Pressure Switch for Type X Purge

fifty60

Senior Member
Location
USA
A piece of equipment has two sections, a 42" X 36" X 16" Hoffman enclosure, and a secondary section that is approximately 7 times larger than the Hoffman enclosure.

There is an opening between the two sections that is approximately the size of a soccer ball. Purged air will be entering the Hoffman enclosure. The end goal is to achieve Type X purge for the enclosure and the secondary area.

Will there be any pressure difference between the Hoffman enclosure and the secondary area? Or will they both maintain approximately the same amount of pressure?

My concern is that there is only one pressure switch, and it is located inside the Hoffman enclosure. With the purged air entering the Hoffman enclosure, will the Hoffman enclosure reach a higher pressure than the secondary enclosure, or will there be equalization between the two areas?
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
is this switch XP?

pressurization is just one part of the deal. you have to purge the enclosures on power up by blowing air or some other noncombustible gas through it to get rid of any flammable gases that might be present.
 

fifty60

Senior Member
Location
USA
The pressure switch is inside the purged enclosure and is not XP. For the initial startup the box is not purged, as the purge needs to begin the process of pushing the 4 volumes of air outside of the box before the machine can start.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
A piece of equipment has two sections, a 42" X 36" X 16" Hoffman enclosure, and a secondary section that is approximately 7 times larger than the Hoffman enclosure.

There is an opening between the two sections that is approximately the size of a soccer ball. Purged air will be entering the Hoffman enclosure. The end goal is to achieve Type X purge for the enclosure and the secondary area.

Will there be any pressure difference between the Hoffman enclosure and the secondary area? Or will they both maintain approximately the same amount of pressure?

My concern is that there is only one pressure switch, and it is located inside the Hoffman enclosure. With the purged air entering the Hoffman enclosure, will the Hoffman enclosure reach a higher pressure than the secondary enclosure, or will there be equalization between the two areas?
That depends on the volume of air you're pushing as to whether or not any back pressure will develop in the smaller enclosure. And if it does, it's probably only going to be a few inches of water. What's the CFM on the purge supply?
 

just the cowboy

Inactive, Email Never Verified
Location
newburgh,ny
No

No

I would not rely on a pressure switch in the small enclosure, The opening between will probably end up full of wires? I would put the pressure switch at the far end of the main enclosure.
 

fifty60

Senior Member
Location
USA
Thanks for the suggestion. The purged air is actually entering the larger enclosure, so the pressure sensor located (without obstruction) in the smaller enclosure should provide the worst case pressure. I will measure the pressure in both locations to confirm.
 

ras

Member
Location
buford, ga 30518
What type of x-purge are you using, you need to pressurize the smallest enclosure first and mount the vent or spark arrestor on the secondary enclosure.
 
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