What does H2 refer to in dⅡct4, which only contains H2?
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Dear experts, I’m a complete beginner in electrical engineering. I would like to ask what exactly is meant by H2 in dⅡct4 – it refers to H2, right? Thank you!
H2 is hydrogen; it contains only H2, that is, it consists solely of hydrogen! dⅡct4 is the explosion protection rating.
Common IIC-class gases include hydrogen, acetylene, carbon disulfide, etc. Among these, acetylene places the highest demands on explosion-proof enclosures; therefore, when obtaining a dIICT4 certificate, flat explosion-proof surfaces are not allowed. Instead, flanged or threaded explosion-proof designs are used, which is much more costly and complex. However, some manufacturers, in order to reduce costs or make it easier to obtain the certificate, claim that their products contain only hydrogen as indicated on the dIICT4 certificate. This allows them to use products with flat explosion-proof surfaces to get the certificate at a lower cost. Yet, the product label may not state that the product contains only hydrogen, but rather just indicate dIICT4. It should be noted that products with such certificates are suitable only for IIC-class hydrogen applications; they cannot be used for other IIC-class gases. The proper way to indicate explosion protection is dIIBT4+H2.
dIICT4 indicates the explosion protection rating, where d stands for flameproof type, IIC refers to an industrial gas environment, T4 denotes the surface temperature of the instrument, and H2 indicates use in a hydrogen environment.