53 2. Planning Item no. Quantity Name Designation, standard designation Components for basic setup Blue wire, 0.5 sq. mm (cross section?) x Cable binder (size?) x Wire end sleeves Bill of materials Assembly plan, electrical Information To optimise work sequences, the order in which work steps are carried out to produce a product should be planned and documented by the production planning department. Task Arrange the work steps in a logical order with the help of the parts list. List the wiring and assembly steps for the electrical components in the setup plan. Electrical components are designated E1, E2, etc. (The Times column refers to a task in a later chapter and can be disregarded for this exercise.) Festo Didactic GmbH & Co. KG A-37

54 2. Planning No. Item no. Work step Tool Times Assembly plan, electrical Add the connecting cables to the image of the electrical components to indicate how they have to be wired according to the circuit diagram prepared earlier Cost calculation Task On the basis of the quotation, determine an estimated sales price for the electrical components and electrical wiring with the help of a simple cost calculation. Manufacturing wages and overheads, as well as administrative and sales costs can be based on figures provided by the appropriate people in your company, researched on the Internet or estimated for the purposes of a rough calculation. Make a rough estimate of the time required for assembly in order to determine labour costs. Use local hourly rates for this. A-38 Festo Didactic GmbH & Co. KG

55 2. Planning Item Quantity Designation Unit price Amount V DC indicator light with mounting bracket Electrical control switch with mounting bracket Electrical start pushbutton with mounting bracket Relay with two changeover contacts Screw terminals core safety laboratory cable Mountable plug block H-rail Rail for control components Table top power supply unit with power cable, 230 V AC, 24 V DC / 4.5 A Net price Quotation (sample prices are not the same as actual prices!) Term Explanation Pieces, hours Amount Total Material costs (1) Material overhead costs (2) Procurement costs for materials, components Purchasing costs, warehousing costs, bookkeeping 5% of (1) Gross material costs (3) Total of (1) + (2) Manufacturing wages (4) Manufacturing overhead costs (5) Wage costs allocated to the product Depreciation, social security costs, training costs, auxiliary materials, tools, premises, payroll accounting Manufacturing costs (6) Total of (4) + (5) Special manufacturing costs (7) Production, outsourced processing (e.g. ready-wired components) Production costs (8) Total of (3) + (6) + (7) Administration and sales (9) Administration, taxes, advertising costs 15% of (8) Cost of sales (10) Total of (8) + (9) Profit (11)... % of (10) Sales price Net price without value added tax Total of (10) + (11) Calculation plan Festo Didactic GmbH & Co. KG A-39

56 2. Planning Test report Information Once electrical assembly has been completed, the wiring, interconnection of the electrical components such as switches and the indicator light and the mechanical attachment of the electrical components are inspected and approved. Task Create a test and approval report with a word processing program which has space for the following entries: - Test points are numbered consecutively in a tabular report and the numbers are added to the image below. - The list includes columns for each item number, the test point designation, a tick mark for approval and comments. - Space is provided at the end of the test report for the name of the inspector and the date. - The comments column must provide adequate space for the entry of any defects detected during inspection. A-40 Festo Didactic GmbH & Co. KG

57 2. Planning Setup with electrical wiring Festo Didactic GmbH & Co. KG A-41

58 2. Planning A-42 Festo Didactic GmbH & Co. KG

59 3. Installation 3.1 Work safety Information Work instructions specify in detail how certain steps have to be carried out. Work instructions are tied to a specific process, a product or a workstation. They form the basis for ensuring that quality standards are met when the company s employees carry out their respective tasks. Initial basic instruction on safety in the workplace and how each person should comply must be completed before specific work instructions are handed out. Observe the safety precautions in the introduction! Safety instructions Mr./Ms. Department Job Received instructions in accordance with 7 UVV, VBG 4 and on the basis of the activities carried out at the workstation. Subject of instruction Date Instructed person (signature) Supervisor (signature) 1. General instructions at the fill-level system 2. Instructions on handling liquids 3. Instructions for electrical components 4. Electrical start-up must only be carried out by appropriately trained personnel. 5. General introduction to: Workshop use Goods in/out Working at a PC Internet and Telephone system Accident prevention regulations specified by trade associations for precision and electrical engineering apply. Festo Didactic GmbH & Co. KG A-43

60 3. Installation 3.2 Preassembly, mechanical Information The components must now be assembled in accordance with the specifications in the assembly plan. Task Complete the mechanical preassembly of the components of the fill-level system first. Supplement the assembly plan you created in the chapter on Planning by assigning assembly procedures to components. Use the technical drawings of the components as an assembly guideline. Engineering drawings of the individual components are included on CD-ROM. Write down the assembly times in the assembly plan prepared earlier and modify it if necessary if you use different steps or discover better alternatives. 3.3 Pre-wiring, electrical Information The components are preassembled in accordance with the basic electrical setup plan. Task First of all, the electrical components are pre-wired. Proceed in accordance with the layout you have already created. Follow the circuit diagram with regard to wiring. Then attach the electrical components to the H-rail. A-44 Festo Didactic GmbH & Co. KG

61 3. Installation Write down the assembly times and modify the assembly plan if necessary if you use different steps or discover better alternatives. Make a note of any changes to the assembly plan. 3.4 Final assembly with component labelling Information All the mechanical and electrical components are put together in the final step. Task During final assembly, screw or clamp all the mechanical and electrical components to the profile plate and the rectangular profiles and connect the electrical components to each other (see CD-ROM). Supplement the components list with the component designations in accordance with the PI flow diagram and the electrical circuit diagram. Write the designations of the components onto the adhesive labels and attach them to the respective system components. Festo Didactic GmbH & Co. KG A-45

62 3. Installation Item no. Graphical symbol Meaning of the graphical symbol Identification 1 P101 2 Measuring point for pressure measurement with display (component: pressure gauge) PI103 3 FI Tank, container (2) B101, B102 Component list per PI flow diagram Item no. Graphical symbol Meaning of the graphical symbol Identification 10 Indicator light, start 11 S1 S1 12 Electrical pushbutton, start S2 13 S3 S3 14 Relay Components list based on electrical circuit diagram A-46 Festo Didactic GmbH & Co. KG

63 4. Commissioning 4.1 Mechanical testing, report Information The fill-level system has now been set up and should first of all be filled. Disconnect the system from the power supply before commissioning. In order to prevent any unpleasant surprises, check the mechanical components both before and during filling. Keep an adequate supply of rags on hand in order to mop up any water which might escape. Task Check the points listed below and acknowledge inspection. Commissioning, report mechanical Characteristic, requirement for component Fulfilled Not fulfilled, comment Stopcock V 105 closed Impeller pump pipe connection complete and securely pushed in place Stopcock V 101 for filling the upper tank from above closed Stopcock V 103 for filling the upper tank from below closed Stopcock V 102, lower tank return line, closed Fill the upper tank, check for leaks Check fittings and tighten further if required Open stopcock V 102 (lower tank return line open) Fill the lower tank, check for leaks Check fittings and tighten further if required Place a bucket underneath, open stopcock V 105 and drain the tank Inspector Date Festo Didactic GmbH & Co. KG A-47

64 4. Commissioning 4.2 Electrical testing, report Information Once mechanical inspection has been completed, the electrical components are tested to ensure they function correctly. This is done by filling the system with water, so that the pump is prevented from running dry. First, the water is only pumped around in a circular direction, i.e. from the bottom container via the impeller pump and back into the lower tank from the upper tank. Task Carry out all the commissioning steps. Evaluate your results and tick off the corresponding entry. If the function is not performed correctly, make a note of the determined status or the sub-function. Discuss appropriate measures for eliminating the cause of error with your trainer. Commissioning, report electrical Function Fulfilled Not fulfilled, comment Connect the 24 V and 0 V leads from the power supply unit to the terminals. Electrical control switch wired Indicator light wired Pump wired Secure wires with cable binder Power supply unit connected to mains power (230 V AC) Switch the power supply unit on, the indicator light on the power supply unit lights up. Control switch ON, indicator light switches on Control switch ON, pump runs Control switch OFF, indicator light does not switch on Pump vented? Control switch OFF, pump does not run Power supply unit OFF, system is shut down Inspector Date A-48 Festo Didactic GmbH & Co. KG

65 4. Commissioning 4.3 Overall commissioning Information You have approved the system s mechanical and electrical parts. Now start an initial, complete test run with all of the system s components. Before each time you commission the system, carry out a visual inspection. Inspect the following before starting the system: Electrical connections Correct fitting, leakproofness and condition of piping and pipe connectors Correct fitting and condition of compressed air connections, if pneumatic valves are used Mechanical components for visible defects (cracks, loose connections etc.) Fill level of tank B101 Eliminate any damage discovered during inspection before commissioning. Supply the system with 24 V DC power via a mains power supply unit. Task Carry out the following steps for (re-)commissioning: 1. Prepare the workstation. 2. Conduct visual inspection. 3. Inspect cable connections. 4. Activate supply power. 5. Fill the tanks. 6. Vent the piping system Set the stopcocks so that the following tasks can be carried out: - Full upper tank B102 from above, stopcock V102 in tank B101 opened about 20%. V101 open, V103 closed. - Fill upper tank B102 from below, stopcock V102 in tank B101 opened about 20%. Open V103, close V101. Festo Didactic GmbH & Co. KG A-49

66 4. Commissioning 4.4 System analysis: evaluation of test reports Information The test reports have to be analysed and conclusions must be drawn based on the work done while setting the system up so that the system s design and layout can be analysed and improvements made. The commissioning test reports for mechanical and electrical components are available and overall commissioning has also been completed. Task Evaluate the test reports and pinpoint any problems. Use the first practical test run to draw conclusions for further work with the system. Analyse the overall layout of the system in order to determine whether or not the assembly and commissioning procedures can be improved. Document your evaluations in writing. 4.5 Shipping and product approvals, performance description Information Once prototypes have been developed, the first samples are produced under series manufacturing conditions. The product is not approved until the function, quality and performance features have been examined and tested. Subsequent series manufactured parts must conform to the same quality standards as the first samples. The product must be approved by general management before it can be launched. All information relevant for sales must be available as a basic prerequisite for the product s introduction onto the market (see chapter 5, Marketing and Sales ). A-50 Festo Didactic GmbH & Co. KG

67 4. Commissioning 5. Marketing and sales 5.1 Quotations Information A great variety of information is required in order to sell a product. For example, the text for a quotation template must be prepared. Task Find out how quotations are laid out and what information is included. Base yourself on the layout and content of a quotation from your company or another manufacturer. Which details are included in a quotation? Create a sample quotation for a customer who wants to purchase the project kit. What does the term ex works mean? Festo Didactic GmbH & Co. KG A-51

68 4. Commissioning 5.2 Product presentation Information The way in which a product is presented plays an important role in how well it will sell. Companies invest large sums of money in product marketing. The most important points are briefly discussed below. Task Various types of product presentations are created in small groups. Brochure, leaflet, foreign languages A brochure or a leaflet should be printed for the project kit. Important content for any printed information includes an overall view of the system, interesting partial views, a functional description, features and technical data of the individual components and notes regarding the user-friendliness of the piping system thanks to the push-in connector system. Write the text for the functional description and the technical data in German and English, and add both languages to the leaflet. The technical data for the various components are included on CD-ROM. Screen presentation The system will be presented to a customer. Create a screen presentation which covers the most important features and functions of the system. Use the texts for the brochure, but condense them for the screen presentation. The screen presentation can also be laid out as a PDF file, so that it can be printed out. Photos of the system are included on the CD-ROM. Internet presentation Edit the screen texts and images so that they can be used in a start-up page for the Internet. Create an HTML page for the project kit with the help of an HTML editor. 5.3 Documentation Information The technical documentation is intended to provide the recipient of the product with information and instructions regarding the system or the product. In addition, the customer is also made aware of safety precautions and provided with operating instructions for the system. A-52 Festo Didactic GmbH & Co. KG

69 4. Commissioning Task The entire project must be documented. The documentation should include the following information: - System layout - Description of functions - Data sheets for the various components - Experiment descriptions - Tables with values and evaluations resulting from the experiments - Findings - Circuit diagrams - Drawings 5.4 Intellectual property rights Information As a result of intellectual property legislation for the protection of industrial property rights, the holder of the rights is granted the opportunity of prohibiting commercial exploitation of the protected objects by any other party. The intellectual property rights are thus rights of prohibition. They are not at least not automatically rights of use. Task Which types of protective rights are there? Research this topic on the Internet. Festo Didactic GmbH & Co. KG A-53

70 4. Commissioning A-54 Festo Didactic GmbH & Co. KG

71 6. Evaluation of learning objectives for plant construction 1. During which phase of system setup is the project structure plan used? 2. What is the function of the project structure plan? 3. Calculate the flat length for the pump bracket assuming a bending radius of 4 mm and a sheet metal thickness of 2 mm. Use a compensation value of How are the following functions designated in a PI flow diagram? Festo Didactic GmbH & Co. KG A-55

72 4. Commissioning 5. Sketch the graphical symbols for a PI flow diagram (see planning): 6. Draw the PI flow diagram for pressure measurement while filling the upper tank from below. A-56 Festo Didactic GmbH & Co. KG

73 4. Commissioning 7. Which information is included in a part list? 8. What s included in a tabular assembly plan? 9. When you buy components, a difference is made between net and gross prices. What is the difference between these prices? 10. Name typical overheads. 11. What s meant by manufacturing costs? Festo Didactic GmbH & Co. KG A-57

74 4. Commissioning 12. During initial testing, you started the pump with a detented switch. Why is a detented start-up switch impermissible in actual practice? 13. Cite one safety precaution each for electrical, pneumatic and mechanical components and process technology 14. Why is a commissioning report prepared after final assembly has been completed and before commissioning? Cite two examples. A-58 Festo Didactic GmbH & Co. KG

75 Part B Practice-based learning: manual measurement, open-loop and closed-loop control 1. Manual measurement B Project task: bath recirculation B Task description B Setting up the system, inspection B Experiment: mechanical pressure measurement B Evaluation and findings B Project task: mixing system B Task description B Experiment: flow measurement B Evaluation and findings B Manual open-loop control B Project task: controlling water supply using hand valves B Task description B Mechanical layout B Setting up the system, inspection B Experiment: filling the upper tank from below B Experiment: filling the upper tank from above B Evaluation and findings B Project task: controlling water supply using 2-way ball valve B Task description B Mechanical layout, inspection B Plans B Commissioning report B Experiment: filling using a pneumatically controlled 2-way ball valve B Evaluation and findings B Project task: electrical control of the pump in the water supply line B Task description B Setting up the system, inspection B Relay circuit with pushbuttons B Electrical circuit diagram B Electrical wiring and setup plan B Commissioning, electrical testing and report B Experiment: filling while simultaneously withdrawing water B Evaluation and findings B Experiment: pump start-up performance and power B Evaluation and findings B-35 Festo Didactic GmbH & Co. KG B-1

76 4. Commissioning 3. Manual closed-loop control B From a control loop system to a control circuit B Project task: controlling the fill-level in the tanks B Task description B Setting up the system, inspection B Experiment: manually keeping the fill level constant in the upper tank B Evaluation and findings B Experiment: controlling the fill level using an analogue controlled pump B Evaluation and findings B Experiment: pressure and flow control B Evaluation and findings B Evaluation of learning objectives for manual measurement, open-loop and closed-loop control B-47 B-2 Festo Didactic GmbH & Co. KG

77 1. Manual measurement 1.1 Project task: bath recirculation Task description Information Typical recirculating processes are used in all baths where liquids have to be filtered. For example, leisure time applications include swimming pools and technical applications include acid baths and galvanising plants. As the filter becomes more and more contaminated, resistance in the piping system increases upstream of the filter in proportion to the degree of contamination. When a specified pressure is exceeded, the filter must be cleaned or replaced. The relationship between resistance (degree of valve opening) and pressure is determined by experimentation. Task Modification in accordance with the PI flow diagram: modify the basic setup with two tanks so that the experiments for manual measurement can be done using a single tank. Stopcock V103 represents the filter for the purpose of the experiment. Filter permeability is simulated by opening and closing the valve. V103 V102 FI 101 PI 103 B101 P101 V105 M Festo Didactic GmbH & Co. KG B-3

78 1. Manual measurement Setting up the system, inspection Work step Done Modify the piping layout in accordance with the photograph. Remove the piping to the upper tank and insert blanking plugs into each of the push-in T-connectors. Close stopcock V105. Check to make sure that all piping connections are correct. Check the piping connections to the impeller pump. Make sure that the pressure gauge is installed directly downstream of the pump! Fill tank B101 with 3 litres of water. Connect the system to the power supply unit (24 V DC). Test execution: Stopcocks V103 and V102 are fully open and V105 is fully closed. The control switch is turned to the ON position and the pump delivers water. Stopcock V103 is closed successively in the test setup. After the experiment has been completed, pull out the main plug and remove the 4 mm safety cable from the power supply unit. The water must be drained from the system via stopcock V105 after testing. B-4 Festo Didactic GmbH & Co. KG

79 1. Manual measurement Experiment: mechanical pressure measurement Fill the tank and then start the pump. Stopcock V103 is open at first and is gradually closed. Stopcock V103 represents the filter for the purpose of experimentation. Filter permeability is simulated by opening and closing the valve. Read pump pressure from the pressure gauge. Observe the volumetric flow rate at the sight glass in the flow meter. Resistance (degree of valve opening) and pressure Degree of valve opening as percentage, V 103 p e [bar] Q [l/min.] Open % % % % 0.22 Closed 0.32 Festo Didactic GmbH & Co. KG B-5

80 1. Manual measurement Evaluation and findings Task Plot the pressure measured in the piping system relative to the degree of valve opening on the graph: How are pressure and volumetric flow rate within a piping system influenced when resistance within the piping system is continuously increased? Why doesn t pressure continue to rise after the stopcock has been fully closed? Explain how an impeller pump works. B-6 Festo Didactic GmbH & Co. KG

81 1. Manual measurement Why is it important to ensure that there s no air in the pump? Which types of pumps can be used in the field of process technology? Use information from various manufacturers in order to research your answer. Create a table with typical characteristics, as well as technical data and the range of applications, for a given type of pump. Pump type (section drawing) Characteristics, technical data, range of applications Festo Didactic GmbH & Co. KG B-7

82 1. Manual measurement Pump type (section drawing) Characteristics, technical data, range of applications B-8 Festo Didactic GmbH & Co. KG

83 1. Manual measurement 1.2 Project task: mixing system Task description Information The ingredients fed to a mixing system are usually required in the defined quantity. Mixing systems of this sort are used, for example, to mix cement. A corresponding amount of water must be fed to the cement mixer in order to produce a specified concrete mix. The quantity is time-controlled. A prerequisite is that a constant volumetric flow rate must be maintained, e.g. 60 litres per hour. The relationships between resistance (degree of stopcock opening), the delivered amount of water and the required amount of time can be determined by means of an experiment. Run the experiment using the existing test setup with one tank. Festo Didactic GmbH & Co. KG B-9

84 1. Manual measurement Experiment: flow measurement The relationships between resistance (degree of stopcock opening) and volumetric flow rate, as well as the amount of water delivered within a specific period of time will be examined. In doing so, we ll look into the question of how long it takes to pump 2 litres of water into the upper tank with various degrees of opening at stopcock V103. Task Read the volumetric flow rate at the sight glass in the flow meter. Set volumetric flow rate to the required flow rate. Fill the upper tank. Measure the time it takes for the water level to rise from the 0.5 to the 2.5 litre mark. Enter measured time in the table. Q [l/hr.] Time [s] Volumetric flow rate per unit of time B-10 Festo Didactic GmbH & Co. KG

85 1. Manual measurement Evaluation and findings Task Plot the measured time values and the volumetric flow rate settings on the graph. Describe your observations on the experiment in a few short sentences: How long would it take to pump 150 litres of water if the flow rate were set to 90 litres per hour? Festo Didactic GmbH & Co. KG B-11

86 1. Manual measurement It takes hours to fill the tank to the 2 litre mark. Calculate the volumetric flow rate for any desired setting for stopcock V101 with the help of the measured time value. Check the selected volumetric flow rate against the results of your calculation. B-12 Festo Didactic GmbH & Co. KG

87 2. Manual open-loop control 2.1 Project task: controlling water supply using hand valves Water storage tank Task description Information Water is pumped into a water tower from springs, rivers and lakes in order to supply households with drinking water. Water is directed to domestic households from the tower. The upper tank will be filled with water during the course of two experiments. There are two ways to fill a tank: either from above or below. The influence of these two methods on the filling process needs to be examined. Festo Didactic GmbH & Co. KG B-13

88 2. Manual open-loop control Mechanical layout B-14 Festo Didactic GmbH & Co. KG

89 2. Manual open-loop control Task Modification according to the PI flow diagram Supplement the PI flow diagram with a second tank as shown in the photo on the preceding page. Set up the basic layout with two tanks according to the revised PI flow diagram. V103 V102 FI 101 PI 103 B101 P101 V105 M Festo Didactic GmbH & Co. KG B-15

90 2. Manual open-loop control Setting up the system, inspection Work step Done The basic setup with two tanks is required in order to conduct the experiments. Close stopcock V105. Check to make sure that all piping connections are correct. Inspect the piping connections. Fill the lower tank with 3 litres of water. Connect the system to the power supply units (24 V DC). Experiment: fill the upper tank from below. Close stopcocks V101 and V102, open stopcock V103 until the flow meter indicates 60 litres per hour. Experiment: fill the upper tank from above. Close stopcocks V102 and V103, open stopcock V101 until the flow meter indicates 60 litres per hour. Remove the 4 mm safety cable from the power supply unit and pull the mains plug. After the experiment has been completed, the system is drained via stopcock V Experiment: filling the upper tank from below Task Close stopcock V103 until the volumetric flow rate is 60 litres per hour. Measure the time it takes to reach various fill levels as of 500 ml (first mark after the taper). Observe pump pressure at the pressure gauge. B-16 Festo Didactic GmbH & Co. KG

91 2. Manual open-loop control Fill level [ml] Time [s] Fill level [ml] Time [s] Fill level [ml] Time [s] Fill levels: filled from below Experiment: filling the upper tank from above Task Close stopcock V101 until the volumetric flow rate is 60 litres per hour. Measure the time it takes to reach various fill levels as of 500 ml. Observe pump pressure at the pressure gauge. Fill level [ml] Time [s] Fill level [ml] Time [s] Fill level [ml] Time [s] Fill levels: filled from above Festo Didactic GmbH & Co. KG B-17

92 2. Manual open-loop control Evaluation and findings Task Which fundamental influence does hydrostatic pressure have on pump performance? Copy the measured values for filling from below and from above onto a diagram. Create a worksheet in Excel with the measured values and the two line diagrams. However, filling from below takes longer than filling from above. What causes this? B-18 Festo Didactic GmbH & Co. KG

93 2. Manual open-loop control What effects can be observed at the surface of the water and with regard to turbulence during the two filling processes? Explain the relationship between the discharge rate and total head when an impeller pump is used. Calculate the pump s total head. Refer to the data sheet on CD-ROM for technical data. Festo Didactic GmbH & Co. KG B-19

94 2. Manual open-loop control 2.2 Project task: controlling water supply using 2-way ball valve Information Process valves with pneumatic actuators are used more and more frequently in modern process engineering because they offer a host of advantages compared with electric and hydraulic actuators. Pneumatic actuators are easier to handle and they re very sturdy and economical. They re exceptionally well suited for use in potentially explosive atmospheres. Please refer to Festo s marketing manual, ABC of Process Automation, for further information. 1: Pump 2: Water storage tower 3: End users Operating principle Task description Information When filling the upper tank, the volumetric flow rate can be changed by opening or closing stopcock V101 or V103. The filling process and the control of the volumetric flow rate will now be partially automated by means of a pneumatically actuated 2-way ball valve. The upper tank is filled from above via the ball valve. Stopcock V102 for lower tank B101 is partially open (20 %). B-20 Festo Didactic GmbH & Co. KG

95 2. Manual open-loop control Mechanical layout, inspection Task Close stopcock V105. The ball valve is installed parallel to stopcock V101 as a bypass. The valve is mounted onto the rectangular profile and then connected to the piping system. The ball valve is opened and closed using a pneumatic actuator. The regulating unit consists of a brass ball valve (2) with semi-rotary actuator (4), a flange-mounted NAMUR valve (1) with solenoid coil (3) and a sensor box (5). The sensor box is used for electro-mechanical position signalling to the control and regulating unit with visual display for the user. Take into account addition information included in the data sheets on CD-ROM. Modify the piping layout so that the ball valve is correctly fitted. Check to make sure that all of the piping connectors are properly fitted. Check the piping connections to the impeller pump. Inspect the mechanical setup and create a test report (see CD-ROM). Festo Didactic GmbH & Co. KG B-21

96 2. Manual open-loop control Plans Task Supplement the PI flow diagram for pneumatic control. V101 B102 V103 V102 FI 101 PI 103 B101 P101 V105 M B-22 Festo Didactic GmbH & Co. KG

97 2. Manual open-loop control Pneumatic circuit diagram Draw the pneumatic circuit diagram for the 5/2-way solenoid valve (1V1) with spring return and the semi-rotary actuator (1A1). What requires special attention when connecting the three components, namely solenoid valve, semirotary actuator and ball valve? Electro-pneumatic circuit diagrams Which possibilities exist for actuating the solenoid valve electrically? Festo Didactic GmbH & Co. KG B-23

98 2. Manual open-loop control Draw circuit diagrams for the three possible means of actuation. Make a decision in favour of one circuit. Mount the components onto the profile rail and wire the circuit. Explain your decision. Variant 1 Variant 2 S5 START S6 STOP Variant 3 B-24 Festo Didactic GmbH & Co. KG

99 2. Manual open-loop control Commissioning report Task The pneumatic components, the ball valve and the functions of all utilised mechanical and electrical components such as switches, pushbuttons and impeller pump can now be commissioned and inspected. The system is filled with water so that the pump is prevented from running dry. The water is pumped back to the lower tank via the ball valve. Make a list of all of the characteristics and requirements for which the components have to be inspected in the commissioning report. Tick the appropriate field after completing each inspection. Characteristic, requirement for component Fulfilled Not fulfilled, comment Connect the 24 V and 0 V leads from the power supply unit to the terminals. Electrical control switch and start and stop pushbuttons wired Indicator light and pump wired, cable binders Ball valve mounted to semi-rotary actuator and solenoid valve Check pneumatic connection of the solenoid valve and the semi-rotary actuator Connect the solenoid valve to the control switch/relay (variants 1 and 2). Connect the solenoid valve to the pushbuttons (variant 3). Power supply unit connected to mains power (230 V AC) Switch the power supply unit on, the indicator light at the power supply unit lights up. Set control switch to Pump on, press the start pushbutton, the indicator light switches on and the pump runs. Variants 1 and 2: set control switch to Open ball valve, water flows into the tank. Set control switch to Close ball valve, water stops flowing into the tank. Variant 3: press Open ball valve pushbutton, water flows into the tank. Press Close ball valve pushbutton, water stops flowing into the tank. Press the stop pushbutton, the indicator light switches off and the pump stops running. Set control switch to Pump off, the indicator light goes out and the pump stops running. Inspector Date Commissioning report Festo Didactic GmbH & Co. KG B-25

100 2. Manual open-loop control Experiment: filling using a pneumatically controlled 2-way ball valve Task Fill the lower tank manually with 3 litres of fresh water. Connect the system to the power supply unit (24 V DC). Open the ball valve and stopcock V102 (approx. 20%). Switch the pump on. Control the filling process by opening and closing the ball valve. Decide on a specific fill level, for example 2 litres, to which the upper tank should be filled. Switch the pump off upon when the fill level has been reached and drain back down to 1 litre. Repeat the filling process. Determine the volumetric flow rate by measuring how long it takes to reach a fill level of 2 litres. Close stopcock V102 to this end. Compare the filling process using the ball valve with the one using stopcock V Evaluation and findings Task Which advantages does the semi-rotary actuator offer in comparison with adjustment by means of a stopcock? Which difficulties are experienced when trying to maintain a specific fill level? B-26 Festo Didactic GmbH & Co. KG

101 2. Manual open-loop control 2.3 Project task: electrical control of the pump in the water supply line Task description Information Filling the water tower is closely associated with water being withdrawn by one or more households. This issue can be clarified with the help of two experiments. In addition, control of the system should also be expanded electrically. Wiring of the electrical components will be adapted in line with the task at hand. The first experiment addresses the question of how the fill level of the upper tank can be kept constant when varying amounts of water are withdrawn. During the second experiment we ll operate the pump with variable voltage values and clarify the relationship between voltage, amperage and volumetric flow rate. Costs incurred during operation of the system will also be ascertained Setting up the system, inspection The system will be operated using the basic setup with two tanks. There s no need to remove the pneumatic process actuator, although it s not required for the experiment. Work step Done Close stopcock V105. Check to make sure that all piping connections are correct. Check the piping connections to the impeller pump. Fill the lower tank with 3 litres of water. Connect the system to the power supply unit (24 V DC). 1 st experiment: fill the upper tank from below. Close stopcock V101, open stopcock V103 such that an initial flow rate of 60 litres per hour is indicated at the flow meter. 2 nd experiment: fill the tank using variable voltages for the pump. Fill the upper tank from below, close stopcock V101, open stopcock V103 so that the flow meter indicates 60 litres per hour. Remove the 4 mm safety cable from the power supply unit and pull the mains plug. After the experiment has been completed, the system is drained via stopcock V105. Festo Didactic GmbH & Co. KG B-27

102 2. Manual open-loop control Relay circuit with pushbuttons Information The system will be expanded electrically. The detented switch will now serve as a mains switch. The indicator light will still indicate the operating state. The system will be started by pressing a green pushbutton and stopped by pressing a red pushbutton. Briefly pressing the respective pushbutton is enough to start or stop the system. Task Which type of circuit has to be set up when pushbuttons are used? Which additional component is required? Why do machines have to be controlled with a self-latching circuit instead of being operated with switches? B-28 Festo Didactic GmbH & Co. KG

103 2. Manual open-loop control Electrical circuit diagram Task The system has to be rewired for the following experiments. Draw the expanded circuit diagram with two pushbuttons, a detented mains switch and an indicator light. Identify the components. Add the connecting cables to the image with the electrical components to indicate how they have to be wired according to the circuit diagram. Festo Didactic GmbH & Co. KG B-29

104 2. Manual open-loop control Electrical wiring and setup plan Task The system will need to be rewired for the following experiments. Assemble the electrical components. They can be prewired before they re mechanically attached to the profile. Proceed according to your layout sketch and the setup plan you prepared in the Planning section of the chapter on Plant construction. Base yourself on the circuit diagram with regard to wiring. Write down your assembly and wiring procedures. Fill out the following setup plan after you have mounted and wired the components. No. Item no. Work step Tool Times Electrical setup plan B-30 Festo Didactic GmbH & Co. KG

105 2. Manual open-loop control Commissioning, electrical testing and report Information The new circuit with the pushbuttons and the functions of the existing electrical components, such as the impeller pump, must now be started up and inspected. This is done by filling the system with water so that the pump is prevented from running dry. The water is simply pumped around in a circular movement, i.e. out of the bottom tank via the impeller pump and back into the lower tank from the upper tank. Task Make a list of all the characteristics and requirements for which the electrical components have to be inspected in the commissioning report. Tick the appropriate entry after completing each inspection. Characteristic, requirement for component Fulfilled Not fulfilled, comment Connect the 24 V and 0 V leads from the power supply unit to the terminals. Electrical control switch and start and stop pushbuttons wired Indicator light wired Pump wired Cables secured with cable binders Power supply unit connected to mains power (230 V AC) Switch the power supply unit on, the indicator light at the power supply unit lights up. Set control switch to On, press the start pushbutton, the indicator light switches on and the pump runs. Press the stop pushbutton, the indicator light switches off and the pump stops running. Set control switch to On, press the start pushbutton, the indicator light switches on and the pump runs. Set control switch to Off, the indicator light switches off and the pump stops running. Set control switch to Off, press the start pushbutton, the indicator light switches off and the pump stops running. Power supply unit Off, system is shut down Inspector Date Festo Didactic GmbH & Co. KG B-31

106 2. Manual open-loop control Experiment: filling while simultaneously withdrawing water The upper tank needs to be filled from below with a constant volumetric flow rate. Stopcock V101 is closed, stopcock V103 simulates resistance in the system by being opened. It s opened until the water flows into the upper tank at a volumetric flow rate of 60 litres per hour. At the same time, the stopcock for discharge to the user is open (approx. 20%). Measure the time it takes to fill the upper tank. Add the values to the table. Fill level [ml] Time [s] Fill level [ml] Time [s] Fill level [ml] Time [s] Filling with open discharge B-32 Festo Didactic GmbH & Co. KG

107 2. Manual open-loop control Evaluation and findings Task Create a line diagram for fill level relative to time. What does the curve tell you? What s meant by the term self-latching circuit? Festo Didactic GmbH & Co. KG B-33

108 2. Manual open-loop control Experiment: pump start-up performance and power The water level in the upper tank can be kept constant while water is withdrawn by changing the volumetric flow rate. Volumetric flow rate will be influenced in this experiment by changing electrical voltage at the power supply unit. You ll need a power supply unit with variable output voltage for this experiment. We ll fill tank B102 with water from below. Stopcock V101 is closed. Stopcock V103 is opened to such an extent that a volumetric flow rate of max. 400 litres per hour is achieved with 24 V DC. Stopcock V102 is only partially opened (approx. 20%). Task What are the volumetric flow rates when the pump is operated with various voltages ranging from 24 to 0 V DC? How does current consumption at the impeller pump change? Record the measured values and add them to the table. Voltage U [V] Current I [A] Electrical power P [W] = U I Volumetric flow rate Q [l/h] Pressure p e [bar] Hydraulic power P [W] = p e Q Filling using varying pump voltages B-34 Festo Didactic GmbH & Co. KG

109 2. Manual open-loop control Evaluation and findings Task Draw a circuit diagram with a voltmeter and an ammeter. Create a diagram with two curves, one for volumetric flow rate Q and the other for electrical current I relative to voltage U. What do the curves tell you about the pump s start-up characteristics? Festo Didactic GmbH & Co. KG B-35

110 2. Manual open-loop control What is the relationship between the three parameters current, voltage and volumetric flow rate? Calculate electrical and hydraulic power, as well as efficiency, for a volumetric flow rate of 200 litres per hour. What is the relationship between the impeller pump s current consumption and its output performance? How high are the electrical power costs when the pump is operated 8 hours a day for one month (30 days) with a volumetric flow rate Q of 200 litres per hour? The cost of electrical power is roughly 0.17 per kwh. B-36 Festo Didactic GmbH & Co. KG

111 3. Manual closed-loop control 3.1 From a control loop system to a control circuit Information Our fill-level system includes open and closed-loop control processes. How they differ will become clear when we consider their respective characteristics. Every process has an input quantity and an output quantity. For example, if we switch on the power supply unit which supplies electrical power to the impeller pump, electrical current (input quantity) flows and the pump begins to rotate and deliver water (output quantity). The input quantity affects the output quantity. Open-loop control However, if the output quantity is not fed back to the input as a signal so that, for example, the power supply unit is switched off when the tank is full, we speak of an open-loop control process. In the case of open-loop control, a process is started and stopped without periodically comparing and changing the variables to be controlled. Closed-loop control If we want to regulate the filling process with a closed-loop control process, we need to continuously record the fill level, for example via observation or a sensor and continuously compare the current fill level (actual value) with the desired fill level (target value). Whenever deviation from the target value is detected, an attempt is made to match the controlled variable (actual value) to the reference variable (target value) by means of appropriate control measures. This type of control has a closed control path, also known as control circuit. Comparison of a human being as a controller and automated control using fill level monitoring as an example: Human being as a controller Specified value Observation Make note of value Open or close valve manually Automated control Setpoints Actual value detection (ultrasonic sensor) Archive Transmit electrical manipulated variable to valve or pump Regulator optimisation Festo Didactic GmbH & Co. KG B-37

112 3. Manual closed-loop control Basic terminology for closed-loop control technology Controlled variable x The quantity to be controlled is designated controlled variable x. In our example this is the fill level or the volumetric flow rate. Manipulated variable y Automated closed-loop control is only possible if the system can be manipulated and the controlled variable influenced. The extent to which the controlled variable can be influenced is manipulated variable y. In the case of closed-loop control of a fill level, the manipulated variable is the degree to which the stopcock is opened, and in the case of closed-loop control of the volumetric flow rate, it s electrical current at the pump. Reference variable w Reference variable w is also known as the controlled variable setpoint. It specifies the desired value of the controlled variable. The reference variable may remain constant over time, but it may also change. The real value of the controlled variable is called the actual value. Disturbance variable z All controlled systems are subject to disturbance. These are often the only reason that closed-loop control is necessary at all. In our example, the stopcock for discharge to the consumer is opened and the fill level changes or the valve setting for filling the upper tank is changed which results in a change to the volumetric flow rate. These interfering influences are designated disturbance variable z. The controlled system is the part of the overall setup within which the controlled variable must be matched with the value of the reference variable. The controlled system can be represented as a system with the controlled variable as the output quantity and the manipulated variable as the input quantity. System deviation xd The difference between the reference variable and the controlled variable is called system deviation xd or e. This difference is calculated as follows: e = w - x Closed-loop controller It is the task of the closed-loop controller to keep the controlled variable as close as possible to the reference variable. The value of the controlled variable is continuously compared with the reference variable by the closed-loop controller. The value of the manipulated variable is calculated on the basis of this comparison, as well as control response, and is read out. Controlled variable x Actual value + System deviation xd Control response ( Algorithm) Manipulated variable y Reference variable w Setpoint Basic function of a regulator B-38 Festo Didactic GmbH & Co. KG

113 3. Manual closed-loop control Control circuit The control circuit contains all the components of the closed loop that are required for automated closedloop control. Controlled system Controlled variable x ( Actual value) Manipulated variable y Controller Reference variable w ( Setpoint) Block diagram of a control circuit Controlled system The controlled system is the part of the machine or system within which the controlled variable is to be matched to the specified value and the disturbance variables are offset by the manipulated variables. The manipulated variable is not the controlled system s only input quantity; interfering influences also occur as input variables. In order to select a closed-loop controller for a controlled system, the performance of the controlled system must first be known. The control technician is not interested in the technical sequences which take place within the controlled system, but only in system performance. 3.2 Project task: controlling the fill level in the tanks Task description In the case of water supply, households withdraw various quantities of water. Two experiments will be used to clarify how a specified fill level can be constantly maintained in the upper tank. Closed-loop control is possible in different ways: Open and close stopcock V101 or V103. Switch the pump on and off. Change voltage supplied to the pump. During the first experiment, manually keeping the fill level constant in the upper tank, we ll attempt to regulate the fill level by switching the pump on and off. We can supply the pump with voltages ranging from 0 to 24 V using the power supply unit. The pump is switched on and off with the pushbuttons. Observe the control process. During the second experiment, controlling the fill level using an analogue controlled pump, we ll operate the pump with variable voltage ranging from 0 to 24 V DC, and thus control the volumetric flow rate and influence the tank s fill level within a certain period of time. You ll need a power supply unit with adjustable output voltage to this end. Festo Didactic GmbH & Co. KG B-39

114 3. Manual closed-loop control Setting up the system, inspection Task Close stopcock V105. Check to make sure that all piping connections are correct. Check to make sure that all electrical wiring connections are correct. Fill the lower tank with 3 litres of water. Connect the system to the respective power supply unit (max. 24 V DC). Carry out the experiment. Remove the 4 mm safety cable from the power supply unit and pull the mains plug. After the experiment has been completed, the system is drained via stopcock V Experiment: manually keeping the fill level constant in the upper tank The upper tank should always have a constant level of water of 2000 ml. Varying quantities of water are withdrawn via stopcock V102 and supplied to a household (lower tank B101). Task Switch the pump on and off with the pushbutton so that the fill level remains constant. B-40 Festo Didactic GmbH & Co. KG

115 3. Manual closed-loop control Evaluation and findings Task Enter the following control technology terms to the block diagram of the system: actual value x, setpoint w, manipulated variable y, switching difference sd, disturbance variable z, closed-loop controller, controlled system. V101 V103 V102 FI 101 PI 103 B101 P101 V105 Reference variable w ( Setpoint, fill-level) M Controlled variable x ( Actual value, fill-level) Manipulated variable y ( Voltage) A fill level of 2100 ml is established as an upper limit and 1900 ml is the lower limit. This results in a switching difference sd of 200 ml. Why are these limit values specified? Festo Didactic GmbH & Co. KG B-41

116 3. Manual closed-loop control Establish the inequality for switching the pump on and off. Inequality is meant here as the greater or smaller relation amongst the actual value, the setpoint and the switching difference. Represent the filling process graphically as a line diagram. Plot the fill level on the ordinate (Y-axis) and time on the abscissa (X-axis). What do we call this type of control? In which types of devices do closed-loop controllers operate on the basis of this principle? Provide several examples. Which features characterise this type of control? B-42 Festo Didactic GmbH & Co. KG

117 3. Manual closed-loop control Experiment: controlling the fill level using an analogue controlled pump Once again, the tank should be filled to a constant level of water of 2000 ml. Varying quantities of water are withdrawn via stopcock V102 and supplied to a household (lower tank B101). The volumetric flow rate is influenced by changing speed, thus enabling the system to react to irregular withdrawals of fresh water from upper tank B102. Vary the pump speed by increasing and decreasing voltage supplied by the power supply unit and observe the volumetric flow rate Evaluation and findings Task Allocate the terms and characteristics from the description of the experiment to the control technology terms. Controlled variable: Manipulated variable: Reference variable: Disturbance variable: First of all, fill the upper tank from above with stopcock V102 fully closed. Then open stopcock V102 according to the specifications in the table and describe what you observe while controlling the process. React to changes in the fill level by varying the power output voltage. Stopcock V102 Control process, observations Closed 10% open 50% open 100% open Test report Why is this also known as continuous control? Festo Didactic GmbH & Co. KG B-43

118 3. Manual closed-loop control Create a graphic representation of the closed-loop control process. Draw a graph which shows the fill level over a period of time as a strictly qualitative characteristic Experiment: pressure and flow control Separately conduct pressure control and flow rate control, also known as volumetric flow rate control. Control pressure and volumetric flow rate by varying the output voltage of the power supply unit between 0 and 24 V DC. Set up the circuit according to the PI flow diagrams. Pressure control V103 PI 103 B101 P101 V105 M B-44 Festo Didactic GmbH & Co. KG

119 3. Manual closed-loop control Flow rate control V103 FI 101 B101 P101 V105 M Evaluation and findings Task Determine the manipulated variable required for maintaining constant pressure, as well as for maintaining constant volumetric flow rate, with varying resistance (stopcock V103). Target pressure (w) = 200 mbar Target volumetric flow rate (w) = 100 l/hr. Add the voltage values for the various stopcock settings to the table. Conduct the experiment once with constant pressure and once with constant volumetric flow rate. Mark the opening values of the stop cock on the rotary cap so that the experiment can be duplicated exactly. Setting for stopcock V103 Pressure control, voltage U (y) where p e = 200 mbar (w) Flow rate control, voltage U (y) where Q = 100 l/hr. (w) Open 20% closed 40% closed 60% closed 40% closed 20% closed Values table Festo Didactic GmbH & Co. KG B-45

120 3. Manual closed-loop control What is the relationship between the stopcock setting and pressure or volumetric flow rate? Constant pressure: Constant volumetric flow rate: B-46 Festo Didactic GmbH & Co. KG

121 4. Evaluation of learning objectives for manual measurement, open-loop and closed-loop control 1. How do pressure and volumetric flow rate of a liquid respond when resistance is increased in the inlet line which feeds the tank? litres of water have to be recirculated using a volumetric flow rate of 200 litres per hour. How long does the pump have to work? 3. Which physical quantities determine hydrostatic pressure? 4. Why does it take longer to fill the upper tank in our system from above than from below? Festo Didactic GmbH & Co. KG B-47

122 3. Manual closed-loop control 5. The filling nozzle at the top can be fitted at a level of, for example, 1.1 metres. How much pump pressure would be required to reach this filling height? 6. Describe how a self-latching circuit functions. Which components are required for such a circuit? 7. The upper tank is continuously filled with water and a certain amount of water is discharged from the tank. In a diagram, the process would be designated asymptotic, i.e. it approaches a specific value. Sketch a graph which shows the fill level over a period of time as a qualitative characteristic. B-48 Festo Didactic GmbH & Co. KG

123 3. Manual closed-loop control 8. Describe in your own words the procedures used for connecting an ammeter and a voltmeter in order to record pump values. 9. You re working with variable voltage within a range of 0 to 24 V. How do volumetric flow rate and amperage I change when voltage is reduced from 24 to 0 V. 10. The maximum pump efficiency is h = What is the meaning of this value with regard to our experimental system and which effects does efficiency have in actual practice? 11. Sketch a pneumatically actuated 5/2-way valve with spring return. Festo Didactic GmbH & Co. KG B-49

124 3. Manual closed-loop control 12. Which fundamental advantages are offered by a 2-way ball valve with electro-pneumatically actuated actuator as opposed to manual operation? 13. Describe the terms open-loop control and closed-loop control using a radiant heater as an example. 14. How are manipulated variable y and controlled variable x related? 15. How does a two-step controller work? 16. Why is an excessively small switching difference disadvantageous? B-50 Festo Didactic GmbH & Co. KG

125 3. Manual closed-loop control 17. What s the fastest way to get the system adjusted to the setpoint? 18. What is the control process called with which the manipulated variable can be continuously varied? 19. Pressure needs to be kept constant within the fill-level system, even when the volumetric flow rate is continuously increased. Which parameter must be changed within the system? 20. How can the volumetric flow rate within the fill-level system be kept constant, even though the pump needs to be operated in an energy-saving fashion? Festo Didactic GmbH & Co. KG B-51

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127 Part C Practice-based learning: automated measurement, open-loop and closed-loop control 1. Basic principles C Computer-aided control technology C System conversion for automated measurement and control C-5 2. Automated measurement C Project task: bath recirculation C Task description C Setting up the system, inspection C Experiment: operating the pump with variable voltage values C Project task: pressure measurement during recirculation C Task description C Setting up the system, inspection C Experiment: pressure measurement using a pressure sensor C Project task: flow measurement C Task description C Setting up the system, inspection C Experiment: flow measurement using a flow sensor C Project task: determine the fill level of the upper tank C Task description C Setting up the system, inspection C Experiment: measuring the fill level using an ultrasonic sensor C Automated open-loop control C Project task: filling process C Task description C Setting up the system, inspection C Experiment: metered filling via the pneumatic actuator C Project task: filtering process in a galvanising plant C Task description C Setting up the system, inspection C Experiment: determining pressure and volumetric flow rate C Experiment: creating a characteristic pump curve C Project task: water supply C Task description C Setting up the system, inspection C Experiment: filling the tank from below using the pump C Experiment: filling the tank from above using the pump C Experiment: filling the tank from above while simultaneously withdrawing water C Project task: dosing an amount of liquid C Task description C Experiment: dosing an amount of liquid C-38 Festo Didactic GmbH & Co. KG C-1

128 Part C Practice-based learning: automated measurement, open-loop and closed-loop control 4. Automated closed-loop control C Project task: controlling the fill level using a two-step controller C Task description C Setting up the system, inspection C Commissioning C Experiment: controlling the fill level using a two-step controller C Project task: controlling the fill level using a continuous controller C Task description C Experiment: controlling the fill level with a continuous controller C Experiment: controlling the fill level using a proportional controller C Experiment: controlling the fill level using an integral controller C Experiment: controlling the fill level using a proportional-integral controller (parallel P and I components) C Project task: refrigerating plant C Task description C Setting up the system, inspection C Commissioning report C Experiment: flow control using a proportional-integral controller C Evaluation of learning objectives for automated measurement, open-loop and closed-loop control C-59 C-2 Festo Didactic GmbH & Co. KG

129 1. Basic principles 1.1 Computer-aided control technology Information This is an introduction to automated control technology and is based on the knowledge of manual control that has already been acquired. You ll learn the basics of computer aided control with the help of practical examples. Every control circuit consists of a controlled system and a controller. 1 Setpoint specification 2 System deviation = setpoint - actual value System deviation is calculated by means of a control function and is transmitted to the controlled system as a manipulated variable (3). The control function is generally processed with the help of software. 3 Manipulated variable 4 The manipulated variable must be boosted so that the actuator s final control element receives a signal with which it can work. 5 The controlled system (e.g. fill level) is changed by means of the manipulated variable. 6 The controlled system s actual value is measured and fed back to point 2. In most cases, the actual value must be electronically converted. Software solutions for a controller in a PC or a PLC work in a cyclical fashion, i.e. points 2 through 6 are run continuously. Festo Didactic GmbH & Co. KG C-3

130 1. Basic principles Examples of controlled systems: Maintain a constant fill level in a tank Change and maintain temperature in a room Keep motor speed at a specified value Travel accurately to an axis position Maintain constant pressure in a piping system Types of controllers: Discontinuous controller These controllers are characterised by the fact that their manipulated variables are only capable of changing between the on and off states, i.e. two-step controller. Continuous controller With continuous controllers, the manipulated variable is infinitely adjustable, e.g. PID controller. In conventional control technology, a difference is made between the following controllers according to how the manipulated variable is determined (simplified excerpt). Controller Graphic symbol Determination of the manipulated variable via the control function 2-step controller The manipulated variable is compared with an upper and a lower limit value. P controller System deviation is influenced by means of a factor. I controller The sum of all system deviations is influenced by means of a factor. PI controller The characteristics of the P-controller and the I-controller are combined. PID controller The manipulated variable is determined by the D parameter based on the time factor by which system deviation is changed. C-4 Festo Didactic GmbH & Co. KG

131 1. Basic principles Technical learning objectives Participants will: Learn to convert electrical actuation to actuation with a PC Become familiar with how to set up and adjust sensor signals Become familiar with practical PC measurement technology Learn to differentiate between various types of controllers and control circuit performance Learn to use continuous and discontinuous control for automated measurement, open-loop and closedloop control Become familiar with using a PC as a control and regulating device in combination with FluidLab PA software 1.2 System conversion for automated measurement and control Information The system is, as in the section on manual measurement, open-loop and closed-loop control, equipped with a control panel used for manual measurement, open-loop and closed-loop control. The system must now be modified so that signals can be transmitted via the EasyPort PC interface. The depicted control panel is not used for automated measurement and control. Festo Didactic GmbH & Co. KG C-5

132 1. Basic principles The basic setup for automated measurement, open-loop and closed-loop control will be demonstrated using pump control as an example: Item Digital pump control, on/off PC transmits Bit3 to EasyPort. EasyPort generates a voltage signal (relay) of 0 V or 24 V. Motor runs at nominal power with 24 V. Analogue control PC transmits a decimal value EasyPort generates a control The motor controller boosts the (e.g. double word) which corresponds to a voltage within a range of 0 to 10 V. signal of 0 to 10 V. signal to within a range of 0 to 24 V. The motor runs at an infinitely adjustable speed. C-6 Festo Didactic GmbH & Co. KG

133 1. Basic principles Task The system will be equipped with a preassembled I/O board. Carry out conversion as described in the following steps: 1. Switch off supply power. 2. Unplug the laboratory cable via with safety valve socket. 3. Unplug the pump motor. 4. Mechanical removal of the control panel from the rectangular profile System with control panel System without control panel Festo Didactic GmbH & Co. KG C-7

134 1. Basic principles 5. Screw the preassembled I/O boards to the rectangular profile. Important modules are required for operation via a PLC or via a PC and EasyPort, in order to process measured values and control the actuator. Assembly Figure Description F-U converter for flow sensor Depending on the flow rate, the flow sensor generates a pulse frequency within a range of 40 to 1200 Hz. This pulse frequency is converted to a voltage value within a range of 1 to 10 V by the F-U converter. Motor controller The analogue manipulated variable of 0 to 10 V from the EasyPort or a PLC is boosted to 0 to 24 V and an appropriate amperage by the motor controller. Amperage must be limited in order to ensure safe operation. Modules on the I/O board Further information is included in the data sheets on the CD-ROM. C-8 Festo Didactic GmbH & Co. KG

135 1. Basic principles 6. Connect the EasyPort to the I/O board with a SysLink cable. 7. Connect the EasyPort to the PC (USB or serial cable). 8. Connect a 24 V power supply unit. 9. Connect the outputs for analogue and binary signals between the I/O board and the EasyPort. Festo Didactic GmbH & Co. KG C-9

136 1. Basic principles 10. Install the software. Install the EasyPort driver from the EasyPort CD-ROM. Install FluidLab PA. 11. Test the system. Supply EasyPort with power. Start FluidLab PA software. Note After starting the software, a message indicates whether or not a connection has been successfully established. If this is not the case, check all connections within the system. Otherwise, exit the software and disconnect the USB plug. Reinsert the USB plug after 5 seconds. Start the software again. 12. Select the Setup menu. The outputs can be activated with the sliders in the user interface. C-10 Festo Didactic GmbH & Co. KG

137 1. Basic principles 13. Assignment of inputs and outputs on the I/O board: Name Device Abbreviation Note Digital output 0 2-way ball valve with pneumatic actuation A0 Spring return Digital output 2 Changeover relay A2 Relay = 0: pump is binary controlled Relay = 1: pump is analogue controlled (0 to 10 V) Digital output 3 Pump A3 Analogue output 0 Pump AOUT 1 Analogue input 0 Fill level (ultrasonic) AIN 0 Analogue input 1 Flow sensor AIN 1 Analogue input 2 Pressure sensor AIN 2 1: I/O terminal 2: Analogue terminal 3: Relay 4: Motor controller 5: Measuring transducer 6: Starting current limiter 7: Motor clamp 8: H-rail Complete layout plan Festo Didactic GmbH & Co. KG C-11

138 1. Basic principles C-12 Festo Didactic GmbH & Co. KG

139 2. Automated measurement 2.1 Project task: bath recirculation Task description Depending on the setup, water can be transferred to lower tank B101 or pumped into upper tank B102 with the pump. The pump can be operated by switching 24 V supply power on or off (output 3). Alternatively, it can be variably supplied with control voltage within a range of 0 to 10 V (analogue output 0). The control signal is boosted by means of a motor controller. The type of control used (on/off or analogue) is selected with a changeover relay (output2). Festo Didactic GmbH & Co. KG C-13

140 2. Automated measurement C-14 Festo Didactic GmbH & Co. KG

141 2. Automated measurement Task The pump will be connected and tested during the following experiment. Simply pumping water into lower tank B101 is sufficient for this function test. Set up the fill-level system with one tank as specified in section 1.1.1, part A. Base yourself on the PI flow diagram. Before commissioning, make sure all the project kit s modules and piping function correctly and do not leak. Replace any damaged parts. V101 B102 V103 V102 FI 101 PI 103 B101 P101 V105 M Festo Didactic GmbH & Co. KG C-15

142 2. Automated measurement Setting up the system, inspection Plug the pump into the I/O board. The allocations are included in the circuit diagram on the CD-ROM. Set up the water circuit (see flow diagram). Note The pipe connection to tank B102 must be interrupted or equipped with a closed stopcock. Close V101 and V105, open V102 and V103. Fill B101 approximately half full with water. Connect the 24 V power supply unit to mains power. Switch the power supply unit on. Start the software (FluidLab PA). Open the Setup menu in the software and operate the system using the buttons (see below). C-16 Festo Didactic GmbH & Co. KG

143 2. Automated measurement Experiment: operating the pump with variable voltage values Select each of the values listed below and document your observations. No. Digital outputs Analogue outputs (set at sliders) Pump (observe) 1 A3 = on A2 = off 0 V 2 A3 = on A2 = on 0 V 3 A3 = off A2 = on 4 V 4 A3 = off A2 = on 8 V 5 A3 = off A2 = on 10 V 2.2 Project task: pressure measurement during recirculation Task description Pressure plays a significant role in fluid systems. In practice pressure changes due to reactions which occur in mixtures, during filtration or recirculation, and must be continuously recorded and documented. In order to be able to read out the value with the help of a PC, the pressure gauge with indicator is replaced by a pressure sensor. As a rule, pressure sensors require 24 V DC supply power and generate an analogue voltage signal within a range of 0 to 10 V, which is proportional to pressure. The purpose of the pressure sensor is to measure liquid pressure directly downstream of the pump. According to the data sheet, the sensor reads out a voltage of 0 to 10 V within a pressure range of 0 to 400 mbar. Festo Didactic GmbH & Co. KG C-17

144 2. Automated measurement Setting up the system, inspection Switch the system off and pull the mains plug. Drain the water via stopcock V105. Install the pressure sensor downstream of the pump. Electrically connect the pressure sensor in accordance with the circuit diagram (CD-ROM). Valve settings: V101 and V105 closed, V102 and V103 open, remove piping to tank 102, insert a blanking plug into the end of the pipe or install a stopcock in the bottom inlet and close it. Fill with water. Set up the software. Set the pressure value at the PC after opening the Setup menu: Determine factor and offset: calculate the physical display value: Physical value = sensor voltage factor + offset If values are to be displayed in bar, the factor is calculated as follows: The following data are specified for the sensor: a pressure range of 0 to 0.4 bar and a voltage range of 0 to 10 V. 0.4bar Factor = = V - 0V C-18 Festo Didactic GmbH & Co. KG

145 2. Automated measurement Default setting for the pressure duct: factor = 0.04 and offset = 0.0 (see figure) 1 Voltage read out by the sensor 2 Factor 3 Offset 4 The signal can be filtered (attenuated). The higher the number, the greater the attenuation. In order to ensure correct representation of the scales in the diagrams, it s important to always enter the maximum physical value and the appropriate unit of measure (see the two right-hand columns in the screenshot). Task At a pressure of 0 to 10 bar, the pressure sensor reads out a voltage within a range of 2 to 10 V. Calculate factor and offset. Final value Factor = = Final voltage -Initial voltage Offset = -Factor Initial voltage = Festo Didactic GmbH & Co. KG C-19

146 2. Automated measurement Experiment: pressure measurement using a pressure sensor Operate the pump with the three following voltage values and make a note of what you observe at the software pressure display. No. Digital outputs Analogue outputs (set at sliders) Pressure display (observe) 1 A3 = on A2 = off 0 V 2 A3 = off A2 = on 5 V 3 A3 = off A2 = on 10 V 2.3 Project task: flow measurement Task description The purpose of the flow sensor is to measure the pump s volumetric flow rate. Liquid flows through the measuring transducer and causes a vane to rotate. The vane is equipped with an inductive sensor which generates pulses. The pulses are converted into a voltage which is proportional to the volumetric flow rate by an F/U converter. At a volumetric flow rate of 0 to 7.5 litres per minute, the flow sensor generates a voltage signal within a range of 0 to 10 V Setting up the system, inspection Switch the system off and pull the mains plug. Drain the water via stopcock V105. Install the flow sensor downstream of the pump. Connect the flow sensor electrically according to the circuit diagram (see CD-ROM). Fill with water. Start the software and open the Setup menu. Set factor and offset: the physical display value is calculated as follows: Physical value = sensor voltage factor + offset Flow rate display in litres per minute, factor = 0.75, offset = 0 C-20 Festo Didactic GmbH & Co. KG

147 2. Automated measurement Experiment: flow measurement using a flow sensor Change the pump speed again by setting supply voltage to three different settings and make a note of what you observe at the flow rate display in the software. No. Digital outputs Analogue outputs (set at sliders) Flow rate display (observe) 1 A3 = on A2 = off 0 V 2 A3 = off A2 = on 5 V 3 A3 = off A2 = on 10 V 2.4 Project task: determine the fill level of the upper tank Task description The ultrasonic sensor measures distance and can be used to detect fill levels. The ultrasonic waves are refracted at the surface of the water and returned to the sensor. At a distance of 50 to 270 mm from the water, the sensor reads out a voltage within a range of 0 to 10 V. The ultrasonic sensor is attached to the inside of the lid of tank B102, from where it measures the fill level. Festo Didactic GmbH & Co. KG C-21

148 2. Automated measurement Setting up the system, inspection LIC 102 V101 B102 V103 V102 FI 101 PI 103 B101 P101 V105 M Mount upper tank B102 and lay piping for the system in accordance with the PI flow diagram. Mount the ultrasonic sensor onto the upper tank. Electrically connect the ultrasonic sensor in accordance with the circuit diagram (CD-ROM). Set the valves so that liquid can be pumped into the upper tank: V101 open, V103 open, V102 approx. 5% open. Start the software and open the Setup menu. Set factor and offset The physical display value is calculated as follows: Physical value = sensor voltage factor + offset C-22 Festo Didactic GmbH & Co. KG

149 2. Automated measurement Depending on which physical quantity is to be displayed, factor and offset are entered as follows: The following applies in the case of a sensor signal within a range of 0 to 3 litres and a voltage of 0 to 10 V: Fill level in litres Factor = 0.27 Offset = 0.0 Fill level in mm Factor = 22 Offset = 0.0 Note The sensor signal lies within a range of 0 and 2.7 l, which corresponds to 0 to 10 V. Due to the fact that the bottom of the tank is conical, measurement begins as of the cylindrical portion of the tank and roughly the first 0.5 l are disregarded in this example Experiment: measuring the fill level using an ultrasonic sensor Fill upper tank B102 according to the entries in the table and document your observations. Complete the table. No. Digital outputs Tank B102, fill level sensor (litres) Observation 1 A3 = off A2 = off Empty = 2 A3 = on A2 = off Approx. 50% full = 100% full = 3 A3 = off A2 = off Festo Didactic GmbH & Co. KG C-23

150 2. Automated measurement C-24 Festo Didactic GmbH & Co. KG

151 3. Automated open-loop control 3.1 Project task: filling process Task description The automated filling process will be demonstrated with the help of the 2-way ball valve with pneumatic actuation. The ball valve is installed between the upper and the lower tank. Information on operating the 2- way ball valve can be found in section 2.2, part B, and in the data sheet (CD-ROM). Set the system up according to the PI flow diagram. LA+ 111 V101 B102 LS 114 V107 V103 V112 V102 FIS+ 101 PIS+ 103 B101 LS 113 P101 V105 M Festo Didactic GmbH & Co. KG C-25

152 3. Automated open-loop control Setting up the system, inspection Switch the system off and pull the mains plug. Drain the water via stopcock V105. Connect 2-way ball valve V102 according to the circuit diagram (CD-ROM). Complete tubing connections for pneumatic actuation (semi-rotary actuator) of the 2-way ball valve (at least 5 bar compressed air). Fill the lower tank with water Experiment: metered filling via the pneumatic actuator Carry out the experiment as indicated in the table and document your observations. No. Digital outputs Step Observation 1 A3 = on A0 = off Pump water into B A3 = off A0 = off 3 A3 = off A0 = on Water flows through V Project task: filtering process in a galvanising plant Task description The acid bath at a galvanising plant has to be continuously recirculated and filtered. As contamination in the acid bath increases, resistance upstream of the filter increases and circulating pressure rises. When a specified pressure is exceeded, the filter must be cleaned or replaced. The cross section in the valve is reduced with hand valve V103. This corresponds to a clogged filter in actual practice. We are thus able to simulate filter contamination with hand valve V103. The experiment is intended to demonstrate the relationship between resistance (filter contamination) and pressure in the piping system. The pump is controlled via the PC and pressure is measured with a pressure sensor. The characteristic pressure curve is recorded in a time diagram. C-26 Festo Didactic GmbH & Co. KG

153 3. Automated open-loop control Setting up the system, inspection First, modify the system according to the PI flow diagram or the figure. A setup including one tank, the pressure sensor and the flow sensor is required. Double check the piping layout and the electrical connections before commissioning. Test the pump, the pressure sensor and the flow sensor for correct functioning. Fill tank B101 with 2 to 2½ litres of water. V103 V102 FI 101 PI 103 B101 P101 V105 M B101 FI101 PI103 P101 Festo Didactic GmbH & Co. KG C-27

154 3. Automated open-loop control Task Connect the EasyPort, start the software and select the settings menu. Enter and double-check factor and offset settings for the sensors. Enter the corresponding values in the table. Setting checked Comment Sensor settings Pressure bar Factor = 0.04 Offset = 0 or pressure kpa Factor = 4 Offset = 0 or pressure PSI Factor = Offset = 0 Volumetric flow rate l/min. Factor = 0.75 Offset = 0 Valve settings V101 V102 V103 Create a commissioning report for the system. Characteristic, requirement for component Fulfilled Failed, comments Piping assembled and leak-proof Pressure sensor installed Flow sensor installed Electrical wiring and connecting cables connected Lower tank filled with 2 to 2½ litres of water Software installed, sensor values adjusted Test pump on/off with PC Test the signal from the pressure sensor Test the signal from the flow sensor C-28 Festo Didactic GmbH & Co. KG

155 3. Automated open-loop control Experiment: determining pressure and volumetric flow rate Measure pressure and volumetric flow rate with changing line resistance. Carry out the steps specified in the table and document your observations. Menu: Control and measure No. Task Data from the diagram Note/observation 1 Pump on, A3 = on Hand valve open completely Pressure = Volumetric flow rate = 2 Slowly close hand valve V103 3 Hand valve V103 closed Pressure = Volumetric flow rate = 0 l/min. 4 Slowly open hand valve V103 1 Volumetric flow rate 2 Pressure Diagram of the sensor signal while closing hand valve V103 Festo Didactic GmbH & Co. KG C-29

156 3. Automated open-loop control Task What is the relationship between the pipe s cross section, volumetric flow rate and pressure? Why is volumetric flow rate reduced with a smaller cross section? How would a significantly longer piping network influence the system? Experiment: creating a characteristic pump curve In this section volumetric flow rate with changing line resistance and analogue pump control will be examined. The pump can be operated with a control voltage within a range of 0 to 10 V with the help of a motor amplifier. Control must also be switched on and off with the help of a relay. 1: Set changeover relay to 1 2: Preset voltage to 0 to 10 V Sample settings in the settings menu C-30 Festo Didactic GmbH & Co. KG

157 3. Automated open-loop control Menu: Select characteristic U-Q curve Carry out the experiments described below, document your observations in the table and create a characteristic curve. No. Task Data Note/observation 1 Increase voltage at the pump from 0 to 10 V, and then decrease it back to 0 V again. Voltage [V] Volumetric flow rate [l/min.] 2 2 Hand valve open all the way 4 3 Take values from the diagram Voltage is increased from 0 to 10 V. 2 Voltage is decreased from 10 to 0 V. Sample characteristic U-Q curve Festo Didactic GmbH & Co. KG C-31

158 3. Automated open-loop control Task How does the pump respond to rising control voltage? What is the effect of varying the speed at which control voltage is changed? What does hysteresis mean? C-32 Festo Didactic GmbH & Co. KG

159 3. Automated open-loop control 3.3 Project task: water supply Task description Water is pumped into a water tower from springs, rivers and lakes in order to supply households with water. Water is directed to domestic households from the tower. The upper tank will be filled with water during two experiments. There are several different ways to fill the tank: The fill pipe enters the upper tank from below. The fill pipe enters the upper tank from above. The fill pipe enters the upper tank from above while water is simultaneously being withdrawn from below. LA+ 111 LA+ 111 V101 B102 LS 114 V101 B102 LS 114 V107 V103 V112 V102 V107 V103 V112 FIS+ 101 PIS+ 103 B101 LS 113 P101 V105 M Setting up the system, inspection Set the system up with two tanks as shown in the flow diagram. Connect and test the pump and the ultrasonic sensor. Base yourself on section 2.4 during setup. Double-check the piping layout and the electrical connections. Festo Didactic GmbH & Co. KG C-33

160 3. Automated open-loop control Experiment: filling the tank from below using the pump Carry out the experiment as indicated in the table and document your observations. No. Task Done Observations 1 V101 closed V107 closed V103 open V102 closed (A0 = off) V112 closed 2 Fill B101 with 3 litres of water. 3 Open the Control and measure menu in the software. Pump A3 = on 4 After roughly 40% filling Pump A3 = off 5 V102 open (A0 = on) V112 open Characteristic curve for filling from below C-34 Festo Didactic GmbH & Co. KG

161 3. Automated open-loop control Experiment: filling the tank from above using the pump Carry out the experiment as indicated in the table and document your observations. No. Task Done Observations 1 V101 open V107 open V103 closed V102 closed (A0 = off) V112 closed (while filling) 2 Fill B101 with 3 litres of water 3 Open the Control and measure menu in the software, pump A3 = on 4 After roughly 40% filling Pump A3 = off 5 V102 open (A0 = on) V112 open Characteristic curve for filling from above Festo Didactic GmbH & Co. KG C-35

162 3. Automated open-loop control Experiment: filling the tank from above while simultaneously withdrawing water Carry out the experiment as indicated in the table and document your observations. No. Task Done Observations 1 V101 open V107 open V103 closed V102 open (A0 = on) V112 20% open! 2 Fill B101 with 3 litres of water. 3 Open the Control and measure menu in the software, pump A3 = on 4 After roughly 40% filling Pump A3 = off 5 V102 closed (A0 = off) Characteristic curve for filling from above while simultaneously withdrawing water C-36 Festo Didactic GmbH & Co. KG

163 3. Automated open-loop control Task Why is the surface of the water less turbulent when the tank is filled from below? How could reverse flow through impeller pumps be prevented? Why does the fill level rise more slowly when water is withdrawn simultaneously? 3.4 Project task: dosing an amount of liquid Task description A certain amount of water must be fed to a mixture of solids in a cement mixer. The quantity is timecontrolled. A constant volumetric flow rate must be maintained as a prerequisite, for example 2 litres per minute. The pump is controlled via a PC. The analogue output is used as the manipulated variable. Volumetric flow is measured with a volumetric flow rate sensor. The characteristic curve is recorded in a time diagram. One litre of water should be added to the mixture. Task Set the system up with one tank in accordance with the PI flow diagram. Connect and test the pump, the pressure sensor and the flow sensor. Double-check the piping layout and the electrical connections before commissioning. Festo Didactic GmbH & Co. KG C-37

164 3. Automated open-loop control Experiment: dosing an amount of liquid Connect the EasyPort to the PC and start the software. Enter the appropriate settings in the settings menu. V103 V102 FI 101 B101 P101 V105 1: Activate the changeover relay 2: Adjust control voltage C-38 Festo Didactic GmbH & Co. KG

165 3. Automated open-loop control Carry out the work steps described below and record your observations in the table. No. Work step Setting checked Comment 1 Volumetric flow Volumetric flow l/min Factor = rate sensor rate Offset = 0 2 Valve settings V101 V102 V103 3 Set to analogue A2 = on mode 4 Adjust Volumetric flow rate Control voltage Increase the manipulated Q = 2 l/min. U = = V manipulated variable variable until Q = 2 l/min. 5 Pump off A3 = off A2 = off 6 Switch pump on for 30 seconds 7 Evaluate the diagram. A3 = off A2 = on Control voltage U = = V Values from the diagram: Volumetric flow rate Q = l/min. Time t = sec. Calculated water quantity over time: Q t = Measure with stopwatch or read from the diagram Festo Didactic GmbH & Co. KG C-39

166 3. Automated open-loop control Sample solution for dosing procedure Task Why isn t the amount of water exactly correct? How long does the pump have to run (Q = 2 l/min.) in order to deliver 0.5 litres of water? C-40 Festo Didactic GmbH & Co. KG

167 4. Automated closed-loop control Information A control circuit always consists of a control device (closed-loop controller) and a device to be regulated (controlled system), for example a fill-level system. Schematic diagram of a regulating system Description The task of the closed-loop controller (control function) is to control the controlled system so that it remains at setpoint w. Actual value x is continuously measured and compared with setpoint w to this end. The regulator calculates manipulated variable y. The manipulated variable influences the process via a final control element. Knowledge of the characteristics of the controlled system is essential for selecting and adjusting the regulator. Characteristics of controlled systems are usually determined during a test run. Discontinuous and continuous controllers: The actual value is measured using analogue sensors for both types of controllers. In the case of discontinuous controllers, the manipulated variable has only two states (on/off). In the case of continuous controllers, the manipulated variable is displayed in an infinitely adjustable fashion (e.g. 0 to 10 V). The characteristics of the controlled system, tank B102, will be observed as described below. The tank will be filled from above via a piping system. Festo Didactic GmbH & Co. KG C-41

168 4. Automated closed-loop control Case 1: tank has no drain In this case, the tank represents an integral system during filling. The container is filled in a linear fashion. Graphic symbol Case 1: tank has a drain If water is withdrawn at the same time via a drain valve, the tank represents a PT1 system (system with equalisation). Graphic symbol Note Due to the minimal fill level (hydrostatic pressure), the exponential function is not very distinctive. C-42 Festo Didactic GmbH & Co. KG

169 4. Automated closed-loop control Systems which demonstrate these characteristics are called 1 st order systems. The characteristic variable is time constant T [seconds]. It s the time required to achieve approximately 63% of the final level. As system performance varies, the control circuit also responds variously. In the experiments described below, we will only examine the performance of a control circuit with a PT1 system. Task How does the integral system perform when the pump is switched off during filling from above? How does the PT1 system perform when the pump is switched off during filling from above? 4.1 Project task: controlling the fill level using a two-step controller Task description In the case of water supply, households withdraw various quantities of water. Two experiments will be used to find out how a specified fill level can be constantly maintained in the upper tank. There are different control methods: Switch the pump on and off: 2-step control. Change control voltage to the pump: analogue control. Disturbance variables include, for example, opening and closing hand valves V101 and V103, as well as 2- way ball valve V102 with pneumatic actuation. Festo Didactic GmbH & Co. KG C-43

170 4. Automated closed-loop control Setting up the system, inspection Set the system up with two tanks according to the PI flow diagram. Connect the pump, the flow sensor and the 2-way ball valve with pneumatic actuation and test them. Double-check the piping layout and the electrical connections. LA+ 111 V101 B102 LS 114 V107 V103 V112 V102 FIS+ 101 PIS+ 103 B101 LS 113 P101 V105 M C-44 Festo Didactic GmbH & Co. KG

171 4. Automated closed-loop control Commissioning Please check all the points listed in the following report and confirm completion of all tasks before commissioning. Task Completed Note/observation Piping assembled and leakproof Flow sensor installed Electrical wiring and connecting cables connected Tank filled with 2.5 litres of water 2-way ball valve with pneumatic actuation installed Software installed, sensor values adjusted Factor = Offset = Test pump on/off using PC Test the signal from the fill-level sensor Experiment: controlling the fill level using a two-step controller Fill-level control (discontinuous control) is to be carried out with the pump in binary mode (on/off). The same experiment, i.e. maintaining a constant fill level by switching the pump on and off manually, was conducted as part of the learning section on manual control. In the current example, the pump will be switched on and off by a software controller. Information The values in the control circuit are specified in a standardised fashion, i.e. 0 and 1 or 0 and 100%. These values are frequently converted to physical values for the user, for example so that the fill level can be specified in litres or the water level in mm. Designations within the control circuit: Term Setpoint Actual value Switching difference Manipulated variable (pump on/off) Symbol w x sd y As a rule, the value of switching difference sd is at the middle of the setpoint. Festo Didactic GmbH & Co. KG C-45

172 4. Automated closed-loop control Fundamental performance of a control circuit as an example of a fill-level system with open outlet (PT1) and a 2-step controller w (0...1) Setpoint Switching difference sd (0...1) Controller Process Manipulated variable Signal amplifier Controlled system Sensor Actual value y (0...1) x (0...1) Where actual value (setpoint - switching difference/2) setpoint with storage = 1 Where actual value (setpoint + switching difference/2) setpoint with storage = 0 2-step controller logic Various settings must be entered in order to test performance. In order to be able to draw any conclusions about the control circuit, it s always advisable to change only one parameter at a time and then conduct the experiment. The respective settings included in the following table are suggestions. C-46 Festo Didactic GmbH & Co. KG

173 4. Automated closed-loop control Start the software and open the Two-step controller menu. Set digital output A3 according to the setpoints and the switching difference from the table. Select each of the values listed below and document your observations. Settings standardised values (0 to 1) Observations Setpoint w Switching difference sd Disturbance variable z: hand valve V % open % open % open % open % open Sample solution for controlling the fill-level with a 2-step controller Festo Didactic GmbH & Co. KG C-47

174 4. Automated closed-loop control Task How does switching difference affect control? How does the interference variable affect the outcome of the experiment? Information about the practical use of 2-step controllers 2-step controllers are used wherever system deviation is reliable. Examples: irons, refrigerators, heaters, solar systems, fill levels for cooling lubricant, fill levels in galvanising systems and swimming pools etc. These systems have a large time-constant, so that only minimal switching frequencies occur despite a small switching difference. C-48 Festo Didactic GmbH & Co. KG

175 4. Automated closed-loop control 4.2 Project task: controlling the fill level using a continuous controller Task description If no system deviation is permissible within the control circuit, continuous controllers must be used. Continuous controllers are characterised by, for example, an analogue manipulated variable in the event that the sensor has generated an analogue signal. Depending on the control function, the manipulated variable is calculated by means of various mathematical formulas. Schematic diagram of a control circuit with a continuous controller A fill-level system with open outlet (PT1 performance), for example, is used within the control circuit. w (0...1) Setpoint Controller Control function Y =... Manipulated Signal amplifier variable y (0...1) Process Controlled system Sensor Actual value x (0...1) The following controller functions (selection) could be used: Controller Graphic symbol Function P controller y = kp e kp = adjustable amplification factor e = system deviation w - x I controller y = esum TA/Ti Adjustable integral time (Ti) esum = sum of system deviation e System deviation e is added up during each cycle. PI controller Y = kp ( e + esum TA/Tn) Adjust kp and reset time (Tn) TA = sampling time, programme cycle time PID controller Y = kp (e+ esum TA/Tn+ (e-e_alt) Tv/TA) Adjust derivative time (Tv), e_alt = system deviation from the previous cycle Note The pump must be operated in the analogue mode for continuous control. Control voltage from the EasyPort to the motor control is between 0 and 10 V. Changeover relay K1 must be set with A2 = 1 to this end. Festo Didactic GmbH & Co. KG C-49

176 4. Automated closed-loop control Experiment: controlling the fill level with a continuous controller In this experiment the fill level will be controlled with a continuous controller. In the example included in the chapter entitled Manual control of fill level, the fill level was kept constant by varying the power supply unit s output voltage. The manipulated value will now be read out by the software. The experiment should be carried out with four different controllers. Various settings must be entered in order to test the performance of the control circuit. In order to be able to draw any conclusions, it s always advisable to change only one parameter at a time and then conduct the experiment. The settings included in the following table are suggestions. Start the software and open the Continuous control menu. Check the software settings: set changeover relay A2 = 1 and specify the setpoint. Carry out the experiment with P, I and PI controllers. Add your observations to the table. Depending on the software revision level, the setpoints may also have to be entered in a sub-window. C-50 Festo Didactic GmbH & Co. KG

177 4. Automated closed-loop control Experiment: controlling the fill level using a proportional controller Note Empty B102 before each start-up! Select each of the values listed below and carry out the experiment. Document your observations. Settings Observations No. Setpoint w, Setpoint w Amplification Disturbance physical (standardised) kp variable z, hand valve V litre % open 2 1 litre % open 3 1 litre % open 4 1 litre % open 5 1 litre % open 6 2 litres % open Sample solution for fill-level control with a P controller Festo Didactic GmbH & Co. KG C-51

178 4. Automated closed-loop control Task Which characteristics is the control circuit (P controller, PT1 system) displaying? Experiment: controlling the fill level using an integral controller Note Empty B102 before each start-up. Software setup The manipulated value of the I controller is calculated as follows: Y = total of all system deviation (e:sum) x sampling time (TA)/integral action time (Ti) This formula makes it clear that Y is quickly changed by the controller when Ti is small, and Y is changed slowly, i.e. the controller is sluggish, when Ti is large. Make sure that Ti does not drop to 0, otherwise Y would be undefined in this case. Switch the software to I controller. The physical setpoint depends on the size of the tank and whether the unit of measure of the fill level will be in litres or in mm. C-52 Festo Didactic GmbH & Co. KG

179 4. Automated closed-loop control Select each of the values listed below and carry out the experiment. Document your observations. Settings Observations No. Setpoint w, Setpoint w Integral Disturbance physical (standardised) action time variable z, hand (Ti) valve V % open % open % open Note It is possible that no stabilisation occurs in an actual system and that continuous oscillation takes place. Sample solution for controlling the fill-level with an I controller Festo Didactic GmbH & Co. KG C-53

180 4. Automated closed-loop control Task What is the effect of integral time? What can we say about system deviation? Experiment: controlling the fill level using a proportional-integral controller (parallel P and I components) In order to take advantage of the positive characteristics of both the P and the I controller, the two will be combined. This can be done in two different ways: The controllers are connected in parallel in the combination shown on the left and in series in the combination on the right. In actual industrial practice, the combination shown on the right is used in accordance with DIN Note Empty B102 before each start-up. Select each of the values listed below for the PI (DIN) controller and carry out the experiment. Document your observations. C-54 Festo Didactic GmbH & Co. KG

181 4. Automated closed-loop control Settings Observations No. Setpoint w (standardised) Amplification kp Reset time Tn Disturbance variable z, hand valve V litres sec. 10% open litres 1 1 sec. 10% open litres 3 1 sec. 10% open litres sec. 10% open Sample solution for controlling the fill-level with a PI controller Task What can we say about reset time Tn? What can we say about system deviation? Festo Didactic GmbH & Co. KG C-55

182 4. Automated closed-loop control 4.3 Project task: refrigerating plant Task description The throughput of a coolant (volumetric flow rate) in a refrigerating plant needs to be controlled. A PI controller is used. Water will simply be pumped to tank B101 for this experiment. PI controller Motor and pump Liquid in piping system Control circuit concept Setting up the system, inspection Set the system up with one tank according to the PI flow diagram, or disconnect the piping to upper tank B102 and seal the bottom outlet of tank B102 with a blanking plug. Connect and test the pump and the flow sensor. V103 V102 FI 101 PI 103 B101 P101 V105 M Install and start the software, and select Continuous controller from the menu. Entries are standardised from 0 to 1. C-56 Festo Didactic GmbH & Co. KG

183 4. Automated closed-loop control Commissioning report Please check all the points listed in the following report and confirm completion of all tasks before commissioning. Task Completed Note/observation Piping assembled and leakproof Flow sensor installed Electrical wiring and connecting cables connected Tank filled with 2.5 litres of water Software installed, sensor values adjusted Factor =, offset = Test pump with PC at 0 to 10 V Changeover relay: A2 = 1 Test the signal from the volumetric flow rate sensor Experiment: flow control using a proportional-integral controller Note Various settings must be entered in order to test performance. In order to be able to draw any conclusions, it s always advisable to change only one parameter at a time and then conduct the experiment. The settings included in the following table are suggestions. Select each of the values listed below and document your observations. Settings Observations No. Setpoint w (standardised) Amplification kp Reset time Tn Disturbance variable z, hand valve V litres sec. 50% open litres 1 1 sec. 50% open litres 3 1 sec. 50% open litres sec. 50% open 5 20% open 6 100% open Festo Didactic GmbH & Co. KG C-57

184 4. Automated closed-loop control Sample solution for flow rate control with a PI controller Task Find a setting at which the controller overshoots only once. How does the interference variable affect the outcome of the experiment? C-58 Festo Didactic GmbH & Co. KG

185 5. Evaluation of learning objectives for automated measurement, open-loop and closed-loop control 1. Describe how to set up a computer aided control circuit. 2. List various controlled systems with one practical example for each. Festo Didactic GmbH & Co. KG C-59

186 4. Automated closed-loop control 3. Describe the performance of a control circuit with a PT1 system. 4. Data (e.g. actual value x) is acquired using sensors. The following, for example, appears in a data sheet for a sensor: pressure range: 0 to 400 mbar, signal: 0 to 10 V. How is the signal processed by the PC so that the physical value is displayed on the PC monitor? C-60 Festo Didactic GmbH & Co. KG

187 4. Automated closed-loop control 5. An ultrasonic sensor provides data in accordance with the following screenshot. Determine factor and offset for a physical representation of the value on the screen. Festo Didactic GmbH & Co. KG C-61

188 4. Automated closed-loop control 6. A pressure sensor is described as follows in the data sheet: : 24 V DC supply voltage 2: 0 V DC earth 3: 0 to 10 V DC voltage output Which pins have to be connected to EasyPort? Which values do factor and offset have to be set to in order to display pressure correctly as a physical quantity? C-62 Festo Didactic GmbH & Co. KG

189 4. Automated closed-loop control 7. How are actuators (e.g. pump motor) controlled with the PC? 8. How is the EduKit PA switched from digital to analogue control? 9. As is the case with all microprocessor controllers, the PC works cyclically according to the IPO model (input, processing, output). The time required for a single sequence is called cycle time or sampling time (TA). For example, a programme has a sampling time of 25 ms. How many measurements can be carried out in one second? Festo Didactic GmbH & Co. KG C-63

190 4. Automated closed-loop control In order to determine the flow rate of a medium as accurately as possible, at least 50 measurements must be performed per second. Determine the required sampling time. 10. A pump fills a tank from above with water. After a given period of time, the pump is switched off. Draw conceivable characteristic fill level curves for two different cases: in case 1 the drain at the bottom of the tank is open. In case 2 the drain is closed. C-64 Festo Didactic GmbH & Co. KG

191 4. Automated closed-loop control 11. An impeller pump causes volumetric flow rate within a circuit. What is the relationship between volumetric flow rate and pressure? Give reasons for your answer. Festo Didactic GmbH & Co. KG C-65

192 4. Automated closed-loop control 12. The following figure depicts a characteristic pump curve. Control voltage is increased from 0 to 10 V in case 1. In case 2, it s decreased back to 0 V. Provide designations for the depicted axes. Give reasons for the shape of the curves. C-66 Festo Didactic GmbH & Co. KG

193 4. Automated closed-loop control 13. A two-step controller can be used for simple control of the fill-level. Explain the structure of a 2-step controller. What is the effect of the switching difference? Festo Didactic GmbH & Co. KG C-67

194 4. Automated closed-loop control 14. After the process, the process, measurement and control data can be stored as ASCII data. Why is ASCII used? How can the data be further processed? C-68 Festo Didactic GmbH & Co. KG

195 Part D1 Plant construction with solutions 1. Process description D Technical reference D Economic reference: market research D Planning D Project management D Work order, requirements specification D Sequence planning and scheduling, project structure plan, performance specification D Purchasing materials and goods D Standards, regulations, data sheets D Risk assessment D Mechanical engineering D Sketches and technical drawings D PI flow diagram D Parts list, mechanical D Assembly plan, mechanical D Quotation and cost calculation D Test report D Electrical engineering D Electrical circuit diagram D Parts list, electrical D Assembly plan, electrical D Cost calculation D Test report D Installation D Work safety D Preassembly, mechanical D Pre-wiring, electrical D Final assembly with component labelling D Commissioning D Mechanical testing, report D Electrical testing, report D Overall commissioning D System analysis: evaluation of test reports D Shipping and product approvals, performance description D1-50 Festo Didactic GmbH & Co. KG D1-1

196 4. Automated closed-loop control 5. Marketing and sales D Quotations D Product presentation D Documentation D Intellectual property rights D Evaluation of learning objectives for plant construction D1-55 D1-2 Festo Didactic GmbH & Co. KG

197 1. Process description 1.1 Technical reference Information The subject of plant construction will be examined in greater detail on the following pages. Although plant construction encompasses several individual disciplines, they can be seen as a whole. Learners will be introduced to the most important aspects of plant construction using a consistent method based on practical examples. The knowledge acquired also provides them with an overview of the interaction which takes place between a variety of professions, such as electrical engineering, mechanical engineering and process engineering. The overall concept of the MPS-PA project kit is also intended to support the vocational orientation of pupils and trainees and to encourage young people to pursue technical careers. General learning objectives Participants are familiarised with the following topics: Project management Process engineering Mechanical and electrical engineering Creating flow diagrams and simple circuit diagrams Analysing results Mechanical and electrical assembly and wiring Commissioning with test report Marketing and sales Festo Didactic GmbH & Co. KG D1-3

198 1. Process description Information Changing and maintaining fill levels are common daily tasks. These processes usually take place in the background or within areas of a machine or system that is not immediately visible. Nevertheless, monitoring process quantities such as fill level, pressure and flow rate offers a great deal of potential. Economy, improved quality and more safety for personnel and machinery are only a few of the aims which can be achieved by consistent process monitoring. Below are a few examples of applications in which these factors play a role. Pressure monitoring Example: galvanising plant The acid bath at a galvanising plant is continuously recirculated and filtered. A filter in the piping system ensures that contamination and particles are removed. During operation, the contamination is deposited on the filter and resistance within the piping system increases. As a result, pressure upstream of the filter rises. Pressure is monitored via a sensor. When a specified pressure is exceeded, the filter must be cleaned or replaced. D1-4 Festo Didactic GmbH & Co. KG

199 1. Process description Flow monitoring Example: water meter A household water meter continuously measures the occupants water consumption by measuring the flow rate in the fresh water supply line. The consumer relies on a uniformly accurate read-out of actually consumed quantities. The water utilities are also dependent on the accuracy of the water meter. Deviation results in a loss for one party and an erroneous gain for the other. Fill level monitoring Example: water tower In order to ensure a constant supply of drinking water, ground, spring or lake water is pumped into water towers where it s stored before being distributed to cities and communities. The fill levels in these towers should be kept as constant as possible, although varying amounts of water are withdrawn by households. Water flows from the water towers via distributors into the storage tanks of domestic household water systems. From there it is accessed directly via a water tap or it s stored again, for example in toilet tanks. Festo Didactic GmbH & Co. KG D1-5

200 1. Process description Further examples of pressure, flow and fill level monitoring: Pressure must be held constant in water jet cutting systems, even in the event of fluctuating water demand. A certain amount of water must be added in order to achieve the desired consistency in a cement mixing system. The volumetric flow rate is time-controlled and flows constantly. Cooling lubricant is pumped into a tank at the machine in order to ensure an uninterrupted supply to machine tools. Cooling lubricant is withdrawn continually during the machining process. The fill level is continuously monitored. Pumps deliver cooling water from car radiators to car engines in order to prevent them from overheating. A storage container compensates for volumetric fluctuation due to thermal expansion and loss. Liquids are pumped from one tank to the next for storage in filling systems. When a given quantity of liquid is withdrawn, for example, the fill level has to be evened out. Fountains are operated with the help of a pump and a storage tank. 1.2 Economic reference: market research Information There are approximately 14,500 water catchment systems in Germany. More than 60% of drinking water is ground water; the rest comes from rivers, lakes, bank filtrate and springs. For example, the supply of water for Baden-Württemberg is assured by a joint management authority consisting of communities, cities and water utilities, namely Bodensee-Wasserversorgung (Lake Constance water supply). Roughly four million people are supplied with water from Lake Constance, which is pumped from a depth of 60 metres near the town of Sipplingen. Approximately 130 million m 3 of water are transported through a piping network that is 1700 kilometres long and includes roughly 30 tanks used for intermediate storage. The largest water tank, with a capacity of 100,000 m 3, is located in Baden- Württemberg s capital city, Stuttgart. Task Find out about water supply in your city or area. Determine the course of the water before it arrives at all the households. D1-6 Festo Didactic GmbH & Co. KG

201 1. Process description Information The fill-level system simulates the supply of water from the withdrawal of raw water, for example from a spring, to the filling of a water tower with the help of a pump up to consumption by households. Two tanks are available for this project, one of which represents the elevated water tower, and the other the household s domestic water tank. The water has to be pumped into the water tower by means of an impeller pump. Volumetric flow rates, pressures and fill levels need to be recorded at the system. Variable valve settings and electrical voltages are used in order to do this. Festo Didactic GmbH & Co. KG D1-7

202 1. Process description D1-8 Festo Didactic GmbH & Co. KG

203 2. Planning 2.1 Project management Work order, requirements specification Information The system is shipped as individual components and must be set up on-site, both mechanically and electrically. Various experiments should be carried out, documented and assessed after the system has been fully set up and tested. The following services, work sequences and documents are specified in the work order to this end by the customer: Mechanical design Documentation (text and images) Develop and create circuit diagrams Generate parts lists/list of components Develop an assembly plan Plan and carry out wiring and connection of electrical components Determine material costs Prepare a presentation on the subject of water supply Create an approval checklist and report Design and implement a graphic evaluation Calculate, record and evaluate time required for activities Create data sheets for recording measured values System commissioning Measured value acquisition as an experiment Process calculations and technical questions Create technical drawings Produce components if necessary Festo Didactic GmbH & Co. KG D1-9

204 2. Planning Sequence planning and scheduling, project structure plan, performance specification Information First of all, in the planning the various tasks, as listed on the work order and the requirements specification, must be organised and divided in the order in which they will be carried out. The requirements specification is prepared by the customer and includes all the services to be rendered. The supplier creates the performance specification on the basis of the stipulations set forth in the requirements specification. In it, the supplier records the services to be rendered, the activities to be carried out, important dates for presentations and meetings etc., deadlines for partial and full performance of the obligations and a project structure plan. The project plan lists the respective activities arranged according to sets of tasks in the form of a flow chart. These sets are subsequently arranged interdependently in chronological order. This schedule is called the project sequence plan. The activity lists indicates the planned duration of each step before the next one can be started. Task The performance specification should be put together during the concept phase (see worksheet for shipment of a completed and functional fill-level system with two tanks). The performance specification is enhanced during the planning phase. Complete the performance specification worksheet (concept phase). Create a project structure plan and use it to develop your project sequence plan with the required procedures in tabular format with a rough time estimate. Use the list of services to be rendered from the work order for orientation. Assemble a project team for the various tasks. Use the performance specification to describe the objectives of the project, the people involved, the quality requirements with regard to setup and functionality of the system, general conditions, deadlines, milestones and the scope of documentation. D1-10 Festo Didactic GmbH & Co. KG

205 2. Planning Performance specification Project name/designation: Order no. Customer: Project employees: Project no. Schedule: Intermediate deadlines: Assembly deadlines: Completion deadline: Terms and conditions of payment: o Advance payment: o According to payment schedule: Concept phase Description of the product Description of the range of applications Description of the function Formulation of the problem/requirements Done Technical data Costs and target prices Planning phase Preliminary calculation of manufacturing costs Personnel and material costs Project costs Festo Didactic GmbH & Co. KG D1-11

206 2. Planning Item Step designation Duration in days Preceding activity Team members 1 Preliminary study and Internet research 2 2 Draft of the project concept and a process sequence Develop and sketch PI flow diagrams and circuit diagrams List of mechanical components Develop mechanical assembly plan 2 3, 4 6 Determine costs for mechanical materials 2 2, 4, 5 7 List of electrical components Create an electrical setup plan 2 3, 4 9 Determine costs for electrical materials 2 2, 7, 8 10 Create performance specification 2 3, 6 11 Carry out mechanical assembly 2 3, 4, 5 12 Complete electrical pre-wiring 2 3, 7, 8 13 Complete cabling 1 3, 8, Create a graphic evaluation Create data sheets for recording measured values System commissioning (test run) 1 11, 12, Carry out experiments Calculations Approval meeting 1 17, Create overall documentation User training, conduct experiments 2 19, Final meeting and presentation 1 20, 21 Project sequence plan D1-12 Festo Didactic GmbH & Co. KG

207 2. Planning Purchasing materials and goods Information Two important aspects of the planning phase include the procurement of materials and goods. These steps should be planned carefully and in detail. The timely completion of a project may depend on this in some cases. The first step of purchasing materials and goods involves finding a suitable supplier. A suitable supplier can be selected using the Internet, as well as visits to, and meetings with, potential suppliers. As a rule, the following steps are completed after selecting a supplier: Issue an RFQ: At this point, product specifications need to be clarified and prices, lead-times and terms and conditions of payment and delivery have to be negotiated. Issue a purchase order: It s important to include the correct information on the purchase order. This includes a precise product designation, the quantity, the price and the delivery date, as well as terms and conditions of shipping and payment. Dispatch the order confirmation: The supplier sends you an order confirmation after he has received your purchase order. All the points which were agreed upon before the order was placed should be reviewed at this time. Important points include the product designation, the price, the quantity, lead-time and terms and conditions of payment. The goods arrive: Goods are usually received by the good inwards department, where the shipment is inspected for damage and/or defects. If any defects are detected, they must be recorded and documented. The resulting documents must then be submitted to the liable party, i.e. the manufacturer or the supplier. The invoice arrives: Before the invoice amount is finally paid, the prices on the invoice are compared with the prices on the purchase order in order to rule out any possible errors. The order is closed once the invoice amount has been paid. Carry out final costing: The purchasing costs are used for final costing. This step is helpful to estimate future projects. Festo Didactic GmbH & Co. KG D1-13

208 2. Planning Standards, regulations, data sheets Information A process engineering system consists of numerous components from various manufacturers. The components must comply with uniform quality standards. These standards are specified in accordance with DIN and EN, as well as ISO, VDE and VDI. The following standards are taken into consideration and the following data sheets are required to plan and design the fill-level system in accordance with current knowledge as of 2008: DIN standard for graphical symbols and flow diagrams for process plants DIN 19227, parts 1 and 2 standard for the graphic representation of process, measurement and control technology symbols DIN EN standards for graphical symbols and identifying letters for mechanical components DIN EN standards for graphical symbols and identifying letters for electrical components DIN ISO standards for graphical symbols and identifying letters for pneumatic components Data sheets for piping, stopcocks and the impeller pump DIN EN 60617, DIN EN standards for graphical symbols and identifying letters... DIN ISO 1219, DIN EN standards for engineering drawings of pneumatic components and function charts The standards and stipulations set forth by DIN and VDE as well as the safety precautions for working with electrical current and voltage, must be observed for all electrical work. Technical information about the components is included in the data sheets on CD-ROM. Electrical components The respective devices are designated in the electrical circuit diagrams in accordance with DIN EN Type of equipment Actuators (servo drive, actuating coil, electrical motor, linear motor) Diodes Auxiliary relays Terminals, terminal blocks, terminal strips Capacitors Circuit breakers, isolating switches Power transistors Indicators (mechanical, optical, acoustic) Relays Identifying letter M R K X C Q Q P K Tubes, semiconductors Contactors (for load) Sensors in general, position switches, proximity switches, proximity sensors etc. Fuses Q B F D1-14 Festo Didactic GmbH & Co. KG

209 2. Planning M RRE/7. 7 2K M2 10 XMA2 1 XA2 O0 24VA 2A4 A1(START) / ADNGA Motor Ansteuerung Motor control - (GND) A2 (ANL) R- 4 3 R+ A D A D Brücke umst ecken für: Digital/Analog Ansteuerung use bridge to choose digital/analog control 0VA 0VA /24VB 24VA_EXT XMA2 9 XA2 24VA NI V42 V0 T UO Anlaufstrombegrenzer current limiter 2A (bk) M 2K1 2 O1 2K VA M3 3 O2 + 2K VA 2M4 4 5 O3 O M5 0VA 0VA 6 O5 0VA 7 O6 0VA 2PA_ BUSY BN BU 8 O7 + 0VA 24VB/6.0 24VA FED BK 0VA 0VB/6.0 24V 2M1 0V 24VA 0VA 2X4 7. 6/ 10C2 XA2 0VA XMA2 11 0VA_EXT 4.9/0VB Example of an electrical circuit diagram MPS PA mixing station, outputs Festo Didactic GmbH & Co. KG D1-15

210 2. Planning Pneumatic components Pneumatic components are designated in circuit diagrams in accordance with DIN ISO All the components included in any given circuit have the same primary identifying number. Letters are assigned depending on each respective type of component. Consecutive numbers are assigned if several components of the same type are included within a single circuit. Pressure lines are designated with a P and are numbered separately. Actuators: 1A1, 2A1, 2A2... Valves: 1V1, 1V2, 1V3, 2V1, 2V2, 3V1... Sensors: 1B1, 1B2... Signal input: 1S1, 1S2... Accessories: 0Z1, 0Z2, 1Z1... Pressure lines: P1, P2... Identifiers for pneumatic components also include a system number ( ) which appears to the left of the circuit number, the component identifier and the component number. D1-16 Festo Didactic GmbH & Co. KG

211 2. Planning V103 V102 8B1_ 6B1_ 12 1M M4 3 max. 2bar 1-1V2 1V1 IST P U 1B1 BN BK 1 BU RU 4 _1B9 2 WH RI 1-3A1 3 _1B V1 1-2V2 1-2V3 1-1A1 4 2 SOLL 3 1 E P PROP_V 1-1V V A V1 1M V2 1-4V3 I 4 1-3V M5 1-3V2 1-3V3 Example of a pneumatic circuit diagram MPS PA filtering station Festo Didactic GmbH & Co. KG D1-17

212 2. Planning Process engineering components Components are designated in the PI flow diagram in accordance with EN ISO and DIN V206 V205 V204 LS+ 201 LS- 202 B201 LA+ 210 LS- 203 B202 LA+ 211 LS- 204 B203 LA+ 212 FI 202 FIC 201 P201 LS+ 205 LS- 206 B204 LA+ 213 V207 V208 V201 V202 V203 P202 M V210 V209 X201 V211 X202 M Example of a PI flow diagram MPS PA mixing station D1-18 Festo Didactic GmbH & Co. KG

213 2. Planning EN ISO standard The layout and function of a process engineering system are described in a piping and instrument flow diagram (abbreviated PI flow diagram). Apparatus or machinery System section or machine if not assigned to one of the following groups Container, tank, hopper, silo Chemical reactor Steam generator, gas generator, oven Filtration device, liquid filter, sieve, separator Gear unit Lifting unit, conveying unit, transfer unit Column Electrical motor Pump Stirrer, stirring container with stirrer, mixer, kneader Centrifuge Dryer Compressor, vacuum pump, fan Heat exchanger Feed and separating equipment, other devices Actuator unit, other than electrical motor Crusher Identifying letter A B C D F G H K M P R S T V W X Y Z Identification of process engineering components DIN standard In addition to system components, process, measurement and control points are also included in PI flow diagrams. The process related functions of the measured quantities are described by means of process, measurement and control points per DIN The identifier should indicate the measured quantity or another input quantity, how it s processed, its direction of control action and its specified location. A process, measurement and control point consists of a circle and is designated with an identifying letter (A to Z). The identifying letters are entered in the top part of the circle and numbering is entered in the bottom part. The order of the identifying letters is as per the table, Process, measurement and control identifying letters per DIN Example L I C Lic First letter Supplementary letter First subsequent letter Fill level Display Automatic control Festo Didactic GmbH & Co. KG D1-19

214 2. Planning The identifying procedure for process, measurement and control points is freely selectable. Consecutive numbering is advisable because each process, measurement and control identifier may only be used once, even if there are several measuring points with the same measured quantity. Further information can be found in DIN 19227, part 1. Process, measurement and control identifying letters per DIN Letter A B C Measured quantity or other input quantity, actuator First letter Supplementary letter Processing Subsequent letter Sequence: O, I, R, C, S, Z, A Error message Automatic control D Density Difference E Electrical quantities Sensor function F Flow, throughput Ratio G Distance, length, position H Manual entry, manual intervention Upper limit value (high) I Display J Sensing of measuring points K Time L Level (also separation layer) Lower limit (low) M Moisture N O Visible sign, yes-no statement P Pressure Q Material characteristics, quality Integral, sum R Radiometric quantities Recording S Speed, frequency Switching, sequence control, logic control T Temperature Measuring transducer function U Combined quantities Combined actuator function V Viscosity Actuator function W X Weight, mass Other quantities Y Z Calculation function Emergency intervention, protection by means of triggering, safety device, safety relevant message + Upper limit value / Intermediate value Lower limit value D1-20 Festo Didactic GmbH & Co. KG

215 2. Planning Task Familiarise yourself with the standards and data sheets. Which information do the above mentioned standards and data sheets provide you with? Create a summary of the most important characteristics for each standard and the components used Risk assessment Information An important aspect of the planning phase is the risk assessment. All machinery and equipment manufacturers are required to carry out a risk assessment for their machines and equipment. This is a legal requirement and is stipulated in the EC machine directive. The directive states: The manufacturer of machinery or his authorised representative must ensure that a risk assessment is carried out in order to determine the health and safety requirements which apply to the machinery. The machinery must then be designed and constructed taking into account the results of the risk assessment. Below is an example of what a risk assessment might look like. Festo Didactic GmbH & Co. KG D1-21

216 2. Planning 2.2 Mechanical engineering Sketches and technical drawings Task The scale of the overall drawing of the fill-level system is 1:5. Add the most important assembly dimensions to the drawings so that it can be used later to set up the system Top view D1-22 Festo Didactic GmbH & Co. KG

217 2. Planning 415 Front view Festo Didactic GmbH & Co. KG D1-23

218 2. Planning Side view, right D1-24 Festo Didactic GmbH & Co. KG

219 2. Planning The rectangular profiles to which the tanks are attached are joined with retaining plates. Manually sketch out the hole pattern for the retaining plates for M5 socket head screws Ø6 The retainer for the impeller pump has to be made. Calculate the length of the sheet metal. Ø42 12 Ø5,5 Ø5, a, b, c... Lengths of bending sections n number of bends v compensation value; v = 3 mm for a sheet metal thickness of 1 mm and a bending radius of 4 mm L = a + b + c n v Where arc sine a = 9 mm/21 mm a = opening angle = L = mm + p 42 mm / mm L = mm Festo Didactic GmbH & Co. KG D1-25

220 2. Planning PI flow diagram Information The piping and instrument flow diagram (PI flow diagram) depicts the technical equipment included in a system with the help of graphical symbols which are connected using lines. The graphical symbols represent the system components and the lines identify lengths of pipe, as well as electrical functions and signals for process measurement and control. The designation V101 from the PI flow diagram is a process designation. Process related tasks are described in a process, measurement and control plan using graphical symbols, i.e. process, measurement and control points. The identifier should indicate the measured quantity or another input quantity, how it s processed, its control action and its specified location. A process, measurement and control point consists of a round, oval or hexagonal symbol and is assigned an identifying letter (A to Z). The identifying letters are entered in the top part of the symbol and a number is entered in the bottom part. The order of the letters is specified in the table entitled Identifying letters for process, measurement and control technology per DIN Task Fill in the missing designations. Create a PI flow diagram for the system using the components from the table. Components list Identification Graphical symbol Meaning of the graphical symbol B101 Tank, container B101 V102 V102 Stopcock FI101 PI103 FI 101 PI 103 Flow rate measuring point with display Pressure measuring point with display P101 P101 Pump Piping inlet Piping outlet D1-26 Festo Didactic GmbH & Co. KG

221 2. Planning PI flow diagram V101 B102 V103 V102 FI 101 PI 103 B101 P101 V105 M PI flow diagram, EduKit PA project kit Festo Didactic GmbH & Co. KG D1-27

222 2. Planning Parts list, mechanical Task The components and their required quantities can be determined from the overall drawing and the PI flow diagram for the purpose of creating a parts list. The part numbers are included in the data sheets and the Festo Didactic product catalogue. Using this information, create a parts list for the basic mechanical setup of EduKit PA without electrical components. D1-28 Festo Didactic GmbH & Co. KG

223 2. Planning Item Quantity Name Part number 1 1 Pump Pressure gauge Float-type flow sensor Stopcock Profile connector 6 3 Rectangular profile, 40 x Tank (container) straight plug connector Push-in T-connector Profile plate, 350 x 200 mm 2 m Straight length of pipe Blanking plug Assembly plan, mechanical Information In order to keep assembly of the system as simple as possible, components are grouped into subassemblies. Task Create an assembly plan for the basic setup of the fill-level system using the table on the next page. Write out a set of procedures, indicating how you would assemble the system. Sub-assemblies are numbered consecutively with the designations B1, B2 and so forth. (The Times column refers to a task in a later chapter and can be disregarded for this exercise.) Festo Didactic GmbH & Co. KG D1-29

224 2. Planning Subassembly Item Work step Tool Work step carried out Times B1 1 Secure pump, tubing and piping length with pipe clip. Screwdriver B1 Return line and outlet connection at pump B2 2 Preassemble pressure gauge and push-in T-connector. B2 3 Connect the float-type flow sensor to the push-in T- connector. B3 4, 9 Connect the transverse line to the tanks with stopcocks (2 ea.), push-in T-connectors (2 ea.), 90 push-in connectors (2 ea.) and pipe. B4 4, 8 Connect the upper feed line to the stopcock (1 ea.), 90 push-in connectors (2 ea.) and pipe. B5 7, 6 Screw the tank brackets (4 ea.) onto the rectangular profiles. Allen key B5 6, 16 Screw rectangular profiles with foot to the profile plate. See above B5 6, 5 Screw rectangular profiles (4 ea.) together with profile connectors. B5 7 Set the tanks into the brackets and secure with socket head screws. See above See above B1 B2 Secure subassembly B1 on the profile plate to the pump retainer. Plug subassembly B2 on B1 into the pump. See above B3 Connect subassembly B3 to the tanks and plug it into B2. B4 Plug subassembly B4 into the push-in T-connector at B3 and feed it through the cover on the upper tank. Tighten all screws once again. See above Assembly plan, mechanical D1-30 Festo Didactic GmbH & Co. KG

225 2. Planning Quotation and cost calculation Information A fill-level system is required in another department within your company for training purposes. First of all, you ll produce a complete basic setup in the form of a prototype in the training department. The fill-level system will then be sold to the respective department. Determine an estimated sales price in the form of a simple cost calculation. Electrical and mechanical components should be listed separately. Use the following quotation as a basis for your calculation: Item Quantity Designation Unit price Amount 1 1 Basic mechanical components kit with aluminium profiles, including all accessories Tank, MPS-PA-B tank, round Pump, Flow meter, Pressure gauge m Pipe, Push-in connector, T-distributor, Push-in bracket, Stopcock, Blanking plug, Net price Quotation (sample prices are not the same as actual prices!) Task Calculate the costs for the fully assembled mechanical portion of the system. Costs are calculated separately for the mechanical and electrical parts while the cost calculation for the electrical components will be completed later (see 2.3.4). The prices of the components can be taken from the above quotation. Manufacturing wages and overheads, as well as administrative and sales costs can be based on figures provided by the appropriate people in your company, researched on the Internet or estimated for the purposes of a rough calculation. Make a rough estimate of the time required for assembly in order to determine labour costs. Use local hourly rates for this. Festo Didactic GmbH & Co. KG D1-31

226 2. Planning Term Explanation Pieces, hours Amount Total Material costs (1) Material overhead costs (2) Procurement costs for materials, components Purchasing costs, warehousing costs, bookkeeping 5% of (1) Gross material costs (3) Total of (1) + (2) Manufacturing wages (4) Manufacturing overhead costs (5) Wage costs allocated to the product Depreciation, social security costs, training costs, auxiliary materials, tools, premises, payroll accounting Manufacturing costs (6) Total of (4) + (5) Special manufacturing costs (7) Production, fixtures, outsourced processing (e.g. hardening) Production costs (8) Total of (3) + (6) + (7) Administration and sales (9) Administration, taxes, advertising costs 15% of (8) Cost of sales (10) Total of (8) + (9) Profit (11)... % of (10) Net sales price Sales price without value added tax Total of (10) + (11) Gross sales price Sales price with value added tax Simple cost calculation for mechanical assembly Task When you buy components, a difference is made between net and gross prices. What s the difference? Calculate the gross sales price for the above example. Net prices are prices which do not include value added tax. Gross prices are prices with value added tax. Net sales price x VAT rate = gross sales price. What s meant by overheads? Fixed costs, for example for warehousing, training, labour, bookkeeping etc. D1-32 Festo Didactic GmbH & Co. KG

227 2. Planning What s meant by manufacturing costs? Manufacturing costs are part of the production costs, but they do not include costs related to materials. Costs for premises and energy are also incorporated into the calculation, as well as special direct costs (special parts) and the costs of production planning and quality control Test report Information Once mechanical assembly has been completed, the fill-level system and all its components must be inspected and approved (i.e. screw connections in the pipe fittings, straightness and parallelism of the piping, tank mounting, profiles and the impeller pump). In actual practice, test reports are used to document the functionality and the condition of the system. Test report requirements are specified either by the customer or by currently valid standards. Task Create a test and approval report with a word processing program which has space for the following entries: - Test points are numbered consecutively in a tabular report and the numbers are added to the picture below. - The list includes columns for each item number, the test point designation, a tick mark for approval and comments. - Space is provided at the end of the test report for the name of the inspector and the date. - The comments column must provide adequate space for the entry of any defects detected during inspection. A sample test report is included on CD-ROM. Festo Didactic GmbH & Co. KG D1-33

228 2. Planning Mechanical assembly without electrical actuation D1-34 Festo Didactic GmbH & Co. KG

229 2. Planning 2.3 Electrical engineering Electrical circuit diagram Information The impeller pump is turned on and off using a detented switch in the basic setup. The pump s on/off status is displayed by an indicator light. The impeller pump is supplied with 24 V DC power via a power supply unit. Task Create an electrical circuit diagram for the system and identify all the components. All the system s electrical components must be designated in accordance with DIN EN Circuit diagram 24 V S1 3 4 P101 M P1 0 V Festo Didactic GmbH & Co. KG D1-35

230 2. Planning Parts list, electrical Information The parts list for the electrical components must be planned. The item numbers for the various components are shown in the following figure. Task Complete a part list for the entire electrical assembly. The part numbers can be taken from the data sheets and the Festo Didactic product catalogue. Put a tick mark in the column Components for basic setup for each component required for this task. Which additional consumables will be required? Estimate the amount. D1-36 Festo Didactic GmbH & Co. KG

231 2. Planning Item no. Quantity Name Designation, standard designation Components for basic setup V DC indicator light with mounting bracket x 11 1 Electrical control switch with mounting bracket x 12 1 Electrical start pushbutton with mounting bracket 13 1 Electrical stop pushbutton with mounting bracket 14 1 Relay with mounting bracket 15 1 Terminal block x 17 1 Wire x 18 1 Mountable plug block x 19 1 H-rail x 20 1 Rail for control components x 1 24 V power supply unit x Blue wire, 0.5 sq. mm (cross section?) Cable binder (size?) x x Wire end sleeves Bill of materials Assembly plan, electrical Information To optimise work sequences, the order in which work steps are carried out to produce a product should be planned and documented by the production planning department. Task Arrange the work steps in a logical order with the help of the parts list. List the wiring and assembly steps for the electrical components in the setup plan. Electrical components are designated E1, E2, etc. (The Times column refers to a task in a later chapter and can be disregarded for this exercise.) Festo Didactic GmbH & Co. KG D1-37

232 2. Planning No. Item no. Work step Tool Times E1 10 to 14 Mount indicator light, pushbuttons (2 ea.), control switch, relay and terminal block on the H-rail. Allen key E1 Cut wire to length, strip insulation and crimp on the wire end sleeves. Wire strippers, crimping pliers E1 10, 11 Connect the following electrical components with blue wires for the basic setup: detented switch and indicator light. Screwdriver E1 Screw the H-rail with the components onto the profile. Allen key E2 1 Connect the pump to the plug. E3 Connect the 24 V DC cable to the terminals. Screwdriver Run cables and bind together neatly, cut the cable ends to length. Wire cutter Assembly plan, electrical Add the connecting cables to the image of the electrical components to indicate how they have to be wired according to the circuit diagram prepared earlier. D1-38 Festo Didactic GmbH & Co. KG

233 2. Planning Cost calculation Task On the basis of the quotation, determine an estimated sales price for the electrical components and electrical wiring with the help of a simple cost calculation. Manufacturing wages and overheads, as well as administrative and sales costs can be based on figures provided by the appropriate people in your company, researched on the Internet or estimated for the purposes of a rough calculation. Make a rough estimate of the time required for assembly in order to determine labour costs. Use local hourly rates for this. Item Quantity Designation Unit price Amount V DC indicator light with mounting bracket Electrical control switch with mounting bracket Electrical start pushbutton with mounting bracket Relay with two changeover contacts Screw terminals core safety laboratory cable Mountable plug block H-rail Rail for control components Table top power supply unit with power cable, 230 V AC, 24 V DC / 4.5 A Net price Quotation (sample prices are not the same as actual prices!) Festo Didactic GmbH & Co. KG D1-39

234 2. Planning Term Explanation Pieces, hours Amount Total Material costs (1) Material overhead costs (2) Procurement costs for materials, components Purchasing costs, warehousing costs, bookkeeping 5% of (1) Gross material costs (3) Total of (1) + (2) Manufacturing wages (4) Manufacturing overhead costs (5) Wage costs allocated to the product Depreciation, social security costs, training costs, auxiliary materials, tools, premises, payroll accounting Manufacturing costs (6) Total of (4) + (5) Special manufacturing costs (7) Production, outsourced processing (e.g. ready-wired components) Production costs (8) Total of (3) + (6) + (7) Administration and sales (9) Administration, taxes, advertising costs 15% of (8) Cost of sales (10) Total of (8) + (9) Profit (11)... % of (10) Sales price Net price without value added tax Total of (10) + (11) Calculation plan Test report Information Once electrical assembly has been completed, the wiring, interconnection of the electrical components such as switches and the indicator light and the mechanical attachment of the electrical components are inspected and approved. Task Create a test and approval report with a word processing program which has space for the following entries: - Test points are numbered consecutively in a tabular report and the numbers are added to the image below. - The list includes columns for each item number, the test point designation, a tick mark for approval and comments. - Space is provided at the end of the test report for the name of the inspector and the date. - The comments column must provide adequate space for the entry of any defects detected during inspection. A sample test report is included on CD-ROM. D1-40 Festo Didactic GmbH & Co. KG

235 2. Planning Setup with electrical wiring Festo Didactic GmbH & Co. KG D1-41

236 2. Planning D1-42 Festo Didactic GmbH & Co. KG

237 3. Installation 3.1 Work safety Information Work instructions specify in detail how certain steps have to be carried out. Work instructions are tied to a specific process, a product or a workstation. They form the basis for ensuring that quality standards are met when the company s employees carry out their respective tasks. Initial basic instruction on safety in the workplace and how each person should comply must be completed before specific work instructions are handed out. Observe the safety precautions in the introduction! Safety instructions Mr./Ms. Department Job Received instructions in accordance with 7 UVV, VBG 4 and on the basis of the activities carried out at the workstation. Subject of instruction Date Instructed person (signature) Supervisor (signature) 1. General instructions at the fill-level system 2. Instructions on handling liquids 3. Instructions for electrical components 4. Electrical start-up must only be carried out by appropriately trained personnel. 5. General introduction to: Workshop use Goods in/out Working at a PC Internet and Telephone system Accident prevention regulations specified by trade associations for precision and electrical engineering apply. Festo Didactic GmbH & Co. KG D1-43

238 3. Installation 3.2 Preassembly, mechanical Information The components must now be assembled in accordance with the specifications in the assembly plan. Task Complete the mechanical preassembly of the components of the fill-level system first. Supplement the assembly plan you created in the chapter on Planning by assigning assembly procedures to components. Use the technical drawings of the components as an assembly guideline. Engineering drawings of the individual components are included on CD-ROM. Write down the assembly times in the assembly plan prepared earlier and modify it if necessary if you use different steps or discover better alternatives. 3.3 Pre-wiring, electrical Information The components are preassembled in accordance with the basic electrical setup plan. Task First of all, the electrical components are pre-wired. Proceed in accordance with the layout you have already created. Follow the circuit diagram with regard to wiring. Then attach the electrical components to the H-rail. D1-44 Festo Didactic GmbH & Co. KG

239 3. Installation Write down the assembly times and modify the assembly plan if necessary if you use different steps or discover better alternatives. Make a note of any changes to the assembly plan. 3.4 Final assembly with component labelling Information All the mechanical and electrical components are put together in the final step. Task During final assembly, screw or clamp all the mechanical and electrical components to the profile plate and the rectangular profiles and connect the electrical components to each other (see CD-ROM). Supplement the components list with the component designations in accordance with the PI flow diagram and the electrical circuit diagram. Write the designations of the components onto the adhesive labels and attach them to the respective system components. Festo Didactic GmbH & Co. KG D1-45

240 3. Installation Item no. Graphical symbol Meaning of the graphical symbol Identification 1 P101 Pump P101 2 PI FI 101 Measuring point for pressure measurement with display (component: pressure gauge) Measuring point for flow measurement with display (components: float-type flow sensor) PI103 FI101 4 V102 Stopcock (4) V101, V102, V03, V105 7 Tank, container (2) B101, B102 B101 Component list per PI flow diagram Item no. Graphical symbol Meaning of the graphical symbol Identification 10 Indicator light, start P1 P1 11 S1 Electrical control switch S1 12 S2 Electrical pushbutton, start S2 13 S3 Electrical pushbutton, stop S3 14 K1 Relay K1 Components list based on electrical circuit diagram D1-46 Festo Didactic GmbH & Co. KG

241 4. Commissioning 4.1 Mechanical testing, report Information The fill-level system has now been set up and should first of all be filled. Disconnect the system from the power supply before commissioning. In order to prevent any unpleasant surprises, check the mechanical components both before and during filling. Keep an adequate supply of rags on hand in order to mop up any water which might escape. Task Check the points listed below and acknowledge inspection. Commissioning, report mechanical Characteristic, requirement for component Fulfilled Not fulfilled, comment Stopcock V 105 closed Impeller pump pipe connection complete and securely pushed in place Stopcock V 101 for filling the upper tank from above closed Stopcock V 103 for filling the upper tank from below closed Stopcock V 102, lower tank return line, closed Fill the upper tank, check for leaks Check fittings and tighten further if required Open stopcock V 102 (lower tank return line open) Fill the lower tank, check for leaks Check fittings and tighten further if required Place a bucket underneath, open stopcock V 105 and drain the tank Inspector Date Festo Didactic GmbH & Co. KG D1-47

242 4. Commissioning 4.2 Electrical testing, report Information Once mechanical inspection has been completed, the electrical components are tested to ensure they function correctly. This is done by filling the system with water, so that the pump is prevented from running dry. First, the water is only pumped around in a circular direction, i.e. from the bottom container via the impeller pump and back into the lower tank from the upper tank. Task Carry out all the commissioning steps. Evaluate your results and tick off the corresponding entry. If the function is not performed correctly, make a note of the determined status or the sub-function. Discuss appropriate measures for eliminating the cause of error with your trainer. Commissioning, report electrical Function Fulfilled Not fulfilled, comment Connect the 24 V and 0 V leads from the power supply unit to the terminals. Electrical control switch wired Indicator light wired Pump wired Secure wires with cable binder Power supply unit connected to mains power (230 V AC) Switch the power supply unit on, the indicator light on the power supply unit lights up. Control switch ON, indicator light switches on Control switch ON, pump runs Control switch OFF, indicator light does not switch on Pump vented? Control switch OFF, pump does not run Power supply unit OFF, system is shut down Inspector Date D1-48 Festo Didactic GmbH & Co. KG

243 4. Commissioning 4.3 Overall commissioning Information You have approved the system s mechanical and electrical parts. Now start an initial, complete test run with all of the system s components. Before each time you commission the system, carry out a visual inspection. Inspect the following before starting the system: Electrical connections Correct fitting, leakproofness and condition of piping and pipe connectors Correct fitting and condition of compressed air connections, if pneumatic valves are used Mechanical components for visible defects (cracks, loose connections etc.) Fill level of tank B101 Eliminate any damage discovered during inspection before commissioning. Supply the system with 24 V DC power via a mains power supply unit. Task Carry out the following steps for (re-)commissioning: 1. Prepare the workstation. 2. Conduct visual inspection. 3. Inspect cable connections. 4. Activate supply power. 5. Fill the tanks. 6. Vent the piping system Set the stopcocks so that the following tasks can be carried out: - Full upper tank B102 from above, stopcock V102 in tank B101 opened about 20%. V101 open, cv103 closed. - Fill upper tank B102 from below, stopcock V102 in tank B101 opened about 20%. Open V103, close V101. Festo Didactic GmbH & Co. KG D1-49

244 4. Commissioning 4.4 System analysis: evaluation of test reports Information The test reports have to be analysed and conclusions must be drawn based on the work done while setting the system up so that the system s design and layout can be analysed and improvements made. The commissioning test reports for mechanical and electrical components are available and overall commissioning has also been completed. Task Evaluate the test reports and pinpoint any problems. Use the first practical test run to draw conclusions for further work with the system. Analyse the overall layout of the system in order to determine whether or not the assembly and commissioning procedures can be improved. Document your evaluations in writing. It s difficult to maintain a specific fill-level using the ON/OFF operating mode for the pump. If the pump continues to run when the storage tank is empty, air is drawn in. This can lead to malfunctioning. 4.5 Shipping and product approvals, performance description Information Once prototypes have been developed, the first samples are produced under series manufacturing conditions. The product is not approved until the function, quality and performance features have been examined and tested. Subsequent series manufactured parts must conform to the same quality standards as the first samples. The product must be approved by general management before it can be launched. All information relevant for sales must be available as a basic prerequisite for the product s introduction onto the market (see chapter 5, Marketing and Sales ). D1-50 Festo Didactic GmbH & Co. KG

245 5. Marketing and sales 5.1 Quotations Information A great variety of information is required in order to sell a product. For example, the text for a quotation template must be prepared. Task Find out how quotations are laid out and what information is included. Base yourself on the layout and content of a quotation from your company or another manufacturer. Which details are included in a quotation? Contact person, company, date of quotation Information regarding services and the product range Designations, prices and quantities of quoted items Lead-times, terms of delivery Terms and conditions of payment Quotation validity Create a sample quotation for a customer who wants to purchase the project kit. What does the term ex works mean? In this case, the contractual obligations of the seller are fulfilled as soon as the ordered goods are ready for pick-up at his factory or warehouse. The costs of loading and shipping the goods to their destination are borne by the buyer. The risk of damage to the goods sustained during transport is transferred to the buyer as soon as loading begins. Festo Didactic GmbH & Co. KG D1-51

246 5. Marketing and sales 5.2 Product presentation Information The way in which a product is presented plays an important role in how well it will sell. Companies invest large sums of money in product marketing. The most important points are briefly discussed below. Task Various types of product presentations are created in small groups. Brochure, leaflet, foreign languages A brochure or a leaflet should be printed for the project kit. Important content for any printed information includes an overall view of the system, interesting partial views, a functional description, features and technical data of the individual components and notes regarding the user-friendliness of the piping system thanks to the push-in connector system. Write the text for the functional description and the technical data in German and English, and add both languages to the leaflet. The technical data for the various components are included on CD-ROM. Screen presentation The system will be presented to a customer. Create a screen presentation which covers the most important features and functions of the system. Use the texts for the brochure, but condense them for the screen presentation. The screen presentation can also be laid out as a PDF file, so that it can be printed out. Photos of the system are included on the CD-ROM. Internet presentation Edit the screen texts and images so that they can be used in a start-up page for the Internet. Create an HTML page for the project kit with the help of an HTML editor. 5.3 Documentation Information The technical documentation is intended to provide the recipient of the product with information and instructions regarding the system or the product. In addition, the customer is also made aware of safety precautions and provided with operating instructions for the system. D1-52 Festo Didactic GmbH & Co. KG

247 5. Marketing and sales Task The entire project must be documented. The documentation should include the following information: - System layout - Description of functions - Data sheets for the various components - Experiment descriptions - Tables with values and evaluations resulting from the experiments - Findings - Circuit diagrams - Drawings 5.4 Intellectual property rights Information As a result of intellectual property legislation for the protection of industrial property rights, the holder of the rights is granted the opportunity of prohibiting commercial exploitation of the protected objects by any other party. The intellectual property rights are thus rights of prohibition. They are not at least not automatically rights of use. Task Which types of protective rights are there? Research this topic on the Internet. Patent Utility model Registered design Variety protection Trademark protection Copyright Festo Didactic GmbH & Co. KG D1-53

248 5. Marketing and sales D1-54 Festo Didactic GmbH & Co. KG

249 6. Evaluation of learning objectives for plant construction 1. During which phase of system setup is the project structure plan used? The project structure plan is used during the planning phase. 2. What is the function of the project structure plan? Activities are arranged hierarchically and in relation to preceding activities in the project structure plan. 3. Calculate the flat length for the pump bracket assuming a bending radius of 4 mm and a sheet metal thickness of 2 mm. Use a compensation value of 4.5. Calculation: where arc sine a = 9 mm/21 mm; a = ; opening angle = L = a+b+c+ -n v L = 2 25 mm mm + p 42 mm / L = mm The flat length of the sheet metal for the pump bracket is mm. 4. How are the following functions designated in a PI flow diagram? Hand valve, no. 102: Measuring point for pressure measurement with display, no. 103: Measuring point for flow measurement with display, no. 102: V102 PI103 FI Sketch the graphical symbols for a PI flow diagram (see planning): P101 Pump P101 Measuring point for flow measurement with display, no. 101: FI101 FI Pneumatic 5/2-way valve, no Festo Didactic GmbH & Co. KG D1-55

250 5. Marketing and sales 6. Draw the PI flow diagram for pressure measurement while filling the upper tank from below. See flow diagram on page Which information is included in a part list? Item number, quantity, designations of the components, standard designation, designation of materials 8. What s included in a tabular assembly plan? Item numbers, module numbers, component designations, auxiliary materials, tools 9. When you buy components, a difference is made between net and gross prices. What is the difference between these prices? Net prices are prices which do not include value added tax. Gross prices are prices with value added tax. 10. Name typical overheads? Fixed costs, for example for warehousing, training, labour, bookkeeping etc. 11. What s meant by manufacturing costs? Manufacturing costs are part of the production costs, but they do not include costs related to materials. Costs for premises and energy are also included in the calculation, as well as special direct costs (special parts) and the costs of production planning and quality control. 12. During initial testing, you started the pump with a detented switch. Why is a detented start-up switch impermissible in actual practice? In actual practice, an on/off switch is impermissible because for safety reasons the system would have to be protected against being restarted after a power failure, or in the event of power interruption due to an emergency stop. The system can only be restarted by activating a pushbutton. D1-56 Festo Didactic GmbH & Co. KG

251 5. Marketing and sales 13. Cite one safety precaution each for electrical, pneumatic and mechanical components and process technology See introduction. 14. Why is a commissioning report prepared after final assembly has been completed and before commissioning? Cite two examples. All of the characteristics of the system are tested with the help of the commissioning report, in order to ensure safe operation. Festo Didactic GmbH & Co. KG D1-57

252 5. Marketing and sales D1-58 Festo Didactic GmbH & Co. KG

253 Part D2 Practice-based learning: manual measurement, open-loop and closed-loop control with solutions 1. Manual measurement D Project task: bath recirculation D Task description D Setting up the system, inspection D Experiment: mechanical pressure measurement D Evaluation and findings D Project task: mixing system D Task description D Experiment: flow measurement D Evaluation and findings D Manual open-loop control D Project task: controlling water supply using hand valves D Task description D Mechanical layout D Setting up the system, inspection D Experiment: filling the upper tank from below D Experiment: filling the upper tank from above D Evaluation and findings D Project task: controlling water supply using 2-way ball valve D Task description D Mechanical layout, inspection D Plans D Commissioning, report D Experiment: filling using a pneumatically controlled 2-way ball valve D Evaluation and findings D Project task: electrical control of the pump in the water supply line D Task description D Setting up the system, inspection D Relay circuit with pushbuttons D Electrical circuit diagram D Electrical wiring and setup plan D Commissioning, electrical testing and report D Experiment: filling while simultaneously withdrawing water D Evaluation and findings D Experiment: pump start-up performance and power D Evaluation and findings D2-35 Festo Didactic GmbH & Co. KG D2-1

254 5. Marketing and sales 3. Manual closed-loop control D From a control loop system to a control circuit D Project task: controlling the fill-level in the tanks D Task description D Setting up the system, inspection D Experiment: manually keeping the fill level constant in the upper tank D Evaluation and findings D Experiment: controlling the fill level using an analogue controlled pump D Evaluation and findings D Experiment: pressure and flow control D Evaluation and findings D Evaluation of learning objectives for manual measurement, open-loop and closed-loop control D2-47 D2-2 Festo Didactic GmbH & Co. KG

255 1. Manual measurement 1.1 Project task: bath recirculation Task description Information Typical recirculating processes are used in all baths where liquids have to be filtered. For example, leisure time applications include swimming pools and technical applications include acid baths and galvanising plants. As the filter becomes more and more contaminated, resistance in the piping system increases upstream of the filter in proportion to the degree of contamination. When a specified pressure is exceeded, the filter must be cleaned or replaced. The relationship between resistance (degree of valve opening) and pressure is determined by experimentation. Task Modification in accordance with the PI flow diagram: modify the basic setup with two tanks so that the experiments for manual measurement can be done using a single tank. Stopcock V103 represents the filter for the purpose of the experiment. Filter permeability is simulated by opening and closing the valve. V103 V102 FI 101 PI 103 B101 P101 V105 M Festo Didactic GmbH & Co. KG D2-3

256 1. Manual measurement Setting up the system, inspection Work step Done Modify the piping layout in accordance with the photograph. Remove the piping to the upper tank and insert blanking plugs into each of the push-in T-connectors. Close stopcock V105. Check to make sure that all piping connections are correct. Check the piping connections to the impeller pump. Make sure that the pressure gauge is installed directly downstream of the pump! Fill tank B101 with 3 litres of water. Connect the system to the power supply unit (24 V DC). Test execution: Stopcocks V103 and V102 are fully open and V105 is fully closed. The control switch is turned to the ON position and the pump delivers water. Stopcock V103 is closed successively in the test setup. After the experiment has been completed, pull out the main plug and remove the 4 mm safety cable from the power supply unit. The water must be drained from the system via stopcock V105 after testing. D2-4 Festo Didactic GmbH & Co. KG

257 1. Manual measurement Experiment: mechanical pressure measurement Fill the tank and then start the pump. Stopcock V103 is open at first and is gradually closed. Stopcock V103 represents the filter for the purpose of experimentation. Filter permeability is simulated by opening and closing the valve. Read pump pressure from the pressure gauge. Observe the volumetric flow rate at the sight glass in the flow meter. Resistance (degree of valve opening) and pressure Degree of valve opening as percentage, V 103 p e [bar] Q [l/min.] Open % % % % 0.22 Closed 0.32 Festo Didactic GmbH & Co. KG D2-5

258 1. Manual measurement Evaluation and findings Task Plot the pressure measured in the piping system relative to the degree of valve opening on the graph: How are pressure and volumetric flow rate within a piping system influenced when resistance within the piping system is continuously increased? As the stopcock is gradually closed, pump delivery pressure increases proportional to the valve setting. The volumetric flow rate within the piping system drops at the same rate. Why doesn t pressure continue to rise after the stopcock has been fully closed? Because the impeller pump is incapable of generating high levels of pressure due to its design. Explain how an impeller pump works. The pump has a rotating impeller. The liquid is accelerated in a circular movement and is fed radially to the outlet. The pump functions hydro-dynamically. D2-6 Festo Didactic GmbH & Co. KG

259 1. Manual measurement Why is it important to ensure that there s no air in the pump? Air in the pump would prevent the liquid from being pumped into the piping system. Not enough delivery pressure is built up in order to pump the liquid upwards. If cavitation occurs, the pump may be damaged. Which types of pumps can be used in the field of process technology? Use information from various manufacturers in order to research your answer. Create a table with typical characteristics, as well as technical data and the range of applications, for a given type of pump. Pump type (section drawing) Characteristics, technical data, range of applications Impeller pump Impeller pumps are the most commonly used type of pump in process engineering systems. Principle: an impeller equipped with blades rotates at high speed in a spiral shaped pump casing. As a rule, the impeller is driven by an electric motor. The liquid to be delivered enters the pump casing through the intake nozzle which is aligned to the rotary axis. It s accelerated radially by the impeller and is discharged from the pump casing through the discharge nozzle. Impeller pumps are capable of relatively large delivery rates with small to moderate total head. Viscous liquids and media which contain solids can be delivered with the help of specially designed impellers. Piston pump The main components of the piston pump include a displacement piston, as well as intake and discharge valves which open and close automatically. During the intake stroke, the discharge valve is closed, the piston generates underpressure and the medium to be delivered is drawn into the pumping chamber via the open intake valve. During the discharge stroke the piston presses the medium through the open discharge valve and out of the pumping chamber (the intake valve is closed). The delivery line is equipped with an air cushion chamber in order to equalise the resulting pressure surges. Discharge pressure is determined by the force which is required to open the discharge valve. In the case of adjustable discharge valves with spring return, discharge pressure can be adjusted with the discharge valve itself (spring preloading). Festo Didactic GmbH & Co. KG D2-7

260 1. Manual measurement Pump type (section drawing) Characteristics, technical data, range of applications Peristaltic pump With the peristaltic pump, only the pipe comes into contact with the medium to be delivered. Peristaltic pumps are used to deliver and dose aggressive media at low output rates. Progressive cavity pump Progressive cavity pumps are suitable for delivering sludge and paste-like media. Diaphragm pump Diaphragm pumps use a diaphragm in order to displace the medium to be delivered. Only the diaphragm and the pump casing come into contact with the medium. Diaphragm pumps are especially well suited for delivering aggressive media. D2-8 Festo Didactic GmbH & Co. KG

261 1. Manual measurement 1.2 Project task: mixing system Task description Information The ingredients fed to a mixing system are usually required in the defined quantity. Mixing systems of this sort are used, for example, to mix cement. A corresponding amount of water must be fed to the cement mixer in order to produce a specified concrete mix. The quantity is time-controlled. A prerequisite is that a constant volumetric flow rate must be maintained, e.g. 60 litres per hour. The relationships between resistance (degree of stopcock opening), the delivered amount of water and the required amount of time can be determined by means of an experiment. Run the experiment using the existing test setup with one tank. Festo Didactic GmbH & Co. KG D2-9

262 1. Manual measurement Experiment: flow measurement The relationships between resistance (degree of stopcock opening) and volumetric flow rate, as well as the amount of water delivered within a specific period of time will be examined. In doing so, we ll look into the question of how long it takes to pump 2 litres of water into the upper tank with various degrees of opening at stopcock V103. Task Read the volumetric flow rate at the sight glass in the flow meter. Set volumetric flow rate to the required flow rate. Fill the upper tank. Measure the time it takes for the water level to rise from the 0.5 to the 2.5 litre mark. Enter measured time in the table. Q [l/hr.] Time [s] Volumetric flow rate per unit of time D2-10 Festo Didactic GmbH & Co. KG

263 1. Manual measurement Evaluation and findings Task Plot the measured time values and the volumetric flow rate settings on the graph. Describe your observations on the experiment in a few short sentences: The delivered quantity of water depends on flow rate and duration. The greater the resistance in the piping system is (stopcock closed), the smaller the volumetric flow rate becomes. How long would it take to pump 150 litres of water if the flow rate were set to 90 litres per hour? Time for 90 litres: 1 hour; time for 1 litre: 0.67 minutes For 150 litres: t = 150 litres x 0.67 min. per litre = 100 minutes 1 hour and 40 minutes are required for 150 litres. It takes hours to fill the tank to the 2 litre mark. Calculate the volumetric flow rate for any desired setting for stopcock V101 with the help of the measured time value. Check the selected volumetric flow rate against the results of your calculation. 2 minutes = hours V 2 l Q = = = 60 l/h t h Festo Didactic GmbH & Co. KG D2-11

264 1. Manual measurement D2-12 Festo Didactic GmbH & Co. KG

265 2. Manual open-loop control 2.1 Project task: controlling water supply using hand valves Water storage tank Task description Information Water is pumped into a water tower from springs, rivers and lakes in order to supply households with drinking water. Water is directed to domestic households from the tower. The upper tank will be filled with water during the course of two experiments. There are two ways to fill a tank: either from above or below. The influence of these two methods on the filling process needs to be examined. Festo Didactic GmbH & Co. KG D2-13

266 2. Manual open-loop control Mechanical layout D2-14 Festo Didactic GmbH & Co. KG

267 2. Manual open-loop control Task Modification according to the PI flow diagram Supplement the PI flow diagram with a second tank as shown in the photo on the preceding page. Set up the basic layout with two tanks according to the revised PI flow diagram. V101 B102 V103 V102 FI 101 PI 103 B101 P101 V105 M Festo Didactic GmbH & Co. KG D2-15

268 2. Manual open-loop control Setting up the system, inspection Work step Done The basic setup with two tanks is required in order to conduct the experiments. Close stopcock V105. Check to make sure that all piping connections are correct. Inspect the piping connections. Fill the lower tank with 3 litres of water. Connect the system to the power supply units (24 V DC). Experiment: fill the upper tank from below. Close stopcocks V101 and V102, open stopcock V103 until the flow meter indicates 60 litres per hour. Experiment: fill the upper tank from above. Close stopcocks V102 and V103, open stopcock V101 until the flow meter indicates 60 litres per hour. Remove the 4 mm safety cable from the power supply unit and pull the mains plug. After the experiment has been completed, the system is drained via stopcock V Experiment: filling the upper tank from below Task Close stopcock V103 until the volumetric flow rate is 60 litres per hour. Measure the time it takes to reach various fill levels as of 500 ml (first mark after the taper). Observe pump pressure at the pressure gauge. D2-16 Festo Didactic GmbH & Co. KG

269 2. Manual open-loop control Fill level [ml] Time [s] Fill level [ml] Time [s] Fill level [ml] Time [s] Fill levels: filled from below Experiment: filling the upper tank from above Task Close stopcock V101 until the volumetric flow rate is 60 litres per hour. Measure the time it takes to reach various fill levels as of 500 ml. Observe pump pressure at the pressure gauge. Fill level [ml] Time [s] Fill level [ml] Time [s] Fill level [ml] Time [s] Fill levels: filled from above Festo Didactic GmbH & Co. KG D2-17

270 2. Manual open-loop control Evaluation and findings Task Which fundamental influence does hydrostatic pressure have on pump performance? If a pump delivers water in an upwards direction within a piping system, hydrostatic pressure within the piping system increases proportional to total head. This counterpressure generates resistance in the piping system. The greater the resistance, the more electrical power is consumed by the pump. Copy the measured values for filling from below and from above onto a diagram. Create a worksheet in Excel with the measured values and the two line diagrams. However, filling from below takes longer than filling from above. What causes this? The liquid flows into the tank in the form of a whirlpool due to its conical shape. The water in the tank represents an increasing resistance against the continuing flow of further liquid. The required energy is made available by reducing pressure. As a result, the system s volumetric flow rate drops. Furthermore, hydrostatic pressure in the piping system increases as the tank is increasingly filled. This acts like resistance in the piping system and thus reduces volumetric flow rate. D2-18 Festo Didactic GmbH & Co. KG

271 2. Manual open-loop control What effects can be observed at the surface of the water and with regard to turbulence during the two filling processes? Air bubbles and noise can be observed when filled from above. The liquid absorbs more air. In addition, reading the fill levels on the wall of the tank becomes difficult. Significantly fewer bubbles occur when filled from below. Turbulence in the water is considerably reduced as the fill level increases. Explain the relationship between the discharge rate and total head when an impeller pump is used. As total head increases, more and more pump pressure is required. With unchanging hydraulic performance due to constant electrical power, the discharge rate (volumetric flow rate) is reduced. Calculate the pump s total head. Refer to the data sheet on CD-ROM for technical data. p = g r h e pe h = g r kg pe = 0.3 bar = 30,000 Pa= 30,000 m s kg 30,000 2 h = m s = 3.06 m m kg s m 2 Festo Didactic GmbH & Co. KG D2-19

272 2. Manual open-loop control 2.2 Project task: controlling water supply using 2-way ball valve Information Process valves with pneumatic actuators are used more and more frequently in modern process engineering because they offer a host of advantages compared with electric and hydraulic actuators. Pneumatic actuators are easier to handle and they re very sturdy and economical. They re exceptionally well suited for use in potentially explosive atmospheres. Please refer to Festo s marketing manual, ABC of Process Automation, for further information. 1: Pump 2: Water storage tower 3: End users Operating principle Task description Information When filling the upper tank, the volumetric flow rate can be changed by opening or closing stopcock V101 or V103. The filling process and the control of the volumetric flow rate will now be partially automated by means of a pneumatically actuated 2-way ball valve. The upper tank is filled from above via the ball valve. Stopcock V102 for lower tank B101 is partially open (20%). D2-20 Festo Didactic GmbH & Co. KG

273 2. Manual open-loop control Mechanical layout, inspection Task Close stopcock V105. The ball valve is installed parallel to stopcock V101 as a bypass. The valve is mounted onto the rectangular profile and then connected to the piping system. The ball valve is opened and closed using a pneumatic actuator. The regulating unit consists of a brass ball valve (2) with semi-rotary actuator (4), a flange-mounted NAMUR valve (1) with solenoid coil (3) and a sensor box (5). The sensor box is used for electro-mechanical position signalling to the control and regulating unit with visual display for the user. Take into account addition information included in the data sheets on CD-ROM. Modify the piping layout so that the ball valve is correctly fitted. Check to make sure that all of the piping connectors are properly fitted. Check the piping connections to the impeller pump. Inspect the mechanical setup and create a test report (see CD-ROM). Festo Didactic GmbH & Co. KG D2-21

274 2. Manual open-loop control Plans Task Supplement the PI flow diagram for pneumatic control. V104 V101 B102 V103 V102 FI 101 PI 103 B101 P101 V105 M D2-22 Festo Didactic GmbH & Co. KG

275 2. Manual open-loop control Pneumatic circuit diagram Draw the pneumatic circuit diagram for the 5/2-way solenoid valve (1V1) with spring return and the semi-rotary actuator (1A1). 1A1 1V Z1 What requires special attention when connecting the three components, namely solenoid valve, semirotary actuator and ball valve? The 5/2-way solenoid valve with spring return controls the position of the semi-rotary actuator. The ball valve is opened and closed by the semi-rotary actuator. When connecting the start and stop switches, ensure that they cause the ball valve to open and close respectively. The initial position of the semirotary actuator is plainly defined by the spring return. Electro-pneumatic circuit diagrams Which possibilities exist for actuating the solenoid valve electrically? Variant 1: direct connection via detented control switch Variant 2: indirect connection via control switch and relay Variant 3: indirect connection with start and stop pushbuttons and relay Festo Didactic GmbH & Co. KG D2-23

276 2. Manual open-loop control Draw circuit diagrams for the three possible means of actuation. Make a decision in favour of one circuit. Mount the components onto the profile rail and wire the circuit. Explain your decision. 24 V 24 V S4 S4 K1 K1 1M1 P1 K1 1M1 P1 0 V 0 V Variant 1 Variant 2 24 V S5 K1 K1 K1 S6 K1 1M1 P1 0 V S5 START S6 STOP Variant 3 D2-24 Festo Didactic GmbH & Co. KG

277 2. Manual open-loop control Commissioning, report Task The pneumatic components, the ball valve and the functions of all utilised mechanical and electrical components such as switches, pushbuttons and impeller pump can now be commissioned and inspected. The system is filled with water so that the pump is prevented from running dry. The water is pumped back to the lower tank via the ball valve. Make a list of all of the characteristics and requirements for which the components have to be inspected in the commissioning report. Tick the appropriate field after completing each inspection. Characteristic, requirement for component Fulfilled Not fulfilled, comment Connect the 24 V and 0 V leads from the power supply unit to the terminals. Electrical control switch and start and stop pushbuttons wired Indicator light and pump wired, cable binders Ball valve mounted to semi-rotary actuator and solenoid valve Check pneumatic connection of the solenoid valve and the semi-rotary actuator Connect the solenoid valve to the control switch/relay (variants 1 and 2). Connect the solenoid valve to the pushbuttons (variant 3). Power supply unit connected to mains power (230 V AC) Switch the power supply unit on, the indicator light at the power supply unit lights up. Set control switch to Pump on, press the start pushbutton, the indicator light switches on and the pump runs. Variants 1 and 2: set control switch to Open ball valve, water flows into the tank. Set control switch to Close ball valve, water stops flowing into the tank. Variant 3: press Open ball valve pushbutton, water flows into the tank. Press Close ball valve pushbutton, water stops flowing into the tank. Press the stop pushbutton, the indicator light switches off and the pump stops running. Set control switch to Pump off, the indicator light goes out and the pump stops running. Inspector Date Commissioning report Festo Didactic GmbH & Co. KG D2-25

278 2. Manual open-loop control Experiment: filling using a pneumatically controlled 2-way ball valve Task Fill the lower tank manually with 3 litres of fresh water. Connect the system to the power supply unit (24 V DC). Open the ball valve and stopcock V102 (approx. 20%). Switch the pump on. Control the filling process by opening and closing the ball valve. Decide on a specific fill level, for example 2 litres, to which the upper tank should be filled. Switch the pump off upon when the fill level has been reached and drain back down to 1 litre. Repeat the filling process. Determine the volumetric flow rate by measuring how long it takes to reach a fill level of 2 litres. Close stopcock V102 to this end. Compare the filling process using the ball valve with the one using stopcock V Evaluation and findings Task Which advantages does the semi-rotary actuator offer in comparison with adjustment by means of a stopcock? The semi-rotary actuator responds more quickly than manual adjustment. The switch for actuating the semi-rotary actuator can be mounted at an external location, allowing for easy observation of the fill level. Volumetric flow rate through the ball valve is greater due to its larger cross section. The electrical solenoid valve makes it possible to intervene in the process with the help of an automated controller. Which difficulties are experienced when trying to maintain a specific fill level? The person who operates the semi-rotary actuator is required to compare the target value with the actual value. However, human reactions, and thus the process, are delayed. The target value is therefore often exceeded or fallen short of. The human system reacts sluggishly within the control circuit. D2-26 Festo Didactic GmbH & Co. KG

279 2. Manual open-loop control 2.3 Project task: electrical control of the pump in the water supply line Task description Information Filling the water tower is closely associated with water being withdrawn by one or more households. This issue can be clarified with the help of two experiments. In addition, control of the system should also be expanded electrically. Wiring of the electrical components will be adapted in line with the task at hand. The first experiment addresses the question of how the fill level of the upper tank can be kept constant when varying amounts of water are withdrawn. During the second experiment we ll operate the pump with variable voltage values and clarify the relationship between voltage, amperage and volumetric flow rate. Costs incurred during operation of the system will also be ascertained Setting up the system, inspection The system will be operated using the basic setup with two tanks. There s no need to remove the pneumatic process actuator, although it s not required for the experiment. Work step Done Close stopcock V105. Check to make sure that all piping connections are correct. Check the piping connections to the impeller pump. Fill the lower tank with 3 litres of water. Connect the system to the power supply unit (24 V DC). 1 st experiment: fill the upper tank from below. Close stopcock V101, open stopcock V103 such that an initial flow rate of 60 litres per hour is indicated at the flow meter. 2 nd experiment: fill the tank using variable voltages for the pump. Fill the upper tank from below, close stopcock V101, open stopcock V103 so that the flow meter indicates 60 litres per hour. Remove the 4 mm safety cable from the power supply unit and pull the mains plug. After the experiment has been completed, the system is drained via stopcock V105. Festo Didactic GmbH & Co. KG D2-27

280 2. Manual open-loop control Relay circuit with pushbuttons Information The system will be expanded electrically. The detented switch will now serve as a mains switch. The indicator light will still indicate the operating state. The system will be started by pressing a green pushbutton and stopped by pressing a red pushbutton. Briefly pressing the respective pushbutton is enough to start or stop the system. Task Which type of circuit has to be set up when pushbuttons are used? Which additional component is required? A self-latching electrical circuit, because the pushbutton only generates a short pulse. A relay is used, which closes the electrical circuit until it is interrupted. Why do machines have to be controlled with a self-latching circuit instead of being operated with switches? In actual practice, an on/off switch is impermissible because for safety reasons the system would have to be protected against being restarted after a power failure or in the event of power interruption due to an emergency stop. The system can only be restarted by activating a pushbutton. D2-28 Festo Didactic GmbH & Co. KG

281 2. Manual open-loop control Electrical circuit diagram Task The system has to be rewired for the following experiments. Draw the expanded circuit diagram with two pushbuttons, a detented mains switch and an indicator light. Identify the components. 24 V 1 S S2 K1 K1 K1 S3 K1 P1 P101 M 0 V Add the connecting cables to the image with the electrical components to indicate how they have to be wired according to the circuit diagram. Festo Didactic GmbH & Co. KG D2-29

282 2. Manual open-loop control Electrical wiring and setup plan Task The system will need to be rewired for the following experiments. Assemble the electrical components. They can be prewired before they re mechanically attached to the profile. Proceed according to your layout sketch and the setup plan you prepared in the Planning section of the chapter on Plant construction. Base yourself on the circuit diagram with regard to wiring. Write down your assembly and wiring procedures. Fill out the following setup plan after you have mounted and wired the components. See part D1 Plant construction with solutions, chapter D2-30 Festo Didactic GmbH & Co. KG

283 2. Manual open-loop control Commissioning, electrical testing and report Information The new circuit with the pushbuttons and the functions of the existing electrical components, such as the impeller pump, must now be started up and inspected. This is done by filling the system with water so that the pump is prevented from running dry. The water is simply pumped around in a circular movement, i.e. out of the bottom tank via the impeller pump and back into the lower tank from the upper tank. Task Make a list of all the characteristics and requirements for which the electrical components have to be inspected in the commissioning report. Tick the appropriate entry after completing each inspection. Characteristic, requirement for component Fulfilled Not fulfilled, comment Connect the 24 V and 0 V leads from the power supply unit to the terminals. Electrical control switch and start and stop pushbuttons wired Indicator light wired Pump wired Cables secured with cable binders Power supply unit connected to mains power (230 V AC) Switch the power supply unit on, the indicator light at the power supply unit lights up. Set control switch to On, press the start pushbutton, the indicator light switches on and the pump runs. Press the stop pushbutton, the indicator light switches off and the pump stops running. Set control switch to On, press the start pushbutton, the indicator light switches on and the pump runs. Set control switch to Off, the indicator light switches off and the pump stops running. Set control switch to Off, press the start pushbutton, the indicator light switches off and the pump stops running. Power supply unit Off, system is shut down Inspector Date Festo Didactic GmbH & Co. KG D2-31

284 2. Manual open-loop control Experiment: filling while simultaneously withdrawing water The upper tank needs to be filled from below with a constant volumetric flow rate. Stopcock V101 is closed, stopcock V103 simulates resistance in the system by being opened. It s opened until the water flows into the upper tank at a volumetric flow rate of 60 litres per hour. At the same time, the stopcock for discharge to the user is open (approx. 20%). Measure the time it takes to fill the upper tank. Add the values to the table. Fill level [ml] Time [s] Fill level [ml] Time [s] Fill level [ml] Time [s] Filling with open discharge D2-32 Festo Didactic GmbH & Co. KG

285 2. Manual open-loop control Evaluation and findings Task Create a line diagram for fill level relative to time. What does the curve tell you? Pressure rises as the fill level increases, and volumetric flow rate is reduced. As the fill level increases, the amount of discharged water increases until an equilibrium is established between intake and discharge. What s meant by the term self-latching circuit? The electrical circuit is closed by means of a normally open contact in the relay and can only be interrupted by activating the normally closed contact in the parallel current path. Restarting is only possible with the start pushbutton. Festo Didactic GmbH & Co. KG D2-33

286 2. Manual open-loop control Experiment: pump start-up performance and power The water level in the upper tank can be kept constant while water is withdrawn by changing the volumetric flow rate. Volumetric flow rate will be influenced in this experiment by changing electrical voltage at the power supply unit. You ll need a power supply unit with variable output voltage for this experiment. We ll fill tank B102 with water from below. Stopcock V101 is closed. Stopcock V103 is opened to such an extent that a volumetric flow rate of max. 400 litres per hour is achieved with 24 V DC. Stopcock V102 is only partially opened (approx. 20%). Task What are the volumetric flow rates when the pump is operated with various voltages ranging from 24 to 0 V DC? How does current consumption at the impeller pump change? Record the measured values and add them to the table. Voltage U [V] Current I [A] Electrical power P [W] = U I Volumetric flow rate Q [l/h] Pressure p e [bar] Hydraulic power P [W] = p e Q < < 0.1 Filling using varying pump voltages D2-34 Festo Didactic GmbH & Co. KG

287 2. Manual open-loop control Evaluation and findings Task Draw a circuit diagram with a voltmeter and an ammeter. 24 V A V P101 M P1 0 V Create a diagram with two curves, one for volumetric flow rate Q and the other for electrical current I relative to voltage U. What do the curves tell you about the pump s start-up characteristics? The pump doesn t start until a voltage of approximately 8 V is reached. Friction in the pump is too great for it to run with smaller voltages. Festo Didactic GmbH & Co. KG D2-35

288 2. Manual open-loop control What is the relationship between the three parameters current, voltage and volumetric flow rate? When voltage is increased, volumetric flow rate rises. When volumetric flow rate is increased, electrical current rises as well. The pump doesn t start delivering water until a voltage of approximately 9 to 10 V is achieved. Calculate electrical and hydraulic power, as well as efficiency, for a volumetric flow rate of 200 litres per hour. P P elektr hydr. P h = P = U I = 16 V 0.4 A = 6.4W = Q hydr. elektr p e dm min = 200 l/h 0.3 bar = min 60 s 1.67 W = = W 3 N 3 cm cm m = 1.67 W 2 dm 10dm What is the relationship between the impeller pump s current consumption and its output performance? Volumetric flow rate must be increased in order to increase pump performance. Amperage rises because electrical power has to be increased. How high are the electrical power costs when the pump is operated 8 hours a day for one month (30 days) with a volumetric flow rate Q of 200 litres per hour? The cost of electrical power is roughly 0.17 per kwh. Costs for 1 month = 0.17 per kwh x kw x 8 hours x 30 days = D2-36 Festo Didactic GmbH & Co. KG

289 3. Manual closed-loop control 3.1 From a control loop system to a control circuit Information Our fill-level system includes open and closed-loop control processes. How they differ will become clear when we consider their respective characteristics. Every process has an input quantity and an output quantity. For example, if we switch on the power supply unit which supplies electrical power to the impeller pump, electrical current (input quantity) flows and the pump begins to rotate and deliver water (output quantity). The input quantity affects the output quantity. Open-loop control However, if the output quantity is not fed back to the input as a signal so that, for example, the power supply unit is switched off when the tank is full, we speak of an open-loop control process. In the case of open-loop control, a process is started and stopped without periodically comparing and changing the variables to be controlled. Closed-loop control If we want to regulate the filling process with a closed-loop control process, we need to continuously record the fill level, for example via observation or a sensor and continuously compare the current fill level (actual value) with the desired fill level (target value). Whenever deviation from the target value is detected, an attempt is made to match the controlled variable (actual value) to the reference variable (target value) by means of appropriate control measures. This type of control has a closed control path, also known as control circuit. Comparison of a human being as a controller and automated control using fill level monitoring as an example: Human being as a controller Specified value Observation Make note of value Open or close valve manually Automated control Setpoints Actual value detection (ultrasonic sensor) Archive Transmit electrical manipulated variable to valve or pump Regulator optimisation Festo Didactic GmbH & Co. KG D2-37

290 3. Manual closed-loop control Basic terminology for closed-loop control technology Controlled variable x The quantity to be controlled is designated controlled variable x. In our example this is the fill level or the volumetric flow rate. Manipulated variable y Automated closed-loop control is only possible if the system can be manipulated and the controlled variable influenced. The extent to which the controlled variable can be influenced is manipulated variable y. In the case of closed-loop control of a fill level, the manipulated variable is the degree to which the stopcock is opened, and in the case of closed-loop control of the volumetric flow rate, it s electrical current at the pump. Reference variable w Reference variable w is also known as the controlled variable setpoint. It specifies the desired value of the controlled variable. The reference variable may remain constant over time, but it may also change. The real value of the controlled variable is called the actual value. Disturbance variable z All controlled systems are subject to disturbance. These are often the only reason that closed-loop control is necessary at all. In our example, the stopcock for discharge to the consumer is opened and the fill level changes or the valve setting for filling the upper tank is changed which results in a change to the volumetric flow rate. These interfering influences are designated disturbance variable z. The controlled system is the part of the overall setup within which the controlled variable must be matched with the value of the reference variable. The controlled system can be represented as a system with the controlled variable as the output quantity and the manipulated variable as the input quantity. System deviation xd The difference between the reference variable and the controlled variable is called system deviation xd or e. This difference is calculated as follows: e = w - x Closed-loop controller It is the task of the closed-loop controller to keep the controlled variable as close as possible to the reference variable. The value of the controlled variable is continuously compared with the reference variable by the closed-loop controller. The value of the manipulated variable is calculated on the basis of this comparison, as well as control response, and is read out. Controlled variable x Actual value + System deviation xd Control response ( Algorithm) Manipulated variable y Reference variable w Setpoint Basic function of a regulator D2-38 Festo Didactic GmbH & Co. KG

291 3. Manual closed-loop control Control circuit The control circuit contains all the components of the closed loop that are required for automated closedloop control. Controlled system Controlled variable x ( Actual value) Manipulated variable y Controller Reference variable w ( Setpoint) Block diagram of a control circuit Controlled system The controlled system is the part of the machine or system within which the controlled variable is to be matched to the specified value and the disturbance variables are offset by the manipulated variables. The manipulated variable is not the controlled system s only input quantity; interfering influences also occur as input variables. In order to select a closed-loop controller for a controlled system, the performance of the controlled system must first be known. The control technician is not interested in the technical sequences which take place within the controlled system, but only in system performance. 3.2 Project task: controlling the fill level in the tanks Task description In the case of water supply, households withdraw various quantities of water. Two experiments will be used to clarify how a specified fill level can be constantly maintained in the upper tank. Closed-loop control is possible in different ways: Open and close stopcock V101 or V103. Switch the pump on and off. Change voltage supplied to the pump. During the first experiment, manually keeping the fill level constant in the upper tank, we ll attempt to regulate the fill level by switching the pump on and off. We can supply the pump with voltages ranging from 0 to 24 V using the power supply unit. The pump is switched on and off with the pushbuttons. Observe the control process. During the second experiment, controlling the fill level using an analogue controlled pump, we ll operate the pump with variable voltage ranging from 0 to 24 V DC, and thus control the volumetric flow rate and influence the tank s fill level within a certain period of time. You ll need a power supply unit with adjustable output voltage to this end. Festo Didactic GmbH & Co. KG D2-39

292 3. Manual closed-loop control Setting up the system, inspection Task Close stopcock V105. Check to make sure that all piping connections are correct. Check to make sure that all electrical wiring connections are correct. Fill the lower tank with 3 litres of water. Connect the system to the respective power supply unit (max. 24 V DC). Carry out the experiment. Remove the 4 mm safety cable from the power supply unit and pull the mains plug. After the experiment has been completed, the system is drained via stopcock V Experiment: manually keeping the fill level constant in the upper tank The upper tank should always have a constant level of water of 2000 ml. Varying quantities of water are withdrawn via stopcock V102 and supplied to a household (lower tank B101). Task Switch the pump on and off with the pushbutton so that the fill level remains constant. D2-40 Festo Didactic GmbH & Co. KG

293 3. Manual closed-loop control Evaluation and findings Task Enter the following control technology terms to the block diagram of the system: actual value x, setpoint w, manipulated variable y, switching difference sd, disturbance variable z, closed-loop controller, controlled system. Controlled system w Controller y V101 Sd B102 x Disturbance variable z V103 V102 FI 101 PI 103 B101 P101 V105 Reference variable w ( Setpoint, fill-level) M Controlled variable x ( Actual value, fill-level) Manipulated variable y ( Voltage) A fill level of 2100 ml is established as an upper limit and 1900 ml is the lower limit. This results in a switching difference sd of 200 ml. Why are these limit values specified? In the case of manual control, the respective setpoints are usually only achieved with a certain amount of delay. In order to provide the closed-loop controller with a certain amount of leeway, a switching difference is established within which the control process functions well. Festo Didactic GmbH & Co. KG D2-41

294 3. Manual closed-loop control Establish the inequality for switching the pump on and off. Inequality is meant here as the greater or smaller relation amongst the actual value, the setpoint and the switching difference. Pump on: actual value < setpoint - switching difference / 2 Pump off: actual value > setpoint + switching difference / 2 Represent the filling process graphically as a line diagram. Plot the fill level on the ordinate (Y-axis) and time on the abscissa (X-axis). What do we call this type of control? In which types of devices do closed-loop controllers operate on the basis of this principle? Provide several examples. Two-step control Iron, stove, hardening furnace etc. Which features characterise this type of control? There are only two states with two-step control: signal on and signal off, i.e. the electrical circuit is closed or open. This type of control is also known as discontinuous control. It is very difficult to keep the setpoint constant. A switching difference (tolerance) is required in order to be able to manage the control process. D2-42 Festo Didactic GmbH & Co. KG

295 3. Manual closed-loop control Experiment: controlling the fill level using an analogue controlled pump Once again, the tank should be filled to a constant level of water of 2000 ml. Varying quantities of water are withdrawn via stopcock V102 and supplied to a household (lower tank B101). The volumetric flow rate is influenced by changing speed, thus enabling the system to react to irregular withdrawals of fresh water from upper tank B102. Vary the pump speed by increasing and decreasing voltage supplied by the power supply unit and observe the volumetric flow rate Evaluation and findings Task Allocate the terms and characteristics from the description of the experiment to the control technology terms. Controlled variable: volumetric flow rate Manipulated variable: electrical voltage Reference variable: 2000 ml fill level Disturbance variable: stopcock V102 First of all, fill the upper tank from above with stopcock V102 fully closed. Then open stopcock V102 according to the specifications in the table and describe what you observe while controlling the process. React to changes in the fill level by varying the power output voltage. Stopcock V102 Closed Control process, observations Control is not possible. 10% open It takes a long time for the control process to change a higher fill level down to a lower level. 50% open The fill level can be controlled effectively with voltage values within a range of 10 to 14 V. 100% open Excessive turbulence, neither fill level nor good flow rate are achieved because there s too much air in the system. Test report Why is this also known as continuous control? The controlled variable is controlled by means of the manipulated variable, namely voltage. This is done continuously. When continuous controllers are involved, manipulated variable y is read out as an analogue signal so that it can be adapted to the process in an infinitely variable manner. Festo Didactic GmbH & Co. KG D2-43

296 3. Manual closed-loop control Create a graphic representation of the closed-loop control process. Draw a graph which shows the fill level over a period of time as a strictly qualitative characteristic Experiment: pressure and flow control Separately conduct pressure control and flow rate control, also known as volumetric flow rate control. Control pressure and volumetric flow rate by varying the output voltage of the power supply unit between 0 and 24 V DC. Set up the circuit according to the PI flow diagrams. Pressure control V103 PI 103 B101 P101 V105 M D2-44 Festo Didactic GmbH & Co. KG

297 3. Manual closed-loop control Flow rate control V103 FI 101 B101 P101 V105 M Evaluation and findings Task Determine the manipulated variable required for maintaining constant pressure, as well as for maintaining constant volumetric flow rate, with varying resistance (stopcock V103). Target pressure (w) = 200 mbar Target volumetric flow rate (w) = 100 l/hr. Add the voltage values for the various stopcock settings to the table. Conduct the experiment once with constant pressure and once with constant volumetric flow rate. Mark the opening values of the stop cock on the rotary cap so that the experiment can be duplicated exactly. Setting for stopcock V 103 Pressure control, voltage U (y) where p e = 200 mbar (w) Flow rate control, voltage U (y) where Q = 100 l/hr. (w) Open 20% closed 40% closed 60% closed 40% closed 20% closed Values table Festo Didactic GmbH & Co. KG D2-45

298 3. Manual closed-loop control What is the relationship between the stopcock setting and pressure or volumetric flow rate? Constant pressure: The further the stopcock is opened, the less resistance there is and the higher the voltage (manipulated variable) has to be set. Constant volumetric flow rate: The further the stopcock is opened, the less resistance there is, and the lower the voltage (manipulated variable) has to be set. D2-46 Festo Didactic GmbH & Co. KG

299 4. Evaluation of learning objectives for manual measurement, open-loop and closed-loop control 1. How do pressure and volumetric flow rate of a liquid respond when resistance is increased in the inlet line which feeds the tank? Pressure rises and volumetric flow rate drops litres of water have to be recirculated using a volumetric flow rate of 200 litres per hour. How long does the pump have to work? 200 litres in 1 hour = 60 minutes 10 litres in 3 minutes 70 litres in 21 minutes 3. Which physical quantities determine hydrostatic pressure? Hydrostatic pressure is the pressure in a liquid which is at rest. It depends on gravitational acceleration g, density r and capillary rise h. Hydrostatic pressure increases as the water column rises. 4. Why does it take longer to fill the upper tank in our system from above than from below? Hydrostatic pressure has nearly no effect at all at a minimal filling height. The fact that water flows into the tapered portion of the tank from below in the form of a whirlpool causes resistance which further increases as the fill level rises. 5. The filling nozzle at the top can be fitted at a level of, for example, 1.1 metres. How much pump pressure would be required to reach this filling height? Min. P e : 0.11 bar 6. Describe how a self-latching circuit functions. Which components are required for such a circuit? When a relay s electrical circuit is closed (brief signal at the ON button), it s maintained by means of a normally open contact in the relay. The circuit is interrupted again by means of a normally closed contact (OFF button). Festo Didactic GmbH & Co. KG D2-47

300 3. Manual closed-loop control 7. The upper tank is continuously filled with water and a certain amount of water is discharged from the tank. In a diagram, the process would be designated asymptotic, i.e. it approaches a specific value. Sketch a graph which shows the fill level over a period of time as a qualitative characteristic. 8. Describe in your own words the procedures used for connecting an ammeter and a voltmeter in order to record pump values. The ammeter is connected to the current path upstream of the pump. The voltmeter is connected parallel to the pump. 9. You re working with variable voltage within a range of 0 to 24 V. How do volumetric flow rate and amperage I change when voltage is reduced from 24 to 0 V. When voltage is reduced, volumetric flow rate and amperage drop. 10. The maximal Pump efficiency is h = What is the meaning of this value with regard to our experimental system and which effects does efficiency have in actual practice? In this case it means that usable pump power is about 25% of applied motor power. In actual practice it must be determined whether or not the additional benefits offered by a pump which is not susceptible to contamination outweigh achievable power. Of course an attempt is made in actual practice to artificially boost efficiency. D2-48 Festo Didactic GmbH & Co. KG

301 3. Manual closed-loop control 11. Sketch a pneumatically actuated 5/2-way valve with spring return. See Festo pneumatics data sheets. 12. Which fundamental advantages are offered by a 2-way ball valve with electro-pneumatically actuated actuator as opposed to manual operation? The valve can be opened by a controller. 13. Describe the terms open-loop control and closed-loop control using a radiant heater as an example. Open-loop control: Closed-loop control: See Control in the Teachware for the solution. 14. How are manipulated variable y and controlled variable x related? Manipulated variable y is a voltage value U used to vary pump speed. This changes volumetric flow rate through the pump and thus the controlled variable, for example the fill level of the tank. 15. How does a two-step controller work? A two-step controller switches back and forth between two adjustable limit values. The difference between the upper and the lower limit values is known as the switching difference or system deviation. 16. Why is an excessively small switching difference disadvantageous? A small switching difference causes the pump to be switched on and off very frequently and thus results in rapid wear and tear (number of switching cycles). 17. What s the fastest way to get the system adjusted to the setpoint? By continuously adjusting the inlet valve or voltage at the pump. Festo Didactic GmbH & Co. KG D2-49

302 3. Manual closed-loop control 18. What is the control process called with which the manipulated variable can be continuously varied? Continuous control with analogue controlled, manipulated value. 19. Pressure needs to be kept constant within the fill-level system, even when the volumetric flow rate is continuously increased. Which parameter must be changed within the system? When resistance in the piping system drops, voltage supplied to the pump must be increased in order to maintain constant pressure. 20. How can the volumetric flow rate within the fill-level system be kept constant, even though the pump needs to be operated in an energy-saving fashion? If the inlet valve is opened further, volumetric flow rate increases, pump voltage can be reduced and power consumption is reduced. D2-50 Festo Didactic GmbH & Co. KG

303 Part D3 Practice-based learning: automated measurement, open-loop and closed-loop control with solutions 1. Basic principles D Computer-aided control technology D System conversion for automated measurement and control technology D Automated measurement D Project task: bath recirculation D Task description D Setting up the system, inspection D Experiment: operating the pump with variable voltage values D Project task: pressure measurement during recirculation D Task description D Setting up the system, inspection D Experiment: pressure measurement using a pressure sensor D Project task: flow measurement D Task description D Setting up the system, inspection D Experiment: flow measurement using a flow sensor D Project task: determine the fill level of the upper tank D Task description D Setting up the system, inspection D Experiment: measuring the fill level using an ultrasonic sensor D Automated open-loop control D Project task: filling process D Task description D Setting up the system, inspection D Experiment: metered filling via the pneumatic actuator D Project task: filtering process in a galvanising plant D Task description D Setting up the system, inspection D Experiment: determining pressure and volumetric flow rate D Experiment: creating a characteristic pump curve D Project task: water supply D Task description D Setting up the system, inspection D Experiment: filling the tank from below using the pump D Experiment: filling the tank from above using the pump D Experiment: filling the tank from above while simultaneously withdrawing water D Project task: dosing an amount of liquid D Task description D Experiment: dosing an amount of liquid D3-38 Festo Didactic GmbH & Co. KG D3-1

304 3. Manual closed-loop control 4. Automated closed-loop control D Project task: controlling the fill-level regulation using a two-step controller D Task description D Setting up the system, inspection D Commissioning D Experiment: controlling the fill level using a two-step controller D Project task: controlling the fill level using a continuous controller D Task description D Experiment: controlling the fill level using a continuous controller D Experiment: controlling the fill level using a proportional controller D Experiment: controlling the fill level using an integral controller D Experiment: controlling the fill level using a proportional-integral controller (parallel P and I components) D Project task: refrigerating plant D Task description D Setting up the system, inspection D Commissioning report D Experiment: flow control using a proportional-integral controller D Evaluation of learning objectives for automated measurement, open-loop and closed-loop control D3-59 D3-2 Festo Didactic GmbH & Co. KG

305 1. Basic principles 1.1 Computer-aided control technology Information This is an introduction to automated control technology and is based on the knowledge of manual control that has already been acquired. You ll learn the basics of computer aided control with the help of practical examples. Every control circuit consists of a controlled system and a controller. 1 Setpoint specification 2 System deviation = setpoint - actual value System deviation is calculated by means of a control function and is transmitted to the controlled system as a manipulated variable (3). The control function is generally processed with the help of software. 3 Manipulated variable 4 The manipulated variable must be boosted so that the actuator s final control element receives a signal with which it can work. 5 The controlled system (e.g. fill level) is changed by means of the manipulated variable. 6 The controlled system s actual value is measured and fed back to point 2. In most cases, the actual value must be electronically converted. Software solutions for a controller in a PC or a PLC work in a cyclical fashion, i.e. points 2 through 6 are run continuously. Festo Didactic GmbH & Co. KG D3-3

306 1. Basic principles Examples of controlled systems: Maintain a constant fill level in a tank Change and maintain temperature in a room Keep motor speed at a specified value Travel accurately to an axis position Maintain constant pressure in a piping system Types of controllers: Discontinuous controller These controllers are characterised by the fact that their manipulated variables are only capable of changing between the on and off states, i.e. two-step controller. Continuous controller With continuous controllers, the manipulated variable is infinitely adjustable, e.g. PID controller. In conventional control technology, a difference is made between the following controllers according to how the manipulated variable is determined (simplified excerpt). Controller Graphic symbol Determination of the manipulated variable via the control function 2-step controller The manipulated variable is compared with an upper and a lower limit value. P controller System deviation is influenced by means of a factor. I controller The sum of all system deviations is influenced by means of a factor. PI controller The characteristics of the P-controller and the I-controller are combined. PID controller The manipulated variable is determined by the D parameter based on the time factor by which system deviation is changed. D3-4 Festo Didactic GmbH & Co. KG

307 1. Basic principles Technical learning objectives Participants will: Learn to convert electrical actuation to actuation with a PC Become familiar with how to set up and adjust sensor signals Become familiar with practical PC measurement technology Learn to differentiate between various types of controllers and control circuit performance Learn to use continuous and discontinuous control for automated measurement, open-loop and closedloop control Become familiar with using a PC as a control and regulating device in combination with FluidLab PA software 1.2 System conversion for automated measurement and control Information The system is, as in the section on manual measurement, open-loop and closed-loop control, equipped with a control panel used for manual measurement, open-loop and closed-loop control. The system must now be modified so that signals can be transmitted via the EasyPort PC interface. The depicted control panel is not used for automated measurement and control. Festo Didactic GmbH & Co. KG D3-5

308 1. Basic principles The basic setup for automated measurement, open-loop and closed-loop control will be demonstrated using pump control as an example: Item Digital pump control, on/off PC transmits Bit3 to EasyPort. EasyPort generates a voltage signal (relay) of 0 V or 24 V. Motor runs at nominal power with 24 V. Analogue control PC transmits a decimal value EasyPort generates a control The motor controller boosts the (e.g. double word) which corresponds to a voltage within a range of 0 to 10 V. signal of 0 to 10 V. signal to within a range of 0 to 24 V. The motor runs at an infinitely adjustable speed. D3-6 Festo Didactic GmbH & Co. KG

309 1. Basic principles Task The system will be equipped with a preassembled I/O board. Carry out conversion as described in the following steps: 1. Switch off supply power. 2. Unplug the laboratory cable via with safety valve socket. 3. Unplug the pump motor. 4. Mechanical removal of the control panel from the rectangular profile System with control panel System without control panel Festo Didactic GmbH & Co. KG D3-7

310 1. Basic principles 5. Screw the preassembled I/O boards to the rectangular profile. Important modules are required for operation via a PLC or via a PC and EasyPort, in order to process measured values and control the actuator. Assembly Figure Description F-U converter for flow sensor Depending on the flow rate, the flow sensor generates a pulse frequency within a range of 40 to 1200 Hz. This pulse frequency is converted to a voltage value within a range of 1 to 10 V by the F-U converter. Motor controller The analogue manipulated variable of 0 to 10 V from the EasyPort or a PLC is boosted to 0 to 24 V and an appropriate amperage by the motor controller. Amperage must be limited in order to ensure safe operation. Modules on the I/O board Further information is included in the data sheets on the CD-ROM. D3-8 Festo Didactic GmbH & Co. KG

311 1. Basic principles 6. Connect the EasyPort to the I/O board with a SysLink cable. 7. Connect the EasyPort to the PC (USB or serial cable). 8. Connect a 24 V power supply unit. 9. Connect the outputs for analogue and binary signals between the I/O board and the EasyPort. Festo Didactic GmbH & Co. KG D3-9

312 1. Basic principles 10. Install the software. Install the EasyPort driver from the EasyPort CD-ROM. Install FluidLab PA. 11. Test the system. Supply EasyPort with power. Start FluidLab PA software. Note After starting the software, a message indicates whether or not a connection has been successfully established. If this is not the case, check all connections within the system. Otherwise, exit the software and disconnect the USB plug. Reinsert the USB plug after 5 seconds. Start the software again. 12. Select the Setup menu. The outputs can be activated with the sliders in the user interface. D3-10 Festo Didactic GmbH & Co. KG

313 1. Basic principles 13. Assignment of inputs and outputs on the I/O board: Name Device Abbreviation Note Digital output 0 2-way ball valve with pneumatic actuation A0 Spring return Digital output 2 Changeover relay A2 Relay = 0: pump is binary controlled Relay = 1: pump is analogue controlled (0 to 10 V) Digital output 3 Pump A3 Analogue output 0 Pump AOUT 1 Analogue input 0 Fill level (ultrasonic) AIN 0 Analogue input 1 Flow sensor AIN 1 Analogue input 2 Pressure sensor AIN 2 1: I/O terminal 2: Analogue terminal 3: Relay 4: Motor controller 5: Measuring transducer 6: Starting current limiter 7: Motor clamp 8: H-rail Complete layout plan Festo Didactic GmbH & Co. KG D3-11

314 1. Basic principles D3-12 Festo Didactic GmbH & Co. KG

315 2. Automated measurement 2.1 Project task: bath recirculation Task description Depending on the setup, water can be transferred to lower tank B101 or pumped into upper tank B102 with the pump. The pump can be operated by switching 24 V supply power on or off (output 3). Alternatively, it can be variably supplied with control voltage within a range of 0 to 10 V (analogue output 0). The control signal is boosted by means of a motor controller. The type of control used (on/off or analogue) is selected with a changeover relay (output2). Festo Didactic GmbH & Co. KG D3-13

316 2. Automated measurement D3-14 Festo Didactic GmbH & Co. KG

317 2. Automated measurement Task The pump will be connected and tested during the following experiment. Simply pumping water into lower tank B101 is sufficient for this function test. Set up the fill-level system with one tank as specified in section 1.1.1, part A. Base yourself on the PI flow diagram. Before commissioning, make sure all the project kit s modules and piping function correctly and do not leak. Replace any damaged parts. V101 B102 V103 V102 FI 101 PI 103 B101 P101 V105 M Festo Didactic GmbH & Co. KG D3-15

318 2. Automated measurement Setting up the system, inspection Plug the pump into the I/O board. The allocations are included in the circuit diagram on the CD-ROM. Set up the water circuit (see flow diagram). Note The pipe connection to tank B102 must be interrupted or equipped with a closed stopcock. Close V101 and V105, open V102 and V103. Fill B101 approximately half full with water. Connect the 24 V power supply unit to mains power. Switch the power supply unit on. Start the software (FluidLab PA). Open the Setup menu in the software and operate the system using the buttons (see below). D3-16 Festo Didactic GmbH & Co. KG

319 2. Automated measurement Experiment: operating the pump with variable voltage values Select each of the values listed below and document your observations. No. Digital outputs Analogue outputs (set at sliders) Pump (observe) 1 A3 = on A2 = off 0 V Pump runs at high speed 2 A3 = on A2 = on 0 V Pump off 3 A3 = off A2 = on 4 V Pump runs at low speed 4 A3 = off A2 = on 8 V Pump runs at high speed 5 A3 = off A2 = on 10 V Pump runs at max. power 2.2 Project task: pressure measurement during recirculation Task description Pressure plays a significant role in fluid systems. In practice pressure changes due to reactions which occur in mixtures, during filtration or recirculation, and must be continuously recorded and documented. In order to be able to read out the value with the help of a PC, the pressure gauge with indicator is replaced by a pressure sensor. As a rule, pressure sensors require 24 V DC supply power and generate an analogue voltage signal within a range of 0 to 10 V, which is proportional to pressure. The purpose of the pressure sensor is to measure liquid pressure directly downstream of the pump. According to the data sheet, the sensor reads out a voltage of 0 to 10 V within a pressure range of 0 to 400 mbar. Festo Didactic GmbH & Co. KG D3-17

320 2. Automated measurement Setting up the system, inspection Switch the system off and pull the mains plug. Drain the water via stopcock V105. Install the pressure sensor downstream of the pump. Electrically connect the pressure sensor in accordance with the circuit diagram (CD-ROM). Valve settings: V101 and V105 closed, V102 and V103 open, remove piping to tank 102, insert a blanking plug into the end of the pipe or install a stopcock in the bottom inlet and close it. Fill with water. Set up the software. Set the pressure value at the PC after opening the Setup menu: Determine factor and offset: calculate the physical display value: Physical value = sensor voltage factor + offset If values are to be displayed in bar, the factor is calculated as follows: The following data are specified for the sensor: a pressure range of 0 to 0.4 bar and a voltage range of 0 to 10 V. 0.4bar Factor = = V - 0V D3-18 Festo Didactic GmbH & Co. KG

321 2. Automated measurement Default setting for the pressure duct: factor = 0.04 and offset = 0.0 (see figure) 1 Voltage read out by the sensor 2 Factor 3 Offset 4 The signal can be filtered (attenuated). The higher the number, the greater the attenuation. In order to ensure correct representation of the scales in the diagrams, it s important to always enter the maximum physical value and the appropriate unit of measure (see the two right-hand columns in the screenshot). Task At a pressure of 0 to 10 bar, the pressure sensor reads out a voltage within a range of 2 to 10 V. Calculate factor and offset. Final value 10 Factor = == = 1.25 Final voltage -Initial voltage 10-2 Offset = -Factor Initial voltage = = -2.5 Festo Didactic GmbH & Co. KG D3-19

322 2. Automated measurement Experiment: pressure measurement using a pressure sensor Operate the pump with the three following voltage values and make a note of what you observe at the software pressure display. No. Digital outputs Analogue outputs (set at sliders) Pressure display (observe) 1 A3 = on A2 = off 0 V 0.3 bar 2 A3 = off A2 = on 5 V 0.1 bar 3 A3 = off A2 = on 10 V 0.27 bar 2.3 Project task: flow measurement Task description The purpose of the flow sensor is to measure the pump s volumetric flow rate. Liquid flows through the measuring transducer and causes a vane to rotate. The vane is equipped with an inductive sensor which generates pulses. The pulses are converted into a voltage which is proportional to the volumetric flow rate by an F/U converter. At a volumetric flow rate of 0 to 7.5 litres per minute, the flow sensor generates a voltage signal within a range of 0 to 10 V Setting up the system, inspection Switch the system off and pull the mains plug. Drain the water via stopcock V105. Install the flow sensor downstream of the pump. Connect the flow sensor electrically according to the circuit diagram (see CD-ROM). Fill with water. Start the software and open the Setup menu. Set factor and offset: the physical display value is calculated as follows: Physical value = sensor voltage factor + offset Flow rate display in litres per minute, factor = 0.75, offset = 0 D3-20 Festo Didactic GmbH & Co. KG

323 2. Automated measurement Experiment: flow measurement using a flow sensor Change the pump speed again by setting supply voltage to three different settings and make a note of what you observe at the flow rate display in the software. No. Digital outputs Analogue outputs (set at sliders) Flow rate display (observe) 1 A3 = on A2 = off 0 V 4.4 l/min. 2 A3 = off A2 = on 5 V 1.1 l/min. 3 A3 = off A2 = on 10 V 4.3 l/min. 2.4 Project task: determine the fill level of the upper tank Task description The ultrasonic sensor measures distance and can be used to detect fill levels. The ultrasonic waves are refracted at the surface of the water and returned to the sensor. At a distance of 50 to 270 mm from the water, the sensor reads out a voltage within a range of 0 to 10 V. The ultrasonic sensor is attached to the inside of the lid of tank B102, from where it measures the fill level. Festo Didactic GmbH & Co. KG D3-21

324 2. Automated measurement Setting up the system, inspection LIC 102 V101 B102 V103 V102 FI 101 PI 103 B101 P101 V105 M Mount upper tank B102 and lay piping for the system in accordance with the PI flow diagram. Mount the ultrasonic sensor onto the upper tank. Electrically connect the ultrasonic sensor in accordance with the circuit diagram (CD-ROM). Set the valves so that liquid can be pumped into the upper tank: V101 open, V103 open, V102 approx. 5% open. Start the software and open the Setup menu. Set factor and offset The physical display value is calculated as follows: Physical value = sensor voltage factor + offset D3-22 Festo Didactic GmbH & Co. KG

325 2. Automated measurement Depending on which physical quantity is to be displayed, factor and offset are entered as follows: The following applies in the case of a sensor signal within a range of 0 to 3 litres and a voltage of 0 to 10 V: Fill level in litres Factor = 0.27 Offset = 0.0 Fill level in mm Factor = 22 Offset = 0.0 Note The sensor signal lies within a range of l, which corresponds to 0 to 10 V. Due to the fact that the bottom of the tank is conical, measurement begins as of the cylindrical portion of the tank and roughly the first 0.5 l are disregarded in this example Experiment: measuring the fill level using an ultrasonic sensor Fill upper tank B102 according to the entries in the table and document your observations. Complete the table. No. Digital outputs Tank B102, fill level sensor (litres) Observation 1 A3 = off A2 = off Empty = 0.05 B102 is empty. 2 A3 = on A2 = off Value increases. Approx. 50% full = 1.5 litres 100% full = 2.95 litres The tank fills up. 3 A3 = off A2 = off The value drops. The tank empties. Drain valve open: water flows back via the pump. Festo Didactic GmbH & Co. KG D3-23

326 2. Automated measurement D3-24 Festo Didactic GmbH & Co. KG

327 3. Automated open-loop control 3.1 Project task: filling process Task description The automated filling process will be demonstrated with the help of the 2-way ball valve with pneumatic actuation. The ball valve is installed between the upper and the lower tank. Information on operating the 2- way ball valve can be found in section 2.2, part B, and in the data sheet (CD-ROM). Set the system up according to the PI flow diagram. LA+ 111 V101 B102 LS 114 V107 V103 V112 V102 FIS+ 101 PIS+ 103 B101 LS 113 P101 V105 M Festo Didactic GmbH & Co. KG D3-25

328 3. Automated open-loop control Setting up the system, inspection Switch the system off and pull the mains plug. Drain the water via stopcock V105. Connect 2-way ball valve V102 according to the circuit diagram (CD-ROM). Complete tubing connections for pneumatic actuation (semi-rotary actuator) of the 2-way ball valve (at least 5 bar compressed air). Fill the lower tank with water Experiment: metered filling via the pneumatic actuator Carry out the experiment as indicated in the table and document your observations. No. Digital outputs Step Observation 1 A3 = on A0 = off Pump water into B102. B102 is empty. 2 A3 = off A0 = off The tank fills up. 3 A3 = off A0 = on Water flows through V102. The tank empties. 3.2 Project task: filtering process in a galvanising plant Task description The acid bath at a galvanising plant has to be continuously recirculated and filtered. As contamination in the acid bath increases, resistance upstream of the filter increases and circulating pressure rises. When a specified pressure is exceeded, the filter must be cleaned or replaced. The cross section in the valve is reduced with hand valve V103. This corresponds to a clogged filter in actual practice. We are thus able to simulate filter contamination with hand valve V103. The experiment is intended to demonstrate the relationship between resistance (filter contamination) and pressure in the piping system. The pump is controlled via the PC and pressure is measured with a pressure sensor. The characteristic pressure curve is recorded in a time diagram. D3-26 Festo Didactic GmbH & Co. KG

329 3. Automated open-loop control Setting up the system, inspection First, modify the system according to the PI flow diagram or the figure. A setup including one tank, the pressure sensor and the flow sensor is required. Double check the piping layout and the electrical connections before commissioning. Test the pump, the pressure sensor and the flow sensor for correct functioning. Fill tank B101 with 2 to 2½ litres of water. V103 V102 FI 101 PI 103 B101 P101 V105 M B101 FI101 PI103 P101 Festo Didactic GmbH & Co. KG D3-27

330 3. Automated open-loop control Task Connect the EasyPort, start the software and select the settings menu. Enter and double-check factor and offset settings for the sensors. Enter the corresponding values in the table. Setting checked Comment Sensor settings Pressure bar Factor = 0.04 Offset = 0 or pressure kpa Factor = 4 Offset = 0 or pressure PSI Factor = Offset = 0 Volumetric flow rate l/min. Factor = 0.75 Offset = 0 Valve settings V101 V102 V103 Create a commissioning report for the system. Characteristic, requirement for component Fulfilled Failed, comments Piping assembled and leak-proof Pressure sensor installed Flow sensor installed Electrical wiring and connecting cables connected Lower tank filled with 2 to 2½ litres of water Software installed, sensor values adjusted Test pump on/off with PC Test the signal from the pressure sensor Test the signal from the flow sensor D3-28 Festo Didactic GmbH & Co. KG

331 3. Automated open-loop control Experiment: determining pressure and volumetric flow rate Measure pressure and volumetric flow rate with changing line resistance. Carry out the steps specified in the table and document your observations. Menu: Control and measure No. Task Data from the diagram Note/observation 1 Pump on, A3 = on Hand valve open completely Pressure = Volumetric flow rate = 2 Slowly close hand valve V103 Pressure rises, volumetric flow rate drops 3 Hand valve V103 closed Pressure = Volumetric flow rate = 0 l/min. Pressure rises to impeller pump s limit value, volumetric flow rate drops 4 Slowly open hand valve V103 Pressure drops, volumetric flow rate increases 1 Volumetric flow rate 2 Pressure Diagram of the sensor signal while closing hand valve V103 Festo Didactic GmbH & Co. KG D3-29

332 3. Automated open-loop control Task What is the relationship between the pipe s cross section, volumetric flow rate and pressure? The smaller the pipe s cross section (valve cross section), the smaller the volumetric flow rate and thus the higher the pressure. Why is volumetric flow rate reduced with a smaller cross section? Impeller pump leakage increases at higher pressures. How would a significantly longer piping network influence the system? Line resistance would be increased and the volumetric flow rate would be reduced Experiment: creating a characteristic pump curve In this section volumetric flow rate with changing line resistance and analogue pump control will be examined. The pump can be operated with a control voltage within a range of 0 to 10 V with the help of a motor amplifier. Control must also be switched on and off with the help of a relay. 1: Set changeover relay to 1 2: Preset voltage to 0 to 10 V Sample settings in the settings menu D3-30 Festo Didactic GmbH & Co. KG

333 3. Automated open-loop control Menu: Select characteristic U-Q curve Carry out the experiments described below, document your observations in the table and create a characteristic curve. No. Task Data Note/observation 1 Increase voltage at the pump from 0 to Voltage [V] Volumetric The pump doesn t start until a setting of 10 V, and then decrease it back to 0 V flow rate approximately 3 V is reached. again. [l/min.] 2 2 Hand valve open all the way 4 3 Take values from the diagram Voltage is increased from 0 to 10 V. 2 Voltage is decreased from 10 to 0 V. Sample characteristic U-Q curve Festo Didactic GmbH & Co. KG D3-31

334 3. Automated open-loop control Task How does the pump respond to rising control voltage? The pump starts up at about 4.5 V. The volumetric flow rate then demonstrates a nearly linear increase up to a pump voltage of 10 V. What is the effect of varying the speed at which control voltage is changed? The slower the control voltage is changed, the smaller hysteresis becomes. What does hysteresis mean? In this experiment, hysteresis is the actual value difference between rising and falling control voltage. D3-32 Festo Didactic GmbH & Co. KG

335 3. Automated open-loop control 3.3 Project task: water supply Task description Water is pumped into a water tower from springs, rivers and lakes in order to supply households with water. Water is directed to domestic households from the tower. The upper tank will be filled with water during two experiments. There are several different ways to fill the tank: The fill pipe enters the upper tank from below. The fill pipe enters the upper tank from above. The fill pipe enters the upper tank from above while water is simultaneously being withdrawn from below. LA+ 111 LA+ 111 V101 B102 LS 114 V101 B102 LS 114 V107 V103 V112 V102 V107 V103 V112 FIS+ 101 PIS+ 103 B101 LS 113 P101 V105 M Setting up the system, inspection Set the system up with two tanks as shown in the flow diagram. Connect and test the pump and the ultrasonic sensor. Base yourself on section 2.4 during setup. Double-check the piping layout and the electrical connections. Festo Didactic GmbH & Co. KG D3-33

336 3. Automated open-loop control Experiment: filling the tank from below using the pump Carry out the experiment as indicated in the table and document your observations. No. Task Done Observations 1 V101 closed V107 closed V103 open V102 closed (A0 = off) V112 closed 2 Fill B101 with 3 litres of water. 3 Open the Control and measure menu in the software. Pump A3 = on 4 After roughly 40% filling Pump A3 = off 5 V102 open (A0 = on) V112 open The tank is filled Pump at standstill, fill level remains unchanged Tank empties faster Characteristic curve for filling from below D3-34 Festo Didactic GmbH & Co. KG

337 3. Automated open-loop control Experiment: filling the tank from above using the pump Carry out the experiment as indicated in the table and document your observations. No. Task Done Observations 1 V101 open V107 open V103 closed V102 closed (A0 = off) V112 closed (while filling) 2 Fill B101 with 3 litres of water 3 Open the Control and measure menu in the software, pump A3 = on 4 After roughly 40% filling Pump A3 = off 5 V102 open (A0 = on) V112 open The tank is filled Pump at standstill, water flows back via the impeller pump Valve open, tank empties. Characteristic curve for filling from above Festo Didactic GmbH & Co. KG D3-35

338 3. Automated open-loop control Experiment: filling the tank from above while simultaneously withdrawing water Carry out the experiment as indicated in the table and document your observations. No. Task Done Observations 1 V101 open V107 open V103 closed V102 open (A0 = on) V112 20% open V112 determines to what extent B102 will be filled! 2 Fill B101 with 3 litres of water. 3 Open the Control and measure menu in the software, pump A3 = on 4 After roughly 40% filling Pump A3 = off The tank is filled. Fill level rises. The higher the fill level, the slower it increases. Tank empties. The fill-level drops. 5 V102 closed (A0 = off) Characteristic curve for filling from above while simultaneously withdrawing water D3-36 Festo Didactic GmbH & Co. KG

339 3. Automated open-loop control Task Why is the surface of the water less turbulent when the tank is filled from below? Because water flowing into the tank is restrained by water already contained in the tank. How could reverse flow through impeller pumps be prevented? By installing a non-return valve downstream of the pump. Why does the fill level rise more slowly when water is withdrawn simultaneously? As the fill level increases, static pressure rises and the outflow velocity is increased. 3.4 Project task: dosing an amount of liquid Task description A certain amount of water must be fed to a mixture of solids in a cement mixer. The quantity is timecontrolled. A constant volumetric flow rate must be maintained as a prerequisite, for example 2 litres per minute. The pump is controlled via a PC. The analogue output is used as the manipulated variable. Volumetric flow is measured with a volumetric flow rate sensor. The characteristic curve is recorded in a time diagram. One litre of water should be added to the mixture. Task Set the system up with one tank in accordance with the PI flow diagram. Connect and test the pump, the pressure sensor and the flow sensor. Double-check the piping layout and the electrical connections before commissioning. Festo Didactic GmbH & Co. KG D3-37

340 3. Automated open-loop control Experiment: dosing an amount of liquid Connect the EasyPort to the PC and start the software. Enter the appropriate settings in the settings menu. V103 V102 FI 101 B101 P101 V105 1: Activate the changeover relay 2: Adjust control voltage D3-38 Festo Didactic GmbH & Co. KG

341 3. Automated open-loop control Carry out the work steps described below and record your observations in the table. No. Work step Setting checked Comment 1 Volumetric flow rate sensor Volumetric flow rate l/min Factor = 0.75 Offset = 0 2 Valve settings V101 V102 V103 3 Set to analogue A2 = on mode 4 Adjust Volumetric flow rate Control voltage Increase the manipulated Q = 2 l/min. U = 5.8 V manipulated variable variable until Q = 2 l/min 5 Pump off A3 = off A2 = off 6 Switch pump on for 30 seconds 7 Evaluate the diagram. A3 = off A2 = on Control voltage U = 5.8 V Values from the diagram: Volumetric flow rate Q = 2.5 l/min. Time t = 30 sec. Calculated water quantity over time: Q t = 1.25 l Measure with stopwatch or read from the diagram Festo Didactic GmbH & Co. KG D3-39

342 3. Automated open-loop control Sample solution for dosing procedure Task Why isn t the amount of water exactly correct? Volumetric flow rate is difficult to measure while the pump is being brought up to speed and decelerated. How long does the pump have to run (Q = 2 l/min.) in order to deliver 0.5 litres of water? 15 seconds D3-40 Festo Didactic GmbH & Co. KG

343 4. Automated closed-loop control Information A control circuit always consists of a control device (closed-loop controller) and a device to be regulated (controlled system), for example a fill-level system. Schematic diagram of a regulating system Description The task of the closed-loop controller (control function) is to control the controlled system so that it remains at setpoint w. Actual value x is continuously measured and compared with setpoint w to this end. The regulator calculates manipulated variable y. The manipulated variable influences the process via a final control element. Knowledge of the characteristics of the controlled system is essential for selecting and adjusting the regulator. Characteristics of controlled systems are usually determined during a test run. Discontinuous and continuous controllers: The actual value is measured using analogue sensors for both types of controllers. In the case of discontinuous controllers, the manipulated variable has only two states (on/off). In the case of continuous controllers, the manipulated variable is displayed in an infinitely adjustable fashion (e.g. 0 to 10 V). The characteristics of the controlled system, tank B102, will be observed as described below. The tank will be filled from above via a piping system. Festo Didactic GmbH & Co. KG D3-41

344 4. Automated closed-loop control Case 1: tank has no drain In this case, the tank represents an integral system during filling. The container is filled in a linear fashion. Graphic symbol Case 1: tank has a drain If water is withdrawn at the same time via a drain valve, the tank represents a PT1 system (system with equalisation). Graphic symbol Note Due to the minimal fill level (hydrostatic pressure), the exponential function is not very distinctive. D3-42 Festo Didactic GmbH & Co. KG

345 4. Automated closed-loop control Systems which demonstrate these characteristics are called 1 st order systems. The characteristic variable is time constant T [seconds]. It s the time required to achieve approximately 63% of the final level. As system performance varies, the control circuit also responds variously. In the experiments described below, we will only examine the performance of a control circuit with a PT1 system. Task How does the integral system perform when the pump is switched off during filling from above? The fill level remains constant. How does the PT1 system perform when the pump is switched off during filling from above? The fill level drops until the tank is empty. 4.1 Project task: controlling the fill level using a two-step controller Task description In the case of water supply, households withdraw various quantities of water. Two experiments will be used to find out how a specified fill level can be constantly maintained in the upper tank. There are different control methods: Switch the pump on and off: 2-step control. Change control voltage to the pump: analogue control. Disturbance variables include, for example, opening and closing hand valves V101 and V103, as well as 2- way ball valve V102 with pneumatic actuation. Festo Didactic GmbH & Co. KG D3-43

346 4. Automated closed-loop control Setting up the system, inspection Set the system up with two tanks according to the PI flow diagram. Connect the pump, the flow sensor and the 2-way ball valve with pneumatic actuation and test them. Double-check the piping layout and the electrical connections. LA+ 111 V101 B102 LS 114 V107 V103 V112 V102 FIS+ 101 PIS+ 103 B101 LS 113 P101 V105 M D3-44 Festo Didactic GmbH & Co. KG

347 4. Automated closed-loop control Commissioning Please check all the points listed in the following report and confirm completion of all tasks before commissioning. Task Completed Note/observation Piping assembled and leakproof Flow sensor installed Electrical wiring and connecting cables connected Tank filled with 2.5 litres of water 2-way ball valve with pneumatic actuation installed Software installed, sensor values adjusted Factor = Offset = Test pump on/off using PC Test the signal from the fill-level sensor Experiment: controlling the fill level using a two-step controller Fill-level control (discontinuous control) is to be carried out with the pump in binary mode (on/off). The same experiment, i.e. maintaining a constant fill level by switching the pump on and off manually, was conducted as part of the learning section on manual control. In the current example, the pump will be switched on and off by a software controller. Information The values in the control circuit are specified in a standardised fashion, i.e. 0 and 1 or 0 and 100%. These values are frequently converted to physical values for the user, for example so that the fill level can be specified in litres or the water level in mm. Designations within the control circuit: Term Setpoint Actual value Switching difference Manipulated variable (pump on/off) Symbol w x sd y As a rule, the value of switching difference sd is at the middle of the setpoint. Festo Didactic GmbH & Co. KG D3-45

348 4. Automated closed-loop control Fundamental performance of a control circuit as an example of a fill-level system with open outlet (PT1) and a 2-step controller w (0...1) Setpoint Switching difference sd (0...1) Controller Process Manipulated variable Signal amplifier Controlled system Sensor Actual value y (0...1) x (0...1) Where actual value (setpoint - switching difference/2) setpoint with storage = 1 Where actual value (setpoint + switching difference/2) setpoint with storage = 0 2-step controller logic Various settings must be entered in order to test performance. In order to be able to draw any conclusions about the control circuit, it s always advisable to change only one parameter at a time and then conduct the experiment. The respective settings included in the following table are suggestions. D3-46 Festo Didactic GmbH & Co. KG

349 4. Automated closed-loop control Start the software and open the Two-step controller menu. Set digital output A3 according to the setpoints and the switching difference from the table. Select each of the values listed below and document your observations. Settings standardised values (0 to 1) Observations Setpoint w Switching difference sd Disturbance variable z: hand valve V % open High switching frequency, fills quickly, empties slowly % open High switching frequency, fills moderately quickly, empties moderately High switching frequency, fills slowly, empties quickly % open Switching frequency higher % open Switching frequency lower % open Fills very slowly, empties very quickly Sample solution for controlling the fill-level with a 2-step controller Festo Didactic GmbH & Co. KG D3-47

350 4. Automated closed-loop control Task How does switching difference affect control? The smaller the switching difference is, the higher the switching frequency and the greater the deviation from the setpoint become. High switching frequencies may lead to premature wear of actuators. How does the interference variable affect the outcome of the experiment? The larger the interference variable is, the slower the tank is filled. Information about the practical use of 2-step controllers 2-step controllers are used wherever system deviation is reliable. Examples: irons, refrigerators, heaters, solar systems, fill levels for cooling lubricant, fill levels in galvanising systems and swimming pools etc. These systems have a large time-constant, so that only minimal switching frequencies occur despite a small switching difference. D3-48 Festo Didactic GmbH & Co. KG

351 4. Automated closed-loop control 4.2 Project task: controlling the fill level using a continuous controller Task description If no system deviation is permissible within the control circuit, continuous controllers must be used. Continuous controllers are characterised by, for example, an analogue manipulated variable in the event that the sensor has generated an analogue signal. Depending on the control function, the manipulated variable is calculated by means of various mathematical formulas. Schematic diagram of a control circuit with a continuous controller A fill-level system with open outlet (PT1 performance), for example, is used within the control circuit. w (0...1) Setpoint Controller Control function Y =... Manipulated Signal amplifier variable y (0...1) Process Controlled system Sensor Actual value x (0...1) The following controller functions (selection) could be used: Controller Graphic symbol Function P controller y = kp e kp = adjustable amplification factor e = system deviation w - x I controller y = esum TA/Ti Adjustable integral time (Ti) esum = sum of system deviation e System deviation e is added up during each cycle. PI controller Y = kp ( e + esum TA/Tn) Adjust kp and reset time (Tn) TA = sampling time, programme cycle time PID controller Y = kp (e+ esum TA/Tn+ (e-e_alt) Tv/TA) Adjust derivative time (Tv), e_alt = system deviation from the previous cycle Note The pump must be operated in the analogue mode for continuous control. Control voltage from the EasyPort to the motor control is between 0 and 10 V. Changeover relay K1 must be set with A2 = 1 to this end. Festo Didactic GmbH & Co. KG D3-49

352 4. Automated closed-loop control Experiment: controlling the fill level with a continuous controller In this experiment the fill level will be controlled with a continuous controller. In the example included in the chapter entitled Manual control of fill level, the fill level was kept constant by varying the power supply unit s output voltage. The manipulated value will now be read out by the software. The experiment should be carried out with four different controllers. Various settings must be entered in order to test the performance of the control circuit. In order to be able to draw any conclusions, it s always advisable to change only one parameter at a time and then conduct the experiment. The settings included in the following table are suggestions. Start the software and open the Continuous control menu. Check the software settings: set changeover relay A2 = 1 and specify the setpoint. Carry out the experiment with P, I and PI controllers. Add your observations to the table. Depending on the software revision level, the setpoints may also have to be entered in a sub-window. D3-50 Festo Didactic GmbH & Co. KG

353 4. Automated closed-loop control Experiment: controlling the fill level using a proportional controller Note Empty B102 before each start-up! Select each of the values listed below and carry out the experiment. Document your observations. Settings Observations No. Setpoint w, Setpoint w Amplification Disturbance physical (standardised) kp variable z, hand valve V litre % open Significant system deviation remains 2 1 litre % open System deviation is smaller 3 1 litre % open System deviation is smaller yet Controller tends to oscillate Fills slowly, empties quickly 4 1 litre % open System deviation drops to litre % open System deviation is great, manipulated variable is large 6 2 litres % open Manipulated variable = 1 Sample solution for fill-level control with a P controller Festo Didactic GmbH & Co. KG D3-51

354 4. Automated closed-loop control Task Which characteristics is the control circuit (P controller, PT1 system) displaying? P controllers react quickly to setpoint changes. System deviation is not entirely eliminated when using a P controller with a PT1 system. The greater kp is, the smaller the remaining system deviation becomes Experiment: controlling the fill level using an integral controller Note Empty B102 before each start-up. Software setup The manipulated value of the I controller is calculated as follows: Y = total of all system deviation (e:sum) x sampling time (TA)/integral action time (Ti) This formula makes it clear that Y is quickly changed by the controller when Ti is small, and Y is changed slowly, i.e. the controller is sluggish, when Ti is large. Make sure that Ti does not drop to 0, otherwise Y would be undefined in this case. Switch the software to I controller. The physical setpoint depends on the size of the tank and whether the unit of measure of the fill level will be in litres or in mm. D3-52 Festo Didactic GmbH & Co. KG

355 4. Automated closed-loop control Select each of the values listed below and carry out the experiment. Document your observations. Settings Observations No. Setpoint w, Setpoint w Integral Disturbance physical (standardised) action time variable z, hand (Ti) valve V % open Controller settles slowly % open System deviation reacts faster % open System deviation reacts faster yet Note It is possible that no stabilisation occurs in an actual system and that continuous oscillation takes place. Sample solution for controlling the fill-level with an I controller Festo Didactic GmbH & Co. KG D3-53

356 4. Automated closed-loop control Task What is the effect of integral time? The smaller the integral time, the faster the controller reacts. What can we say about system deviation? The I controller causes overshooting. After a period of overshooting, it settles at zero with a PT1 system (system deviation = 0) Experiment: controlling the fill level using a proportional-integral controller (parallel P and I components) In order to take advantage of the positive characteristics of both the P and the I controller, the two will be combined. This can be done in two different ways: The controllers are connected in parallel in the combination shown on the left and in series in the combination on the right. In actual industrial practice, the combination shown on the right is used in accordance with DIN Note Empty B102 before each start-up. Select each of the values listed below for the PI (DIN) controller and carry out the experiment. Document your observations. D3-54 Festo Didactic GmbH & Co. KG

357 4. Automated closed-loop control Settings Observations No. Setpoint w (standardised) Amplification kp Reset time Tn Disturbance variable z, hand valve V litres sec. 10% open Controller is very sluggish litres 1 1 sec. 10% open P component becomes stronger litres 3 1 sec. 10% open P component becomes stronger yet litres sec. 10% open I and P components very strong Sample solution for controlling the fill-level with a PI controller Task What can we say about reset time Tn? The smaller Tn, the greater the effect of the I component. What can we say about system deviation? Well-adjusted PI controllers demonstrate minimal overshooting and settle quickly. Festo Didactic GmbH & Co. KG D3-55

358 4. Automated closed-loop control 4.3 P roject task: refrigerating plant Task description The throughput of a coolant (volumetric flow rate) in a refrigerating plant needs to be controlled. A PI controller is used. Water will simply be pumped to tank B101 for this experiment. PI controller Motor and pump Liquid in piping system Control circuit concept Setting up the system, inspection Set the system up with one tank according to the PI flow diagram, or disconnect the piping to upper tank B102 and seal the bottom outlet of tank B102 with a blanking plug. Connect and test the pump and the flow sensor. V103 V102 FI 101 PI 103 B101 P101 V105 M Install and start the software, and select Continuous controller from the menu. Entries are standardised from 0 to 1. D3-56 Festo Didactic GmbH & Co. KG

359 4. Automated closed-loop control Commissioning report Please check all the points listed in the following report and confirm completion of all tasks before commissioning. Task Completed Note/observation Piping assembled and leakproof Flow sensor installed Electrical wiring and connecting cables connected Tank filled with 2.5 litres of water Software installed, sensor values adjusted Factor =, offset = Test pump with PC at 0 to 10 V Changeover relay: A2 = 1 Test the signal from the volumetric flow rate sensor Experiment: flow control using a proportional-integral controller Note Various settings must be entered in order to test performance. In order to be able to draw any conclusions, it s always advisable to change only one parameter at a time and then conduct the experiment. The settings included in the following table are suggestions. Select each of the values listed below and document your observations. Settings Observations No. Setpoint w (standardised) Amplification kp Reset time Tn Disturbance variable z, hand valve V litres sec. 50% open Controller is very sluggish litres 1 1 sec. 50% open P component becomes stronger litres 3 1 sec. 50% open P component becomes stronger yet litres sec. 50% open I and P components very strong 5 20% open 6 100% open Festo Didactic GmbH & Co. KG D3-57

360 4. Automated closed-loop control Sample solution for flow rate control with a PI controller Task Find a setting at which the controller overshoots only once. Kp = 2.0 Tn = 0.5 How does the interference variable affect the outcome of the experiment? The interference variable can only be corrected as long as the controller is within its respective controlling range. D3-58 Festo Didactic GmbH & Co. KG

361 5. Evaluation of learning objectives for automated measurement, open-loop and closed-loop control 1. Describe how to set up a computer aided control circuit. The PC must have an interface for data communication. Default values: analogue from -10 to +10 V, digital 0 and 24 V, the values are amplified for the actuator (e.g. motor amplifier for pump motor), and the value is adapted electronically and by the software for the sensors. The controller runs as software via the PC. The setpoints are entered on the PC. 2. List various controlled systems with one practical example for each. PT1 system Heater, pneumatic pressure, electrical motor with machine tool, fill level if outlet is open I system Hydraulic cylinder, screw spindle with motor for positioning P system Liquid flow, electrical booster 3. Describe the performance of a control circuit with a PT1 system. P controller Acts very quickly, system deviation is not entirely eliminated. I controller Acts sluggishly but settles down to zero, overshooting occurs. 4. Data (e.g. actual value x) is acquired using sensors. The following, for example, appears in a data sheet for a sensor: pressure range: 0 to 400 mbar, signal: 0 to 10 V. How is the signal processed by the PC so that the physical value is displayed on the PC monitor? Physical value = voltage factor + offset Factor = physical max. value/(max. voltage min. voltage) = 0.4/(10-0) = 0.04 Offset = 0 Festo Didactic GmbH & Co. KG D3-59

362 4. Automated closed-loop control 5. An ultrasonic sensor provides data in accordance with the following screenshot. Determine factor and offset for a physical representation of the value on the screen. Formula: Variables: UPLV = upper physical limit value LPLV = lower physical limit value UVV = upper voltage value LVV = lower voltage value Factor = (UPLV - LPLV)/( UVV - LVV) Offset = LPLV - factor LVV Physical value = voltage value factor + offset Factor = ( )/( ) = Offset = *2.76 = Example: 5 V is being applied. How many litres does the display indicate? Physical value = = 1.2 litres D3-60 Festo Didactic GmbH & Co. KG

363 4. Automated closed-loop control 6. A pressure sensor is described as follows in the data sheet: : 24 V DC supply voltage 2: 0 V DC earth 3: 0 to 10 V DC voltage output Which pins have to be connected to EasyPort? Pin 2 to earth at the EasyPort analogue input Pin 3 to the analogue input Which values do factor and offset have to be set to in order to display pressure correctly as a physical quantity? The following simple formula can be used: Factor = physical max. value/(max. voltage min. voltage) = 100/10 = 10 Offset = 0 7. How are actuators (e.g. pump motor) controlled with the PC? An analogue voltage within a range of 0 to 410 V is transmitted via EasyPort and is boosted to the required motor power by means of an amplifier and an adapter module. A digital value (bits) is transmitted from the PC to EasyPort. EasyPort switches a small relay (0/24 V). Small actuators can be controlled directly with the relay, but for larger actuators a power contactor is switched with the help of the signal. Festo Didactic GmbH & Co. KG D3-61

364 4. Automated closed-loop control 8. How is the EduKit PA switched from digital to analogue control? This is achieved with the help of a changeover relay (output 2). Output 2 = 0 signal: digital control is active (output: 3.0 to 24 V). Output 2 = 1 signal: analogue control is active (analogue output: 0.0 to 10 V). 9. As is the case with all microprocessor controllers, the PC works cyclically according to the IPO model (input, processing, output). The time required for a single sequence is called cycle time or sampling time (TA). For example, a programme has a sampling time of 25 ms. How many measurements can be carried out in one second? Number = 1000 ms/25 ms = 40 measurements In order to determine the flow rate of a medium as accurately as possible, at least 50 measurements must be performed per second. Determine the required sampling time. TA = 1000/50 = 20 ms 10. A pump fills a tank from above with water. After a given period of time, the pump is switched off. Draw conceivable characteristic fill level curves for two different cases: in case 1 the drain at the bottom of the tank is open. In case 2 the drain is closed. D3-62 Festo Didactic GmbH & Co. KG

365 4. Automated closed-loop control 11. An impeller pump causes volumetric flow rate within a circuit. What is the relationship between volumetric flow rate and pressure? Give reasons for your answer. Volumetric flow rate is reduced as pressure rises. Reason: When pressure rises, leakage increases at the pump. Rotary frequency decreases with non-controlled pump motors. 12. The following figure depicts a characteristic pump curve. Control voltage is increased from 0 to 10 V in case 1. In case 2, it s decreased back to 0 V. Provide designations for the depicted axes. Horizontal axis = control voltage in V Vertical axis = volumetric flow rate in l/min. Give reasons for the shape of the curves. Case 1: The pump requires a certain amount of control voltage in order to overcome the static pressure caused by the water column above the pump. After this pressure has been overcome, volumetric flow rate is roughly proportional to control voltage. Case 2: When control voltage is reduced, rotary frequency at the pump is decreased; the effect of inertia is the opposite of the effect observed during start-up, thus resulting in hysteresis. Festo Didactic GmbH & Co. KG D3-63