Welding on a compressor tank :-(

When I bought my Speedaire compressor it had a welded repair in the same area you mention. I scrapped the tank but cut off and saved the motor mounting plate. I used this plate when I mounted the compressor head and motor to a good used horizontal tank. Steve

OK, thanks to all. I will not use the tank for compressed air. Maybe for pig roasting or some such.

Aren't compressor tanks subject to regulation and inspection in most (or all) US states, on the assumption that if your tank blows up and takes out half the neighborhood it's bad for society?

You are expecting an explosive failure that will cause actual damage from

I welded only one compressor tank. I kept getting holes, and was puzzled to see only more bubbles each time I restarted and sprayed. Then I remembered the time I pulled the engine in my old Chebbie truck and changed ONE freeze plug. Found that they all equally corrode, and that one leaking was only a symptom of them all being bad. Pulled it a second time and replace all of them.

I cut the compressor tank in half and found that it had rot all along the bottom where the water had stood and corroded it out. Every time I'd fix one hole, it would pop another. I doubt that explosion would be a risk on a lot of tanks, as they would just pop a hole in the weakest place, and not hold enough pressure to explode. Also, the popoff valve would never let it get that overpressurized, even IF the old compressor motor could pull it off and pump it up that high. Explosions come from rapid failure all along a joint joined with serious overpressurization. Most go off with just a big fizz. But not all.

As evidenced in that Dallas gas yard explosion, the popoffs and low melting point sealants don't always work the way they were intended. I would suspect compressors to be the same, but the amount of pressure is a lot less, and generally, a popoff valve is present even on old units.

Steve

"Tim Wescott" wrote

They aren't that big, and they don't have that much pressure. Plus, it's only air. Danger is relative to distance, and the danger falls off exponentially with distance.

Steve

Only air????

There's a reason the pressure test is done with water.....and never air.

I was thinking overnight. If the issue is fatigue from vibration, what if I take the motor and pump off, set them up somewhere else, weld and test the tank, and use it as air receiver tank at a slightly lower pressure (say, 120-150 PSI).

Then further fatigue will not be an issue, as there will not be further vibration.

I was thinking overnight. If the issue is fatigue from vibration, what if I take the motor and pump off, set them up somewhere else, weld and test the tank, and use it as air receiver tank at a slightly lower pressure (say, 120-150 PSI).

Then further fatigue will not be an issue, as there will not be further vibration.

I guess you missed the part with the point.

Steve

You can make a nice BBQ from an air tank.

Iggy, we all like to save a buck. But sometimes you just have to do the right thing. Existing fatigue crack and pressure vessel sounds like any repair is the wrong thing to do. Salvage the pump, use the tank for a BBQ grill.

Just take the tank out beh> I was thinking overnight. If the issue is fatigue from vibration, what

A good hydro test should restore your confidence

How long is the crack?

You should be able to weld repair a small vibration crack in the upper area of a tank, with little or no danger to the overall integrity of the tank.

If in doubt, fill it with water, and test it to 5/3 or double the operating pressure of the tank.

But their should be no need to derate the operating pressure of the tank, or move the motor and compressor. If you want to reduce the possibility of the crack returning, mount the motor and compressor and a separate plate, and rubber mount the plate back to the tank in the same location. You would also want to add a flex hose between the compressor and the tank.

Not if it's fatigued, and it probably is. A hydro test won't tell you how much fatigue life is left on the tank.

Taking the pump off certainly will help, but it sounds like false economy to me. Fatigue is nasty stuff, hard to detect and impossible to repair.

-- Ed Huntress

I have very little confidence in old compressors because they generally (999 times out of 1,000) were never drained, or were never used with a water trap. Once it starts leaking, it's easier, faster, and cheaper to just buy another. The only thing I would trust is to roll the tank with ball bearings, flush, dry, and endoscope to inspect the inside, particularly the bottom where the water has sat for years.

If the OP does cut the tank open, I'd be curious about a report of inner condition and corrosion.

STeve

Approximately 2 inches.

Which was my plan.

The hose is copper. I think that this plan may be workable, I will sit on it for a day or so.

Steve, the tank is not leaking from the bottom, it is cracked on top.

It's not fatigue from the pump vibration, it is fatigue from the expansion of the tank under air pressure. Every time you pump up the tank, it expands a few thousandths of an inch. Any weakness or corrosion concentrates that stress.

Jon