Explosion proof typeExplosion proof certificationtechnology

1、 Explosion proof principle of explosion-proof type "d"

Explosion proof typeExplosion proof type is to enclose all components of the equipment that may ignite explosive gas mixtures in a single enclosure. The enclosure can withstand the internal explosion of combustible mixtures that penetrate through any joint surface or structural gap of the enclosure without damage, and will not ignite an explosive environment formed by one or more gases or vapors from the outside（See alsoGB 3836.2standard）. Place all components that may generate sparks, arcs, and hazardous temperatures into an explosion-proof enclosureZhongnuo TestingSeparate the internal space of the device from the surrounding environment. There are gaps in the explosion-proof shell, which may contain explosive gas mixtures due to the breathing and gas permeation effects of electrical equipment. When an explosion occurs, the shell can withstand the generated explosion pressure without damage. At the same time, the structural gaps of the shell can cool the flame, reduce the flame propagation speed or terminate the acceleration chain, preventing flames or dangerous flame products from crossing the explosion-proof gap and igniting the external explosive environment, thus achieving the purpose of explosion-proof.

2、 Main explosion-proof measures:

1. Requirements for material of explosion-proof shell

（1）The explosion-proof shell needs to withstand the explosive pressure generated by the internal explosive gas explosion, and cannot rupture or deform to damage the explosion-proof performance, such as the gap at the joint surface increasing during the explosion.

（2）The explosion-proof shell must meet two basic conditions:

A. The shell has sufficient mechanical strength to withstand internal explosive pressure without damage and without permanent deformation that affects explosion-proof performance.

B. All seams and pores on the shell wall that are open to the outside world are smaller than the corresponding maximum experimental safety gap

2. The gap length and width of the explosion-proof joint surface, as well as the surface smoothness requirements.

The casing of electrical equipment is generally composed of a casing and a cover, and there are often rotating shafts (such as rotating motors), control rods, and other components on the casing wall. The joints between the cover and the shell, as well as between the above-mentioned components and the shell, form a path from the inside out. Combustible gases enter the interior of the equipment shell through these gaps. When an explosion occurs inside, the explosion flame will pass throughZhongnuo TestingThese gaps spread to the outside of the casing, igniting the explosive environment around them. If the gap is small and the path from the inside out is relatively long, the flame cannot be transmitted to the outside of the shell. The standard defines such a joint as an explosion-proof joint surface.

3. Requirements for fasteners and threaded holes

The fasteners of the explosion-proof shell must withstand the tensile force generated by the explosion inside the shell, such as a side length of0.5mThe cube explosion-proof shell of the cover bears the pressure when hydrogen gas explodes inside the shell22Tons. If the lid is used8If each fastening screw is tightened, the tensile force that each screw bears during the overpressure test is4Tons. As can be seen from the above, the requirements for the fasteners themselves and screw holes of the explosion-proof shell are very high.

4. Requirements for transparent parts

5. Requirements for adhesives and sealing agents

6. Grounding

7. Cable and conduit entry devices

8. Chain and warning signs, etc.

3、 Applicable standards:

1GB3836.2-2010-Electrical equipment for explosive gas environments2Part: Composed of explosion-proof shell"D"Protected equipment

4、 Classification of Explosion proof Equipment

Explosion proof type "d" is classified according to the types of explosive gas environments it is allowed to useIClass andIIAIIBIICClass. This explosion-proof type of equipment is suitable for12District premises.

Class II explosion-proof electrical equipment according toZhongnuo TestingMaximum test safety gapMESG（Mm）Divided intoIIAIIBIICThree levels:

The so-called maximum test safety gap is at a length of25mm, in compliance withIEC79-1Aof8Ascending the ball describes the gap in the test within the product

MESG.

Note: Class IIC electrical equipment can replaceIIAIIBLevel equipment;

Class IIB electrical equipment can replaceIIALevel equipment;