However,use will depend on the protected enclosure’s integrity and normal pressure setting. How much purging gas is used?Īverage protective gas consumption during pressurization at a 0.10 inch(2.5mm) enclosure pressure should fall somewhere between 0.1 to 3.5 SCFH per cubic foot (2.83 to 99.11 l/hr) of enclosure volume. In rare circumstances,enclosure pressures as high as 2.5inches (63.5mm) of water may be required to offset sudden atmospheric pressure fluctuations, such as those created near missile launching or off-shore drilling platforms. In some circumstances, a minimum enclosure pressure of 0.50 inches (12.7 mm) of water is required to protect against ignitable dust.īut in all cases, a higher enclosure pressure should be maintained to create a reasonable safety factor. One psi is equal to 27.7 inches of water. Most purging applications require a minimum enclosure pressure of 0.10 inches (2.5 mm) of water.

Some companies purge with nitrogen – you can use other inert gases but nitrogen is commonly available. The flow rate and duration depends on the enclosure volume and national & international standards. Generally, we purge with instrument-grade compressed air. The equipment inside the enclosure does not require approvals or certifications. Purge & pressurization enables you to use any electrical equipment inside an enclosure in a hazardous location.īefore control units power-up electrical equipment, they first flush hazardous gas and dust from the enclosure or panel, cabinet, motor housing, etc., with clean uncontaminated air.

Only pressurization is required in a Class II, dust atmosphere.

Pressurization is the process of bringing compressed air or inert gas within an enclosure to a pressure where there is no ingress of hazardous gasses or combustible gas.īoth purging and pressurization are required in a Class I,gas atmosphere. Purging is the process of supplying enclosures with compressed air or inert gas at the proper flow and pressure in order to reduce the hazardous gas inside the enclosure to a safe level. Purge & Pressurization Systems Interview Questions

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