J. Phil Thien's Projects

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.

We have completed a separator using a 30 gal galvanized steel trash can ahead of a HF 2HP collector and have retained the 4" HF wye feeding the separator.  We now want to add protection to avoid collapsing the can should there be a suction blockage.

For permanent protection, we plan on building the relief valve described by johncarl in his 6/24/09 post.  It apparently works, and is quite sexy.  And maybe we will add stiffening rings as well.

But in the interim, we were thinking of adding a simple rupture disc-type device.  It would simply be a thin membrane that would replace the end cap on one of the wye ends feeding the separator.  Maybe nothing more that plastic wrap (with a few pinhole starter holes) attached with a rubber band like shown in the image below.

Do you think this would work? Or is this a dumb idea?  Has anyone tried it and come up with a membrane that is proven to work?  Would appreciate any and all input and ideas.

Thanks to Phil for this innovative, most useful device, and to the contributors to this Board, the ideas of whom I have liberally stolen.

Anyway, I am in the midst of designing a mobile base for my HF/Thien Separator and have a question about orienting the elbow that the dust hose attaches to, which is coupled to inlet elbow feeding the separator.  I am using 4" ABS SD pipe.  Should the dust hose elbow be coplaner with the separator inlet elbow, or rotated 90 or 270 deg on the axis - or does it matter?

Thanks for any advice!