《BS-5345-7-1979.pdf》由会员分享，可在线阅读，更多相关《BS-5345-7-1979.pdf（16页珍藏版）》请在三一文库上搜索。
1、BRITISH STANDARD BS 5345-7: 1979 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 7: Installation and maintenance requirements for electrical
2、 apparatus with type of protection N UDC 696.6:621.3 7:614.83 Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:59:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5345-7:1979 This British Standard, having been prepared under the direction of the General Electrotechnical Engineering Standard
3、s Committee, was published under the authority of the Executive Board and comes into effect on 30 November 1979 BSI 02-2000 The following BSI references relate to the work on this standard: Committee reference GEL/114 Draft for comment 75/20865 DC ISBN 0 580 11038 9 Cooperating organizations The Gen
4、eral 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: The organizations marked with an asterisk in the above list, together wi
5、th the following, were directly represented on the committee entrusted with the preparation of this British Standard: British Electrical and Allied ManufacturersElectronic Components Industry Federation* Association (BEAMA)*Electronic Engineering Association British Radio Equipment ManufacturersEngi
6、neering Equipment Users Association* AssociationHealth and Safety Executive* British Steel CorporationHome Office Department of Energy (Electricity)Institution of Electrical Engineers* Electric Cable Makers Confederation*Ministry of Defence* Electrical Contractors Association*National Coal Board* El
7、ectrical Contractors Association of ScotlandOil Companies Materials Association* Electrical Research Association*Post Office* Electricity Supply Industry in England andTelecommunication Engineering and Wales*Manufacturing Association (TEMA)* Association of Consulting EngineersDepartment of the Envir
8、onment Association of Mining Electrical andDepartment of the Environment (Building Mechanical EngineersResearch Establishment) (Fire Research British Electrical Systems AssociationStation) (BEAMA)Department of Trade (Marine Division) British Gas CorporationFire Offices Committee British Industrial M
9、easuring and ControlFire Protection Association Apparatus Manufacturers AssociationGeneral Council of British Shipping British Industrial Truck AssociationInstitute of Petroleum CBMPEInstitution of Gas Engineers Chief and Assistant Chief Fire OfficersInstitution of Mining Engineers AssociationLighti
10、ng Industry Federation Ltd. Council for Electrical Equipment forRotating Electrical Machines Association Flammable Atmospheres (BEAMA)(BEAMA) Council for Underground MachineryScientific Instrument Manufacturers ManufacturersAssociation Department of Energy (Petroleum) (OIL) Amendments issued since p
11、ublication Amd. No.Date of issueComments 4516July 1984Indicated by a sideline in the margin Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:59:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5345-7:1979 BSI 02-2000i Contents Page Cooperating organizationsInside front cover Forewordii 0Int
12、roduction1 Section 1. General principles 1Scope2 2References2 3Definitions and explanation of terms2 4Concept of Zone 23 5Description of technique3 6Relevant specifications3 7“Division 2 approved” apparatus3 Section 2. Selection of apparatus 8General4 9Permissible Zone of use4 10Temperature classifi
13、cation4 11Apparatus subgrouping4 12Environmental conditions5 13Requirements for certification of apparatus5 Section 3. Installation recommendations 14General5 15Wiring systems5 Section 4. Inspection, maintenance and testing 16General6 17Tests6 18Initial and periodic inspections6 19Maintenance7 20“Di
14、vision 2 approved” apparatus7 Appendix A Marking of apparatus9 Appendix B Comparison between type of protection N and “Division 2 approved” apparatus10 Appendix C Test for restricted breathing10 Table 1 Inspection schedule for apparatus with type of protection N8 Publications referred toInside back
15、cover Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:59:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5345-7:1979 ii BSI 02-2000 Foreword Many gases, vapours, mists and dusts encountered in industry are flammable. When ignited, they may burn readily and with considerable explosive forc
16、e if mixed with air in the 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 in order to reduce the lik
17、elihood of ignition of any 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 procedures. Eit
18、her the electrical apparatus 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 pro
19、tection of electrical apparatus 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
20、 safety features of these 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 therefore takes account
21、of the significant developments 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. It is important to note that this code of practice deals with explosion hazar
22、ds due to the presence of flammable gas/air mixtures; it does not provide guidance on the extra precautions to be taken where such gases involve a toxic hazard. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for t
23、heir 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 ii, pages 1 to 10, an inside back cover and a back cover. This standard has been updated
24、(see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 14:59:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5345-7:1979 BSI 02-20001 0 Introduction This document
25、is Part 7 of code of practice BS 5345. The code gives guidance in the selection, installation and maintenance of electrical apparatus for use in areas where flammable materials are generated, processed, handled or stored, and that are therefore potentially hazardous. In common with the earlier code
26、of practice for the use of electrical 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 that may be use
27、d to achieve electrical safety, or with basic requirements and considerations that are fundamental to the use of electrical apparatus in hazardous areas, and that therefore provide the basis for the other Parts of this code. The full list of Parts is as follows: Part 1: Basic requirements for all Pa
28、rts of the code; Part 2: Classification of hazardous areas1); Part 3: Installation and maintenance requirements for electrical apparatus with type of protection “d”. Flameproof enclosure; Part 4: Installation and maintenance requirements for electrical apparatus with type of protection “i”. Intrinsi
29、cally safe apparatus and systems; Part 5: Installation and maintenance requirements for electrical apparatus with type of protection “p”. Pressurization and continuous dilution1); Part 6: Installation and maintenance requirements for electrical apparatus with type of protection “e”. Increased safety
30、; Part 7: Installation and maintenance requirements for electrical apparatus with type of protection N; Part 8: Installation and maintenance requirements for electrical apparatus with type of protection “s”. Special protection1); Part 9: Installation and maintenance requirements for electrical appar
31、atus with type of protection “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 detector
32、s1). This Part of the code should be read in conjunction with the other Parts, particularly Parts 1 and 2 which, taken together, describe the fundamental considerations that affect the selection, installation and maintenance of all electrical apparatus used in hazardous areas. BS 5345 is based on th
33、e concept of area classification which recognizes the differing degrees of probability with, which explosive (flammable) concentrations of flammable gas or vapour may arise in installations in terms of both the frequency of occurrence and the probable duration of existence on each occasion. The deta
34、iled considerations that should be taken into account in deciding on an area classification are described in Part 2 of the code. For completeness, and for the convenience of readers, the definitions appropriate to area classification are repeated here. It should be noted that whereas, formerly, clas
35、sified areas were known as Divisions, they are now called Zones. Three Zones are recognized viz.: It should be noted that this concept of area classification deals only with risks due to flammable gases and vapours and, by implication, mists. It does not deal with flammable dusts, which may lie quie
36、scent 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 that is not classified as Zone 0, 1 or 2 is deemed to be a non-hazardous or safe area. If doubt exists as to the classification
37、 of an area that 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 code). 1) In course of preparation Zone 0 In which an explosive gas/air mixture is conti
38、nuously 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 operation, and if it occurs it will only exist for a short time. Licensed Copy: sheffieldun
39、sheffieldun, na, Fri Dec 01 14:59:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5345-7:1979 2 BSI 02-2000 Electrical apparatus used in each of the classified Zones should be suitably protected by design and manufacture, and should also be installed and maintained in a manner to ensure its safe us
40、e. BS 5345, in offering guidance in the selection, installation and maintenance of suitably protected apparatus, replaces CP 1003 and should be used for all new installations. It should also be used for changes to existing installations, though it is recognized that minor changes only to certain exi
41、sting 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 application of the installation recommendations of this code to existing install
42、ations, 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 installation and maintenance recommendations given in this code are supplementary to, and not alternative to, re
43、quirements which would apply to general industrial installations (see also Part 1 of this code). Section 1. General principles 1 Scope This Part of BS 5345 describes the concept of ensuring electrical safety in Zone 2 hazardous areas by means of type of protection N and gives guidance in the selecti
44、on, installation and maintenance of this type of electrical apparatus. Reference should be made to Part 1 of this code for other types of protection which are suitable for use in Zone 2. This code does not apply to the underground mining industry, where other precautions are necessary, though it is
45、recognized that the code may be applied to the surface installations of mines. Apparatus with type of protection N is designed for use in areas with flammable gas and vapour risks. For the use of this apparatus in areas with flammable dust risks see Part 10 of the code. 2 References The titles of th
46、e publications referred to in this code are listed on the inside back cover. 3 Definitions and explanation of terms The definitions and terms which are generally applicable to hazardous areas and electrical apparatus used therein are included in Part 1 of this code, to which reference should be made
47、. The definitions and terms which are particularly relevant to individual types of protection are indicated in the appropriate Parts of this code. For the purposes of this Part, the following definitions and terms apply. 3.1 type of protection N a type of protection applied to electrical apparatus s
48、uch that, in normal operation, it is not capable of igniting a surrounding explosive atmosphere, and a fault capable of causing ignition is not likely to occur 3.2 enclosure the external casing protecting the electrical and mechanical parts of apparatus. The term excludes cables 3.3 restricted-breat
49、hing enclosure an enclosure which is not hermetically sealed, but which is designed to prevent or restrict the entry of gases 3.4 enclosed-break device a device incorporating an electrical contact that is made and broken, the enclosure of which will withstand an internal explosion of the flammable gas or vapour which may enter it without suffering damage and without communicating the internal flammation to the external flammable gas or vapour, the net volume of the enclosure being not greater than 20 cm3 NOTEAn enclosed-break device does not nee