Got the air compressor going!

[egon]

Chances are you have it all figured out and it will work well Pat. To really spiff it up add a PSV or blowout membrane [bursting plate] at the end of the pipe run.

The prechilled air would indicate a chiller/cooler between the air compressor and the dryer. Many staged compressors have have interstage coolers and water removal systems.

Egon [img]/forums/images/icons/grin.gif[/img]

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] Pat, I'm reading in one post that you have a single stage and in the other post a two-stage. I DOUBT if your compressor is a single stage if it was factoree set for 175 PSI. At that pressure, the output in CFM from a single stage would be quite low. If your compressor is continuously bleeding air back from the unloader port on the pressure switch while it is RUNNING, then the unloader is blamo. If it is bleeding continuously from the unloader port while the compressor is stopped, then the tank check valve is blamo. The dual-tank arrangement is thee ideal setup. That will give you the best of all possible worlds. [img]/forums/images/icons/smile.gif[/img] PVC is OK for air piping as long as the system isn't under pressure all the time. PVC pipe does fatigue over time; that's the awful truth. Needless to say, a PVC air piping system would want to be made from the heavy-heavy, ....heavy wall PVC. [img]/forums/images/icons/crazy.gif[/img] This will be my last day at my computer for a couple of weeks. [img]/forums/images/icons/tongue.gif[/img] I know how much you'll miss my posts, [img]/forums/images/icons/wink.gif[/img] but what can I do? Should be back on line somewhere around the 20th? [img]/forums/images/icons/crazy.gif[/img]

[Pat]

Dave, I got the new pressure switch and did the R&R new for old. The pressure switch/head unloader thingy cuts off the compressor at about 175 PSI and leaks a little air continuously thereafter. If through demand or just waiting until the lower limit is hit by leak down the compressor will not restart and is stalled trying till the protection device stops the motor from trying. (IT will reset and try again and again but will fail so I turn off the manual switch to prevent all this) I have to bleed down the tank pressure to about 30 lbs to get the compressor to start OK when I switch it back on.

There are a couple possibilities:

1. the new switch is defective (a replacement is coming from Sears)
2. maybe there is a wrong way to install it???

If you gently wiggle the little air line that runs from the pressure switch to the tank you change the leak rate. The leak is coming from inside the pressure switch assy, not a loose fitting problem due to me.

Do they ever put a check valve in the tank fitting where the "other" end of the air line from the switch assy goes?

If I try to use the compressor normally it pumps up to pressure and when I use enough air (or the leak lets enough air out) it tries to start the compressor but it is stalled as if the head pressure was never let off.

I get the same symptoms with the new switch assy as with the original one.

I don't think either switch assy is unloading the compressor properly and they both leak air and eventually drain the tank.

Pat

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] Pat, that fitting that screws into the tank IS a check valve. It has a tapped port for the unloader on the side and a bigger thread for the compressor discharge line on the top. The check valve should hold the tank pressure completely, no leak should come from the unloader after about four or five seconds after shutdown. If air is leaking, then the check is letting the air leak back and into the discharge side of the compressor and that's why it cannot start. The best way to take the check valve out is with a deep socket. It should come right out of there no problem. I bought a new tank check valve from SURPLUS CENTER 1-800-488-3407 Lincoln Nebraska. They have them in 1/2". 3/4", and 1" tank thread. The 3/4" sells for 16.99...... You could also autopsy the defective check valve and see if it has something holding it open..... like a piece of packing material under the valve seat. You'll have to take it out anyway so look it over carefully and you may find it to be fixable. [img]/forums/images/icons/tongue.gif[/img]

[Pat]

Dave, Thanks bunches man. I had never fussed with a compressor before. I treated them as totally black box, an appliance that works or doesn't BUT when I started thinking about my unit's symptoms... I got suspicious there might be more moving parts than met the eye, like maybe a check valve exactly where you confirmed there is one.

OK, we move on. Too bad sears and I are wasting time shuttling parts back and forth due to my ignorance.

Now about my 30 gal Devilbiss which failed and is the reason I hooked up the other compressor.

The good news is that it runs and pumps air. The bad news is that it runs continuously and never pumps up the tank beyond 30-35 PSI. It didn't suffer a gradual reduction in function, just one day I turned it on and it ran and ran and ran but made only 30-35 PSI.

Any hints or suggestions for this one beyond using it as a storage/buffer tank for 100 PSI air down stream of the 175 PSI unit? If it isn't more expensive and hassle to fix it than buying a new one I'd like to get it working as it is on wheels and light enough to load into a pickup so I can go mobile with the plasma cutter or spray paint rig.

Thanks again for the jump start on compressors. I'll check Sears parts price and if they are too proud of theirs I will try SURPLUS CENTER.

Pat

[Pat]

Dave, Thanks again man, I took the check valve out, sprayed it with brake cleaner and then silicone spray, blew in it, sucked on it, poked sharp objects through the circle of 8 holes around the outside, etc and convinced myself it was working and put it back in. Compressor was in the way so had to use crunchit (Crescent style HF) wrench to R&R the check valve. Everything works fine now. All I have left is to take the pressure switch which is on the way and slap the label on it UPS dropped off to use for the return of the defective unit. I will keep the original (working OK but didn't know) pressure switch as a spare. IF it messes up again I will order a new check valve.

Now if I can get the 30 gal Devilbiss working right all will be good. It will run and run but not make over 30-35 PSI. The day before the malfunction it worked normally. Its performance did not degrade gracefully.

Compressed air drier number 2 was delivered a little while ago. The first one was really banged up badly in shipping via FEDEX.

Pat

[egon]

Pat; how fast does this other compressor lose pressure? [img]/forums/images/icons/grin.gif[/img]

Egon [img]/forums/images/icons/grin.gif[/img]

[Pat]

Egon, Quite slow if any leak down now that I removed, fussed with, and reinstalled the check valve that Dave confirmed the existence of in so timely a manner. It is working fine now.

Previously it would pump up to 175, shut off and then in a few minutes it would bleed down to 140 and turn the motor back on but the motor would be locked up because the head pressure was not relieved.

For the time being it is working OK and thanks to Dave if/when it messes up I know what part to replace.

Pat

[egon]

It was the other compressor I was referring to Pat. [img]/forums/images/icons/grin.gif[/img]

Sometimes when a valve goes it will hotter than the others. That was something we always had to check on compressors when the output was not up to requirements. [img]/forums/images/icons/grin.gif[/img]

Egon [img]/forums/images/icons/grin.gif[/img]

Egon [img]/forums/images/icons/grin.gif[/img]

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] I'm with egon on this one, Pat. The problem is most likely in the head; a valve has failed or is stuck. If that is a two-stage unit then it could be that one stage has a valve problem. It isn't unheard of for a piece of piston ring to come off and lodge under a valve seat. Pieces of piston rings have imbedded themselves into human flesh when the compressor is set up with a bottom-of-tank discharge and somebody was using a blow gun to dust themselves off. [img]/forums/images/icons/frown.gif[/img] As you so stated, this symptom just "occurred" it wasn't a gradual decrease in capacity over time. I'm going with the valve suspect on this one. [img]/forums/images/icons/tongue.gif[/img] Glad to hear that the big compressor is running normally now. Doncha love it when a plan comes together? [img]/forums/images/icons/crazy.gif[/img]