Diagnosing Peter Thiel separator suction loss

[Doug Hobkirk]

I built a Peter Thiel separator for my Craftsman shop vac. Recently it's stopped working properly - I lose too much suction.
1) With 40' 1.5" hose connected directly to 2.5" Craftsman hose, I can lift a quart can easily with suction at the end of the hose.
2) With 40' 1.5" hose connected directly to the separator and 2.5" Craftsman hose going into the separator, I can NOT lift a quart can, although I can easily lift a pint can.

So I figure there must be a vacuum leak.
* The plywood lid fits so snugly I can lift the can by lifting the lid.
* But while I can not pick up a quart can, it provides enough suction to suck in the sides of my 25 gallon galvanized pail. (It pops back when I turn off the vac).

Any suggestions? (Other than brace the can so it can't collapse)

Thanks

[Wayne Lomman]

It's most likely vacuum loss due to the extra friction introduced with the separator. Vacuum leaks will be easily detectable. You would have found them by now. Also, it will improve things no end if you use smooth bore hose. Corrugated hose is disastrous for flow loses. Cheers

[Pete Staehling]

You mean Phil Thien, not Peter Thiel right?

There may be some loss due to friction within Thien baffle system, but I didn't find it to be all that significant in my system. I'd continue to check for leaks. Maybe puff some smoke near all potential leakage points and watch for where the smoke goes.

[Frederick Skelly]

You mean Phil Thien, not Peter Thiel right?

I wondered that too, Pete.

[Dan Friedrichs]

No, the Thiel version is better than the Thien version, but you have to watch out for it making political campaign contributions when you're not watching :)

As others said, it must be a vacuum leak. The test you are using - picking up something heavy - is a test of static pressure (ie - maximum pressure differential possible with no air moving). As such, any friction losses due to the separator don't exist, because there is no air moving during this test (unless you have a leak). So it has to be a vacuum leak.


A more granular way to test this would be to build a manometer.

[Doug Hobkirk]

You mean Phil Thien, not Peter Thiel right?

DAMN! That's embarrassing.

[Doug Hobkirk]

No, the Thiel version is better than the Thien version, but you have to watch out for it making political campaign contributions when you're not watching :)

As others said, it must be a vacuum leak. The test you are using - picking up something heavy - is a test of static pressure (ie - maximum pressure differential possible with no air moving). As such, any friction losses due to the separator don't exist, because there is no air moving during this test (unless you have a leak). So it has to be a vacuum leak.

A more granular way to test this would be to build a manometer.

I like Thien, don't like Thiel, so doubly red faced...

I'd think the collapsing sides of the can indicate I have a tight seal, but maybe that's causing a leak when it's happening. I will admit I was shocked the first time this happened.

How and where do you attach a manometer? I wanted to check it at the end of the hose, so I can compare the impact of 40' of 1.5" pool hose against 10' of 2.5" shop vac hose (etc.). If I attach it to the separator top, will that reflect the impact of the different hoses?

Or is there a link you recommend?

At any rate, thank you much!


PS - I get your point about static pressure, but I was proud of my test. I even contemplated building a special container so I could add weights to make more "granular" measurements.

[Nick Decker]

Doug, I know where you would mount a manometer on a dust collector, not sure how (or if) it would work on a shop vac.

A longer hose will definitely cost you suction. The measurement method I use is, does it suck up what I need sucked up? If not, shorten the hose. :)