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Temperature Measurement · Glossary

What is Temperature Class?

T1 to T6Temperature Measurement

Temperature class is the maximum surface temperature of electrical equipment in a hazardous area, coded T1 to T6.

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Temperature Class Explained

Equipment must not get hot enough to ignite the gas present. The T class of the equipment must be lower than the autoignition temperature of the gas.

Process heat also matters: a sensor head on a hot pipe can exceed its marked class through conduction.

Temperature Class: Typical Values

T1450 °C
T2300 °C
T3200 °C
T4135 °C
T5100 °C
T685 °C
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Calculators for Temperature Class

CalculatorTemperature Class CalculatorFree online calculator with formula and worked example.CalculatorDust Ignition Temperature CalculatorFree online calculator with formula and worked example.

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ToolEx Marking DecoderFree interactive tool on instrumentationblog.in.

Frequently Asked Questions

What is Temperature Class?

Temperature class is the maximum surface temperature of electrical equipment in a hazardous area, coded T1 to T6.

Is T6 better than T4?

T6 means a lower maximum surface temperature, so it suits more gases; T4 is enough for most hydrocarbons.

Where is T class marked?

On the Ex marking, for example Ex db IIC T4 Gb.

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