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1、BRITISH STANDARD BS 7481:1992 Code of practice for Testing venting systems and shields for lead-acid starter batteries Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:29:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7481:1992 This British Standard, having
2、been prepared under the direction of the Light Electrical Engineering Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 28 February 1992 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference LEL/1
3、2 Draft for comment 90/23817 DC ISBN 0 580 20012 4 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Light Electrical Engineering Standards Policy Committee (LEL/-) to Technical Committee LEL/12, upon which the following bodies were repres
4、ented: Association of Manufacturers Allied to the Electrical and Electronic Industry (BEAMA Ltd.) British Industrial Truck Association British Railways Board British Telecommunications plc Electric Vehicle Association of Great Britain Electricity Industry in United Kingdom Institute of Wastes Manage
5、ment Lighting Industry Federation Ltd. London Regional Transport Ministry of Defence Power Supply Manufacturers Association PSMA (BEAMA Ltd.) Society of British Battery Manufacturers Society of Motor Manufacturers and Traders Limited Amendments issued since publication Amd. No.DateComments Licensed
6、Copy: London South Bank University, London South Bank University, Fri Dec 08 12:29:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7481:1992 BSI 07-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Safety precautions1 3Preparation for testing1 Appendix A Preconditioni
7、ng4 Appendix B Gassing test4 Appendix C Spark test4 Appendix D Explosion containment test5 Appendix E Performance5 Figure 1 Test fixture2 Figure 2 Explosion test chamber (schematic)3 Publication(s) referred toInside back cover Licensed Copy: London South Bank University, London South Bank University
8、, Fri Dec 08 12:29:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7481:1992 ii BSI 07-1999 Foreword This British Standard has been prepared under the direction of the Light Electrical Engineering Standards Policy Committee. The purpose of this British Standard is to indicate some of the means by w
9、hich the hazards are reduced but it needs to be pointed out that some of the means can be defeated over a period of time by poor maintenance or arduous conditions. Future standards will cover other types of rechargeable cells and batteries. The recommendations made in BS 6604 concerning the safe ope
10、ration of starter batteries are always relevant. Lead-acid starter batteries contain an aqueous electrolyte of dilute sulphuric acid. They can, and often do, emit hydrogen and/or oxygen gas during use, particularly during charging; hydrogen gas when mixed with air or oxygen will explode, if ignited
11、over a wide range (approximately 4 % (V/V) to 96 % (V/V) hydrogen concentration). When such mixtures are ignited a violent explosion ensues and when the gas mixture is in the confines of the cells in a battery it explodes with sufficient force to shatter the container. Pieces of the container and dr
12、oplets of electrolyte are ejected with considerable force and may cause serious damage to adjacent equipment and to people in the vicinity. Ignition of the gases within a cell may be caused by an internal fault but in the majority of cases the ignition is initiated by a cause exterior to the battery
13、. A commonly used preventive method is to fit remote venting which channels away the gas mixture from likely ignition sources to the external atmosphere via a gas-tight tube attached to the battery. The use of an effective flame arrester in the venting system will, under normal circumstances, preven
14、t an external explosion propagating into the battery and hence reduce the likelihood of the battery exploding. In the event of an explosion from whatever cause, it is essential that damage to the person, particularly in the region of the eyes, be prevented. This is most positively achieved by a well
15、 ventilated permanent shield offering a mechanical barrier to the products of the explosion. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does no
16、t of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This w
17、ill be indicated in the amendment table on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:29:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7481:1992 BSI 07-19991 1 Scope This British Standard recommends procedures for testing the v
18、enting systems and shields which are fitted to lead-acid starter batteries in order to reduce hazards of an explosion. Appendix A describes the method for preconditioning venting systems before testing. Appendix B, Appendix C and Appendix D describe methods of testing venting systems and shields to
19、assess their effectiveness and Appendix E describes the performance of effective venting systems and shields. NOTEThe title of the publication referred to in this standard is given on the inside back cover. 2 Safety precautions WARNING. Testing of a venting system can result in an explosion and the
20、testing of a protective shield essentially does result in one. It is necessary that extreme caution be exercised to avoid personal injury. Absolutely no testing should be permitted where the safety precautions and procedures recommended in this British Standard are not followed. 2.1 The gas source,
21、spark electrodes and test fixture, where used, should be fully contained in an externally vented explosion test chamber which can be viewed indirectly by means of a mirror system from a brick or concrete walled safety area. 2.2 The battery charging source should be located outside the explosion test
22、 chamber and convenient to the control of the testing personnel. The charging circuit should have two emergency disconnect switches located: a) where they are readily accessible to the testing personnel; and b) at a remote position at least 3 m from the explosion test chamber. These emergency switch
23、es should not be used under normal circumstances, but in cases of emergency only, since their use may damage some types of charger. 2.3 A suitable test area should be designated, of size 3 m square or more. Signs prohibiting unauthorized persons from entering this area should be posted and observed
24、while any electrical circuit in the explosion test chamber is or could be energized. 2.4 During testing, entry to the area in which the explosion test chamber is located should be clearly marked to prohibit all persons not fully familiar with all the safety precautions and not wearing full protectio
25、n from the hazard to be encountered (see 2.6). 2.5 It is essential that smoking, naked flames or other spark sources not associated with the tests are not permitted in the area during testing. Any lighting should be of the explosion-proof type. 2.6 Full face protection devices should be worn by all
26、persons within the restricted area. Additionally, suitable ear defenders should be worn against the considerable noise that can be generated by an exploding battery. 2.7 The spark generating circuit should have an emergency disconnect switch readily accessible to the testing personnel. 2.8 The exhau
27、st fan of the explosion test chamber should be operating during the entire spark and explosion containment test procedures (see Appendix C and Appendix D). On completion of any test sequence, charging and sparking circuits into the explosion test chamber should be interrupted for at least 5 min with
28、 the exhaust fan operating before anyone is permitted access to the chamber. This time interval allows any hydrogen to be purged from the chamber and to preclude the possibility of a delayed explosion occurring due to a sustained “hidden” flame. WARNING. Hydrogen gas can burn without visible flame.
29、Failure of the venting system can result in the battery splitting with subsequent loss of electrolyte and the explosion containment test always has this result. Reference should be made to the starter battery code of practice (BS 6604) for advice on electrolyte spillage. 3 Preparation for testing 3.
30、1 Spark test conducted on a venting system fitted to the battery 3.1.1 The test battery system should be checked for gas leakage at any place other than the venting holes, e.g. with a soap solution whilst on charge. 3.1.2 Check that the spark source functions properly. 3.1.3 The battery to which the
31、 testing vent is fitted should be fully charged and gassing vigorously. 3.1.4 The test venting system should be preconditioned by following the procedure described in Appendix A. 3.2 Spark test conducted with a venting system only 3.2.1 The gas inlet to the test fixture should be well below the wate
32、r level, as shown in Figure 1, to prevent ignited gases from reaching the gas source. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:29:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7481:1992 2 BSI 07-1999 3.2.2 Fill the test fixture with water to a level
33、 3 mm below the underside of the top. Place the hold-down frame over a 0.025 mm thickness of polyethylene film cut as shown in Figure 1. Place the frame, with the film in place, over the four studs so that the film covers the open area between the fixture and the frame. Tighten the frame down finger
34、 tight with wing nuts to ensure a gas-tight seal around the gasket. Fit the vent system to be tested into the fixture. 3.2.3 The whole system should be checked for gas leakage at any place other than the vent opening, e.g. with a soap solution whilst charging the gas source battery. 3.2.4 Make sure
35、the ignition source works and that the gas source battery is fully charged. Figure 1 Test fixture Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:29:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7481:1992 BSI 07-19993 NOTEThe length, width and height shoul
36、d be approximately twice those of the largest battery on test. Figure 2 Explosion test chamber (schematic) Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:29:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7481:1992 4 BSI 07-1999 Appendix A Preconditioning A
37、.1 Place the vent system in a cold box at 18 C for 16 h. A.2 Remove from the cold box and place it in an oven at + 70 C for 8 h. A.3 Repeat this sequence for a total of three full cycles. A.4 At the completion of the third cycle, fit the venting system to the test fixture or battery for which it is
38、intended, if it is a removable system, and proceed to carry out the gassing test in accordance with Appendix B. Appendix B Gassing test NOTEThis test is sometimes of dubious accuracy when the venting system is attached to a test fixture. B.1 Apparatus B.1.1 Water bath, capable of being controlled at
39、 40 C. B.1.2 Charging source, either as described in C.2.1.2 or in C.1.1.2, according to which spark test is to be performed (see clause 3). B.1.3 Cold box, capable of maintaining a temperature of 18 C for 16 h. B.1.4 Oven, capable of maintaining a temperature of 70 C for 8 h. B.1.5 Blotting paper B
40、.2 Procedure B.2.1 Place the battery in the water bath, at a temperature of 40 C. Place the blotting paper close to the vent orifices. B.2.2 Charge the battery fitted with a test vent at a current equal to the maximum charge rate recommended by the manufacturer. B.2.3 After the battery has been on c
41、harge for 16 h, observe whether any droplets can be detected on the blotting paper. B.2.4 Within 2 h proceed to the spark test described in Appendix C. Appendix C Spark test C.1 Spark test for vent fitted to a battery C.1.1 Apparatus C.1.1.1 Explosion test chamber, e.g. as shown in Figure 2, with an
42、 explosion-proof fan of adequate size to produce approximately one chamber volume change per minute, vented directly to the exterior of the building. C.1.1.2 Charging source, capable of current control, with at least an output equal to the manufacturers maximum recommended charge rate for the batter
43、y. C.1.1.3 Suitable spark source, e.g. a mains supplied transformer-rectifier-capacitor unit with a switch to a spark gap probe. The components have to be capable of producing a spark of at least 0.02 mJ across a gap of 0.5 mm to 2.0 mm consistently. C.1.1.4 Battery, to which the venting system is t
44、o be fitted, prepared in accordance with clause 3. C.1.2 Procedure C.1.2.1 Place the test battery and equipment in the test chamber at an ambient temperature of 20 5 C. C.1.2.2 Charge the test battery at the maximum rate recommended by the manufacturer. C.1.2.3 Allow the gas flow to stabilize. NOTET
45、his should occur after between 1 min and 5 min. C.1.2.4 Create a spark of not less than 0.02 mJ of energy 10 mm from the test vent opening(s) in the path(s) of the gas flow. C.1.2.5 Repeat the spark at 10 s intervals for a minimum of six times per vent to ensure that evolved gases are given ample op
46、portunity to ignite. NOTEIf the ignited gases ignite the battery, time has to be allowed for the battery to self extinguish or ignite the gas mixture within the battery. C.1.2.6 Observe whether gas ignition takes place within the battery. C.1.2.7 Repeat the procedure given in C.1.2.2 to C.1.2.6 four
47、 times with the charge current reduced successively each time by one fifth of the maximum rate used in C.1.2.2. C.1.2.8 Repeat the procedure given in C.1.2.2 and C.1.2.3. C.1.2.9 Terminate the charge current and wait 1 min before repeating the procedure given in C.1.2.4 to C.1.2.6 with no charge cur
48、rent flowing. C.2 Spark test for vent only C.2.1 Apparatus C.2.1.1 Explosion test chamber, e.g. as shown in Figure 2, with an exhaust fan of the explosion-proof type and of adequate size to produce a minimum of one chamber volume change per minute, vented directly to the exterior of the building. C.
49、2.1.2 Charging source, capable of current control of up to the manufacturers maximum recommended charge rate of the largest battery for which the vent is intended. C.2.1.3 Suitable spark source, e.g. a mains supplied transformer-rectifier-capacitor unit with a switch to a spark gap probe. The components have to be capable of producing a spark of at least 0.02 mJ across a gap of 0.5 mm to 2.0 mm consistently. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:29:50 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7481:19
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