【文章內(nèi)容簡介】 cts, mutators, brushes or the like。 ? by discharge of an accumulated electrostatic charge。 ? by radiated energy (. electromagic 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 6124114: 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 bustible 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 overcurrents, internal shortcircuits, 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. Page 5 EN 61241?1:2020 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 mon 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 A Practice B W ritten principally as performancebased requirements W ritten principally as prescriptivebased requirements Maximum surface temperature is determined with 5 mm layer of dust and installation rules require 75 K margin between the surface temperature and ignition temperature of the particular dust Maximum surface temperature is determined with 12,5 mm layer of dust and installation rules require 25 K margin between the surface temperature and ignition temperature of the particular dust Method of determining dust ingress is according to IEC 60529 – IP Code Method of determining dust ingress is in accordance with the heat cycling test Page 6 EN 61241?1:2020 ELECTRICAL APPARATUS FOR USE IN THE PRESENCE OF COMBUSTIBLE DUST – Part 1: Protection by enclosures “tD” 1 Scope This part of IEC 61241 is applicable to electrical apparatus protected by enclosures and surface temperature limitation for use in areas where bustible 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 612410. NOTE IEC 6124114 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 600790. 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 dusttight or dustprotected enclosures. The application of electrical apparatus in atmospheres which may contain explosive gas as well as bustible 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 bustion, 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 bustible dust. This standard does not take account of any risk due to an emission of flammable or toxic gas from the dust. 2 Normative references The 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 60529:2020, Degrees of protection provided by enclosures (IP Code) IEC 612410, Electrical apparatus for use in the presence of bustible dust – Part 0: General requirements 1 —————— 1 To be published. Page 7 EN 61241?1:2020 3 Terms and definitions For the purposes of this document, the terms and definitions given in IEC 612410, as well as the following definitions, apply. dust ignition protection type “tD” all relevant measures specified in this standard (. dust ingress protection and surf