Product description
Ex p Control unit
APEX
mv
Page 18 of 80
01-37A2-7D0005_MV_Manual_Exp-Control-Unit_2021005_0_en.docx
Rev. 0
3
Product description
General information
The Ex p type of protection, referred to as “pressurised enclosure”, is based on
the measure of purging out any explosive gases that are in a closed enclosure
and then generating and maintaining a level of pressure that is higher than that
of the ambient atmosphere. As the pressure inside the enclosure is higher as the
atmospheric pressure, it is not possible at any time for explosive gases to
penetrate the inside of the enclosure. This creates an Ex-free area in which
electrical devices that are not themselves explosion-proof can be mounted and
operated.
The APEX control units described in these operating instructions function on the
principle of “pressurised enclosure with leakage loss compensation”.
Specifically, this means that an overpressure in an enclosure is maintained by
the addition of purging gas to compensate for the leakage losses from the
enclosure.
To ensure that an explosive atmosphere that has penetrated during downtimes
cannot become a hazard, the enclosure must be flushed with purging gas
(compressed air or inert gas) before commissioning. The quantity depends on the
inspection carried out during initial commissioning. The rate of flow is measured
or determined at the outlet of the pressurised enclosure.
Since a safe state in the enclosure is only reached when the operation phase is
started, it is necessary to use explosion-proof versions of the APEX control unit
with its system components.
