Differential pressure (leak down) tester air requirement, compressor?

frtrkap

frtrkap

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frtrkap
Hi,

Couldn't find the info, I was wondering if someone had an answer.

What is the CFM requirement for a differential pressure tester? I wouldn't think it would be much, but I am looking for a small compressor that would work.

Thanks
 
I use a little pancake compressor and don't have any problems with that approach.
 
I think my compressor is 5 or 6 cfm at 100 psi. It works fine for compression tests. I have heard you can use a small air tank charged to 125 psi, but never tried it.
 
Consider the size of the tank. If the tank is small (1-4 gallon) it will run out of reserve quickly. I now have a 30 gallon at the airport.
 
I have a 20 gallon air tank. Charged to 125 PSI by the home compressor, it is more than enough to complete a compression test. The remaining air is used to blow dry wheel bearings, etc, and air left over to top off tires for the next 6 months.
 
Porter-Cable C2002R 150 PSI 6 Gallon Oil-Free Pancake Compressor works fine for compression testing
 
frtrkap said:
What is the CFM requirement for a differential pressure tester?
Click to expand...
To add to the above, pressure rating/ability more important than CFM. You're not running an air-tool or consuming vasts amount of air unless you have one heck of a leak. Have used everything from small 12v compressors to air tanks, as mentioned previously, to perform compression tests. Main issue is that it can deliver the correct PSI for the tester you are using.
 
I'm sure if you looked hard enough, you could find a 12 volt portable compressors that doesn't deliver sufficient pressure / flow.
You only need to blow 80 psi through an 0.040 inch orifice (0.060 inch for "big bore" engines).

Personally, I like the California Air Tools stuff due to the lack of noise.

According to this chart you would need 4.6 scfm for a .060" orifice, but in an engine that would correspond to 0/80 "compression" and if your engine is that bad, there is no need for the actual leak test. Figure half that. And if your compressor has a tank, figure about 1 or 2 scfm would keep up with the intermittent use as you go from cylinder to cylinder.

But I ain't no A&P and if you listen to my advice your airplane will probably crash into a school for children of personal injury attorneys.
 
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Thank you all for your help! I will probably try a small 2 gallon 125 PSI one and go from there!
 
frtrkap said:
Thank you all for your help! I will probably try a small 2 gallon 125 PSI one and go from there!
Click to expand...

I used to use a Campbell Hausfeld 2 gallon compressor:

220400_400x400.jpg


It got the job done but I really believe you'd be better served with 6 gallon or more. While this one did what I needed it to do it ran quite a bit as I did the test on all six cylinders. I didn't care that it ran so much but it was noisy and slow to refill.

The old saying is true, "buy the best and cry once."

YMMV ... but I doubt it.
 
The most of the little compressors will over load the old hangars I frequent, have 15 AMP wall lets. my compressor requires a 25 AMP input.
So when buying a compressor the AMP requirement becomes the important requirement. most any compressor will the job.
 
Witmo said:
For what? A jackhammer?
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I have no idea what jackhammers require.
This thread is about differential compression testers.
This is the spec required by the original SB. I doubt it has changed much.
 
Silvaire said:
Unless you've got one hell of a leak you don't need any cfm
Click to expand...
but it's a TCM.....he'll need a big un. ;)

BTW...tanks size is not what you want. That's the kind of stuff the marketing dept loves....it's the pump "flow" or CFM that's the metric to shop. Also, the starting in-rush current for those little pumps will exceed 15 amps....and many will trip hangar breakers. Good luck wit dat.
 
I have done compression tests for years with a small pancake compressor...even used an air tank with no problems. If the cylinders are at tc and no leaks, you will not use a lot of air.
 
It takes very little flow to do a compression check. If it is big enough for a nail gun it is big enough to do a compression check.
 
OK, so help me out here. I'm doing a series for Kitplanes mag (*) on doing a full hangar 12 volt solar system, including (if I can find one) a decent 12 volt compressor for only two jobs ... leakdown test and tire inflation. I'm not going to do impact wenches (sic) or rivet guns or the like.

Does anybody have a favorite 12 volt reasonably priced compressor? So far, the little Harbor Freight seems to be my unit of choice, but I'm willing to look at anything.

(*) The title of the series is "The HOG System (Hangar Off Grid)".

Jim
 
https://www.sears.com/craftsman-3-gallon-portable-air-compressor/p-00915362000P

I've used this one for several years and have been happy with it. Small enough to not trip the breaker (as long as I throttle back my 1000W worklamp) but large enough for a leakdown test. Oil lubrication is more durable than "oil-free" aka plastic. It's direct drive which is noisier/cheaper but they don't seem to sell any 1hp belt drives anymore. This unit is/was available from many suppliers. The supplied accessories (hose, tools) are junk but the compressor seems OK.
 
weirdjim said:
OK, so help me out here. I'm doing a series for Kitplanes mag (*) on doing a full hangar 12 volt solar system, including (if I can find one) a decent 12 volt compressor for only two jobs ... leakdown test and tire inflation. I'm not going to do impact wenches (sic) or rivet guns or the like.

Does anybody have a favorite 12 volt reasonably priced compressor? So far, the little Harbor Freight seems to be my unit of choice, but I'm willing to look at anything.

(*) The title of the series is "The HOG System (Hangar Off Grid)".

Jim
Click to expand...

Not to be confused with Harley Owners Group?

Here's a heavy duty 12V compressor but the price...ouch!

https://www.ebay.com/itm/OASIS-Air-...672?_trksid=p2349526.m4383.l4275.c10#viTabs_0

Seriously, a typical 12V compressor will not have near the power of a 120V unit for obvious reasons. My suggestion is to connect a large (20+ gallon) tank to it to compensate. The user would have to be patient and allow several minutes charging time between each cylinder that is leak tested. Also, the duty cycle of the compressor with a large tank would have to be high for durability. Most 12V compressors do not have fan cooling of the cylinder and thus a low duty cycle. Perhaps you could add an external cooling fan?
 
weirdjim said:
Does anybody have a favorite 12 volt reasonably priced compressor?
Click to expand...
Define "reasonably priced." I have a Puma 12v with a 2 gallon tank that went for $250 or so. Performs the items you wish and even can buck a rivet or 2 if needed. But if I were looking today California Air has a 12v model w/ tank for around $320 that I would buy instead.
 
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weirdjim said:
OK, so help me out here. I'm doing a series for Kitplanes mag (*) on doing a full hangar 12 volt solar system, including (if I can find one) a decent 12 volt compressor for only two jobs ... leakdown test and tire inflation. I'm not going to do impact wenches (sic) or rivet guns or the like.

Does anybody have a favorite 12 volt reasonably priced compressor? So far, the little Harbor Freight seems to be my unit of choice, but I'm willing to look at anything.

(*) The title of the series is "The HOG System (Hangar Off Grid)".

Jim
Click to expand...
Not exactly what you are asking for, but with a 12v powered battery charger, you could run a lot of tools. Including a compressor. I have this one, and it's kept up with my needs. The small tank means it runs continuously on big jobs, but that's true for all small compressors.



https://www.homedepot.com/p/RYOBI-1...table-Air-Compressor-Tool-Only-P739/305269932

https://www.homedepot.com/p/RYOBI-1...ger-for-use-with-12V-DC-Outlet-P131/100342149
 
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