I picked-up this old air compressor on a whim while browsing craigslist. The guy wanted to trade for a small, portable compressor and I had just the ticket. He spoke very highly of this old compressor on the phone and said all the right things; mainly that it works great, is quiet and drained clear. Well, I bit, and now I'm having a concern. I was all caught up in the moment of a great trade and the serious-ness and DANGER of using a bad tank had escaped me.

The tank is rated for 200 psi working pressure and is currently set to stop filling around 115. I've brought it up to 115 numerous times in the few days I've owned it, and it does work great... BUT... Something tells me I'm playing with fire if I don't get this tank checked out...

I've tapped on it with a ball peen hammer (while empty) in various places and the sound does seem consistent. By no means a true test, I know... Anyone have any ides? I've heard of hooking up a pressure washer and bringing it up to 150% of its rating, but would that ruin my pump? Is there some kind of ultrasonic wall-thickness test that won't break the bank?

Also, each half of this tank has a 2-5/8" hex-shaped access cap. What is this for? My thought is for clean-out, but it already has a drain on the bottom... Maybe a BETTER clean-out? My other thought is that it's for hooking-up a bigger tank?

Well, at least it has a certification tag on it, even if it is 80 years overdue for recertification ;P

The rust is on the inside, not the outside, so looking at it doesn't tell you anything. The plugs are for inspection, but good luck getting them out after all this time.

Do NOT try to pressure test it using a pressure washer, that is a good way to destroy a nearby building.

There are folks who can test it properly , and it doesn't cost all that much, the general theory is to fill it ***entirely*** with water so there is no air to be compressed that can explode if suddenly released by the tank failing. The pressure has to be accurate, and reasonable, you aren't testing it to 1500 pounds!, probably just to 300, you just want to test the tank, not destroy it -P

Personally, I would not use a tank from 1938, even if it tests ok,metal  fatigue is a concern for stuff made before the 50's....

2c

PS: In case you didn't know, .140 is the thickness of the tank and end caps when it was new, 10 ga sheet metal ;P

How thick is it now? ......

rusty, I'm going to have to borrow your WD40 and get those caps off and look inside. ;)

*I think* the area most vulnerable to rust would be along the bottom, where the water collects... I have no idea how to check the thickness of that.

If the thickness of an OLD tank was .140, I wonder what the thickness of a NEW tank from LOWZ is... Hmmm. I have my suspicion, but I could be wrong... :)

>*I think* the area most vulnerable to rust would be along the bottom, where the water collects...

Generally, yes, because rust/sludge trap the water there when you drain down the tank and keep it wet.

But another thing to look for is carbon or oil, when compressors get old and tired, they leak oil past the rings, the oil goes into the tank. Compressor oil has a high flash point, but motor oil doesn't, and you don't know the history of the machine, if some klutz  was putting motor oil it , it can create a flash/explosion hazard also.  (Old machines are fun, but they can be a little scary too , A millwright I know told me he saw an IR compressor blow the head off and send it through a wall for no apparent reason whatsoever....so check out the compressor also )

The plugs aren't coming out, trust me ;P

OK, since you probably are as stubborn as I am, Ponder: the tank has been expanding and contracting lengthwise as it fills up and empties out , for the last 70 years, the plugs are not round any more...

Quote from: rusty on April 11, 2012, 09:01:22 PM
>*I think* the area most vulnerable to rust would be along the bottom, where the water collects...

Generally, yes, because rust/sludge trap the water there when you drain down the tank and keep it wet.

But another thing to look for is carbon or oil, when compressors get old and tired, they leak oil past the rings, the oil goes into the tank. Compressor oil has a high flash point, but motor oil doesn't, and you don't know the history of the machine, if some klutz  was putting motor oil it , it can create a flash/explosion hazard also.  (Old machines are fun, but they can be a little scary too , A millwright I know told me he saw an IR compressor blow the head off and send it through a wall for no apparent reason whatsoever....so check out the compressor also )

The plugs aren't coming out, trust me ;P

OK, since you probably are as stubborn as I am, Ponder: the tank has been expanding and contracting lengthwise as it fills up and empties out , for the last 70 years, the plugs are not round any more...

Yes, I'm stubborn. And that sounds like a challenge. ... I'll let you know how I fare, and what I find...

The oil in the pump does appear to be motor oil. ... That was actually another question I had... Whatever it is, it's keeping this pump working good because 2 people can stand over it while it's running and have a normal conversation... I guess I'll have to check inside the tank for oil leakage too, WHEN I get those caps off... ;)

Thanks for all the input so far, BTW.

Jesse

Rusty's fibbing!

Those inspection ports will pop right out, of course if the tank is in sorry shape it just might become free form sculpture in the process.  Given the date of manufacture I'll bet the inspec ports were doped with Litharge & glycerin when they were installed.

Method A- hydraulic wrench - you probably don't own one.

Method B- slugging wrench & sledge - heating the boss helps with this method.

Method C- drill a large hole through the center of the plug.  Insert sawzall in hole and cut nearly to the threads in 6 directions.  Grab a decent sized punch or cold chisel and collapse the sections into the hole you drilled.  A Parker 401 air hammer works best.

Shouldn't take more than 20 minutes if you use an air hammer.

I have heard stories of tanks exploding and such but when my air compressor tank let loose it was just a small pop and a rush of air as just the weak spot on the bottom of the tank that rusted through from the inside let loose. Nothing to hurt anyone just a little surprise and some mess to cleanup after the tank puked all over the cellar floor. Maybe I was just lucky. That was when I learned about draining the water out of a tank. :)

Well, I have some good news, and some potentially bad news. First the good...





BAM!




Never underestimate the power of a 24" pipe wrench :) Probably the best $3 I spent last summer.




Now the potentially bad...


I did some probing around with a bore light and extension magnet and this is what I got... The paper is 8.5x11.





Well, those chunks are scary but I'm holding out hope for this. They look big but I think the are immensely enlarged due to two factors; the natural property of rust and oxidation, and the fact that they are completely infused with oil.

At this point I'm going to look into tank certification and see what it will cost to have this tested (because I have no idea). If it's under $100 I'm in. At this point it's educational. Maybe someone will read this thread and learn to steer clear of old tanks. Or maybe we'll be surprised and they will learn not to write them off. I'm thinking it's probably the former, and that I will be throwing good money after bad, but you never know...

Quote from: Lewill2 on April 12, 2012, 08:42:54 AM
I have heard stories of tanks exploding and such but when my air compressor tank let loose it was just a small pop and a rush of air as just the weak spot on the bottom of the tank that rusted through from the inside let loose. Nothing to hurt anyone just a little surprise and some mess to cleanup after the tank puked all over the cellar floor. Maybe I was just lucky. That was when I learned about draining the water out of a tank. :)

Thanks, Lewill2. I've heard stories similar to yours. I've also heard it can be equivalent to a couple sticks of dynamite. So I'm not sure what to think. ... I suppose they're both possible, depending on different factors...

Since you've heard stories, how about some pictures?

>can be equivalent to a couple sticks of dynamite

Remember, diesel engines work by causing oil to explode...tiny quantities of oil...

> I'm going to look into tank certification

It already failed, it has oil impregnated rust.

You need to get all that oil out of there first.

Then you can hydrostat the tank....

PS: That oil came from somewhere....need to address that also..
PPS: I *am* impressed you got the plugs out :)

Aunt Phil, that's heinous... But I'm not sure what, exactly, we're looking at? Did the shut-off valve go bad so it just kept filling until...  Or is this what happens when you try filling a compressor tank with argon (ala 2000+ PSI)? 

As messy as it is around there, I'm not surprised SOMETHING went wrong... ;)

fire extinguisher guys have testing  tanks, so do some oxy acet places.

Skip

Quote from: JessEm on April 13, 2012, 12:10:02 PM
Aunt Phil, that's heinous... But I'm not sure what, exactly, we're looking at? Did the shut-off valve go bad so it just kept filling until...  Or is this what happens when you try filling a compressor tank with argon (ala 2000+ PSI)? 

As messy as it is around there, I'm not surprised SOMETHING went wrong... ;)

Those pics are of a formerly neat garage after a free compressor with a slight leak in the tank ruptured.  According to the owner of the free compressor he was watching the machine build pressure, and it was around 120psi when it let go.

There is one hell of a lot of stored energy in an air receiver and it should be respected.  Unfortunately I've seen a number of people who know that completely fail to respect the potential disaster.