Electrical explosion protection class for coal water slurry gasification and coal grinding plant
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There is a project that uses the water-coal slurry gasification process; rod mills are employed for slurry preparation, and the water used for this purpose contains organic volatile components. The flammable and explosive substances involved include coal dust, DMF, toluene, propylene, triethylamine, and isopropanol. What electrical explosion protection rating should be chosen? Is an IP55 protection rating for the motor along with an explosion-proof rating of EXdⅡBT4 sufficient? Is EXdⅢCT4 still needed?
For coal dust protection, it is best to choose a model with IP65 rating; there is no issue with the explosion-proof rating.
Should explosion protection use IIB or IIIC?
Definition of explosion-proof equipment: Electrical equipment that will not cause ignition in the surrounding explosive environment under specified conditions. They are divided into two categories: Category I: Electrical equipment used in coal mines; Category II: Electrical equipment intended for use in all other explosive gas environments outside of coal mines and underground sites. Category II can be further divided into IIA, IIB, and IIC types. Devices designated as IIB can be used under the same conditions as those of category IIA; devices of category IIC can be used under the conditions applicable to both IIA and IIB devices. The ⅡC rating represents a higher level of explosion protection, but it does not mean that the equipment has the best performance. Maximum surface temperature: The highest temperature reached by any component of an electrical equipment that could cause ignition in an explosive environment surrounding it, when the equipment is operating under the most unfavorable conditions within its specified range. The maximum surface temperature should be below the flammability temperature. For example: if the ignition temperature of the explosive gas in the environment surrounding the explosion-proof sensor is 100°C, then under the most severe operating conditions, the highest surface temperature of any component of the sensor should be below 100°C. Temperature categories: Electrical equipment for explosive environments is classified into groups T1–T6 based on its maximum surface temperature. T1: 450 ℃ ； T2: 300 ℃ ； T3: 200℃ ； T4: 135 ℃ ； T5: 100 ℃ ； T6: 85℃. In my opinion, an explosion protection rating of dⅡCT4 is more than sufficient.
One that is resistant to dust explosions should be chosen
CLASS II Dust, ⅡC Hydrogen – Minimum ignition spark energy: 0.019 mJ. The letter C indicates that the gas is hydrogen, while B indicates that the gas is ethylene. The requirement for Class C is higher. As for coal slurry grinding mills, I haven’t found any strict specifications regarding whether B or C applies; it depends on the owner’s choice
The original poster might not have understood; there is now a difference between grades II and III. When choosing grade IIB, the main consideration is explosion protection for organic components, whereas explosion protection for bituminous coal dust is explicitly classified under grade IIIC. In this case, which factor should take precedence when making a choice? Do ⅢC and ⅡB include concepts within them, and which one should be given priority? Should both be chosen?