1、BRITISH STANDARD AEROSPACE SERIES BS 3G 100-2.3.5:1972 Specification for General requirements for equipment in aircraft Part 2: All equipment Section 3: Environmental conditions Subsection 3.5: Explosion-proofness UDC 629.7.05/.06:629.7.067.8.001.4BS 3G 100-2.3.5:1972 This British Standard, having b
2、een approved by the Aerospace Industry Standards Committee, was published under the authority of the Executive Board of the Institution on 14 June 1972 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference ACE/58 Draft for comment 70/26885 ISBN 0 580 07163
3、 4 Amendments issued since publication Amd. No. Date of issue CommentsBS3G100-2.3.5:1972 BSI 12-1999 i Contents Page Foreword ii 1 Scope 1 2 Definitions and terms 1 2.1 Explosion proof 1 2.2 Enclosure 1 2.3 Intrinsically safe 1 3 Equipment design 1 3.1 Equipment design and construction 1 3.2 Integri
4、ty of protection 1 4 Categories of equipment and enclosure for various environments 1 4.1 General 1 4.2 Environments 1 4.3 Categories 2 5 Explosion-proofness requirements 2 5.1 Environment I 2 5.2 Environment IIa 2 5.3 Environment IIb 2 5.4 Environment III 2 5.5 Environment IV 2 5.6 Alternative requ
5、irements 2 6 Tests 2 6.1 General requirements 2 6.2 Test specimens 2 6.3 Test mixtures 2 6.4 Acceptance tests 2 6.5 Test equipment and test procedures 3 7 Information to be stated in the relevant specification 4 Appendix A Recommendations for installations in areas where an explosion hazard may aris
6、e 8 Appendix B Numerical procedure for Category X enclosures 8 Figure 1 Apparatus for testing in explosive atmospheres 7 Table 1 Basic requirements for explosion-proof equipment 5 Table 2 Acceptable flange and hole dimensions for enclosure Categories C and D 7 Table 3 Composition of test mixtures 7B
7、S3G 100-2.3.5:1972 ii BSI 12-1999 Foreword This British Standard is part of a composite standard in the Aerospace Series of British Standards that specifies general requirements for equipment in aircraft. An introduction to the complete British Standard is given in BS 3G 100-0. This subsection of BS
8、 3G 100 replaces the explosion-proofness requirements specified in Clauses 221 and 222 of BS 2G 100-2. It details explosion-proofness requirements and in Appendix A the relevant installation recommendations, against which aircraft equipment should be designed for use in various environments. It also
9、 defines tests to demonstrate that the equipment complies with these explosion-proofness requirements. This standard makes reference to the following British Standards: BS 2G 100, General requirements for electrical equipment and indicating instruments for aircraft Part 2: Environmental and operatin
10、g conditions. BS 3G.100, General requirements for equipment in aircraft Part0:Introduction Part 1: Identification, declaration and construction Part2.3X: Sealing requirements 1) . BS 1259, Intrinsically safe electrical apparatus for use in explosive atmospheres. BS 4683, Electrical apparatus for exp
11、losive atmospheres Part: The construction and test of intrinsically safe electrical apparatus 1) . NOTEInformation concerning metric (SI) units is given in BS 350, “Conversion factors and tables”, and BS3763, “The International System of units (SI)”. A British Standard does not purport to include al
12、l the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and
13、 ii, pages 1 to 8 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. 1) In course of preparation.BS3G100-2.3.5:1972 BSI 12-1999 1 1 Scope This British Standard specif
14、ies design requirements for aircraft equipment that may come into contact with flammable fluids and vapours. It also specifies test requirements to demonstrate that the equipment meets these requirements. The standard does not relate to potentially dangerous environments occurring as a result of lea
15、kage from goods carried on board by passengers or as part of their baggage, or cargo, which may be the subject of separate regulations. It refers to normal and fault conditions occurring in categories of equipment in five types of environment. The standard should also be read in conjunction with BS
16、3G 100-0. 2 Definitions and terms For the purposes of this British Standard the following apply: 2.1 explosion proof equipment is explosion proof when there is negligible risk that it will cause an explosion of a flammable gas or vapour within the declared environment 2.2 enclosure a box or casing,
17、including any ducting, which is part of the equipment and not an aircraft compartment 2.3 intrinsically safe equipment is intrinsically safe when any spark or thermal effect produced normally (e.g. by. making or breaking a circuit) or accidentally (e.g. by a short circuit or earth fault) is incapabl
18、e, under prescribed test conditions, of causing ignition or a prescribed gas or vapour 3 Equipment design 3.1 Equipment design and construction. Equipment that may come into contact with flammable fluids or vapours and which 1) in normal operation 2)may produce arcs, sparks or hot surfaces, shall be
19、 so designed, having regard to its likely manner of installation, as to be explosion proof; 2) under fault conditions 2)may produce arcs, electrical sparks, friction sparks or hot surfaces, shall be so designed and installed as to reduce to an acceptable minimum the overall risk of a fault occurring
20、 such as to ignite the flammable vapours. 3.2 Integrity of protection. The required degree of protection under any condition of operation shall be achieved by means that are not dangerously affected by wear of the equipment and are not unduly dependent upon dimensional tolerances or accuracy of asse
21、mbly. NOTEAppendix A gives recommendations for the installation of electrical wiring and cennections, and the ventilation of equipment in areas that may be contaminated with flammable vapours. 4 Categories of equipment and enclosure for various environments 4.1 General. This clause details the basic
22、 requirements for explosion-proof equipment, discusses the risk of explosion in different environments and provides for various categories of enclosure (see Table 1). 4.2 Environments. The five environments. recognized by this standard are as follows: 1) Environment I. An atmosphere in a space in, w
23、hich uncovered flammable fluids or vapours exist, or can exist either continuously or intermittently by intention: e.g. in fuel tanks or within fuel systems. 2) Environment IIa. An atmosphere in which flammable mixtures can be expected to occur only as a result of spillage or leakage, and where an e
24、xplosive environment is likely to occur at a rate greater than one hour per hundred thousand flying hours; e.g. in the vicinity, of fuel systems. 3) Environment IIb. An atmosphere in which flammable mixtures can be expected to occur as a result of spillage or leakage, and when an explosive environme
25、nt is likely to occur at a rate less than one hour per hundred thousand flying hours; e.g. where the use of flammable fluids is limited and well contained. 4) Environment III. An atmosphere where the probability of flammable mixtures arising from aircraft systems is sufficiently low to be disregarde
26、d; e.g. within passenger cabins and well ventilated areas not containing flammable fluids. 5) Environment IV. An atmosphere within a designated fire zone. 2) The risk of explosion occuring under normal and fault conditions is referred to in clause 4.BS3G 100-2.3.5:1972 2 BSI 12-1999 4.3 Categories.
27、The various categories of enclosure shall be as detailed in Table 1. 5 Explosion-proofness requirements The requirements for explosion proof equipment or enclosures shall be as follows: 5.1 Environment I. The equipment shall be either contained in an enclosure to the standard of explosion-proof Cate
28、gories A1, B1 or D listed in Table 1 or shall meet the intrinsically safe Category ISA requirements of BS 4653:Part 3) . It should not be possible for any fault to: 1) adversely affect the integrity of the enclosure, or 2) raise the temperature of any external surface to a level capable of causing i
29、gnition 4) . 5.2 Environment IIa. The equipment shall be either contained in an enclosure to the standard of any one of the explosion-proof categories listed in Table 1 or shall meet the intrinsically safe Category ISA or ISB requirements of BS 4683-1 3) . It should not be possible for any fault to:
30、 1) adversely affect the integrity of the enclosure, or 2) raise the temperature of any external surface to a level capable of causing ignition 4) . 5.3 Environment IIb. The equipment shall be either contained in an enclosure to the standard of any one of the explosion-proof categories listed in Tab
31、le 1 or shall meet the intrinsically safe Category ISA or ISB requirements of BS 4683:Part 3) . There shall be a low probability of any fault: 1) adversely affecting the integrity of the enclosure, or 2) raising the temperature of any external surface to a level capable of causing ignition 4) . 5.4
32、Environment III. There are no requirements for equipment to be explosion proof under normal or fault conditions. 5.5 Environment IV. Equipment that may spark under normal conditions shall be enclosed to the standard of any one of the categories of explosion-proofness listed in Table 1 or be intrinsi
33、cally safe to Category ISA or ISB of BS4683:Part 3) . There are no additional requirements for equipment to be explosion-proof under fault conditions. 5.6 Alternative requirements. When individually specified, alternative requirements may be acceptable for items of equipment which, because of their
34、construction or environment, do not fall within any of the other categories of explosion-proofness given in Table 1. In this instance, Category X requirements (see6.4.5) shall be complied with, in order that the probability of an explosion is reduced to an acceptable low level. 6 Tests 6.1 General r
35、equirements. Table 1 gives details of the basic requirements in relation to the explosion hazards. In order to be assured that equipment will fulfil these requirements one or more of the following types of tests are required to determine: 1) gas tightness; 2) strength; 3) intrinsic incendivity of th
36、e equipment (without its enclosure); 4) the probability that an explosion in the enclosure will produce incendive flames outside it; 5) intrinsic safety. The applicability of these tests for the various categories is given in 6.4. The effects of environmental temperatures shall be taken into account
37、 when specifying the appropriate test conditions particularly in relation to intrinsically safe equipment (see 6.4.4). 6.2 Test specimens. The selection of test specimens shall take account of manufacturing variations and the effects of ageing or wear (e.g. of bearings, commutators or contacts) in s
38、o far as these may affect the explosion-proof properties of the equipment. 6.3 Test mixtures. Unless otherwise stated in the relevant specification the test mixtures used in the following tests shall be in accordance with Table 3. 6.4 Acceptance tests. Tests for the acceptance of equipment to the re
39、quirements of this British Standard shall be conducted on test specimens in accordance with the requirements of Table 1 and the following sub-clauses relevant to the appropriate category of enclosure. 6.4.1 Category A enclosures. Equipment having Category A enclosures shall be tested for gas tightne
40、ss and strength as follows. 3) In course of preparation. In the interim period other standards acceptable to the approving authority may be used. Equipment complying with the requirements of BS 1259 may also be used. 4) Guidance information and the characteristics of various fluids will be given in
41、a British Standard Specification currently being prepared.BS3G100-2.3.5:1972 BSI 12-1999 3 6.4.1.1 Gas tightness. The enclosure shall be accepted as being sufficiently gas tight if it withstands the test for hermetically sealed equipment specified in BS 3G 100:2:3.X 5) , having substituted the press
42、ure conditions given in Table 1 for those in that standard. 6.4.1.2 Strength test. The strength of the enclosure shall be accepted as sufficient if it is shown to be so by calculation, by a pressure test or by an appropriate internal explosion test. 6.4.2 Category B enclosures. Equipment having Cate
43、gory B enclosures shall be tested for gas tightness and strength as follows. 6.4.2.1 Gas tightness. A series of tests with the venting system attached shall be made to determine the maximum pressure attained, when an internal explosion is created by using a charge of Test Mixture No.1 inside the enc
44、losure. The equipment shall then be tested for gas tightness using either the test for hermetically sealed equipment specified in BS 3G.100:2:3.X 5)having substituted the pressure conditions given in Table 1 for those in that standard, or a suitable test that may be specified by the relevant equipme
45、nt specification. 6.4.2.2 Strength test. The strength of the enclosure shall be accepted as sufficient if it is shown to be so by calculation, by a pressure test or by an appropriate internal explosion test as specified in Table 1. NOTEEquipment with Category B enclosures are only acceptable for use
46、 with the types of ducting with which they have been tested. 6.4.3 Category C and D enclosures. Equipment having Category C and D enclosures shall be tested for strength by filling with, and surrounding in, Test Mixture No. 2. The mixture within the enclosure shall be exploded. The enclosure shall b
47、e acceptable if ten repetitions of this test procedure produce no explosion in the ambient atmosphere and no permanent distortion of the flange gap or hole dimensions beyond the limits specified in Table 2. NOTEWhen flame traps axe fitted to the enclosure, and evidence is available to confirm that t
48、he performance of these flame traps is equivalent to the protection given by the flange gap and hole dimensions specified in Table 2, the equipment may be acceptable as being Category C. The preferred test apparatus for this test is described in 6.5.1. 6.4.4 Intrinsically safe equipment. Tests shall
49、 be conducted in accordance with BS4683:Part 6) . Confirmation that the standard of intrinsic safety has been met shall be obtained from an appropriate specialist test establishment acceptable to the approving authority 7) . 6.4.5 Category X enclosures. This category comprises all equipment for which the requirements of the foregoing categories cannot be met. In these cases acceptability, or otherwise, can only be decided by taking into account the following factors: 1) the intended environment (as enumerated in Clause4); 2) the number of items to be install
