Check Valve Plastic Valve

On Tuesday when I was putting my compressor back together the check valve leaked noticeably. After several attempts to clean and polish the
faces to mate I gave up and dropped an O-ring into the valve to seal it up until I get a replacement valve.
It got to bothering me though. In all the time I have owned the compressor I don't think that check valve ever really closed up perfectly. If I happen to be working outside on a day when I had the shop shutdown and the air valve turned off I would notice the compressor would cycle on at least once in a day's time. I just lived with it, and if I was going to be out of the shop for more than a couple days I would turn the compressor off entirely.
When I turned off the air and closed the ball valve Tuesday night the compressor gage read 145. Wednesday morning it had dropped maybe 2 lbs. It was still above 140. I think that's an order of magnitude better than it ever was before. It was about the same today. It got me to thinking.
You might recall I mentioned the plastic valve looked like it was made of PEEK. PEEK is a pretty hard plastic. In 3000 PSI air guns Acetal is often used for the valve against a brass or aluminum seat. PEEK is sometimes used in higher pressure airguns because above around 3500-3800 PSI Acetal may start to "flow." Those valves are typically a tapered plug that fits into a different angle or even edge radius tapered hole. The has a minimal contact area for sealing but because its a plug in a hole pressure causes it to center and seal pretty well. I've got a 3000 PSI Marauder in my back shop I haven't had to refill in nearly a year. I use it for pests in my garden.
Anyway, I was thinking it might be useful to design my own compressor check valve using acetal instead of PEEK using proven valave tech like that in an air gun. PEEK might just be to hard to form a good seal easily at the low pressure of shop air. Sure a plug in a hole design might stick a little more than the "flat ring" design the compressor manufacturer used, but the pressure differential should quickly over come that. Peak pressure might show a smidgeon high until the vale opened, but not for very long. As soon as the valve opened up it would equalize pressure and flow fine until the compressor motor turned off.
Since there is an unloader the compressor would never sit with excessive back pressure.
Heck at the relatively low pressure of shop air even HDPE might work as the valve against a smooth metal seat.
I don't mind buying a check valve. I actually already ordered 2. They are $10 each and some change. I just don't want to install one to have it be just the same as the old one.
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On Thu, 19 Apr 2018 12:11:09 -0700
<huge snip>

Many years ago when I was a tween Dad brought home a small single stage air compressor that needed a motor. We scrounged up 1/3 hp and I put it together along with a new hose and fittings. The check valve had problems so I just removed it. Without the check valve it wouldn't pump up much and the motor would stall out. Something like 40-50 psi max. Of course it wouldn't hold pressure either, leaking back through the pump when I pulled the plug... So I cleaned up the check valve and put it back in. Then it would pump up to over 100 psi before the motor stalled out. The point being is that the check valve was cycling back and forth with each stroke of the pump. It didn't just open and then close when the pump shut off.
I learned a lot about air compressors, quick disconnects... with that little project. I think Dad planned it that way :)
--
Leon Fisk
Grand Rapids MI/Zone 5b
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On 4/19/2018 12:46 PM, Leon Fisk wrote:

That is good feedback. I had not considered that an air compressor does not provide constant pressure above the check valve. I guess when I need to repair/replace that check valve (soon probably) an experiment might be in order. Should be pretty easy to add an upstream gage to see what is happening. Might have to use a digital gage with a data output of some kind so swings can be logged faster.
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On Thu, 19 Apr 2018 13:24:39 -0700
<snip>

It was a loooong time ago... I think I tried putting the pressure gauge ahead of the check valve too. Rather than on the tank. Needless to say the needle did a lot of pulsing back and forth. Ooops!
--
Leon Fisk
Grand Rapids MI/Zone 5b
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On 4/19/2018 1:36 PM, Leon Fisk wrote:

Oh, no. I wouldn't do that. Just a temporary one to see what is happening. I used a flexible hard (somewhat) plastic airline in a loop for my link so I can remove it without kinking it like if I used copper. I did the same thing on my portable roll around compressor years ago when I replaced its pump. Its held up fine, but the shutoff pressure is about 20 PSI lower.
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On Thu, 19 Apr 2018 13:44:40 -0700
<snip>

Nah, not you. Dumb kid did that. I had one of those "DUH!" moments and found another spot to try :)
--
Leon Fisk
Grand Rapids MI/Zone 5b
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wrote:

I made a cam lever that replaces the pull ring on my compressor's pressure relief valve to unload it enough to start on a small generator. When the valve is open it pulses like an engine exhaust. (Amazon.com product link shortened) -jsw
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wrote:

Dads are great that way, aren't they? I learned woodworking and automotive repair from mine, with some physics on the side. Cut my eye teeth tuning up his metal spoke rims on the Austin Healey 100-4 he ran in gymkhanas and autocrosses.
If Bob's new valve leaks, I hope he calls the mfgr and raises hell.
--
When a quiet man is moved to passion, it seems the very earth will shake.
-- Stephanie Barron
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