The minimum IP rating for pressurised enclosures is IP4X (IP 3X for alarmed pz enclosures),
Not all enclosures are suitable for pressurisation, but the seals may only be designed to
prevent entry of contaminants, not to maintain an over-pressure within the enclosure.
Enclosures must therefore be appropriately designed, be strong enough to withstand impact tests
and internal over-pressure, and have effective and correctly oriented seals.
The enclosure ducts shall be capable of withstanding a minimum overpressure of 200Pa (2mBar). They must also withstand an over-pressure equivalent to 1.5 times the maximum working over-pressure, or the maximum over-pressure with all outlet ducts closed.
Enclosure covers/doors #
Where the interior of a type px enclosure can be accessed via doors/covers without the use of tools or keys, an interlock is required to automatically de-energise the electrical supply when the door/cover is opened.
Doors/covers must display the warning: “Do not open when an explosive atmosphere may be present”.
When pressurised enclosure contains components which have hot surfaces, or are energy-storing (e.g. capacitors), doors/covers should be fitted with warning notices which state the necessary time delay after isolation of the supply before opening the covers.
