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Explosion-ProofElectricalEquipmentEngineeringPlastics|TechnicalSpecifications

Technical Specifications

Explosion-Proof Electrical Equipment Engineering Plastics

In the realm of engineering structural materials, particularly with engineering plastics, it’s crucial to assess not just their mechanical and electrical characteristics, but also their thermal stability and ability to resist static electricity.

engineering plastics

Thermal Stability

For explosion-proof electrical equipment, the plastic materials used in casings are required to demonstrate superior thermal stability. In specified testing conditions, the maximum temperature decrease should be 20K compared to the Temperature Index (TI) at 20000 hours on the heat resistance curve.

Anti-static Capabilities

Plastic materials must possess effective anti-static properties, which include measures to avert the generation and accumulation of static electricity. This can be achieved by adding appropriate conductive additives to lower the material’s volume and surface resistivity. When tested under specified conditions (10mm electrode distance), if the surface insulation resistance of modified plastic components does not exceed 10Ω, the material is deemed effective in preventing static build-up.

Beyond modifying the plastic material, static fire hazards can also be mitigated by limiting the exposed surface area of plastic casings (or parts) in explosion-proof electrical devices. Table 1 details the limits on the maximum surface area of plastic casings (or parts), while Table 2 specifies the diameter or width of elongated plastic parts, and the thickness of plastic coatings on metal surfaces.

Maximum Surface Area for Plastic Casings (or Parts)

Equipment category and levelEquipment category and levelMaximum area S/m ²Maximum area S/m ²Maximum area S/m ²
II100001000010000
IIHazardous areasZone 0Zone 1Zone 2
IIIIA level50001000010000
IIIIB level25001000010000
IIIIC level40020002000

Maximum Restricted Dimensions for Special Plastic Parts

Equipment category and levelEquipment category and levelThe diameter or width of a long strip/mmThe diameter or width of a long strip/mmThe diameter or width of a long strip/mmMetal surface plastic coating thickness/mmMetal surface plastic coating thickness/mmMetal surface plastic coating thickness/mm
II202020222
IIHazardous areasZone 0Zone 1Zone 2Zone 0Zone 1Zone 2
IIIIA level33030222
IIIIB level33030222
IIIIC level120200.20.20.2

Furthermore, plastics used for making casings (or components) of explosion-proof electrical devices should also exhibit excellent flame resistance and pass various tests like heat and cold resistance, and photoaging.

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