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Air compressor problem

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682bear

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#1
I looked at an air compressor that is for sale this morning. It is a Porter Cable 80 gallon 2 stage, model # CPLKC7080V2. We checked the oil and turned it on. The seller said thats the first time its been powered up in at least 10 years.

We let it run about 5 minutes, it was pumping air, but, in my opinion, way too slowly. In 5 minutes, the pressure pumped up to around 100 psi. The compressor is rated at 175 psi... I'm guessing 10 minutes or more to reach shutoff, maybe?

It didn't appear (to my highly calibrated 'eyeball tachometer') to be turning the 3450 RPMs that the tag on the motor claimed... maybe half that...

Also, I removed the pulley guard and turned the pump by hand, and could not feel hardly any compression... but I'm not sure how much compression should be felt in a compressor pump.

It was pushing a good bit of air out of the crankcase breather... more than I thought it should...

Not being a compressor expert, I decided that I didn't feel comfortable paying the $500 he was asking... at least without doing a little research first.

Any ideas, opinions, or info is appreciated.

-Bear
 

Nogoingback

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#2
I sounds like the pump is just worn out and needs a rebuild. If the motor is running slowly with a worn out pump, it's no good either. Keep looking.
 

aliva

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#3
I have 2 stage Gardner Denver the rpm is around 750 so I don't think you should expect 3450rpm. As Nogoingback suggested keep looking. sounds like rebuild time
 

Tim9

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#4
If I owned it... and If it hasn't been run in 10 years...Quite possible that a piece of trash or rust scale may be keeping a read valve open. If you can pull the valves off without pulling the head...I'd do that lickedy split. Check valve seats / reed valves.

But...I would do as others advise and keep looking. A tank sitting for 10 years with a closed drain valve will still build moisture from condensation. The tank may also be rusted on the inside.
 

682bear

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#5
Yeah, I have already passed on it, but it is a friend of mine that is trying to sell it, so I'm trying to get some ideas about what may be wrong with it to help him out.

I sort of had an idea that a valve may be stuck open, but I've never been inside a compressor pump, so I'm not sure exactly how they are built.

-Bear
 

Tim9

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#6
Yeah, I have already passed on it, but it is a friend of mine that is trying to sell it, so I'm trying to get some ideas about what may be wrong with it to help him out.

I sort of had an idea that a valve may be stuck open, but I've never been inside a compressor pump, so I'm not sure exactly how they are built.

-Bear
Most of the compressors I've had were designed so the reed valves could be accessed fairly easily. Usually some sort of plate or a nut which you could remove fairly simply. Check out the diagram of the compressor in this link. Like I said..It may very well might be a bad reed valve (cracked disc) or a piece of trash in the valve. https://servicenet.dewalt.com/docum...nual/Porter-Cable/200-2882-A,PXCMV5248069.pdf

Numbers 15, 16, 17, 18 are the valves on page 24
 

Cooter Brown

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#7
The reed valves are very easy to make, use metal pallet banding strap works great. I fixed a friends compressor that is used daily for bodywork, 2 hp motor....
 

GoceKU

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#8
It's a slippery slope with all old machines, your friend may invest money in rebuild and never get them back after the sale, if is in good shape sale it as is or just scrap it.
 
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#9
If it was a single stage it may take that long but two stage should have done it in 5-6 minutes . Did you bleed it off to see if it came back on and how long it took to rebuild pressure ? , When you do get one plumb a drain line out where you can blow out the moisture DAILY, I USED A 1/4 pipe ball valve and black iron pipe for mine it's now about thirty years old.
 

Old Mud

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If your even thinking about using a compressor that has been sitting for 'at least 10 years" . And it ran fine my first thing to do would be check out that tank carefully. Compressor tanks don't like sitting with water in them that long. I agree on the possibility of the valves being crudded up. Another is stuck rings Even one would affect the pumping.
 

westerner

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#11
The reed valves are very easy to make, use metal pallet banding strap works great. I fixed a friends compressor that is used daily for bodywork, 2 hp motor....
Yup- I fixed a friend's pump with a slightly modified feeler gauge, chosen for the "carefully measured:cautious:" flex. Many older units I have seen run a disc shaped reed, which might complicate the fix.
If your even thinking about using a compressor that has been sitting for 'at least 10 years" . And it ran fine my first thing to do would be check out that tank carefully. Compressor tanks don't like sitting with water in them that long.
I was very fortunate- my uncle found my compressor for me. A "Westinghouse" 2 horse 220v single phase, dual stage, 80 gallon horizontal manufactured in 1949 by the tag on the tank. It lived it's entire life in a service station run by a very fussy owner with strict rules for his employees. My cousin was one, mid seventies. Draining the tank at the end of shift was NOT optional. You oughta see this motor. Big as a 5 gallon bucket, 100 lbs of AMERICAN horses. The tag says 2 horse. It draws about 27 amps! Runs cool, dead quiet, original bearings. The tank has been drained very religiously since I have owned it, I have run a hammer over the bottom of it more than once, and I trust it completely.
 

NortonDommi

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#12
Try dropping the transfer pipe and the second stage to tank pipe and squirting some WD-40 or similar into the intake on both cylinders when running and listen for a change in sound also check the check valve,( one-way valve into the tank), as sometimes they stick and it will take forever to get any sort of pressure rise. Check the motor power and the drive ratio to see if the motor is powerful enough,(may have been swopped), and that the drive ratio is in the ball park for operating speed.
With the pipes off you may be able to look at the outlet valve on each cylinder at least.
 

jdedmon91

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#13
If your even thinking about using a compressor that has been sitting for 'at least 10 years" . And it ran fine my first thing to do would be check out that tank carefully. Compressor tanks don't like sitting with water in them that long. I agree on the possibility of the valves being crudded up. Another is stuck rings Even one would affect the pumping.
Yep check the tank. Here is what happened to mine.


Sent from my iPhone using Tapatalk
 

NortonDommi

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#14
jdedmon91,
That is scary, good thing it was outside. Pretty light gauge steel though.
I've got a new much larger than my Ingersoll Rand type 30 compressor awaiting a new dedicated home. I'm going to be coating the inside of the tank with some of that U.S. Tank Sealer that is made for fuel tanks as I think it will stand up to time better than PA 10 in the application before using though as wall thickness is only 6 mm.
Present use tank is locally made 30 Gallon 1/2" HT steel that has lasted 40 + years so far but it does get drained regularly and was coated with PA 10 before use.
 

jdedmon91

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jdedmon91,
That is scary, good thing it was outside. Pretty light gauge steel though.
I've got a new much larger than my Ingersoll Rand type 30 compressor awaiting a new dedicated home. I'm going to be coating the inside of the tank with some of that U.S. Tank Sealer that is made for fuel tanks as I think it will stand up to time better than PA 10 in the application before using though as wall thickness is only 6 mm.
Present use tank is locally made 30 Gallon 1/2" HT steel that has lasted 40 + years so far but it does get drained regularly and was coated with PA 10 before use.
It was a light duty oil less compressor that was 25 years old. I don’t run air tools very seldom, just inflate tires and blow things off


Sent from my iPad using Tapatalk
 

Tim9

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#16
Yup- I fixed a friend's pump with a slightly modified feeler gauge, chosen for the "carefully measured:cautious:" flex. Many older units I have seen run a disc shaped reed, which might complicate the fix.

I was very fortunate- my uncle found my compressor for me. A "Westinghouse" 2 horse 220v single phase, dual stage, 80 gallon horizontal manufactured in 1949 by the tag on the tank. It lived it's entire life in a service station run by a very fussy owner with strict rules for his employees. My cousin was one, mid seventies. Draining the tank at the end of shift was NOT optional. You oughta see this motor. Big as a 5 gallon bucket, 100 lbs of AMERICAN horses. The tag says 2 horse. It draws about 27 amps! Runs cool, dead quiet, original bearings. The tank has been drained very religiously since I have owned it, I have run a hammer over the bottom of it more than once, and I trust it completely.
 

Tim9

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Westerner- I had one of those Westinghouse Air Brake compressors in my shop back in the day. I think my tag said something like 1946. That was one beautiful beast of an air compressor. I had the cut off pressure set at 175psi...And with a body man, 2 mechanics... In ground air over hydraulic lifts, and air tools running ....It would maintain 150 psi all day long. That was just an incredible old air compressor. You just couldn't overwork it and the pressure was always maintained. I loved that air compressor.
By the way...Its fairly easy to do a redneck hydro test of an air tank. Fill it with water, and pressurize it with nitrogen. I know that's not truly how they test tanks, but if you fill it to the brim with water, you can give it a test pressure of 1.5 times the working pressure and at least have some confidence that it won't explode on you. That said, I kind of think those older tanks were very over built compared to the Chinese crap we now have which isn't even ASME certified.
( I think ASME tests at 2 times or 2.5 times the working pressure)
 

Boswell

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#18
By the way...Its fairly easy to do a redneck hydro test of an air tank. Fill it with water, and pressurize it with nitrogen.
Why Nitrogen? I would think that when the vessel is filled with water you could use any gas (non-flammable) such are Air from another air compressor. This is not advise, just wanting to understand.
 
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