Page 1 of 9 ` STANDARD SPECIFICATION FOR FLOW INSTRUMENTS DOCUMENT NO : 44-LK-5102-00/J.02/0006-A4 Rev No. Issue Date Pages Rev Description Prepared A 12.08.08 9 Issued for Comments / Approval By Checked By Approved By NSA SPM BSP
DOCUMENT NO :44-LK-5102-00/J.02/0006-A4 Date : 12.08.08 STANDARD SPECIFICATION FOR FLOW INSTRUMENTS Page 2 of 9 Revision No.: A 1.0 PURPOSE 2.0 SCOPE 3.0 TECHNICAL REQUIREMENTS TABLE OF CONTENTS 3.1 ORIFICE PLATES 3.2 VENTURI METERS & FLOW NOZZLES 3.3 AVERAGING PITOT TUBES 3.4 DP TYPE FLOW TRANSMITTERS 3.5 VARIABLE AREA FLOW METERS 3.6 TURBINE & POSITIVE DISPLACEMENT TYPE FLOW METERS 3.7 CORIOLIS MASS FLOW METERS 3.8 THERMAL MASS FLOW METERS 3.9 MAGNETIC FLOW METERS 3.10 TARGET FLOW METERS 3.11 VORTEX FLOW METERS 3.12 ULTRASONIC FLOW METERS 3.13 FIELD BUS DEVICES GUIDELINES 4.0 RELATED DOCUMENTATION 5.0 ATTACHMENTS
DOCUMENT NO : 44-LK-5102-00/J.02/0006-A4 Date : 12.08.08 STANDARD SPECIFICATION FOR FLOW INSTRUMENTS Page 3 of 9 Revision No. :A 1.0 PURPOSE 2.0 SCOPE The purpose of this specification is to define the minimum requirements of design and manufacture of Flow Instruments. The scope of work shall include design, manufacture, testing and supply of flow instruments. 3.0 TECHNICAL REQUIREMENTS 3.1 ORIFICE PLATES 3.1.1 Orifice plate shall be the standard flow measurement device except for the following conditions where other type of instrument shall be selected. - where required accuracy is not obtained - where flow rate varies in wide range - where allowable pressure drop is limited - for high viscosity liquids and slurries - where other types of flow meters are more advantageous, like batching applications 3.1.2 Flow measurement shall be normally carried out using square edged concentric orifice plate mounted between a pair of weld neck flanges of minimum 300# ANSI rating for line size 2" and above. Flange taps shall be used for line sizes upto 12" while D-D/2 taps shall be used for line sizes 14" and above. EPCC Contractor to check fouling of tapping point with respect to welding of flange. In case of fouling, flange tap shall only be used. The material of the orifice plates shall be normally SS 316, as a minimum. Orifice flange, gaskets, bolts & nuts material shall be as per the relevant Piping material Specification. 3.1.3 Quadrant edge or quarter circle orifice plates shall be used for highly viscous liquids and for pipe Reynolds number below 10,000. The Beta Ratio for these plates shall not exceed 0.6. 3.1.4 Conical entrance type of orifice plates shall preferably be used for highly viscous liquids upto throat Reynolds number of 250. These shall be fabricated as per BS 1042 Part I. The Beta Ratio for these plates shall not exceed 0.3. 3.1.5 Eccentric orifice plates shall be used for fluids containing two phases. Eccentric orifice plates shall have the bottom of the orifice bore flush with the bottom I.D. of the pipe. Eccentric or segmental orifice plates shall be used on liquids containing large amounts of solid, or slurries. Eccentric or segmental orifice plates shall be used in horizontal runs only. 3.1.6 Vent / drain hole shall be provided for orifice plate having bore greater than 25mm. 3.1.7 Orifice plate dimensions and machining tolerances shall be as per BS 1042 Part 1. 3.1.8 Sizing of orifice plates shall be carried out in accordance with ISO 5167. Other sizing methods like AGA Report No.3, BS-1042, 'Flow measurement - Engineering Handbook' by R.W. Miller shall be used when specified.
DOCUMENT NO :44-LK-5102-00/J.02/0006-A4 Date : 12.08.08 STANDARD SPECIFICATION FOR FLOW INSTRUMENTS Page 4 of 9 Revision No.: A 3.1.9 Honed metering runs in accordance with AGA tolerances or integral orifice type transmitter shall be used in lines with 1½" (40 mm) nominal diameter or below. The integral flow assembly shall be supplied as an integral assembly consisting of upstream and downstream straight pipes, integral orifice of 316 SS (as a minimum) and transmitter installed along with manifold.end flanges shall be as per piping specifications. Upstream and downstream pipes shall be honed from inside to achieve smooth surface. Integral orifice meters, when used, shall be installed with block and bypass valves. 3.1.10 Upstream and downstream straight length shall be provided based on maximum d/d ratio of 0.75, in general. Where it is difficult to meet this requirement, the actual d/d ratio can be considered for reducing the straight length as permitted by the codes. The recommended practice shall be as per API-MPMS Recommended Practices and AGA Report No.3. The piping layout, where possible, shall be arranged such that straightening vanes are not required. 3.1.11 Orifice plates shall be installed on horizontal lines when practical. Vertical meter runs may be used for down flow of vapour and up flow of liquids. 3.1.12 Meter taps shall be horizontal for liquids, condensible vapours and steam. The taps shall be on top for gas, non-condensible vapour, or liquids, which boil at or below the maximum design ambient temperature at operating pressure. Where piping clearances are a factor, taps may be located upto 45 below the horizontal centre line for liquids and upto 45 above the horizontal centre line for condensible vapour and steam. The taps may be located upto 60º from vertical for gas and non condensible vapour. 3.1.13 Each orifice plate shall be provided with a tab that is clearly visible in the final installed position. The tab will be stamped, or deep engraved, on the upstream face with the tag number, orifice plate material, measured bore, I.D. of the pipe, flange size and rating. The tab shall also be in line with the Drain or Vent hole and shall indicate the direction of flow 3.1.14 Flanges shall be as per ANSI B16.36 and shall generally be of weld-neck type. 3.1.15 Flanges larger than 3" shall have a pair of jack-screws. The mating flanges shall be so aligned that jack-screws will be diametrically opposite. 3.1.16 Orifice flanges used at pressure ratings up to 600 lb. shall be tapped ½" female NPT; for 900 lb. and above - ¾" female NPT. Orifice connections for Vena Contracta taps or pipe taps shall be ½" "Sockets" or equal. Material and schedule number of "Sockets" shall be in accordance with applicable piping specifications related to a specific service. 3.1.17 Maximum meter flow shall equal nearest preferred factor greater than or equal to 1.5 normal flow if only the normal flow is known and shall be greater than or equal to 1.1 max. flow, if max. flow is given. 3.1.18 Differential ranges for all liquid flow meters shall not exceed 5000 mm (200 inches) of water. Typical ranges for gas, steam or vapour meters are as follows: Static Pressure Differential pressure kg/cm²g (psig) mm of water (inches of water) 0.35 to 2.5 (5-35) 500-1250 (20-50) 2.5 to 6 (35-85) 1250 to 2500 (50 to 100) Above 6 (above 85) 2500 to 5000 (100 to 200)
DOCUMENT NO : 44-LK-5102-00/J.02/0006-A4 Date : 12.08.08 STANDARD SPECIFICATION FOR FLOW INSTRUMENTS Page 5 of 9 Revision No. :A Where practical, the differential range will be 2500 mm (100 inches) water column. Other preferred ranges are 500, 625, 1250, 5000 mm of water. 3.1.19 Where compressible fluids are metered using differential pressure producing device, the selected differential in mm of water shall preferably not numerically exceed 5.5 times the upstream static absolute pressure in kg/cm² x 100. 3.1.20 The diameter ratio of orifice plates shall be as follows: Type Diameter Ratio Corner taps 0.23 to 0.8 Flange taps 0.2 to 0.75 Radius contracts taps 0.2 to 0.75 Inspite of the above mentioned criteria, it is preferable to select between 0.3 and 0.65. Orifice bore of less than 0.125 inches shall be avoided. 3.1.21 Flow transmitter shall have 100:1 rangebility. 3.1.22 For deriving more than one signals from a single orifice plate, separate tappings shall be provided for each transmitter. 3.1.23 In case of single measurement of flow for steam export/import, two different transmitters shall be used in place of single transmitter with compound range. 3.2 VENTURI METER & FLOW NOZZLES Venturi meter & flow nozzles with piezometers rings may be considered for gas / air flow measurement in large size pipes / ducts, where high accuracy is required and lower permanent pressure loss to be low. For high velocity steam or similar fluid, flow nozzles may be used in place of orifice plates to avoid problems due to erosion. 3.3 AVERAGING PITOT TUBES Averaging pilot tubes shall be considered for low pressure loss, high velocity steam, large diameter lines and air ducts. This shall be installed on 1 ½ size nozzle for small lines and 3 for large lines or lines with high velocity. The averaging pitot tube shall be of 316 SS material as a minimum, shall be provided with end support, whenever required. Retraction arrangement with ball valves shall be provided for each averaging pitot tube installation. 3.4 DIFFERENTIAL PRESSURE TYPE FLOW TRANSMITTERS Differential Pressure type flow transmitters shall be as per the requirements specified in Standard Specification for Pressure Instruments (Doc. No. 3188-JSS-106). The above flow transmitters shall be provided with integral 3 way manifold valves. 3.5 VARIABLE AREA FLOWMETER 3.5.1 Variable Area Flowmeters or rotameters shall be as per ISA-RP 16.1, 16.2, 16.3, 16.4, 16.5 and 16.6 and shall be used for viscous or corrosive services or where rangeability in flow precludes the use of an orifice. Metal tube rotameters shall be used for all
DOCUMENT NO :44-LK-5102-00/J.02/0006-A4 Date : 12.08.08 STANDARD SPECIFICATION FOR FLOW INSTRUMENTS Page 6 of 9 Revision No.: A process fluids. External devices for indicating or transmitting shall be magnetically coupled to the float or extension. Magnetic coupling shall be glandless type. The tube and flanges shall be SS316 as a minimum and shall be weatherproof to IP 66. 3.5.2 Glass tube rotameters shall be used for low pressure utility services for local indication and where line size is 1-1/2" (40 mm) or less. Glass tube rotameters shall not be used if outlet line is connected to a line or vessel containing hazardous or toxic fluid unless a check valve is installed at the downstream side of rotameter. Glass tube meters shall be mechanically protected and may only be used on non-hazardous fluid services, with temperatures up to 130ºC, and on fluids always above freezing. 3.5.3 Linearity should be better than 5% for indication-only rotameters and better than 1% for rotameter transmitter. Accuracy shall be 2% (or better) of full scale for general purpose and metal tube rotameters. 3.5.4 Variable Area Flowmeters (purge rotameters) fitted with a constant flow regulator shall only be used for fixed rate flows such as flushing or purging. 3.5.5 For low cost measurement of high flow rates generally 2 and larger sizes, bypass rotameters shall be used. 3.6 TURBINE & POSITIVE DISPLACEMENT TYPE FLOW METERS 3.6.1 These flow meters shall be used for highly accurate volumetric flow measurement. These meters can be applied in custody transfer operation or in batch-transfers. 3.6.2 Turbine / PD flow meters shall be used for relatively clean liquid services. Strainers and vapour Accuracy / Repeatability to be indicated, eliminators shall be used with these meters. 3.6.3 As a minimum, the rotor shall be of 316 SS material. Turbine meter shall have tungsten carbide bearings and shall be designed with hydraulic balance to keep the rotor in place. Designs using thrust bearings are not advisable. 3.6.4 Whenever PD meter is selected, these shall be of double casing type with inner casing of 316 SS as a minimum. 3.6.5 Transmitter signal shall be of pulse type. Pulser and the transmitter selected shall be compatible and should have a proven combination reference. 3.6.6 While selecting turbine flow meters, due considerations to be given to the fluid viscosity. Viscocity affects the linearity of turbine meter, so on high viscosity line it is advisable to size the meter so that its maximum permitted flowrate is as close as possible to the application maximum flowrate. 3.7 CORIOLIS MASS FLOW METER 3.7.1 Coriolis mass flowmeter shall be used for high-rangeabilty, high-accuracy applications requiring mass flow measurement. It shall also be used where liquid physical properties will vary, for slurry services and corrosive services. This is also recommended for custody transfer. This flow meter may also be used for measuring density. 3.7.2 As a standard, sensor tube material to be SS 316L. Accuracy shall be within +/- 0.1% of reading.
DOCUMENT NO : 44-LK-5102-00/J.02/0006-A4 Date : 12.08.08 STANDARD SPECIFICATION FOR FLOW INSTRUMENTS Page 7 of 9 Revision No. :A 3.7.3 While selecting the meter size, due considerations shall be given to the loss of pressure with respect to tube size and degradation of sensor tube accuracy as the flow rate decreases. 3.7.4 Velocity To reduce the erosive wear on wetted parts by abrasive fluids, the fluid stream velocity should be limited to about 3 m/sec. 3.7.5 Coriolis Mass Flowmeter shall be Dual Tube type. 3.8 THERMAL MASS FLOW METERS Thermal mass flow meters may be considered as a special application device: - for high reliability flow switching, no-flow detection, reverse-flow detection. - For measuring very low flow rates. - For measuring flow rates of highly corrosive fluids or difficult-to-meter fluids. - For measuring air flow to furnace. - Flue gas measurement. 3.9 MAGNETIC FLOW METER 3.9.1 Magnetic type flow meters shall be used for electrically conductive slurry, cooling water or corrosive services and shall be installed with line size bypass, with block and clean out valves, at the lowest point in piping to ensure that meter run is always liquid filled. Grounded rings shall be used whenever required. If the electrical conductivity is equal to or more than 20 microsiemens/cm most of the conventional magnetic flowmeter can be used. Special types, which will measure the flow of liquids with threshold conductivity as low as 0.1 microsiemens/cm may also be used. While selecting meter, effect of fluid temperature on conductivity shall be considered. 3.9.2 Magnetic flowmeter shall be used with a full pipe so that the measurement is accurate. 3.9.3 Magnetic flow meters shall be installed with required straight lengths. 3.10 TARGET METERS Target meters shall be considered for highly viscous hydrocarbon streams such as asphalt, tar, polymers, etc. 3.11 VORTEX FLOW METER 3.11.1 Vortex flow meters shall be considered for following applications: - Where higher rangeability is required - Where high accuracy is required - Where no maintenance spare is expected - Where process is a clean service - Where mechanical vibrations are not existent in pipe and sufficient straight lengths can be provided. - For steam flow measurement. 3.11.2 Vortex flowmeter shall not be used for the following services: - High viscous and slurry service.
DOCUMENT NO :44-LK-5102-00/J.02/0006-A4 Date : 12.08.08 STANDARD SPECIFICATION FOR FLOW INSTRUMENTS Page 8 of 9 Revision No.: A - Liquids having large concentration of solids and two phase flow or pulsating flow service. 3.11.3 Meter shall be selected such that cavitation does not occur for given line pressure. 3.12 ULTRASONIC FLOW METER Ultrasonic flow measurement shall be considered where non-intrusive flow measuring is required. This type of flow meter shall normally be used for flare gas flow measurement. 3.13 FIELD BUS DEVICES GUIDELINES 3.13.1 The Field bus transmitter shall be 2 wire system and shall have minimum facility as - Foundation fieldbus output compliant to ITK 4.6 or above. - Shall employ device description to facilitate interoperability. 3.13..2 It shall not be sensitive to the polarity of the wiring connection. 3.13.3 It shall operate on 9 to 32 V dc, with current draw capacity of 17mA maximum. This low power consumption shall allow more devices to be connected to a segment. 3.13.4 The digital integral LCD display shall be capable of displaying any other variable from any device on same segment. 3.13.5 Vendor to specify Response time (including dead time, time constant and min damping) 3.13.6 The foundation fieldbus transmitter must have the following essential facilities to facilitate complete FF functionality including control in the field as and when required. - Shall have multiple FF compliant analog input (AI) blocks (2 Nos with execution rate of 30 ms or below) and VCRs (at least 12 Nos or above) to allow control in the field Multiple AI blocks shall provide flexibility in using transmitter data for calculations and alarming, while VCR s used for communication between function block both within a device as well as amongst different devices shall be sufficient to execute all inter block data transfers. - Shall have a characterizer block for strapping tables. - Shall have a integrator block for totalisation. - Shall have a arithmetic block for functions such as level or density calculation. - Shall have a input selector block for voting or averaging applications. - Shall have a PID function block with PID. - Shall provide a back up link active scheduler ( LAS) so as to improve the reliability and security of the FF network. - Shall have software download capability for upgrades or product enhancement via fieldbus segment with the segment in operation. - Shall have guided routine (methods) for calibration and restoration of sensor defaults. - Shall have block execution times less than 45ms. 3.13.7 Diagnostics The transmitter shall perform continuous self diagnostics, be capable of self test functions and be able to provide specific diagnostic information locally on the LCD meter and remotely via digital FF communications protocol. The diagnostic capabilities shall include the following features-
DOCUMENT NO : 44-LK-5102-00/J.02/0006-A4 Date : 12.08.08 STANDARD SPECIFICATION FOR FLOW INSTRUMENTS Page 9 of 9 Revision No. :A - Shall detect and alert or alarm during process abnormal situations using statistical methods. - Shall provide a variety of standard statistical monitoring configuration defaults for detection such as plugged impulse line detection and flame instability. - Shall have an easy system for alert and understanding of faults, failures and anomalies either in the sensor, electronic circuits or process. 4.0 RELATED DOCUMENTATION Nil 5.0 ATTACHMENTS Nil