Temperature Classification: T Class

We have already covered Ignition temperatures of material or gases in Section 5.5 and we stated the following:

The ignition temperature of a material, formerly known as auto-ignition temperature is the minimum temperature, under prescribed test conditions, at which the material can ignite and sustain combustion, when mixed with air at normal pressure, without a source of ignition.

Now we are talking about the Temperature Classification of Equipment ! Temperature classification is based on the maximum temperature which any relevant part of the equipment, which may be in contact with a flammable (explosive) gas, can reach, when operating within normal design ratings of -20°c to + 40°c.

Temperature classification is a system of classification of equipment into one of six temperature ranges from 850C up to 4500C. T Class ratings are based on a design range of the equipment being used in a minimum ambient air temperature of -200C and maximum of +400C.

The direct result of establishing the ignition temperature for a gas is to ensure that the maximum temperature which any relevant part of the equipment, which may be in contact with a flammable (explosive) gas, can be maintained at a temperature well below this figure. To aid this task both gases and equipment are given a temperature classification.

Selection of equipment must therefore ensure that the maximum surface temperature must not exceed the Ignition Temperature of the explosive mixture.