【BS英國標準】BS EN 61241-1-2004 Electrical apparatus for use in the presence of combustible dust — Part 1 Protection by enclosures “t—” .doc

british standardbs en61241-1:2004incorporating corrigenda nos. 1 and 2electrical apparatus for use in the presence of combustible dust part 1: protection by enclosures “td”the european standard en 61241-1:2004 has the status of abritish standardics 29.260.20 bs en 61241-1:2004national forewordthis british standard was published by bsi. it is the uk implementation of en 61241-1:2004, incorporating corrigendum december 2006. it should be read in conjunction with bs en 61241-0. it is identical with iec 61241-1:2004. together with bs en 61241-0, it supersedes bs en 50281-1-1:1999 which will be withdrawn on 1 october 2008. it partially supersedes bs 6467-1:1985 and bs 6467-2:1988 which are withdrawn.the uk participation in its preparation was entrusted by technical committee gel/31, electrical apparatus for explosive atmospheres, to subcommittee gel/31/20, apparatus for use in the presence of combustible dust.a list of organizations represented on this subcommittee can be obtained on request to its secretary.this publication does not purport to include all the necessary provisions of a contract. users are responsible for its correct application.compliance with a british standard cannot confer immunity from legal obligations.amd. no.datecomments15758corrigendum no. 125 november 2005revision of supersession details16958corrigendum no. 228 february 2007revision of en foreword and supersession details in national foreword, and addition of annex zzthis british standard was published under the authority of the standards policy and strategy committee on13 january 2005 bsi 2007isbn 0 580 45200 xamendments issued since publicationeuropean standarden 61241-1norme europenneeuropische normjune 2004ics 29.260.20english versionelectrical apparatus for use in the presence of combustible dustpart 1: protection by enclosures td(iec 61241-1:2004)matriels lectriques pour utilisationen prsence de poussires combustibles partie 1: protection par enveloppes td (cei 61241-1:2004)elektrische betriebsmittel zur verwendung in bereichen mit brennbarem staubteil 1: schutz durch gehuse td (iec 61241-1:2004)this european standard was approved by cenelec on 2004-06-01. cenelec members are bound to comply with the cen/cenelec internal regulations which stipulate the conditions for giving this european standard the status of a national standard without any alteration.up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the central secretariat or to any cenelec member.this european standard exists in three official versions (english, french, german). a version in any other language made by translation under the responsibility of a cenelec member into its own language and notified to the central secretariat has the same status as the official versions.cenelec members are the national electrotechnical committees of austria, belgium, cyprus, czech republic, denmark, estonia, finland, france, germany, greece, hungary, iceland, ireland, italy, latvia, lithuania, luxembourg, malta, netherlands, norway, poland, portugal, slovakia, slovenia, spain, sweden, switzerland and united kingdom.ceneleceuropean committee for electrotechnical standardization comit europen de normalisation electrotechnique europisches komitee fr elektrotechnische normungcentral secretariat: rue de stassart 35, b - 1050 brussels 2004 cenelec - all rights of exploitation in any form and by any means reserved worldwide for cenelec members.ref. no. en 61241-1:2004 epage 15en 612411:2004forewordthe text of document 31h/168/fdis, future edition 1 of iec 61241-1, prepared by sc 31h, apparatus for use in the presence of combustible dust, of iec tc 31, electrical apparatus for explosive atmospheres, was submitted to the iec-cenelec parallel vote and was approved by cenelec as en 61241-1 on 2004-06-01.this part of en 61241 is to be read in conjunction with en 61241-0.the following dates were fixed: latest date by which the en has to be implemented at national level by publication of an identicalnational standard or by endorsement(dop)2007-07-01 latest date by which the national standards conflictingwith the en have to be withdrawn(dow)2008-10-01this european standard was prepared under a mandate given to cenelec by the european commission and the european free trade association and supports the essential requirements of directive 94/9/ec.annexes za and zz have been added by cenelec.endorsement noticethe text of the international standard iec 61241-1:2004 was approved by cenelec as a europeanstandard without any modification.contentsintroduction . 41scope . 62normative references . 63terms and definitions . 74construction . 75practice a and practice b . 76supplementary requirements for electrical apparatus protected by enclosures forpractice a for use in zones 20, 21 and 22 . 77supplementary requirements for electrical apparatus protected by enclosures forpractice b for use in zone 20 or 21 . 87.1joints . 87.1.1plain joints . 87.1.2spigotted joints. 87.1.3gasketed joints. 97.2operating rods, spindles or shafts . 97.2.1general . 97.2.2running contact seals . 97.2.3power shafts . 97.2.4operating rods. 107.3clearance of bolts . 108verification and tests . 118.1general . 118.2type tests . 118.2.1tests for dust exclusion by enclosures . 118.2.2thermal tests . 139marking . 13annex za (normative) normative references to international publications with theircorresponding european publications . 14annex zz (informative) coverage of essential requirements of ec directives .15bibliography. 16figure 1 plain joints . 8figure 2 spigotted joints . 8figure 3 gasketed joints .9 figure 4 power shafts for speeds of 100r/min or more . 10figure 5 clearance of bolts . 11table 1 plain joints . 8table 2 gasketed joints .9 table 3 power shafts for speeds of 100 r/min or more . 10table 4 power shafts for speeds of less than 100 r/min . 10introductionmany dusts which are generated, processed, handled and stored, are combustible. w hen ignited they can burn rapidly and with considerable explosive force if mixed with air in the appropriate proportions. it is often necessary to use electrical apparatus in locations where such combustible materials are present, and suitable precautions must therefore be taken to ensure that all such apparatus is adequately protected so as to reduce the likelihood of ignition of the external explosive atmosphere. in electrical apparatus, potential ignition sources include electrical arcs and sparks, hot surfaces, and frictional sparks.areas where dusts, flyings and fibres in air occur in dangerous quantities are classified as hazardous and are divided into three zones according to the level of risk.generally, electrical safety is ensured by the implementation of one of two considerations, i.e. that electrical apparatus be located where reasonably practicable outside hazardous areas and that electrical apparatus be designed, installed and maintained in accordance with measures recommended for the area in which the apparatus is located.combustible dust can be ignited by electrical apparatus in several ways:by surfaces of the apparatus that are above the minimum ignition temperature of the dust concerned. the temperature at which a type of dust ignites is a function of the properties of the dust, whether the dust is in a cloud or layer, the thickness of the layer and the geometry of the heat source;by arcing or sparking of electrical parts such as switches, contacts, commutators, brushes or the like;by discharge of an accumulated electrostatic charge;by radiated energy (e.g. electromagnetic radiation);by mechanical sparking or frictional sparking or heating associated with the apparatus. in order to avoid ignition hazards it is necessary that:the temperature of surfaces on which dust can be deposited, or which would be in contact with a dust cloud, is kept below the temperature limitation specified in this standard;any electrical sparking parts, or parts having a temperature above the temperature limit specified in iec 61241-14:-are contained in an enclosure which adequately prevents the ingress of dust, or-the energy of electrical circuits is limited so as to avoid arcs, sparks or temperatures capable of igniting combustible dust;any other ignition sources are avoided.compliance with this part of iec 61241 will only provide the required level of safety if the electrical apparatus is operated within its rating and is installed and maintained according to the relevant codes of practice or requirements, for example in respect of protection against over-currents, internal short-circuits, and other electrical faults. in particular, it is essential that the severity and duration of an internal or external fault be limited to values that can be sustained by the electrical apparatus without damage.several techniques are available for the explosion protection of electrical apparatus in hazardous areas. this standard describes the safety features of these types of explosion protection techniques and specifies the installation procedures to be adopted.it is most important that the correct selection and installation procedures be followed to ensure the safe use of electrical apparatus in hazardous areas.two different types of practice, a and b, are specified in this standard and are intended to provide an equivalent level of protection.both of these practices are in common use and the requirements of each should be followed without mixing either the apparatus requirements and selection/installation requirements of the two practices. they adopt different methodology with the primary differences being:practice apractice bw ritten principally as performance-based requirementsw ritten principally as prescriptive-based requirementsmaximum surface temperature is determined with 5 mm layer of dust and installation rules require 75 k marginbetween the surface temperature and ignition temperature of the particular dustmaximum surface temperature is determined with12,5 mm layer of dust and installation rules require25 k margin between the surface temperature and ignition temperature of the particular dustmethod of determining dust ingress is according toiec 60529 ip codemethod of determining dust ingress is in accordance with the heat cycling testelectrical apparatus for use in the presence of combustible dust part 1: protection by enclosures “td”1scopethis part of iec 61241 is applicable to electrical apparatus protected by enclosures and surface temperature limitation for use in areas where combustible dust may be present in quantities which could lead to a fire or explosion hazard. it specifies requirements for design, construction and testing of electrical apparatus.this standard supplements the general requirements in iec 61241-0.note iec 61241-14 gives guidance on the selection and installation of the apparatus. apparatus within the scope of this standard may also be subjected to additional requirements in other standards for example, iec 60079-0.the ignition protection is based on the limitation of the maximum surface temperature of the enclosure and on other surfaces which could be in contact with dust and on the restriction of dust ingress into the enclosure by the use of dust-tight or dust-protected enclosures.the application of electrical apparatus in atmospheres which may contain explosive gas as well as combustible dust, whether simultaneously or separately, requires additional protective measures.w here the apparatus has to meet other environmental conditions, for example, protection against ingress of water and resistance to corrosion, additional methods of protection may be necessary. the method used should not adversely affect the integrity of the enclosure.this standard does not apply to dusts of explosives which do not require atmospheric oxygen for combustion, or to pyrophoric substances.this standard is not applicable to electrical apparatus intended for use in underground parts of mines as well as those parts of surface installations of such mines endangered by firedamp and/or combustible dust.this standard does not take account of any risk due to an emission of flammable or toxic gas from the dust.2normative referencesthe following referenced documents are indispensable for the application of this document. for dated references, only the edition cited applies. for undated references, the latest edition of the referenced document (including any amendments) applies.iec 60529:2001, degrees of protection provided by enclosures (ip code)iec 61241-0, electrical apparatus for use in the presence of combustible dust part 0: general requirements 11 to be published.3terms and definitionsfor the purposes of this document, the terms and definitions given in iec 61241-0, as well as the following definitions, apply.3.1dust ignition protection type “td”all relevant measures specified in this standard (e.g. dust ingress protection and surface temperature limitation) applied to electrical apparatus protected by an enclosure to avoid ignition of a dust layer or cloud4constructionin addition to the requirements of clause 4 of iec 61241-0, the following applies. apparatus for use in zone 20:if the enclosure of the equipment is in accordance with the requirements of this standard, and all gaskets preventing the ingress of dust are not stressed by moving parts (e.g. shaft, operating rod), the enclosure is considered as infallible and the fault analysis is only applicable to the electrical circuit.5practice a and practice btwo different types of practice, a and b, are specified in this standard. both are intended to provide an equivalent level