Quatech INTERBUS S manual Ex-1.3.4 Temperature classes, Ex-1.3.5 Types of ignition protection

4 • Application in Explosive Environments

Classification meeting CENELEC and IEC

Ex-1.3.4 Temperature classes

The maximum surface temperature for electrical components of explosion protection group I is 150 °C (danger due to coal dust deposits) or 450 °C (if there is no danger of coal dust deposit).

In line with the maximum surface temperature for all ignition protection types, the electrical components are subdivided into temperature classes, as far as electrical components of explosion protection group II are concerned. Here the temperatures refer to a surrounding temperature of 40 °C for operation and testing of the electrical components. The lowest ignition temperature of the existing explosive atmosphere must be higher than the maximum surface temperature.

Temperature classes	Maximum surface	Ignition temperature
	temperature	of the combustible materials
T1	450 °C	> 450	°C
T2	300 °C	> 300	°C ≤ 450 °C
T3	200 °C	> 200	°C ≤ 300 °C
T4	135 °C	> 135	°C ≤ 200 °C
T5	100 °C	>100 °C ≤ 135 °C
T6	85°C	> 85	°C ≤ 100 °C

The following table represents the division and attribution of the materials to the temperature classes and material groups in percent:

Temperature classes
T1	T2	T3	T4		T5	T6	Total*
26.6 %	42.8 %	25.5 %
	94.9 %		4.9 %		0 %	0.2 %	432
Explosion group
IIA	IIB	IIC					Total*
80.2 %	18.1 %	0.7 %					436
				* Number of classified materials

Ex-1.3.5 Types of ignition protection

Ignition protection defines the special measures to be taken for electrical components in order to prevent the ignition of surrounding explosive atmospheres. For this reason a differentiation is made between the following types of ignition protection:

WAGO-I/O-SYSTEM 750 Modular I/O-System