How to make leaking air tanks safe...

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Anonymous-0

Well-known Member

• Sep 6, 2010

• #1

Since it comes up almost weekly, I think I have a solution for people who don't want to replace their old rusted out or leaking air compressor tank. Try and fix it anyway you like but then put it inside a larger container full of water and use it that way. The water will provide two things; 1. It will show any leaks 2. If it decides to suddenly let go, the water will contain the explosion. Of course you have to make sure you don't get electrocuted having the compressor motor in the water too but if you're willing to risk an explosion anyway, it shouldn't be a big deal.:wink: Dave

 

Hendrik

Member

• Sep 6, 2010

• #1

Are you serious?
Yes, the water will show you the leaks but the water will NOT do much in containing the explosion. Sea mines do kill, remember?
The only safe way to deal with rusty or leaky compressor tanks is to retire and scrap them.

 

MarkB_MI

Well-known Member

Location

Motown USA

• Sep 6, 2010

• #1

Dave, I suppose your tongue-in-cheek suggestion is based on hydrostatic testing. But there's one important difference: Hydrostatic testing is done with water INSIDE the tank. Just placing the air-filled tank inside a water-filled vessel doesn't eliminate the tank's latent energy.
Hydrostatic testing

 

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al in ark

Member

• Sep 6, 2010

• #1

dave i have to admit another stroke of genius al

 

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ASEguy

Well-known Member

Location

Festus MO

• Sep 6, 2010

• #1

I know some portable air tanks have a date stamped on the top of them for when you are supposed to get rid of them, but I don't know about smaller air compressors. Maybe someone here knows. I think I'll just leave this one alone. Whew.

 

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markiz41

Member

• Sep 6, 2010

• #1

I prefer bourbon. When the tank lets go, you can celebrate.

 

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buickanddeere

Well-known Member

• Sep 6, 2010

• #1

????????????????????????? Kidding right?

 

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Bus Driver

Well-known Member

• Sep 6, 2010

• #1

135 has disagreed with me before. I had a propane tank, about 30 gallon vertical size, that had pinholes rusted from the outside on the lower dome end. I welded those, welded a pipe fitting in the other end, placed the new fitting at the top, filled the tank with water, installed pipe tee with 500 PSI pressure gauge and grease fitting and started with grease gun. The pipe tee cracked at about 410PSI and a few teaspoons of water leaked out. The tank has been used for the last 30 years for air service at 150PSI with no problem.

 

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Bob - MI

Well-known Member

• Sep 6, 2010

• #1

Water is a non-compressable liquid. It's just like oil when it comes to hydraulic energy - a great transfer media.

The words "contain the explosion" should be all we need to know here.

 

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Fred Martin

Member

• Sep 6, 2010

• #1

I will go along with Mark B on this one. Don't claim to be authority on this but, about half our machine shop job orders on navy tenders was globe and gate valve repair, hydrostatic testing was daily. Some of the steam valves were high pressure (super heated steam?)and as I remember, they had to hold 7 or 8 hundred lbs. steam pressure. They lapped in the seat with the mating part and they always put a nickel between the valve stem and it...and if the thing passed the hydro test, they left the nickel in there. This is from 43 yrs. ago...uncle Sam's canoe club. ohfred

 

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RodinNS

Well-known Member

• Sep 6, 2010

• #1

I'm not a big fan of repairing air tanks simply because of the corrosion that's often there anyway... and you can spend a lot of time chasing pinholes... but if you got a sound tank that for some reason just had a hole... repairing and then hydro testing to 150-200% of nominal ought to be safe enough.

Rod

 

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Anonymous-0

Well-known Member

• Sep 6, 2010

• #1

No I wasn't serious. How's a compressor motor going to work underwater? Considering that almost all the posts regarding repairs to air tanks are for cheap throw away compressors, just get a new one. Dave

 

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Dalex

Well-known Member

• Sep 6, 2010

• #1

I don't know why you guys think the tank will explode , it will just leak at the next weak spot if its rotten , just like it did the first time . The only reason for it to explode is if the safety valve sticks. If an area has several holes , its prolly junk , but 1 pinhole with solid metal around it is perfectly repairable.

 

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Anonymous-0

Well-known Member

• Sep 6, 2010

• #1

Yes I'm kidding about the air tank. Dave

 

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Anonymous-0

Well-known Member

• Sep 6, 2010

• #1

You obviously have more welding experience than most people on here and were smart enough to test it in a safe manner before putting it in service. Dave

 

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Rod (NH)

Well-known Member

• Sep 6, 2010

• #1

Some <a href="http://www.dli.mn.gov/ccld/boilerincidentsair3.asp">pinhole leak</a>. You can never be certain about the actual failure method; pinhole leak or explosion. Don't risk it by a "home repair" that will never be properly inspected or tested. Any repair should only be undertaken after a complete internal visual inspection (by borescope if necessary) to determine the extent of corrosion and ultrasonic thickness testing (UT) to verify remaining wall thickness as satisfactory for continued safe operation. In other words, don't go chasing pinholes. Proper final hydrostatic testing is good but is no substitute for a careful visual inspection and UT beforehand, both inside and out. The typical air tank used in the home shop is simply not worth bothering with for a correct repair. Replace it instead. Just because someone else has done a half-baked repair and has gotten away with it doesn't mean it's a recommended practice.

 

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Stan in Oly, WA

Well-known Member

• Sep 6, 2010

• #1

Hi Fred,

I'm not familiar enough with the equipment you're describing to be able to visualize the part about putting in the nickel. Could you explain?

Thanks, Stan

 

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buickanddeere

Well-known Member

• Sep 6, 2010

• #1

Compressed gasses store potential energy which will continue forcing on the tank walls. The tank will burst into shrapnel and/or launch with speed and drive.
Liquids under pressure have little to no compression. If the tank ruptures during a pressure test. It just squirts a little.

 

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Puddles

Well-known Member

• Sep 6, 2010

• #1

Not a very good picture of a UT scope, but best I have. Inspector testing a pipe weld at the ferry terminal north end of Vashon Island.
To find a bad spot, (plus depth) in the weld the inspector has to be very good with trigonometry.

 

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Anonymous-0

Well-known Member

• Sep 6, 2010

• #1

You have to really know what you're doing to read ultra sound oscillographs(sp). That's how they test for proper fusion of chromium carbide overlayed pipe and also nozzles on vessels because they can't be X-rayed. UT license is one of the harder ones to get. Excellent way to test the integrity of an air tank. Might cost more than the cost of a small air tank to have it done though. LoL Dave

 

MarkB_MI

Well-known Member

Location

Motown USA

• Sep 6, 2010

• #1

I don't think anyone has said that a repaired, rusted-out air tank "will" explode. But it's a known historical fact that such tanks MAY explode, and when they do the consequences are catastrophic and often tragic.

Let me put it this way: Suppose I hand you my .357 Magnum and tell you: "This revolver MAY be loaded, but I really don't know for sure." Would you point it at your own head and pull the trigger? I doubt it. When you're talking about a rare event with potentially fatal consequences, why take chances?

 

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Fred Martin

Member

• Sep 6, 2010

• #1

I guess I could describe a globe valve has a hand wheel, stem, a packing gland with usually graphite impregnated packing, a bonnet to cover all this, a valve itself (male part of valve)that sort of floated on the stem so that it could seat on the valve seat below it. When the valve and seat were renewed accurately, they wanted the male part to go in square and the nickel was to keep them from chattering, I think...and the body with a flange on each side with a bolt pattern on them. Maybe another reason the stem floated was to allow a bit of mismatch. Hope this works or I'd have to hunt books or web....or you could join up. Smile. ohfred

 

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Anonymous-0

Well-known Member

• Sep 6, 2010

• #1

That's an excellent link! Check out the boiler that blew up!!! Sometimes seeing actual pictures of what can happen smartens people up, sometimes not. Dave

 

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Ken Macfarlane

Well-known Member

• Sep 7, 2010

• #1

A local guy took a good shot to the face when his old tank blew at the rusty seam. There is a lot of energy stored in compressed air, a new tank is cheap.