Is safe to buy a used air compressor?

[Trboatworks]

It just depends on condition.
I just bought a US made DeVillbis 6.5 hp 15 CFM with a 60 gallon vertical tank to run the ram on an air over hydraulic bender.
The thing was built in 1996 and it’s perfect.
The owner was into vintage cars and used it occasionally to top off the tires and kept the tank drained.
$450 out of the penny saver.

A shop near me bought a huge horizontal compressor which had a welded on patch 15”x 36” on the bottom to “fix” a rusted out mess.

I told them to cut the tank up and toss it before it blows up and kills somebody.

Condition is everything- it may be perfect or ready to be tossed.

 

[steve-l]

Yes but how do you do it on a tank with out cutting a hole in it to mic thickness? Or maybe I am overthinking it and you can just calibrate it to some of the steel at the top where the motor and compressor mount? It probably is similar to the tank material but no guarantee and it may be painted on both sides which may also effect the readings.

Plus with ultrasound does it work with paint as I am not sure I would want a potential buyer removing spots of paint on a tank just to tell me if he's willing to buy it.

You are over thinking it. These tools work well. They have to be adjusted for the material you are measuring of course. Sound wave transit time is different for every material. Yes, paint and rust will change the reading a little bit, but not much especially if you use a good coupling fluid like glycerin or a good oil on the transducer. A good way to make this test is to check thickness on the top, sides and bottom. It would be the difference of these different readings that would be meaningful, because rust would be on the bottom and not so much at the top.

 

[RC Mech]

I agree you’re over thinking this. As with any machine purchase, what does the general shop condition tell you about their maintenance strategy (if any)?

No auto drain valves, scrap everywhere, dank coolant smell, dimly lit shit hole?

IME you’ll never get the inspection ports off an old tank. The 1” socket ports on my LeRoi-Dresser will lift the whole 1600 lb works and rack it’s bolted to before breaking free. If you can get a 3/8” bore scope through the air outlet, all the better.

CFM is the only metric that matters for your use case. Tank volume determines time between recharge. Max psi is generally within the same 30 psi window for stationary machine shop type compressors. For sand blasting I’d want a 45-50 CFM compressor which corresponds to 10 hp minimum.

You’ll also want a refrigerated air dryer capable of handling the max comp CFM.

 

[tnmgcarbide]

get a borescope . cost about $10 from ebay . you can dip the thing into the tank and
see if it's mildly corroded or just plain fucked .

5.5mm Industrial Endoscope Borescope IP67 Waterproof Inspection Camera w/6 LED | eBay

1 X Endoscope. Lens waterproof: IP67. 6 adjustable white LED lights. If item is defective after 3 months, you can still send it back to us. We will send you a new one after receiving the defective item.

www.ebay.com

 

[rons]

A horizontal tank will not drain as well as a vertical tank. Unless the horizontal is sloped.
But a horizontal tank is easier to work on and will not fall on your foot.

 

[dalmatiangirl61]

I always thought that the old ones were made thicker heavier walls than the new stuff we're getting and he won't know if that's true?

The ASME tag also has wall and head thickness info, yes, they are thicker than any of the sheetmetal tanks mass produced for the consumer market today, but don't think there is some magic cut-off year where ASME tagged tanks got thinner. While shopping take pics of all the tags, prove me wrong

 

[michiganbuck]

Buying a used plug-in compressor be sure the three-prong plug is in good condition and properly wired, It is not uncommon for guys to use the plug in and out rather than using the on/off switch on the machine.
Such use can destroy the third plug prong and make the machine not properly grounded... so making an electrocution machine of it.

 

[cyanidekid]

some good suggestions here.
I'll just add the old marine hull inspectors trick of taking a 20 oz ballpien and whacking the shit out of it, if it rebounds smartly and sounds similar all over the bottom, yer good. the water line is where you get the most corrosion, inside a tank, or outside a ship, excepting local galvanic action.
I herd from one inspector ( Captain Jerry, here in NYC on Spring st at the Ear) he had the hammer go right through one hull.

 

[CarbideBob]

Buy new and no worry.
Too all others despite the net stuff of being stuck by lighting or winning the lottery tell us about your tank fails.
Not some shit on the net but you and personal.

 

[Ron Hofer]

I look for used quincy QR-325 compressors. These commercial quality units are made to run 24x7x52. A 20 year old one is just broke in.
I did have to do a head rebuild on my last one, parts on ebay just $150 or so. This unit will outlast whom ever buys it at my estate sale.

When might that be? Asking for a friend.

 

[dana gear]

I look for used quincy QR-325 compressors. These commercial quality units are made to run 24x7x52. A 20 year old one is just broke in.
I did have to do a head rebuild on my last one, parts on ebay just $150 or so. This unit will outlast whom ever buys it at my estate sale.

I really like Quincys, for recip compressors, We run several of them. 60 thousand hour compressor heads. Older Kellogg Americans are very good as well, just have to be sure to get the American built unit as sometime back the operation was sent to China and turned to crap.

 

[CarbideBob]

One will replace pumps on a tank a few or many times.
So .. tank. The net has oh shit stuff. The net also has many lottery winners and those struck by lighting.
How many here with a blown though tank?? Was it bad.
Do not show me I saw this or what on the net. Personal and in close.

 

[scsmith42]

My Trinco blast cabinet requires at least 20cfm continuous air. My older 25cfm (7.5HP) compressor would run it and ”occasionally” cycle. The current 10hp 35cfm cycles more frequently when I’m blasting.

As others have stated, screw type compressors are ideal if you do a lot of blast work.

 

[dalmatiangirl61]

Buy new and no worry.
Too all others despite the net stuff of being stuck by lighting or winning the lottery tell us about your tank fails.
Not some shit on the net but you and personal.

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!

 

[john.k]

Ive seen quite a few rusted compressor tanks ........never seen a blowup with a STEEL tank .........first symptom is a pool of oily water all over the floor where the shell pinholed thru.......hard to ignore...........I would estimate I have bought and sold 1000 compressors over the years .......now and again ,I would get a claim for a faulty pressure switch ,or a motor that needs replacing............a few hits with a ball hammer will detect thin metal .

 

[RC Mech]

One will replace pumps on a tank a few or many times.
So .. tank. The net has oh shit stuff. The net also has many lottery winners and those struck by lighting.
How many here with a blown though tank?? Was it bad.
Do not show me I saw this or what on the net. Personal and in close.

I’m not of the opinion one should chance their life on a questionable tank. But wtf are you trying to say?

Several of your posts have elucidated that you’re not of the Chicken Little mindset. So chance it and blow yourself up? Or William Blake mind-forged manacles it’s all in your head?

 

[CarbideBob]

I’m not of the opinion one should chance their life on a questionable tank. But wtf are you trying to say?

Lets put this straight since you do not know me.
1) Never ever harm an employee. This includes a finger cut from a metal chip. They did not sign on for this and it is on you.
2) In bigger shops I was know as the hatred safety guy as leader, supervisor or manger. Why, rule one.
3) These things do not blow up like a bomb. They leak and hiss and you do not patch. No-no-no.

For sure I will take risk in the occupation but I will Dick-slap my employees is they do the same.
They have families and doing a job for a skinny paycheck.

I have seen bad in the auto world many years ago.
Machine repair guy got into a big press and it cycled. Half in and half out. WTF to do?
Open the press and he is out of the building. But he is fully alive and able to speak.
So what to do? First is to contact family. Wife and kids come in but there is no escape but he is fluent and talking.
At some point you have to give the order to open it.
These are my nightmares that will never go away.
Bob

 

[Milland]

Tanks do occasionally go boom (not hiss):

and many more with a quick search.

 

[Gordon Heaton]

That one looks like garbage to begin with. Sure, they're out there but what's missing are all the things that led up to catastrophic failure. Poor/cheap construction, over-pressuring (either intentional or because of failed or disabled safety devices, neglect, outright abuse etc. The whole story is always enlightening. You can 'what if' yourself into doing nothing forever. What a waste.

Use your head. If yours isn't up to the task, get help.

 

[Milland]

You can 'what if' yourself into doing nothing forever. What a waste.

Or you can "what the heck" yourself to oblivion. It's wise to use that head to think, then act sensibly.