This part of GB 12476 specifies general requirements for the design, construction, testing and marking of electrical apparatus protected by any recognized safeguard technique for use in areas where combustible dust may be present in quantities that could lead to a fire or explosion hazard.
This standard is supplemented or modified by the following parts of GB 12476 concerning specific types of protection:
——Part 4: Protection by Intrinsic Safety “iD”;
——Part 5: Protection by Enclosures tD;
——Part 6: Protection by Encapsulation mD;
——Part 7: Type of Protection pD;
Note: GB 12476.2 gives guidance on the selection and installation of the apparatus. Apparatus within the scope of this part may also be subjected to additional requirements in other standards C for example, GB 3836.1.
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.
This part does not specify requirements for safety, other than those directly related to the explosion risk.
Where 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 is not to adversely affect the integrity of the enclosure.
This part is applicable to combustible dust atmosphere under atmospheric conditions.
This part does not apply to dusts of explosives that 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 fire damp 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.
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.
GB/T 70.1-2008 Hexagon Socket Head Cap Screws (ISO 4762: 2004, MOD)
GB/T 1040.2-2006 Plastics — Determination of Tensile Properties — Part 2: Test Conditions for Moulding and Extrusion Plastics (ISO 527-2: 1993, IDT)
GB/T 1043.1-2008 Plastics — Determination of Charpy Impact Properties — Part 1: Non-instrumented Impact Test(ISO 179-1: 2000, IDT)
GB/T 1408.1-2006 Insulating Materials—Test Methods for Electric Strength—Part 1:Test at Power Frequencies(IEC 60243-1: 1998, IDT)
GB/T 1800.2-2009 Geometrical Product Specifications (GPS) — Limits and Fits — Part 2: Tables of Standard Tolerance Grades and Limit Deviations for Holes and Shafts (ISO 286-2: 1988, MOD)
GB/T 2516-2003 General Purpose Metric Screw Threads — Limit Deviations(ISO 965-3: 1998, MOD)
GB 3836.1-2010 Explosive Atmosphere — Part 1: Equipment — General Requirements(IEC 60079-0-2007, MOD)
GB 3836.3-2010 Explosive Atmospheres—Part 3:Equipment Protection by Increased Safety e(IEC 60079—7: 2006, IDT)
GB 3836.4-2010 Explosive Atmospheres—Part 4:Equipment Protection by Intrinsic Safety i(IEC 60079-11: 2006, MOD)
GB 4208-2008 Degrees of Protection Provided by Enclosure (IP Code) (IEC 60529: 2001, IDT)
GB/T 4942.1-2006 Degrees of Protection Provided by the Integral Design of Rotating Electrical Machines (IP Code) - Classification(IEC 60034-5: 2000, IDT)
GB/T 5008.1-2005 Lead-acid Starter Batteries—Technical Conditions(IEC 60095-1: 2000, MOD)
GB/T 5277-1985 Fasteners—Clearance Holes for Bolts and Screws(eqv ISO 273: 1979)
GB/T 5782-2000 Hexagon Head Bolts(eqv ISO 4014: 1999)
GB/T 5783-2000 Hexagon Head Bolts — Full Thread(eqv ISO 4017: 1999)
GB/T 6031-1998 Rubber, Vulcanized or Thermoplastic — Determination of Hardness (Hardness between 10IRHD and 100IRHD) (ISO 48: 1994, IDT)
GB/T 6170-2000 Hexagon Nuts, Style 1 (eqv ISO 4032: 1999)
GB/T 8897.1-2008 Primary Batteries—Part 1:General (IEC 60086—1: 2007, MOD)
GB/T 9144-2003 General Purpose Metric Screw Threads — Preferable Plan (ISO 262: 1998, MOD)
GB/T 9341-2008 Plastics — Determination of Flexural Properties (ISO 178: 2001, IDT)
GB/T 11026.1-2003 Electrical Insulating Materials — Properties of Thermal Endurance — Part 1: Ageing Procedures and Evaluation of Test Results(IEC 60216-1: 2001, IDT)
GB/T 11026.2-2000 Guide for the Determination of Thermal Endurance Properties of Electrical Insulating Materials—Part 2: Choice of Test Criteria(IEC 60216-2: 1990, IDT)
GB 12476.2-2010 Electrical Apparatus for Use in the Presence of Combustible Dust — Part 2: Selection and Erection of Electrical Equipment (IEC 61241-14: 2004, IDT)
GB 12476.5-2013 Electrical Apparatus for Use in the Presence of Combustible Dust—Part 5: Protection by Enclosures tD (IEC 61241-1: 2004, IDT)
GB/T 12476.8-2010 Electrical Apparatus for Use in the Presence of Combustible Dust—Part 8:Test Methods—Methods for Determining the Minimum Ignition Temperatures of Dust(IEC 61241-2-1: 1994, IDT)
GB/T 13259-2005 High-pressure Sodium Lamp (neq IEC 60662: 2002)
GB 14048.3-2008 Low-voltage Switchgear and Controlgear — Part 3: Switches, Disconnectors, Switch-disconnectors and Fuse-combination Units(IEC 60947-3: 2005, IDT)
GB/T 15142-2011 Secondary Cells and Batteries Containing Alkaline or Other Non-acid Electrolytes-vented Nickel-cadmium Prismatic Rechargeable Single Cells(IEC 60623: 2001, IDT)
GB/T 16422.1-2006 Plastics - Methods of the Exposure to Laboratory Light Sources — Part 1: General Guidance(ISO 4892-1: 1999, IDT)
GB/T 19639.1-2005 Technical Conditions of Small-sized Valve-regulated Lead-acid Batteries(IEC 61056-1: 2002, MOD)
GB/T 23126-2008 Low Pressure Sodium Lamps — Performance Requirement(IEC 60192;2001, MOD)
HG 492-2009 Air Quality—Vocabulary
ISO 1818: 1975 Vulcanized Rubbers of Low Hardness (10 to 35 IRHD) — Determination of Hardness
IEC 60285: 1993 Alkaline Secondary Cells and Batteries — Sealed Nickel-cadmium Cylindrical Rechargeable Single Cells
IEC 61150: 1992 Alkaline Secondary Cells and Batteries — Sealed Nickel-cadmium Rechargeable Monobloc Batteries in Button Cell Design
3 Terms and Definitions
For purpose of this part, the following terms and definitions apply.
3.1
dust
small solid particles including fibres and flyings in the atmosphere which settle out under their own weight, but which may remain suspended in air for some time (includes dust and grit as defined in HG 492-2009)
3.2
combustible dust
dust, fibres or flyings that can burn or glow in air and could form explosive mixtures with air at atmospheric pressure and normal temperatures
3.3
conductive dust
dust, fibres or flyings with electrical resistivity equal to or less than 103 Ω?m
3.4
explosive dust atmosphere
mixture with air, under atmospheric conditions, of flammable substances in the form of dust, fibres or flyings in which, after ignition, combustion spreads throughout the unconsumed mixture
