1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 6704 : 1996 NO COPYING
2、 WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Code of practice for Selection, installation and maintenance of intrinsically safe electrical equipment in coal minesThis British Standard, having been prepared under the direction of the Engineering Sector Board, was published under the a
3、uthority of the Standards Board and comes into effect on 15 November 1996 BSI 1996 First published August 1987 Second edition November 1996 The following BSI references relate to the work on this standard: Committee reference MRE/3/3 Draft for comment 94/705033 DC ISBN 0 580 25195 0 BS 6704 : 1996 A
4、mendments issued since publication Amd. No. Date Text affected Committees responsible for this British Standard The preparation of this British Standard was entrusted by Technical Committee MRE/3, Mining electrical equipment, to Subcommittee MRE/3/3, Intrinsic safety, upon which the following bodies
5、 were represented: Association of British Mining Equipment Companies British Aggregate Construction Materials Industries British Iron and Steel Producers Association Confederation of United Kingdom Coal Producers Health and Safety Executive Transmission and Distribution Association (BEAMA)BS 6704 :
6、1996 BSI 1996 i Contents Page Committees responsible Inside front cover Foreword ii Code of Practice Section 1. General 1.1 Scope 1 1.2 References 1 1.3 Definitions 1 1.4 Information on legislation 2 1.5 Information on certification 3 1.6 Information on certification of electrical apparatus and syst
7、ems 3 1.7 Marking of apparatus certified to BS 5501 : Part 7 6 Section 2. Selection and installation of electrical apparatus and systems 2.1 Selection 8 2.2 Installation 9 Section 3. Inspection and testing 3.1 General 12 3.2 Inspection 12 3.3 Routine inspection 12 3.4 Insulation and earth continuity
8、 testing 13 3.5 Records 13 Section 4. Maintenance and repair 4.1 General 14 4.2 Maintenance work in a hazardous area 14 4.3 Maintenance work in a non-hazardous area 14 4.4 Cable disconnection 14 4.5 Batteries 14 4.6 Electrical measuring instruments 14 4.7 Repair and overhaul 15 Annexes A (normative)
9、 Competence of personnel 16 B (informative) Characteristics of mining type cables 16 Tables 1 Standards dealing with the design, construction and testing of electrical apparatus for use in hazardous atmospheres 4 B.1 Telephone cable inductance and resistance ratios (nominal values) 16 B.2 Signalling
10、 cable inductance and resistance ratios (nominal values) 17 B.3 Electrical characteristics of pliable wire armoured cables to BS 6708 : 1991 (nominal values) 17 B.4 Electrical characteristics of two-core steel wire armoured cable generally in accordance with BS 6346 (nominal values) 17 Figures 1 Cer
11、tification mark 3 2 Example of marking of apparatus for connection to other apparatus and which does not incorporate a power source 7 3 Example of marking of a mains driven power supply unit contained within a flameproof enclosure 7 List of references 18ii BSI 1996 BS 6704 : 1996 Foreword This revis
12、ion of BS 6704 has been prepared by Subcommittee MRE/3/3 and reflects changes in legislation since the first edition was published in 1987. This standard provides guidance on the correct selection, installation and maintenance of intrinsically safe electrical equipment for use in potentially explosi
13、ve atmospheres in coal mines. This standard supersedes BS 6704 : 1987 which is withdrawn. As a code of practice, this British Standard takes the form of guidance and recommendations. It should not be quoted as if it were a specification and particular care should be taken to ensure that claims of co
14、mpliance are not misleading. Attention is drawn to the Health and Safety at Work etc. Act 1974 1 and the Mines and Quarries Act 1954 2, the Regulations made under these Acts and also any other appropriate statutory requirements or Bye-laws. These place responsibility for complying with specific safe
15、ty requirements on the manufacturer and the user. The addresses of the recognized certification test houses appointed by the Secretary of State for Employment under the Electrical Equipment for Explosive Atmospheres (Certification) Regulations 1990 3 are: Health and Safety Executive, Electrical Equi
16、pment Certification Service (EECS), Harpur Hill, Buxton, Derbyshire, SK17 9JN. SIRA Certification Service, (SCS) Saighton Lane, Saighton, Chester, CH3 6EG. Compliance with a British Standard does not of itself confer immunity from legal obligations.BS 6704 : 1996 BSI 1996 1 Section 1. General 1.1 Sc
17、ope This British Standard describes the concept of ensuring electrical safety in hazardous atmospheres in coal mines by means of the type of protection i (intrinsic safety), provides background information and gives recommendations on the selection, installation, inspection and testing, and maintena
18、nce and repair of intrinsically safe electrical apparatus, systems and networks. Electrical safety of apparatus installed outside the hazardous atmosphere, or which is safeguarded by a type of protection other than intrinsic safety, is also considered in so far as the selection, installation and mai
19、ntenance of such apparatus could affect intrinsically safe circuits. Only explosion risks due to the presence of flammable gases and vapours are considered. Combustible dusts are excluded except for coal dust layers which could be ignited by elevated surface temperatures. Design or performance aspec
20、ts of intrinsically safe apparatus pertinent to operational safety are not considered. 1.2 References 1.2.1 Normative references This British Standard incorporates, by dated or undated reference, provisions from other publications. These normative references are made at the appropriate places in the
21、 text and the cited publications are listed on page 18. For dated references, only the edition cited applies; any subsequent amendments to or revisions of the cited publication apply to this British Standard only when incorporated in the reference by amendment or revision. For undated references, th
22、e latest edition of the cited publication applies, together with any amendments. 1.2.2 Informative references This British Standard refers to other publications that provide information or guidance. Editions of these publications current at the time of issue of this standard are listed page 18, but
23、reference should be made to the latest editions. 1.3 Definitions For the purposes of this British Standard the following definitions apply. 1.3.1 intrinsic safety A protection technique based upon the restriction of electrical energy within both apparatus and interconnecting wiring, exposed to a pot
24、entially explosive atmosphere, to a level below that which can cause ignition by either sparking or heating effects. NOTE. Because of the method by which intrinsic safety is achieved it is necessary to ensure that not only the electrical apparatus exposed to the potentially explosive atmosphere but
25、also other electrical apparatus with which it is interconnected is suitably constructed. 1.3.2 intrinsically safe circuit A circuit in which no spark nor any thermal effect produced under prescribed test conditions (which include normal operation and specified fault conditions) is capable of causing
26、 ignition of a given explosive atmosphere. 1.3.3 electrical apparatus An assembly of electrical components and circuits or parts of circuits, usually contained within a single enclosure. NOTE. An apparatus may occasionally be in more than one enclosure, e.g. a telephone instrument or a portable radi
27、o transceiver with a hand microphone. 1.3.4 intrinsically safe electrical apparatus Electrical apparatus in which all the circuits are intrinsically safe. 1.3.5 associated electrical apparatus Electrical apparatus in which the circuits are not all intrinsically safe but which contains circuits that
28、can affect the safety of intrinsically safe circuits connected to it. NOTE. Associated electrical apparatus may be either: a) electrical apparatus that has an alternative standard type of protection suitable for its use in the appropriate potentially explosive atmosphere, e.g. a flameproof enclosure
29、 containing an intrinsically safe power supply; or b) electrical apparatus not protected for use in a potentially explosive atmosphere, e.g. a recorder that is installed in a safe area on the surface, connected to an intrinsically safe transducer situated within a potentially explosive atmosphere un
30、derground and where only the recorder input circuit is intrinsically safe. 1.3.6 intrinsically safe system Two or more items of electrical apparatus and interconnecting wiring in which any circuits intended for use in a potentially explosive atmosphere are intrinsically safe circuits. 1.3.7 intrinsi
31、cally safe network Two or more intrinsically safe systems that are interconnected in a defined manner. 1.3.8 intrinsically safe equipment A term embracing intrinsically safe apparatus, systems and networks. 1.3.9 normal operation The operation of intrinsically safe electrical apparatus or associated
32、 electrical apparatus when it conforms electrically and mechanically to its design specification and is used within the limits specified by the manufacturer. 1.3.10 fault A defect of any component, or a defective connection between components, upon which the intrinsic safety of a circuit depends. NO
33、TE. If a fault can lead to a subsequent fault, or faults, the primary and subsequent failures are considered to be a single fault.2 BSI 1996 BS 6704 : 1996 Section 1 1.3.11 safety coupler A device that is used to limit the transfer of electrical energy between intrinsically safe circuits. 1.3.12 saf
34、ety barrier A device that is used to limit the transfer of electrical energy from a non-intrinsically safe to an intrinsically safe circuit. 1.4 Information on legislation 1.4.1 Legislation affecting the use of electricity in British mines 1.4.1.1 The Electricity at Work Regulations 1989 4 supported
35、 by the Health and Safety Executive (HSE) approved code of practice, The use of electricity in mines 5, govern the use of electricity in all mines. Additional requirements for coal mines are also contained in the Coal and Other Mines (Locomotives) Regulations 1956 6, the Coal and Other Mines (Safety
36、 Lamps and Lighting) Regulations 1956 7, the Coal and Other Safety-Lamp Mines (Explosives) Regulations 1993 8, the Coal and Other Mines (Ventilation) Regulations 1956 9, and the Management and Administration of Safety and Health at Mines Regulations 1993 10. 1.4.1.2 The principal statutory safeguard
37、s against the risk of a firedamp ignition by electricity can be summarized as follows. a) In potentially gassy parts of a mine the use of electrical equipment which is capable of producing incendive sparking in normal working is not permitted. See Regulation 19 of the Electricity at Work Regulations
38、 1989 4 and 1.4.1.3. b) Regular periodic testing of the mine environment using gas detectors and methanometers is required by the Coal and Other Mines (Ventilation) Regulations 1956 9 and the Management and Administration of Safety and Health at Mines Regulations 1993 10, and where the amount of fla
39、mmable gas in the general body of the mine air exceeds 1.25 % by volume the supply of electricity has to be cut off. Signals, telephones, caplamps, gas detectors and other similar essential safety equipment are excluded from the requirement providing they are of a type approved by the Health and Saf
40、ety Executive (Mines Inspectorate) as being suitable to remain energized when flammable gas concentrations exceed the stipulated limit. c) Under the Management and Administration of Safety and Health at Mines Regulations 1993 10, the mine manager is required to ensure that all plant and equipment is
41、 safely installed and commissioned and to provide and implement a scheme to ensure the proper inspection, examination, testing and maintenance of all electrical equipment and to appoint a sufficient number of suitably qualified and competent persons to direct and manage, supervise and undertake all
42、the above activities. 1.4.1.3 Regulation 19 of the Electricity at Work Regulations 1989 4 prohibits the use of certain electrical equipment at safety-lamp mines in zones below ground in which firedamp is likely to occur in a quantity sufficient to indicate danger. The manager of the mine is responsi
43、ble for deciding which parts of the mine can be considered free from flammable gas and, using his discretion, he has to identify the zones where Regulation 19 of the Electricity at Work Regulations 1989 4 applies and show them on a plan of the mine. There are no absolute rules governing the identifi
44、cation of such zones since circumstances and conditions may vary greatly from mine to mine, but guidance is given in the Coal and Other Mines (Ventilation) Regulations 1956 9 on the method to be used in order to declare a roadway free from flammable gas. However, in general all places within 300 m o
45、f a working face and all places ventilated by auxiliary ventilation should, in the absence of evidence to the contrary, be considered hazardous zones. 1.4.1.4 It is generally accepted that electrical equipment certified by a European notified body (see 1.5.1) as conforming to the appropriate standar
46、ds for flameproof or intrinsically safe electrical equipment for use in group I atmospheres (class 1 in earlier standards), is acceptable for use in hazardous zones in coal mines. 1.4.1.5 Regulation 20 of the Electricity at Work Regulations 1989 4 contains the requirement for the supply to all elect
47、rical apparatus, with the exception of approved signalling, telephone, gas detection or other equipment required for the safety of persons, to be switched off if the amount of flammable gas in the general body of air at the place in question exceeds 1.25 % by volume. The aim is to ensure that only a
48、pparatus essential for safety remains energized in an explosive atmosphere. Such approved apparatus is normally certified as intrinsically safe in accordance with either BS 1259 or category ia of BS 5501 : Part 7 : 1977. NOTE. The types of electrical equipment approved by the Health and Safety Execu
49、tive (HSE) for the purpose of Regulation 20 of the Electricity at Work Regulations 1989 4 are mentioned in 1.4.1.2b. The HSE also approves other equipment for the purposes of other Regulations. For example shot firing equipment and locomotives should not be confused with the Regulation 20 equipment, as they are neither intrinsically safe equipment, nor allowed to remain energized when flammable gas concentrations exceed 1.25 %. 1.4.2 European legislation 1.4.2.1 EU article 100 directives Within the European Union under Article 100 of the T
