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Unread 05-31-2010, 09:59 PM   #1
Mackinac Movies
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Join Date: Apr 2010
Location: Northern Michigan
Posts: 161
Default Pressure relief valve

Going to share my weekend science project.

I am a little worried about my 1HP b-Air blower and my CB 16x8 screen. So I have been thinking about an easy home-made device to vary the pressure inside the screen without using the zipper, which I am worried could fail being 1/2 unzipped.

I used a salvaged 3" gate valve, a 4" (3") T, and a 5" to 4" rubber fermco coupler.

I thought the gate valve would dump enough air out the T that the screen would partially deflate, and that I could slowly close it until the screen was at a good working pressure, without building up too much pressure. My results were a little interesting.

The construction was straight forward. Since schedule 40 PVC has several hundred working psi, I was not worried about even gluing the parts together for this test. It turn out the fermco coupler will actually tighten onto the rectangular blower opening with the band clamp.
As you can see, the gate valve is all the way open. When I inflated the screen I was running about 4 1/2-5 " of pressure, where I previously established that operating should be about 4 ".
OK, so maybe the 3" T opening isn't venting enough air. I removed the gate valve and tried blowing up the screen again. This is the interesting part: The screen inflated properly without any air coming out of the open hole! After the screen inflated, the air vented, and established about a 4 1/2 " pressure rating as before.

I don't have access to a 4" gate valve to test, and I think the cost is too much to justify the experiment. But I am kinda thinking now, that I may run my little contraption with the open hole to lower the max psi rating on my 16x8 screen. I figure it has to be a little better then just unzipping the vent and putting the stress on the stitching.
-- Neil --

Last edited by Mackinac Movies : 05-31-2010 at 10:04 PM.
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