The order of explosion-proof ratings is straightforwardly recorded as A < B < C.
III | C | T 135℃ | Db | IP65 |
---|---|---|---|---|
III Surface dust | T1 450℃ | Ma | IP65 | |
T2 300℃ | Mb | |||
T3 200℃ | ||||
A Flammable flying flocs | Da | |||
T4 135℃ | ||||
Db | ||||
B Non conductive dust | T2 100℃ | Dc | ||
C Conductive dust | T6 85℃ |
For the ‘T’ rating, it’s remembered by its numerical order: the larger the number, the higher and safer the rating.
Therefore, an explosion-proof rating of BT4 surpasses that of AT2.
It’s important to clarify that ‘T’ denotes the maximum surface temperature of electrical devices. A T4 rating, set at 135°C, is applicable for explosive gases with flash points exceeding 135°C.