BS-4683-1-1971.pdf

BRITISH STANDARD BS 4683-1: 1971 Specification for Electrical apparatus for explosive atmospheres Part 1: Classification of maximum surface temperatures UDC 621.3-7:614.83 Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 01:49:28 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4683-1:1971 This British Standard, having been approved by the Electrical Industry Standards Committee, was published under the authority of the Executive Board on 12 March, 1971 © BSI 02-1999 The following BSI references relate to the work on this standard: Committee reference ELE/ELCP/4 Draft for comment 67/25790 ISBN 580 06168 X Co-operating organizations The Electrical Industry Standards Committee under whose supervision this British Standard was prepared consists of representatives from the following Government departments and scientific and industrial organizations: Associated Offices Technical CommitteeElectronic Engineering Association Association of Consulting Engineers*Engineering Equipment Users Association* Association of Mining Electrical andInstitution of Electrical Engineers Mechanical Engineers*Lighting Industry Federation Limited Association of Supervisory andMinistry of Technology* Executive EngineersMinistry of Defence* British Electrical and AlliedMinistry of Defence, Army Department Manufacturers Association*Ministry of Defence, Navy Department British Railways BoardMinistry of Power* British Radio EquipmentMinistry of Public Building and Works* Manufacturers AssociationMunicipal Passenger Transport Association Crown Agents for Oversea(Incorporated) Governments and AdministrationsNational Inspection Council for Electrical Department of Employment and Productivity*Installation Contracting Electric Cable Makers Confederation* National Physical Laboratory Electrical Contractors Association(Ministry of Technology) (Incorporated)Oil Companies Materials Association* Electrical Contractors Association of ScotlandPost office * Electrical Research Association*Public Transport Association (Incorporated) Electricity Council, the Central Electricity South of Scotland Electricity Board Generating Board and the Area Boards in England and Wales* The Government departments and scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the Committeee entrusted with the preparation of this British Standard: British Industrial Truck AssociationBritish Chemical Engineering Contractors Council of Underground Machinery Association ManufacturersNational Coal Board Fire Offices CommitteeBritish Industrial Measuring and Control Fire Protection AssociationApparatus Manufacturers Association Institute of PetroleumCouncil of British Manufacturers of Institution of Mining EngineersPetroleum Equipment Telecommunication Engineering and Manufacturing Association Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 01:49:28 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4683-1:1971 © BSI 02-1999i Contents Page Co-operating organizationsInside front cover Forewordii 1Scope1 2Definition1 3Classification1 4Marking1 Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 01:49:28 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4683-1:1971 ii © BSI 02-1999 Foreword In order to keep abreast of progress in the industries concerned, British Standards are subject to periodical review. Suggestions for improvements will be recorded and in due course brought to the notice of the committees charged with the revision of the standards to which they refer. A complete list of British Standards, numbering over 9,000, fully indexed and with a note of the contents of each, will be found in the BSI Catalogue which may be purchased from BSI Sales Department. The Catalogue may be consulted in many public libraries and similar institutions. This Part of BS 4683 is concerned with the surface temperature of all electrical equipment for use in hazardous areas where there is a risk of fire or explosion from the presence of an explosive atmosphere. This Part of BS 4683 is technically the same as the first edition of IEC Publication 79-8, “Classification of maximum surface temperature”. 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 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, page 1 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 Copy: sheffieldun sheffieldun, na, Fri Dec 01 01:49:28 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4683-1:1971 © BSI 02-19991 1 Scope This Part of this British Standard specifies six preferred maximum surface temperatures for electrical apparatus for use in explosive atmospheres. A system of marking is specified. 2 Definition For the purposes of this Part of this British Standard, the following definition applies: maximum surface temperature The highest temperature attained under practical conditions of operation within the rating of the apparatus (and recognized overloads, if any, associated therewith) by any part of any surface the exposure of which to an explosive atmosphere may involve a risk. NOTEFor flameproof apparatus, the surface to be considered is the external surface. For other types of apparatus, internal surfaces are equally important, if the explosive atmosphere has access to them. 3 Classification The classification is as shown in Table 1. A peak ambient temperature of 40 °C is assumed unless otherwise stated and marked (see 4.3). Table 1 Classification 4 Marking 4.1 Apparatus designed to operate at a maximum surface temperature not greater than one of the preferred maximum surface temperatures given in Table 1 shall be clearly marked with the symbol indicating the class, or with the preferred maximum surface temperature of the class, or both. 4.2 It is recognized that it may be expedient to design apparatus for a particular application in circumstances such that it would be undesirable for economic reasons to classify the equipment according to the next highest preferred maximum surface temperature. In that event, the apparatus shall be clearly marked with the maximum surface temperature at which it is designed to operate and may, in addition, be marked with the appropriate classification symbol given in Table 1. NOTE 1To avoid confusion between ordinary apparatus (see 4.1) and special apparatus (see 4.2), it is recommended that when the marking includes both a non-preferred temperature and a classification symbol, the symbol should follow the temperature and be put within brackets. NOTE 2Apparatus designed for a maximum surface temperature greater than 450 °C should be marked with the temperature only. 4.3 For special applications the maximum surface temperature may be based on a peak ambient temperature other than 40 °C. Higher ambient temperatures shall be, and lower ambient temperatures may be, taken into account in determining the rating of the apparatus. In that event, the value of the peak ambient temperature shall be clearly marked on the apparatus. ClassMaximum surface temperature °C T1450 T2300 T3200 T4135 T5100 T685 For example:Ordinary apparatus:T1 450 °C Special apparatus:350 °C (T1). 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