Videotec MAXIMUS MHXT - Manual (Page 44)

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44
A Appendix - Gas group classification
The table below shows the classification of some gases and vapours, according to the explosion-proof
protection group and the temperature class. For a complete list see IEC/EN 60079-12 and IEC/EN 60079-20.
GAS GROUP CLASSIFICATION
Temperature class (Maximum surface temperature of the housing) 1
Class
T1
450°C (842°F)
T2
300°C (572°F)
T3
200°C (392°F)
T4
135°C (270°F)
T5
100°C
T6
85°C (185°F)
I Methane
IIA Acetone
Ethanol
Ethyl acetate
Ammonia
Pure benzene
Acetic acid
Carbon monoxide
Methanol
Propane
Toluene
N-Butane
N-Butyl
Petrol
Diesel fuel
Avgas
Heating oil
N-Hexane
Acetaldehyde
Ether
Ethyl nitrate
IIB Ethylene
IIC Hydrogen Acetylene Carbon disulphide
Tab. 14 The above temperature classes automatically cover the lower classes (T6 is better than T1). Class IIB also covers class IIA. Class
IIC also covers classes IIB and IIA.
TEMPERATURE CLASS T1 T2 T3 T4 T5 T6
Maximum allowed surface temperature (°C) for the housing in the
corresponding class
450 300 200 135 100 85
Tab. 15 Normally referred to the maximum ambient temperature of installation. The lowest ignition temperature of the explosive
atmospheres must be higher than the maximum surface temperature of the housings.
The maximum surface temperature is determined for a 5mm-thick layer of powder and the installation
regulations require a margin of 75K between the surface temperature and the ignition temperature of the
powder under consideration.