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1、BRITISH STANDARD BS 5345-4: 1977 Code of practice for Selection, installation and maintenance of electrical apparatus for use in potentially explosive atmospheres (other than mining applications or explosive processing and manufacture) Part 4: Installation and maintenance requirements for electrical
2、 apparatus with type of protection “i” Intrinsically safe electrical apparatus and systems UDC 696.6:621.3 7:614.825:614.83 Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:59:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5345-4:1977 This British Standard, having been prepared under the
3、direction of the General Electrotechnical Engineering Standards Committee, was published under the authority of the Executive Board on 30 December 1977 BSI 02-2000 The following BSI references relate to the work on this standard: Committee reference GEL/114/5 Draft for comment 75/22154 ISBN 0 580 09
4、527 4 Cooperating organizations The General Electrotechnical Engineering Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Associated Offices Technical Comm
5、ittee*Electronic Components Board British Approvals Service for ElectricElectronic Engineering Association Cables LtdEngineering Equipment Users Association* British Electrical and Allied ManufacturersHealth and Safety Executive* Association (BEAMA)*Home Office British Radio Equipment ManufacturersI
6、nstitution of Electrical Engineers* AssociationMinistry of Defence* British Steel CorporationNational Coal Board* Department of Energy (Electricity)Oil Companies Materials Association* Electric Cable Makers Confederation*Post Office* Electrical Contractors Association*Radio and Electronic Components
7、 Electrical Contractors Association of ScotlandManufacturers Federation* Electrical, Electronic, Telecommunications andTelecommunication Engineering and Plumbing Union (TUC)Manufacturing Association (TEMA) Electrical Research Association* Electricity Supply Industry in England and Wales The organiza
8、tions marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: British Electrical Systems AssociationDepartment of Energy Petroleum (OIL) (BEAMA)Department of the Environment Building B
9、ritish Gas CorporationResearch Establishment (Fire Research British Industrial Measuring and ControlStation) Apparatus Manufacturers AssociationDepartment of Trade (Marine Division) CBMPEFire Offices Committee Chief and Assistant Chief Fire OfficersGeneral Council of British Shipping AssociationInst
10、itute of Petroleum Council for Electrical Equipment forInstitution of Gas Engineers Flammable Atmospheres (BEAMA)Lighting Industry Federation Ltd. Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:59:23 GMT+00:00 2006, Uncontr
11、olled Copy, (c) BSI BS 5345-4:1977 BSI 02-2000i Contents Page Cooperating organizationsInside front cover Forewordiii 0Introduction1 Section 1. General 1Scope2 2References2 3Definitions and explanation of terms2 4Permissible zones of use3 5Relevant specifications3 6Certification of electrical appara
12、tus and systems3 Section 2. Selection of electrical apparatus and systems 7General4 8Permissible zones of use4 9Temperature classification4 10Grouping of intrinsically safe electrical apparatus and systems5 11Certification of electrical apparatus and systems5 12Environmental conditions5 Section 3. I
13、nstallation requirements 13General5 14Assurance of safety5 15Specific requirements6 16Earthing of intrinsically safe systems8 17Diode safety barriers8 Section 4. Inspection and test of intrinsically safe systems and self-contained intrinsically safe apparatus 18General9 19Initial inspection9 20Routi
14、ne inspections11 21On-site electrical testing11 22Records12 Section 5. Maintenance 23General12 24Removal of electrical apparatus12 25Maintenance work on installed intrinsically safe systems and self-contained intrinsically safe electrical apparatus12 26Maintenance in a workshop13 27Shunt diode safet
15、y barriers13 Appendix A Organizations through which advice on intrinsic safety applications may be obtained14 Appendix B Illustrations of typical intrinsically safe installations14 Appendix C Typical procedural stages for intrinsically safe installations17 Figure 1 Self-contained apparatus: paging s
16、ystem14 Figure 2 Simple apparatus: thermocouple with direct deflection indicator15 Figure 3 Certified associated apparatus15 Figure 4 Certified apparatus with compatible parameters15 Figure 5 Other combinations of certified apparatus: solenoid valve with barrier16 Figure 6 Certified systems: microph
17、one and loudspeaker system16 Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:59:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5345-4:1977 ii BSI 02-2000 Page Table 1 Minimum conductor sizes6 Table 2 Minimum clearance distances7 Publications referred toInside back cover Licensed Copy: sh
18、effieldun sheffieldun, na, Fri Dec 01 14:59:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5345-4:1977 BSI 02-2000iii Foreword Many gases, vapours, mists and dusts encountered in industry are flammable. When ignited they may burn readily and with considerable explosive force if mixed with air in t
19、he appropriate proportions. It is often necessary to use electrical apparatus in locations where such flammable materials may be present, and appropriate precautions should therefore be taken to ensure that all such apparatus is adequately protected so as to reduce the likelihood of ignition of any
20、external explosive atmosphere. When using electrical apparatus, potential ignition sources include electrical arcs and sparks, hot surfaces and, in certain circumstances, frictional sparks. In general electrical safety is ensured by implementing one of two considerations. Either the electrical appar
21、atus should be located, whenever practicable, outside hazardous areas; or the electrical apparatus should be designed, installed and maintained in accordance with measures recommended for the area in which the apparatus is located. Several techniques are available for the protection of electrical ap
22、paratus in hazardous areas. Some of these techniques (or “types of protection” as they are known) have been used for many years and have come to be regarded as traditional. Other types of protection have been introduced only recently. This code of practice describes the basic safety features of thes
23、e types of protection, full details of which are given in the relevant standards, and recommends the selection, installation and maintenance procedures that should be adopted to ensure the safe use of electrical apparatus in hazardous areas. This code takes account therefore of the significant devel
24、opments that have taken place in area classification and in the design, manufacture and use of electrical apparatus for hazardous areas since the preparation of the earlier code of practice CP 1003. For ease of reference Part 1 of this code has been divided into a number of sections, each dealing wi
25、th a particular aspect of the safe use of electrical apparatus in hazardous areas. This code of practice represents a standard of good practice and takes the form of recommendations. Compliance with it does not confer immunity from relevant statutory and legal requirements. Summary of pages This doc
26、ument comprises a front cover, an inside front cover, pages i to iv, pages 1 to 18, an inside back cover 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. Licensed C
27、opy: sheffieldun sheffieldun, na, Fri Dec 01 14:59:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:59:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5345-4:1977 BSI 02-20001 0 Introduction This document is Part 4 of code of practice
28、BS 5345. The code offers guidance in the selection, installation and maintenance of electrical apparatus for use in areas where flammable materials are generated, processed, handled or stored, and which are therefore potentially hazardous. In common with the earlier code of practice for the use of e
29、lectrical apparatus in hazardous areas, CP 1003-1:1964, CP 1003-2:1966 and CP 1003-3:1967, the present code is divided into a number of Parts. Each Part deals with the installation and maintenance requirements appropriate to one of the types of protection which may be used to achieve electrical safe
30、ty, or with basic requirements and considerations which are fundamental to the use of electrical apparatus in hazardous areas, and which therefore provide the basis for the other Parts of the code. The full list of Parts is as follows: Part 1: Basic requirements for all Parts of the code; Part 2: Cl
31、assification of hazardous areas1); Part 3: Installation and maintenance requirements for electrical apparatus with type of protection “d”. Flameproof enclosure1); Part 4: Installation and maintenance requirements for electrical apparatus with type of protection “i”. Intrinsically safe apparatus and
32、systems; Part 5: Installation and maintenance requirements for electrical apparatus with type of protection “p”. Pressurisation and continuous dilution1); Part 6: Installation and maintenance requirements for electrical apparatus with type of protection “e”. Increased safety1); Part 7: Installation
33、and maintenance requirements for electrical apparatus with type of protection N1); Part 8: Installation and maintenance requirements for electrical apparatus with type of protection “s”. Special protection1); Part 9: Installation and maintenance requirements for electrical apparatus with type of pro
34、tection “o”. Oil-immersed apparatus and with type of protection “q”. Sand filled apparatus1); Part 10: Installation and maintenance requirements for electrical apparatus for use with combustible dusts1); Part 11: Specific industry applications1); Part 12: The use of gas detectors1). This Part of the
35、 code should be read in conjunction with the other Parts, and in conjunction particularly with Parts 1 and 2 which, taken together, describe the fundamental considerations which affect the selection, installation and maintenance of all electrical apparatus used in hazardous areas. The code of practi
36、ce is based on the concept, which is accepted internationally, of dealing with the risk of fire and explosion by area classification. This concept recognizes the differing degrees of probability with which explosive (flammable) concentrations of combustible gas or vapour may arise in installations i
37、n terms of both the frequency of occurrence and the probable duration of existence on each occasion. The detailed considerations which are to be taken into account are described in Part 2 of the code. For completeness, and for the convenience of readers, the definitions appropriate to area classific
38、ation are repeated here. It should be noted that whereas formerly classified areas were known as Divisions, they are now called Zones. Three sets of conditions are recognized, viz: It should be noted that this concept of area classification deals only with risks due to flammable gases and vapours an
39、d, by implication, mists. It does not deal with combustible dusts which may lie quiescent for long periods of time until disturbed into suspension by a suitable mechanism. An area classification concept is being developed for dusts. By implication, an area which is not classified as Zone 0, 1 or 2 i
40、s deemed to be a non-hazardous or safe area. If doubt exists as to the classification of an area which is judged to be hazardous or potentially hazardous, guidance should be sought at an early stage from the authority having jurisdiction in the industry or area concerned (see Parts 1 and 2 of the co
41、de). 1) In course of preparation. Zone 0 In which an explosive gas-air mixture is continuously present or present for long periods. Zone 1 In which an explosive gas-air mixture is likely to occur in normal operation. Zone 2 In which an explosive gas-air mixture is not likely to occur in normal opera
42、tion, and if it occurs it will exist only for a short time. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:59:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5345-4:1977 2 BSI 02-2000 Electrical apparatus used in each of the classified Zones should be suitably protected by design and man
43、ufacture, and should also be installed and maintained so as to ensure its safe use. The code of practice BS 5345, in offering guidance in the selection, installation and maintenance of suitably protected apparatus, should be used for all new installations. It should also be used for changes to exist
44、ing installations, though it is recognized that minor changes only to certain existing installations may need to be made in accordance with the recommendations of the earlier code. It is intended however, that CP 1003-1, CP 1003-2 and CP 1003-3 will eventually be withdrawn from use. Notwithstanding
45、application of the installation recommendations of the code to new installations and changes to existing installations, the recommendations for maintenance should be applied to all electrical apparatus and installations, irrespective of age and date of installation. It should also be noted that the
46、installation and maintenance recommendations described in the code are supplementary to and not alternative to any regulations which would apply to installations in non-hazardous areas (see also Part 1 of the code). Section 1. General 1 Scope This Part of BS 5345 considers the concept of ensuring el
47、ectrical safety in hazardous areas by means of type of protection “i”: intrinsic safety, and offers guidance on the installation and maintenance of electrical apparatus and systems, which are protected in accordance with this type of protection, in hazardous areas. Only explosion risks due to the pr
48、esence of flammable gases and vapours are considered in this Part of the code. Combustible dusts are excluded from this Part and are dealt with in Part 10. NOTEExpert advice on the application of intrinsic safety may be obtained through the organizations listed in Appendix A. 2 References The titles
49、 of the publications referred to in this code are listed on the inside back cover. 3 Definitions and explanation of terms The definitions and explanations of terms given in Part 1 of this code of practice apply equally to this Part. The definitions and explanations of terms which apply particularly to the concept of type of protection “i” are as follows: 3.1 intrinsic safety a protection technique based upon the restriction of electrical energy within apparatus and of interconnecting wiring, exposed to a potentially explos
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