The Stovebolt Site Forums The Shop Area The Tool Chest Evaluating an old compressor

My question is, what should I look out for in buying a fairly old compressor? Been looking at a Kellogg American. This may not be the exact one for me but an older used compressor is definitely a good possibility.

This one is Model #B 321 UB so fairly low air capacity. The new ones are rated 8.8 CFM at 823 RPM. The tank was made by Buehler Tank and welding works of Orange, CA. It is an 80 gal tank with a serial number of 16543 N.B. This compares to other serial numbers from the 1960s (from a very limited online search). The motor is a 3 horse single phase 220 volt 18 amp Westinghouse with serial # 7404 (made in 1974?)

The pump turns smoothly by hand but is not wired so I do not know if the unit runs or not. Sounds a lot like my trucks when I purchased them. Asking price is $250.

Good deal or should I run away?

I'm guessing it's a good deal, can't go that bad even if it needs a rebuild.

One issue with old tanks is rust inside. I'm sure here are rules and probably even laws about how long one can be in service before either replacement or hydrostatic testing. Might want to look into that, as an air tank explosion is a very serious thing.

Grigg

Some of the old ones are very good.I bought a new Ingersol Rand a few years back. I also have an old Champion compressor sitting in my shop.I have not been able to locate parts for it,and might consider having a professional fix it up.It worked great for me for a number of years,then it started leaking off after the compressor stopped running. Afew years back I put new valves in it.

Dale, there's a Champion Air Compressor factory in Princeton IL 61356, they've been there for some forty some years that I know of. They're called "Champion A Gardner Denver Company air compressors" now.

3101 N.Euclid Ave.
Princeton IL. 61356

Phone (815)875-3321

Maybe you could call, or write them.

Hope this helps. Brian

A badly rusted tank would certainly be a deal breaker. Are compressor tank explosions a common thing with old tanks?

On line I found a bit of discussion on old tanks developing pin holes and not holding pressure rather than exploding. Fortunately I don't know anything about it first hand.

Will check out champion compressors next.

Thanks for the feedback.

55SHAKER,THX.a lot,I will check it out

Finally bought a nice used compressor. http://www.picturetrail.com/sfx/album/view/23503717

It is a 60 gallon receiver tank built in 1948. The shell is 0.2391 inch and the head is 0.187 inch. The pump is a replacement single stage unfortunately but should put out all the air I need. Will clean up the outside and clear coat it to keep the patina and then make a small shed for it.

The tank has in interesting drain system. Instead of a hole drilled in the bottom of the tank, the drain plug is in the middle of one of the ends. It has a fitting with an angled copper tube that points downward and extends to the bottom of the tank.

Are you able to take a few evaluations on compressor prior to purchase?

These are not scientific and maybe not the best of testing but should tell you if it is broke or should run.

IF so
HYDRO test
measure circumferance of tank. Tape measure will do - especially if you can get down to say 1/32 increments.
Install vent to let air out of tank. Attach quick shutoff on garden hose. Hook garden hose to tank and fill tank COMPLETELY full of water - ideally no air at all. Would be handy to have gage on it use say 50 to 75 psi gage.
Shut off hose then shut vent. Crack the valve and pressurize tank.
Record pressure. Look for leaks - especially your test fittings. Try to maintain the same pressure. Remeasure circumferance. If no change that is a good tank for sure. I would expect some change in circumferance and would not worry about say a 1/8 change - all tanks will change. What you are really looking for is bulging.

Generally they fail like a hot water tank small hole that gets bigger and bigger. Rusting by itself will generally NOT cause a tank to blow up. They can fail and can explode but that is for other reasons than just rusting - ie very rapid pressurization, dieseling etc BUT that is generally with high pressure air ie 3000 and higher.

Compressor - if you can put known length of pipe capped and whose volume you know on discharge - install a pressure gage - probably 0 to 20 psi. Turn compressor a turn and record pressure. If no big result then try 3 to 5 turns. If you are confident of your readings then you can use the known volume of your test pipe and calculate volume per time (CFM absolute) and compression ratio
Vol / one (or 2 or 3) revs and
PVT = PVT

If it generates pressure and can hold it you have a pretty good idea rings are OK and if it holds pressure valves are OK.
I would not be surprized if it does not hold pressure for more than 10 second.

Motor go across line leads. This size is more than likely capacitive start and cap run. I would guess 5 ohms or so is OK - no ohms something is wrong probably open winding. Check from one line lead to ground on motor case should get better than one mehohm on a good motor. If these are OK then you are probably in good shape. If you have doubts take to motor shop and have em test run it. Cost maybe 50 to test but that motor to replace is probably 2 to 300.

Compressor shaft look for endplay and slop in bearing. IF they will let you drain the oil and look for metal in first part of draining - coffee filters are great for this.

Dan Bentler

Hi Dan,

Thanks a million for the tips. It's a done deal. The compressor is mine so I will run the tests with my fingers crossed. As you might imagine the price was very reasonable so it won't break the bank if this turns out to be a bad purchase.

The motor is a huge old 2 horse 3 phase unit. It was also made in 1948 so perhaps original. I will have to find a good single phase motor before using the compressor but can run the tests with my little Emglo Airmate.

There is a lot to say about the old motors and a lot of that is good. Three phase are slightly more efficient and less maintenance intensive than single phase.

I would consider keeping the old motor and drive it off a VFD intended to take a 230 VAC single phase supply. This may be less expensive than replacing the motor.

There are a couple provisos on this though
1. Check the nameplate - if motor is a dual voltage ie 230/460 then at 230 you should have no problem with the higher voltages imposed by VFD.
2. I would ensure the motor shaft is grounded to prevent bearing erosion cause by current imposed in shaft. Need not be complicated use a brush holder out of a starter motor. If possible best to ground both shaft ends.
3. Find a good distributor who really knows VFDs. In this case I do not recommend Grainger. Take a photo of the nameplate to them so they know what kind of motor they are dealing with.
4. Unless you have an unloader I would not get a V/F type VFD but would recommend a vector type - better starting capability.

Whichever way you go do NOT scrimp on the conductors feeding this unit. If mine I would go up one and probably two wire sizes to ensure it has minimal volt drop when starting.

Dan Bentler

Definetly a good way top save some$$$.Only thing I would have against buying an old compressor is,if it breaks down,can you buy parts for it today.Or what would the cost of a professional rebuild set you back.That is if that breakdown occurred.I have an old Champion,that was in my shop when bought this house.It worked good for a few years,then uh oh,it is now leaking off. Tried to locate parts for it,but to no avail. Someone [posted on here about an outfit in IL.that had parts.When I contacted them,and gave them the specs.on my compressor they replied that it was too old and they no longer carried parts for the compressor.My local Tractor Supply had a sale on Ingersol Rands,so I took the easy way out and purchased a new one,which works very well.

leitmotif, if the compressor has a centrifugal unloader, isn't he going to have a bit of a problem by just simply turning the pump?

Hmmm did not consider that.

Don't even know if there is some "magic HP number where this is installed.

Yes he would have to defeat unloader OR take volume reading on unloader discharge port.

I just gotta get a better crystal ball.

Dan Bentler