WIKA 55 - Page 10

EN
11583747.07 12/2021 EN/DE/FR/ES
10 WIKA additional operating instructions model 55 (ATEX)
Hazardous dust atmosphere
For dusts, the procedure specied in ISO/IEC 80079-20-2 for
determining the ignition temperature has to be applied. The
ignition temperature is determined separately for dust clouds and
dust layers, respectively. For dust layers, the ignition temperature
depends on the dust layer thickness per EN/IEC 60079-14.
Ignition temperature
of dust
Maximum permissible medium
temperature (in the measuring system)
Dust cloud T
cloud
< 2/3 T
cloud
Dust layer T
layer
< T
layer
− 75 K − (reduction depending on the
layer thickness)
The permissible maximum medium temperature must not exceed
the lowest determined value, even in case of a malfunction.
Explosive atmosphere consisting of hybrid mixtures
The instruments must not be used in areas in which an
atmosphere consisting of explosive hybrid mixtures (dusts mixed
with gases) can occur.
3) Mount the instrument in such a way that, taking into consideration
the inuence of convection and heat radiation, no deviation above or
below the permissible ambient and medium temperatures can occur.
4) The instruments must be earthed via the process connection.
This is why electrically conductive sealing should be used at
the process connection. Alternatively, take other measures for
grounding. External sources of stray electric currents depend on
end use application and must be assessed by the end user.
5) Avoid handling of materials that react dangerously with the
materials used for the instrument, and substances liable to
spontaneous combustion.
3. Special conditions for use (X conditions)