ATEX Temperature Classes T1-T6: What Do They Mean for Exproof Fans?
In explosive gas atmospheres, an excessively hot surface can become an ignition source even without an electrical spark. T1-T6 temperature classes therefore limit the maximum surface temperature that explosion-protected equipment may reach.
Why temperature class matters
The surface temperature of equipment used in a hazardous area must remain below the ignition temperature of the gas or vapour that may be present. The T class communicates this limit in a standard marking and is a key parameter in exproof fan selection.
What are the T1-T6 limits?
- T1: 450°C
- T2: 300°C
- T3: 200°C
- T4: 135°C
- T5: 100°C
- T6: 85°C
What changes as the T number increases?
As the T number increases, the permitted maximum surface temperature decreases. For an application requiring T4, suitable T4, T5 or T6 equipment may be considered. T3 equipment allows a surface temperature up to 200°C and therefore does not meet a T4 requirement.
Fan and motor must be evaluated together
The motor marking is important, but the operating conditions of the complete fan must also be considered. Bearings, possible mechanical friction, process temperature and conveyed-air temperature can influence surface temperatures. Ambient-temperature limits stated in the certificate must also be respected.
Information needed for correct selection
Provide the required temperature class or gas ignition temperature together with the zone and gas group. On the performance side, specify airflow, pressure and conveyed-air temperature. This allows the safety classification and fan duty to be verified in one selection process.