Technical Update - Maximum Surface Temperature
What is maximum surface temperature?
As per IEC 60079-0 "Maximum Surface Temperature" is the highest temperature which is attained in service under the most adverse condition (but within the specified tolerances) by any part or surface of Ex equipment.
Why is this so important?
The maximum surface temperature, determined by the tests outlined in IEC60079 is used by manufacturers of Ex Equipment to assign a temperature class (T class). See below classification table for group II electrical equipment:
| T1 | ≤ 450 °C |
| T2 | ≤ 300 °C |
| T3 | ≤ 200 °C |
| T4 | ≤ 135 °C |
| T5 | ≤ 100 °C |
| T6 | ≤ 85 °C |
Once fully certified and assigned, the temperature class of Ex equipment can be related to auto-ignition temperature (AIT). AIT is the lowest temperature (of a surface) at which, under specified conditions, an ignition of a flammable gas or vapour in mixture with air or air/inert gas occurs.
So, the maximum surface temperature can be used to assign the T class of Ex equipment which in turn allows users to select Ex equipment suitable for their particular application.
Sound complicated? Wondering how to navigate temperature classification with an Ex p panel?
Expo Technologies solution: PressurEx Enclosure
PressurEx enclosures from Expo Technologies are a standardised range of enclosures available in 20 sizes, with a range of selectable options, assembled and tested together with a right-sized purge controller.
When ordered with Expo Technologies' populated panel certification you can be sure that you are safe and compliant with complete system certified for T4 applications.