Hazardous Area Temperature Class Calculator
Find the temperature class (T1 to T6) of Ex equipment from its maximum surface temperature, or the class required for a gas or vapour with a known autoignition temperature.
- The highest class whose limit is not exceeded by 120 °C
Temperature classes
| Class | Maximum surface temperature |
|---|---|
| T1 | 450 °C |
| T2 | 300 °C |
| T3 | 200 °C |
| T4 | 135 °C |
| T5 | 100 °C |
| T6 | 85 °C |
Temperature Classes (IEC 60079-0)
T4 ≤ 135 °C T5 ≤ 100 °C T6 ≤ 85 °C
The equipment’s maximum surface temperature, at the rated ambient, must be below the autoignition temperature of every gas or vapour that may be present.
Worked example
Hydrogen sulphide ignites at about 260 °C, so equipment must be T3 (≤ 200 °C) or better. A device with a 120 °C surface is T4.
Frequently Asked Questions
What is a temperature class?
A rating of the maximum surface temperature of Ex equipment, from T1 (450 °C) to T6 (85 °C).
Can T6 equipment be used where T3 is required?
Yes. A lower maximum surface temperature is always acceptable.
Is temperature class the same as gas group?
No. Gas group (IIA, IIB, IIC) relates to ignition energy and flame paths; temperature class relates to hot surface ignition.
Learn more on the blog
Temperature classes in hazardous areas
A practical, field focused guide on instrumentationblog.in that explains the theory behind this calculator and how engineers apply it on real plants.
Read Full Article