Users Guide for the Test on electric cables under fire conditions IEC

Transcription

1 Issue 1.4: July 2007 REF: Cable Manual 1.4 July 2007.doc Users Guide for the Test on electric cables under fire conditions IEC Issued by: Fire Testing Technology Limited Incorporating Stanton Redcroft Charlwoods Road East Grinstead West Sussex RH19 2HL United Kingdom Telephone: +44 (0) Fax: +44 (0) Web

2 IMPORTANT NOTE This guide does not purport to replace or overrule any sections of IEC or any relating standard to this apparatus. It is recommended that this standard, or the most recent version, is read in conjunction with this guide. Users finding difficulties with these procedures, or encountering anomalous conditions not described in the documentation are urged to contact Fire Testing Technology Limited. User comments are specifically invited, and will be incorporated into future editions of this guide. Telephone: +44 (0) or Fax: +44 (0) Some specimens may produce severe flaming during a test. Therefore, adequate means of extinguishing the specimen should be available. Recommended means of extinguishment are a fire hose or compressed nitrogen with can be directed to the burning area along with any other means such as fire extinguishers etc. Fire Testing Technology will not be held responsible for any damage caused, by fire, to the chamber or other associated equipment on this apparatus. 2

3 Contents 1 The FTT Electric cables test Introduction Definitions Safety Precautions and Procedure Propane Colour and Odour First Aid Measures Fire Fighting Measures Handling and Storage Disposal Services Extraction Electrical power Air Supply Gas Supply Fire test rig room Test Apparatus Main Components Burners and propane supply system Smoke Exhaust System General Measurement Section Equipment Smoke Measurement System General details Data Acquisition System Test Procedure Introduction Test pieces Determination of number of test pieces Test sample and categories Test sample and categories Mounting of the test sample Ignition source Positioning of ignition source

4 3.7 Test procedure Burner and Propane Gas Supply System Performance requirements and retest procedure Retest procedure Guidance for cable selection for type approval test Selection of test pieces Method of attachment...26 Appendix A: Drawings...27 Appendix B Spares list

5 1 The FTT Electric cables test 1.1 Introduction The Euro classification of reaction electric cables under fire conditions parts 1 and 2 Figure 1.1: - Photograph of cable test showing cables and burner(s) 5

6 1.2 Definitions IEC refers to various definitions, together with the following during the standard: Test sample: Pieces of cable Designations F/R and F: Front / Rear and Front 1.3 Safety Precautions and Procedure Some specimens may produce severe flaming during a test. Therefore, adequate means of extinguishing the specimen should be available. Recommended means of extinguishment are a fire hose or compressed nitrogen with can be directed to the burning area along with any other means such as fire extinguishers etc. Fire Testing Technology will not be held responsible for any damage caused, by fire, to the chamber or other associated equipment on this apparatus. If the performance of a cable is not understood, then FTT recommends that a preliminary test be performed with a low loading density of cables on the test ladder. Also FTT recommend that the performance of the cable in a Category C test is understood before considering performing a Category A or B test. This test method may involve hazardous materials, operations and equipment. Therefore, we specifically exclude any liability whatsoever for claims arising from use or misuse of this equipment. It is the responsibility of whoever uses the equipment to consult and establish appropriate health and safety practices and determine the applicability of regulatory limitations prior to use All service inputs must be made secure. The equipment must be supervised at all times. This equipment must only be operated by authorised personnel who are fully conversant with the safety requirements. The operator must have a thorough knowledge of the chemical properties of the materials under test and what combustion products can be expected from them. Care should be taken to avoid contact with hot surfaces produced from the burning of the material. It is recommended that heat-protective gloves (not household rubber) are worn when working in burner area and when removing a test samples. The products of pyrolysis and burning of the materials under test may be carcinogenic, toxic, or otherwise hazardous. An auxiliary breathing device and protective glasses may have to be worn before opening the test room door. It may be noted that highly corrosive residues may permeate and degrade heat-protective gloves. Butyl gloves must be worn underneath the heat-protective gloves for complete protection in such cases. 6

7 The installation, siting and provision of services to the equipment must have the approval of the Safety Officer. The supplied electric winch on the chamber is only designed to lift maximum 500kg do not attempt to lift loads heavier than 500kg damage will occur Propane Colour and Odour Propane is a colourless gas and has a sweetish odour. Note that it is stored as a liquefied gas under pressure First Aid Measures Propane is toxic by inhalation. In high concentrations it may cause asphyxiation or death. Symptoms may include loss of mobility and/or consciousness and the victim may not be aware of asphyxiation. In low concentrations it may cause narcotic effects, where symptoms may include dizziness, headache, nausea, and loss of co-ordination. In the event of inhaling propane, the victim should be removed to an uncontaminated area and kept warm and rested. Apply artificial respiration, if necessary, and seek medical advice. In the event of skin or eye contact from liquid spillage, flush with water for at least 15 minutes, apply a sterile, dry dressing and seek medical advice as soon as possible Fire Fighting Measures Exposure to fire may cause cylinders to rupture/explode, and propane is extremely flammable. Carbon monoxide may be formed from incomplete combustion. All known extinguishants can be used. If possible the flow of propane from the cylinder should be stopped, the cylinder moved to a cool area or cooled with water from a protected position. Do not extinguish a leaking propane gas flame unless absolutely necessary since spontaneous/explosive re-ignition may occur. In confined spaces self-contained breathing apparatus must be used. The fire brigade should be informed about the presence of propane on your premises Handling and Storage Cylinders should be stored upright, below 50 C in a well-ventilated area. Backfeed and the suck back of water into the container must be prevented. Propane cylinders must be segregated from acetylene, oxidant gases and other oxidants in store. Propane cylinders must be adequately earthed to prevent static discharge. Do not smoke when handling propane Disposal Waste gas should be flared through a suitable burner with a flash back arrestor. Empty cylinders still contain flammable vapour and must be returned to the supplier. 7

8 1.4 Services Extraction The clients exhaust system must be capable of continuously extracting a volume flow, of 0.50m 3 /s to 2m 3 /s and be connected to the FTT electric cable fire test rig Electrical power Electrical power providing 230VAC 50/60 Hz 10A at the control panel must be available. The control panel is supplied with all the required mating connectors with live, neutral and earth (ground). All supplies are to be switched and fused Air Supply Pressure regulated clean, oil-free shop air at a maximum flow rate of 200 l/min. Alternatively, a small compressor situated on the roof. Connection is ½" BSP male Gas Supply A supply of commercial propane 95% minimum purity at a pressure between 3-4bar. Connection is ½" BSP male. THE PROPANE SUPPLY MUST BE PRESSURE REGULATED, CLEAN & OIL-FREE. FIRE TESTING TECHNOLOGY WILL TAKE NO RESPONSIBILITY FOR DAMAGE CAUSED AS A RESULT OF FAILURES AND DAMAGE CAUSED BY THE CUSTOMER, SUCH AS CONTAMINATION. 1.5 Fire test rig room The fire test rig room shall have outer dimensions of height 4.0 +/- 0.1m and width of 1.0 +/- 0.1m and Depth of 2.0m +/- 0.1m and be raised from the floor to allow air flow. The wall material shall be constructed from thermal insulation, mineral wool approximately 65mm thick with suitable external cladding to give a coefficient of heat transfer of approximately 0.7 W/ (m².k). One wall of the fire test rig shall have an opening to allow the operator access to the test samples. This opening should have a window to allow viewing during testing. CAUTION: NO PERSON SHOULD ENTER THE ROOM WHEN THE BURNERS ARE LIT 8

9 Figure 1.2: - Test Room 9

10 2 Test Apparatus 2.1 Main Components FTT Electric cable test ducting Qty 1 Fan suitable for 2m Hood Qty 1 Speed controller to match fan spec Qty 1 2m x 2m x 625mm Hood Qty 4 Hood Skirts Qty 1 Plenum Qty 2 90 Bends Qty Straight ducting section Qty 3 2m Straight ducting section Qty 2 1m Straight ducting section See appendix A for proposed ducting layout drawing Issue 1 FTT Gas Diverter (As shown in Figure 2.1.1) The gas diverter apparatus consists of two identical gas paths comprising of the following:- Gas mass flow controller Air mass flow controller Low air pressure switch Flash back arrestor Venturi Gas and air control valves Gas outlet ball valves are ¾" BSP A filter is fitted on the gas input to filter any particles from entering the system. Two filters are fitted to the air; one filter removes sub-micron particles and converts oil and water mist to liquid form to drain away. 10

11 Gas Diverter Connectors Mains In (A) Three Pin Male (Supply s mains in from Control Panel) Control 1 (B) Fourteen Pin Male (All Burner 1 controls from Control Panel) Control 2 (B) Fourteen Pin Male (All Burner 2 controls from Control Panel) Figure 2.1.2:- Gas Diverter Layout FTT Gas Control Box (As shown in Figure 2.2.3) Note: The propane flow of 442 mg/s corresponds to a heat release of 20.5 kw. 11

12 Btu/h / kw Propane mg/s Air mg/s 70,000 / ,000 / The Gas Control Box controls the flow level to the burners while incorporating several safety features to prevent the client inadvertently filling the test room with propane. An Emergency Off switch is supplied which should be positioned in a suitable position away from the Gas Control Box to enable the gas flow to be switched off in an emergency. One position could be inside the Test Room, although the user should never be inside the room when the flame is on. As shown in Figure the Power On switch turns on the Digital Meters which displays the mass flow rate (mg/s) and the Mass Flow Controller. When first applying power to the unit only this switch should be switched on. Should the warm up time of the mass flow controller wish to be avoided (approx. 30mins.), leave the Power On switched on over night. Points to observe are:- The Emergency key switch in the centre of the Gas Control Box shuts of the power to the entire gas supply system. THE KEY FOR THIS SWITCH SHOULD ONLY BE AVAILABLE TO PERSONNEL TRAINED TO USE THE CABLE TEST RIG. THE POWER ON SWITCH ALONE SHOULD BE LEFT ON IN BETWEEN TESTING; SWITCH OFF ALL OTHER SWITCHES TO ENSURE THERE IS NO GAS FLOW. The Gas On switch will only initialise if the system extraction is running. The gas flow to the either burner will only remain on if the thermocouple detector has sensed a flame. 12

13 Figure 2.2.3: - Gas Control Box (Burner 1 and 2) The gas control box comprises of the following controls. Each burner has three levels of control Level 1 / Level 2 and Variable, for the gas and air. Each level can be set by adjusting the ten turn potentiometers and locking into position by the black leaver located on the bottom of each potentiometer. Levels can be selected uses the three position switch between Overide and Air On. This sends the set voltage to the gas and air mass flow controllers. Each meter on the front panel indicates the mass flow rate of propane or air. The ignite button is to ignite the burner. Overide will override the thermocouple sensor during a test, if material has moved the sensor. Air On (Red Lamp) button opens the main gas and air solenoid valves. Interlocks made will light (Green) when all interlocks are correctly made for example E-Stops are made and exhaust is running. Low Air will light (Yellow) when air pressure is low when burner is running. 13

14 Note: Each Burner can run independently of each other. Figure 2.1.4: - Gas Control Box (Power On / Air In and Emergency Off) Power On turns Power On to mass flow controllers and digital meters. Emergency Off switch shuts off the power top the entire unit. Air in Lamp will light (Green) when the correct air pressure is supplied. 14

15 Gas Control Box Connectors Mains In Three Pin Plug (Mains in) Mains Out Three Pin Socket (Supply s mains in Diverter Panel) Exhaust In 3-way Din Socket (Contact closure from exhaust system) Emergency Stop 2-way Socket (Contact closure from Emergency Stop) MassFlow 12-way Socket (Signals connection to data logger) Signals Out Burner 1 MFC Gas 5-way Din Socket (Signals to Burner 1 Gas Mass Flow Controller) MFC Air 6-way Din Socket (Signals to Burner 1 Air Mass Flow Controller) Control Fourteen Pin Socket (Burner 1 controls to Diverter Panel) TC Type K Socket (Thermocouple detector) Burner 2 MFC Gas 7-way Din Socket (Signals to Burner 2 Gas Mass Flow Controller) MFC Air 8-way Din Socket (Signals to Burner 2 Air Mass Flow Controller) Control Fourteen Pin Socket (Burner 2 controls to Diverter Panel) TC Type K Socket (Thermocouple detector) All the equipment such as tubes, couplings, flow meters, etc. is approved for propane. 15

16 2.2 Burners and propane supply system The fire test apparatus contains two identical ribbon burners, each having the capacity of approximately 20.5 kw. The burners are equipped with spark ignition. There is a solenoid valve for immediate and automatic cut-off of the gas supply in case of extinction of the burners which is detected via thermocouple detectors. The propane used should be commercial propane 95% minimum purity. The propane is supplied through a mass flow controller with a range of mg/s (for burner 1) and mg/s (for burner 2) and an accuracy of ±2% full scale. Each controller is housed on the Gas Diverter plate on the outside of the room; this is enclosed by a mesh cover. 2.3 Smoke Exhaust System NOT FITTED 2.4 General Measurement Section Equipment NOT FITTED 2.5 Smoke Measurement System NOT FITTED 2.6 General details Enclosure and air supply The test rig comprises of a vertical test chamber having a width of 1000mm +/- 100mm, a depth of 2000mm +/- 100mm and a height of 4000mm +/- 100mm; the floor of the chamber should be raised above ground level. The test chamber should be nominally airtight along its sides, air being admitted at the base of the test chamber through an aperture of 800mm +/- 20mm x 400mm +/- 10mm situated 150mm +/- 10mm from the front wall of the test chamber. The air flow should be adjusted to a rate of 5000 l/min +/- 500 l/min at a constant controlled temperature of (20 +/10) C and measured at the inlet side before the test commences. These parameters should be preferably regulated during the test. An outlet 300mm +/- 30mm x 1000mm +/- 100mm should be made at the rear edge of the top of the test chamber. The back and sides of the test chamber should be thermally insulated to give a coefficient of heat transfer of approximately 0.7W/ (m².k). For example, external cladding is satisfactory. The distance between the ladder and the rear wall of the chamber is 150mm +/- 10mm and between the bottom rung of the ladder and the ground 400mm +/- 16

17 5mm. The clearance between the lowest point of the test piece and the ground is approximately 100mm. Ladder types There are two types of ladder; a standard ladder of 500mm width and a wide ladder of 800mm width. Details of the types of ladder and the methods of mounting to be used are provided in Section 3 figure 3.10 (Test procedures). 2.7 Data Acquisition System NOT FITTED 17

18 3 Test Procedure 3.1 Introduction The following test procedure has been taken from the current IEC standard. 3.2 Test pieces Determination of number of test pieces. In order to calculate the appropriate number of test pieces, it is necessary to determine the volume per metre of non-metallic materials of one test piece. A section of cable which should not be less than 0.3m is carefully cut to ensure that the surfaces are at tight angles to the cable axis, thus enabling precise measurements of its length. Each non-metallic material C should be extracted from the test piece and weighed. Any less than 5% of the total non-metallic weight should be discarded. Where semi-conducting screens cannot be removed from the insulating material, the components may be considered as one for the purpose of measuring their weight and specific gravity. The specific gravity of each non-metallic component (including cellular material) should be measured in an appropriate way e.g. clause 8 of IEC , in order to obtain values expressed to the second decimal place. Tapes and fibrous components should be assumed to have an effective specific gravity of 1. The volume V (litres per metre of cable) of each non-metallic material C is calculated as follows: Where M is the mass of the component C (kg) P is the specific gravity of the component C (kg/dm ³) I is the length of the section of cable (m) The total volume, V of the non-metallic contained in one metre of cable is equal to the sum to the sum of the individual volumes V1, V2, etc. The closest integer (0.5 and above corresponding to 1) of the number of test pieces to be mounted is obtained by dividing the volume per metre of the test category specified in section 3.3 of this manual by the total volume, V, of non-metallic per metre of cable. 18

19 3.3 Test sample and categories Test sample and categories The test sample should comprise a number of test pieces of cable from the same length, each having a minimum length of 3.5m. The total number of 3.5m test pieces in the test sample should be in accordance with one of the three categories as follow: Category A The number of test pieces required to provide a nominal total volume of non-metallic material of 7 litres per metre. Category B The number of test pieces required to provide a nominal total volume of non-metallic material of 3.5 litres per metre. Category C The number of test pieces required to provide a nominal total volume of non-metallic material of 1.5 litres per metre. 3.4 Mounting of the test sample The methods of mounting the pre-determined number of test pieces to form the test sample are fully described in section 3.11 Two methods of mounting (designations F/R and F) are applicable to category A. Only designation F applies to categories B and C. For Identification purposes the following abbreviated notations may be used: Category A, designation F/R A F/R Category A, designation F A F Category B, designation F B F Category C, designation F C F 19

20 3.5 Ignition source The ignition source is one or two ribbon-type propane gas burners which have their own set of mass flow controllers, complete with venture mixer, and whose flameproducing surface consists of a flat metal plate 341mm long and 30mm wide through which 242 holes of 1.32mm in diameter are drilled on 3.2mm centres in three staggered rows of 81, 80 and 81 holes each to form an array having the nominal dimensions 257mm x 4.5mm as shown in figure Each burner has means of controlling the fuel and air input flow rates. For the purpose of this test, the air should have a dew-point not higher than 0 C and the input should be /- 140 mg/s; the propane flow rate should be 442 +/- 15 mg/s to provide a nominal 20.5 kw). Figure Gas Burner 3.6 Positioning of ignition source For the test the burner should be arranged horizontally at a distance of 75mm +/- 5mm from the front surface and 600mm +/- 5mm above the floor of the test chamber. The point of application of the burner flame should lie in the centre between two crossbars on the ladder and at least 500mm +/- 5mm above the lower end of the sample. Adjustment of air and gas flows prior to the test may be carried out away from the test position. Where two burners are used in tandem for test category A designation F in combination with the wide ladder they should be positioned as shown in figure Figure Single Burner Position with Standard Ladder 20

21 Figure Dual Burner Position with Wide Ladder 3.7 Test procedure The test should not be carried out if the external wind speed measured by an anemometer fitted on the top of the test rig is greater than 8m/s and should not be carried out if the temperature of the inside walls is below 5 C or above 40 C measured at a point approximately 1.5m above floor level, 50mm from a side wall, and 1.0m from the door. The enclosure door shall be closed throughout the test. 21

22 3.8 Burner and Propane Gas Supply System The Gas Control Box controls the flow level to the burners while incorporating several safety features to prevent the client inadvertently filling the test room with propane. An Emergency Off switch is supplied which should be positioned in a suitable position away from the Gas Control Box to enable the gas flow to be switched off in an emergency. One position could be inside the Test Room, although the user should never be inside the room when the flame is on. The cables or test pieces forming the test sample should be conditioned at a temperature of (23 +/- 5) C for at least 16 hours before commencing the test. The test chamber should be dry. 3.9 Performance requirements and retest procedure After burning has ceased, the test sample should be wiped clean. If burning has not ceased after a maximum time of 1 hour from the completion of the test flame period, the flame should be extinguished. All soot is to be ignored if, when wiped off, the original surface is undamaged. Softening or any deformation of the non-metallic material is also to be ignored. The maximum extent of the damage is measured to one decimal place from the bottom edge of the burner to the onset of char, which is defined as follows: Press against the cable surface with a sharp object, e.g. a knife blade. Where the surface changes from a resilient to a brittle (crumbling) surface, this indicates the onset of char. The maximum extent of the charred portion measured on the test sample should not have reached a height exceeding 2.5m above the bottom edge of the burner, neither at the front nor the rear of the ladder Retest procedure In the case of doubt, two further tests should be undertaken as detailed in section 3.7 The test should be deemed as satisfactory if both tests meet the requirements of Guidance for cable selection for type approval test The choice of conductor cross-section for type approval tests should be agreed between purchaser and manufacturer but it shall comply with the following restrictions. 22

23 The limited capacity of the ladders requires consideration of the conductor crosssection selected for testing to ensure that the volume of non-metallic material can be accommodated within the prescribed method of mounting. Moreover, the testing of a sample consisting of a single test piece shall also be avoided. Category A, designation F/R For cables having a conductor cross-section greater than 35mm ², the selection of cable shall not require the placement on each face of the ladder of more cables than the number necessary to form a single layer of 300mm width on each side, allowing for a space between each cable equal to half the cable diameter but not exceeding 20mm Category A, designation F For cables having a conductor cross-section greater than 35mm ², the selection of cable shall not require the placement on each face of the ladder of more cables than the number necessary to form a single layer of 600mm width on each side, allowing for a space between each cable equal to half the cable diameter but not exceeding 20mm Category B, designation F For cables having a conductor cross-section greater than 35mm ², the selection of cable shall not require the placement on single face of the ladder of more cables than the number necessary to form a single layer of 300mm width on each side, allowing for a space between each cable equal to half the cable diameter but not exceeding 20mm Category C, designation F The size of cable selected shall require a sample of at least two test pieces to be mounted. For cables having a conductor cross-section greater than 35mm², the selection of cable shall not require the placement on single face of the ladder of more cables than the number necessary to form a single layer of 300mm width on each side, allowing for a space between each cable equal to half the cable diameter but not exceeding 20mm Where designation F is used for categories A, B and C, and where the cable size is 35mm² or smaller, there is no restriction on the conductor cross-section selected. This applies also to telecommunication, data transmission and optical cables. 23

24 Figure 3.10 shows the two ladder types 3.11 Selection of test pieces The number of test pieces should be selected to provide a nominal total non-metallic volume of 7 litres/metre calculated according to section A summary of the test conditions is given in Table For approval test the cable conductor cross-sections should be chosen in accordance with section

25 Table

26 Method of attachment For cables having a conductor cross-section exceeding 35mm² For Such cables, only the method of mounting designation F is applicable. The test pieces should be placed touching on the front of the standard ladder in one or more layers so that the width of test sample does not exceed 300mm. There should be a minimum distance of 50mm between the edge of the test sample and the inside of the ladder uprights. 26

27 Appendix A: Drawings Proposed Ducting Layout Drawing Issue 1 27

28 28

29 Appendix B Spares list The spare parts list for the electric cable test is given in the following pages. Please contact FTT or their agents if there are any spares items not included on the list that you require or for prices. 29

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