Pressure Test Results and Pressure Relief Disc Design - HFDC/Thien Set-up

[bill70j]

I completed pressure testing and installing a vacuum relief device to prevent my separator can from collapsing under dead-head conditions.  Thanks to Vodkaman (3/27/11 post) for your ideas on the design.

I began by installing a pressure gage on my mobile rig as shown in the very last image.  Then while watching the gage, began closing the blast gate on the inlet wye until I saw the can start to deflect.  That happened with the blast gate about 90% closed at a reading of about 7.2" of W.C.

I converted the 7.2" of W.C. to psi.  (7.2/12X14.7/33.91) = 0.26psi.  Then I converted that to pounds force on a 3.5"D disc.  (0.26X1.75X1.75X3.14159) = 2.5 pounds force.  I took out my box of springs and, using the kitchen scale, found one that compressed well to the 2.5 pound figure (assuming for this design that pounds mass and pounds force are the same).

Then I got materials I had laying around to build the device.  I had on hand the 1/2" MDF, 3/4" dowel stock, Lexan, 5/16" hex bolt, and 2" ABS SD pipe - so needed only to buy the 3.5" O-ring.

I built the device, installed it, adjusted the spring to the 2.5 pound mark and fired up the blower.  I began closing the blast gate.  And as it approached the fully closed position, I could see the spring begin to compress, opening up the disc.  That happened at about 7.3" of W.C.  So it looks like my can is safe under all conditions.

Hope this can be helpful to others.

[Vodkaman]

Well thought out. Good job with the valve.

And that's engineering.

Dave

[bill70j]

Thanks again for your help, Dave.  Everything seems to work.  I haven't decided what to do with the manometer.  Maybe leave it hooked up to see if it can help determine when to backflush the Wynn cartridge.  But that may be a loooong time from now judging by how well the Thien separator is working.  I have had virtually nothing carry over into the HF poly bag after dumping several trashcanfulls of stuff.