Picked up a used compressor. Anything to check?

[edgood1]

I'd been on a casual search for a new compressor for a while and a deal finally came up so I jumped on it. This is a 6.5hp 80 gallon unit. The brand is blue point. It looks like it's made by devilbiss. Delivers 17cfm at 90psi.

When I picked it up I ran it till it kicked off. It held pressure for a while with no leaks.

It was a monster to move with my pickup truck. I heard some water sloshing around the tank while I took it out of the truck. I drained it and there wasnt much water at all. Just a little oil and clear water .. maybe 20 oz or so. Very clear no rust color.

Anything I should look out for before I put it into service?
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1987 Syncro Westfalia powered by Subaru
1963 Panel to Deluxe Bus project :::: (photo album)
'65 Westfalia

[[email protected]]

Not sure what you paid, but that is a higher end unit, good on you.

[edgood1]

[vwracerdave]

Just like buying a used car I would change the oil in it and clean the intake air filters.
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2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK

[Erik G]

New piston is super cheap and easy. Makes it quiet again too which is nice
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[busdaddy]

That looks an awful lot like the pump on mine, 20+ years so far so good. It keeps up with a sandblaster but it does get hot after 1/2-1 hour when using the big 10 gal pressure pot unit. If I open the door on it's house and give it lots of air it sometimes helps but sooner or later the air coming out the end of the hose is warm and the moisture condenses out at the sandblaster's mixing valve instead of in the tank or one of the traps. It'll run the cabinet all day long with no issues.
Change the oil for sure just because.
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[edgood1]

Thanks for the advise from everyone. I have another question or rather seeking clarification. Here are the specs on the tag:

This requires a 40amp breaker, right? The place I had picked it up from had it wired in to 30amp outlet and presumably a 30amp breaker which seems wrong to me. I thought that the rating on the breaker carries 80% of the rated load... So a 40a breaker can do 32 amps. I can't see how it could have worked with a 30a setup... Unless it was a 30a receptical with a 40a+ breaker (bad)
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1987 Syncro Westfalia powered by Subaru
1963 Panel to Deluxe Bus project :::: (photo album)
'65 Westfalia

[rusty busty]

I'm not an electrician but I do a lot of electrical work as an hvac mechanic including adding new circuits for a/c's and heat pumps occasionally.

The 80% rule is based on a continuous load of more than 4 hours run time (like lighting that will be on all day). The compressor isn't a continuous load as it will cycle on and off and won't run for more than 4 hours at a time. The rating plate says 30a so a 30a breaker would be appropriate. A 40a breaker wouldn't be a good idea because it could allow 25% more current than the compressor is rated for and it wouldn't be properly protected in an over current situation.
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[edgood1]

the plot thickens...

i rolled the compressor over to where it will sit and i heard water sloshing inside.... with the drain valve still open...

i took the drain valve out completely and it dripped some water. I poked a tail up into the hole and it freed up some gunk and a ton of sludgy rusty water poured out. a gallon or maybe more... made a huge mess.

i have no idea how long the thing sat with water in it. is it possible that the integrity of the tank has been compromised by rust? is there any way to test it?
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1987 Syncro Westfalia powered by Subaru
1963 Panel to Deluxe Bus project :::: (photo album)
'65 Westfalia

[KTPhil]

I don't think you can tell other than an overpressure test, which I don't recommend.

Another thought... never done this on a compressor, so the experts should weight in... treat it with ospho like you would a gas tank, to convert the rust, then coat the inside with a light oil. Will a separator remove that oil when used for a dry application or a paint sprayer?

[busdaddy]

Aside from an X-ray or hydrotest there's no real way to tell, perhaps a thorough massage with a hammer on the bottom to feel for soft spots or break open pin holes might expose something. I've never tried the rustmort/ospho but I have treated a few with waxoil like rust inhibitor once it's dried out.

I've never seen a rusted tank explode myself when used normally, lots have sprung leaks through pinholes, but if the safety valves and pressure switches are functional it's not likely to fail catastrophically.
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[Major Woody]

I have some experience with rusty receivers.
When a weld fails, you could have a catastrophic BOOM. When rust causes damage, typically you will get a pinhole leak. However, you know you have rust scale floating around in there and that it will only get worse.
What I would suggest is you remove the motor and pump, remove the fittings on the tank including the huge ones, and flush it clean with water until you don't hear things rattling around in there anymore. Look in the big holes and determine how far up the sides of the receiver the scale extends. The scale is porous and until you get it out of there, you will never be able to coat the interior of the tank.
Then plug all the openings in the tank and pour in a mix of muriatic acid and water and let it sit for a couple hours. Drain that without causing a bunch of environmental damage (maybe drain it into a large plastic container temporarily) and then neutralize the interior surface by pouring in water and a big Costco bag of baking soda. The acid should eat all the rust.
Then treat with Ospho or Picklex-20 or "Prep N Etch" (sold at Home Depot). Prep N Etch is phosphoric acid--that's all it is. I would throw in a length of heavy chain with the phosphoric acid and agitate the tank around. I did this on an old sheet of plywood in the driveway. You only need about two gallons to do a good job. The chain will take care of anything else that is still in the receiver.
Now stand it up, remove all the plugs, drain out any remaining liquids and you will need to get it good and dry. I used my shop vac in "blowing" mode to blow a steady stream of warm air into the tank. After several hours, the inside was a uniform powdery gray color and totally dry.
Now you are ready to coat it. Order a quart of POR-15 from Amazon. Plug all the holes again and dump in enough POR so that you can roll the receiver around, invert it etc and get an completely even coat of POR on the inside of the receiver. When you've thoroughly coated it, remove all the plugs one last time and let any residual POR drain out the bottom hole.
Now you have killed the rust and coated the receiver with something that will protect it permanently.
The rust was caused by lack of maintenance. Going forward, I suggest you install a galvanized pipe elbow into the fitting at the bottom of the tank--the largest size that will fit. Then add a section of pipe after that, and your drain valve. This section of pipe and elbow is where condensation will collect in the future, rather than in the bottom of your receiver.
I installed an automatic drain valve on mine but if you're fairly diligent in remembering to drain yours during use, you should be fine with manual draining.
If you are going to run the machine for long periods of time, such as with blasting or needle scaling, you should install an aftercooler before your filter. Otherwise moisture will condense in your air line and play havoc with your sandblaster, spray gun or air tools.
You can make your own aftercooler out of 3/4" copper pipe for short money. I mounted mine on the wall and it works excellent.

[edgood1]

Thanks major woody. I will attempt this. I plan to hydro test it first to make sure I'm starting with something I can work with. Great info!

In looking around a little I also found some used CNG tanks which were taken out of service. They are rated for 3600p psi and they're free. The guy has a ton of them and has used them as receivers for air compressors. If my tank is bad I might grab one. They are labeled 90270 cubic inches which equates to about 390 gallons
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1987 Syncro Westfalia powered by Subaru
1963 Panel to Deluxe Bus project :::: (photo album)
'65 Westfalia

[nsracing]

That tank is fine...practically new. Unless you see chunks of rust peeling off, nothing to worry.

Change the oil and run it. Listen for loud noises. If the compressor checks out then good to go. While that tank is full, open the petcock down below and let her drain till no more water is in there.

You only use 90 lbs of pressure in the service line.

I sold one like that to a friend not long ago. Served me many years. I now have a 3-phase 100 gal commercial w/ a 2-stage cast iron compressor.

That setup is plenty for just doing stuff in the garage. But for continous use not desirable.

The 30 amp circuit is fine as it says in the plate. But make sure you have the proper gauge wire to go along.

[edgood1]

I stuck the borescope down into the tank and this is what I saw. It looks pretty bad in there. I'm thinking about replacing the tank to be on the safe side:


Link


at around 3:30 the camera gets to the bottom and you can see the wet sludge of rust/debris down there.
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1987 Syncro Westfalia powered by Subaru
1963 Panel to Deluxe Bus project :::: (photo album)
'65 Westfalia

[Erik G]

Not going to advise you on the tank.

Replace the piston like said above. I agree 100% make it quiet and fill faster
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