Ex "Px" Motors

[NickParker]

Upon reading "Px" - Pressurization, it indicates that the pressurization reduces the classification within the pressurized enclosure from Zone 1 to non-hazardous.
What does this mean? If the enclosure is effectively reduced to non-hazardous, how can it still be used in Zone 1?

 

[Gr8blu]

Usually the pressurization is done using a non-volatile gas (like nitrogen) - or with "clean dry air" from a non-hazardous area.

What this means is that the INTERNALS of the machine are now in a non-hazardous area - which then allows higher surface temperatures and (possibly) arcing contacts. However the EXTERNAL surfaces - and anything that is not specifically within the pressurized enclosure (such as outboard exciter or ground brush) must meet the hazardous (Zone 1) requirements.

The sheet metal (or other materials) used to form the enclosure therefore acts as a physical barrier between the two levels of hazard - much the same as a concrete wall of a building.

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