HEYLO PV 4200 EX Bedienungsanleitung Seite 15

Explosion protection | Classification
Explosion groups, temperature classes
If the device group and the device category is used to determine, in which zone an apparatus may be
used, the explosion group and the temperature class determines, for which media the apparatus may
be used within the zones. In turn, the type of ignition does not present a quality characteristic, but is a
constructive solution chosen for the apparatus to realise the explosion protection.
Division into explosion groups
Depending on the type of ignition protection the explosion-proof apparatuses for gas, fogs and
vapours are divided up into three explosion groups (IIA-IIB-IIC). The explosion group is a measures for
the flammability of gases (explosive atmosphere). The demands on the apparatus increase from II A
to II C.
IIA IIB IIC
Increasing demands
Division into temperature classes
In case of explosion-proof apparatuses which are installed within the ex area, a division into six
temperature classes (T1 to T6) is made. As is wrongly assumed frequently, the temperature class is
not the application temperature of the apparatus, but the maximum permissible surface temperature of
the apparatus, which relative to an ambient temperature of +40 deg. C must not be exceeded at any
part of the surface and at no point in time. The maximum surface temperature must definitely be lower
than the ignition temperature of the surrounding medium. The demands on the apparatus increase
from T1 to T6.
EN
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