Is safe to buy a used air compressor?

[usolutions]

Tanks do occasionally go boom (not hiss):

and many more with a quick search.

It looks rusted through

 

[Gordon Heaton]

. . .It's wise to use that head to think, then act sensibly.

That's what I was trying to say. The rub arises when one person's 'sensibly' conflicts with someone else's.
Fortunately, for the time being at least, much of the world is largely free to determine that for themselves. Sort of. Sometimes.

 

[john.k]

I have a $100 Chinese compressor .....light weight ,easy to move about ......,excellent value for money .......and I will probably have to modify my comment that Ive never seen a tank blow up........but until that happens ......anyhoo,at least they dont go like a boiler ..1/2 " thick steel plate shell turns itself inside out ....thats an explosion.

 

[snowman]

My first real compressor was old and free, fired it up and it had pinhole leaks in the bottom, in my ignorance I welded a big patch over the bottom. It was bolted to a slab behind the shop, ran for 2 years before compressor died, did not blow up, nobody dieded. YMMV!

I did the same thing.

There's more patch jobs out there than we give credit for.

I also scrapped it out once I figured out how dangerous it was. But that was a few years at least.

 

[steve45]

A fellow about a block away from me was injured when his air compressor blew up. I don't know what happened, I heard the story third hand. Supposedly the regulator didn't shut off the motor, and the pressure relief valve failed. Sounds like either a defective tank or somebody was messing around with the PRV and regulator settings. The fire department investigated, but I never heard any results.

To the original poster, you CAN buy replacement tanks!

 

[snowman]

The more common failure is a line blows, or a catastrophic leak of some sort opens up, and then the motor just keeps going, and then starts on fire.

 

[Trboatworks]

The more common failure is a line blows, or a catastrophic leak of some sort opens up, and then the motor just keeps going, and then starts on fire.

I am always careful that the compressors are off when I leave the shop for this reason.

 

[john.k]

Best compressor (not) fail Ive seen was the plastic mould shop down from me .......their compressor was running half submerged in floodwater when the creek came up.........spectacular rooster tail of water from the big pulley inside a wire guard..........It ran all through the flood ,because for some reason the power co didnt shut of the power to the flooded area.

 

[snowman]

I am always careful that the compressors are off when I leave the shop for this reason.

I put a timer on mine. Best money ever spent. It's literally a $20 timer switch you get at lowes. 5 minute, 15 minute, 60 minute, "on". I then wired it to a 240 volt contactor which feeds the compressor.

It's rare I need air more than 5 or 60 minutes.

I've also had them wired into the light switch, so that when you turn the lights off, you also turn the compressor off.

 

[Trboatworks]

Thanks for that.
I could use something to simplify my shutdown list when I leave the shop.

 

[snowman]

Thanks for that.
I could use something to simplify my shutdown list when I leave the shop.

No problem! I just used one of these boxes to hold the contactor, stole a leg of the 220 and ran it to the switch. If it were three phase, I'd wire it directly to the motor starter, but this is a home shop environment, 240 single phase compressor.

WIEGMANN N1 WEIGMANN 8 in. W x 8 in. H x 4 in. D Carbon Steel Gray Screw-Cover Wall Mount Box, 1-Pack SC080804RC - The Home Depot

WIEGMANN NEMA 1 enclosure is designed for use as a wiring box or junction box. Enclosure is fabricated from carbon steel. The finish is ANSI-61 gray polyester powder inside and out.

www.homedepot.com

 

[casement]

I second the borescope recommendation. USB borescopes are cheap online and work with your phone or a notebook. You can pull a fitting and look inside the air tank for corrosion as they're lighted. (They're also nice for top end and bore inspection on assembled engines.) No need to pull a (probably rusted solid) large plug to use one as they'll fit inside a 1/4" pipe bushing (not the pipe itself) which are common for various fittings. I have freed a few large plugs with a pipe wrench and cheater pipe though.

I'm hunting a 10HP compressor head since 5HP are pathetic for blasting. I had no trouble finding a good industrial air tank and a new in box 15HP electric motor but compressor heads are harder to source. Look for three phase compressors as they're harder to sell since most users don't have three phase or a beastly RPC.

 

[bhigdog]

I was wondering what the general opinions are on buying a used air compressor?

Pretty much all of my tools are bought used as my preference is to buy quality used tools versus cheap new ones.

I need something primarily for sandblasting which I think puts me in the 5hp 60+ gallon tank range if that sounds about right?

When it comes to air compressors I can find a lot of nice ones in the area at reasonable prices that meet my needs, however tank condition always makes me nervous.

I see all few of the older USA made brands available locally which one would think may have thicker tanks than our modern value engineered ones. I even have a brand new 5HP compressor duty motor lying around in case I need it. However it all comes down to the tank being safe. Any thoughts on inspecting one? Maybe it's time to get a boroscope too will they be useless looking inside at determining how bad any likely rust is?

I occasionally buy, repair and flip compressors. Mostly with tired pumps. In my experience the pumps don't wear out usually the valves go bad. usually a bit of lathe or surface grinder work or maybe a spring replacement or two brings them right back at no cost. I always hydro test to 50% over tag rating. Easy peasy.
I opened and bore scoped a couple of tanks. You will see rust on the bottom that tells you nothing.
Here's a pix of a really tired early 1930,s IR T-30 I bought for $50 just because I liked it. Passed the hydro test. Needed the valves rebuilt at no cost. The bores showed less than .001 wear and still showed some cross hatching. You can't wear these things out. After repairs, a used 5 HP motor, and a new coat of paint it looks and runs like new. I use it to pump up tires.
As for blasting you don't say what kind. My daily use 5HP, 80 gallon T-30 will more than keep up with my bead blast cabinet or a 50 pound capacity pot.
Anything more than that you should be looking at something bigger if you want to blast non stop............bob

 

[CarbideBob]

Old compressors and old used machine tools are bad.
Only buy brand new stuff. This is the way to go.

 

[metalmagpie]

I have a 5hp 2-stage Champion with 80 gallon tank. It has proved to be not quite up to sandblasting. However, I don't sandblast that often. It's entirely doable in my area to rent a compressor on a trailer that's good for like 185 cfm - that will keep up with anybody's blasting cabinet. So rent a compressor for 1 day every couple of years. Much cheaper than buying way more compressor than you need for at home. A better requirement is can your compressor keep up with a medium sized air tool like a die grinder or needlegun. Mine can, so as far as I'm concerned it earns its keep.

As to the tank, well, I also like to make meat smokers out of old air tanks. So I've cut into a few of them and cleaned them out on the inside pretty intimately. The most recent one I did was a vertical tank. It did have some corrosion and pitting but it was all in one small area of one end, a bit bigger than a dinner plate. The whole rest of the tank was beautiful like-new steel with a light coating of oil. So if you are going to go after an old compressor tank I say go after a vertical tank. Smaller footprint in your shop anyway.

 

[john.k]

For limited output compressors to keep up,fit an extra tank or two to your system ....this will nearly always keep up with beadblasting and small air tools.........wont keep up with biggies tho..........I have an Atlas Copco 7" disc grinder that takes 40 cfm.by my estimate ........magic in a factory air situation ,a million percent better than an electric ,as there is no momentum in rotating parts ...release the trigger,and it stops instantly ,as the rotor is then compressing air.

 

[boslab]

I found myself running out of air on a piston job so I hired a screw compressor, comp air I think it was the smallest, I remember 60 cfm but I soon discovered the fact that screw compressors spit a bit of water out!
Had to get a dryer as the media was clumping, great after, the thing wasn’t that noisy and would go all day, or until you got fed up.
Receivers are important , old ones are usually rusted at the bottom, no one bothers to drain them, a camera through the access plug ( if you can get it out!) is wise
Mark

 

[projectnut]

I may hold the record for the oldest working compressor in captivity. I have a Henke Pacemaker (Kellogg American) built in 1965. It's been in the shop over 30 years. When I purchased it I also bought a couple rebuild kits thinking I was going to need them at some point in time.

The compressor doesn't get used on a daily basis but more as a backup when times are busy. It gets regular maintenance and draining, and so far, hasn't needed anything more than some valves and a new unloader.

 

[john.k]

Nope ..1960s air compressors are common....I used to get lots of them from the army auctions.........the one Im using now is WW2,and has been under floods at least twice .

 

[mmurray70]

I may hold the record for the oldest working compressor in captivity. I have a Henke Pacemaker (Kellogg American) built in 1965. It's been in the shop over 30 years. When I purchased it I also bought a couple rebuild kits thinking I was going to need them at some point in time.

The compressor doesn't get used on a daily basis but more as a backup when times are busy. It gets regular maintenance and draining, and so far, hasn't needed anything more than some valves and a new unloader.

Nope. I run my shop every day hard use with a 1946 brunner compressor. I love this thing so much. Would never dream of trading it for a brand new one.

To the original poster... never buy a new compressor unless your completely stuck. New stuff is complete garbage compared to older stuff.