Thread: Air Compressor receiver tank.

So.....

I decided to make some efforts to clean up my air compressor. It's an Atlas-Copco Aerman AE7, direct drive, about 25 CFM. The receiver is about 110 litres capacity. The compressor can run up to 10 bar or 145psi. I aim to run it at 125 psi or about 8.5 bar. It's been sitting on my verandah for about two years waiting on three phase.

I removed the inspection plate for the receiver tank and discovered loose flaking rust in the bottom and a water line about half way up the tank. Not impressed. The joys of second hand gear!

I doubt that anyone near me has the facilities to test the tank. I am thinking that I will strip the tank of fittings then get out as much of the rust as possible before filling the tank with water and 1 or 2 litres of "Evaporust". The aim being to get the tank back to clean bare metal. Should I spray the interior with spraycan of galmet paint ? Clearly I'll need to keep water out in the future and will probably go with a refrigerator dryer between the compressor and the tank.

I am concerned about the tank failing in service and don't have much experience with compressed air. A catastrophic tank failure would be way more experience than I require. So for those with some experience of compressors, is this a reasonable plan of attack or do I just buy another receiver?

Cheers

The Beryl Bloke
+

Are you able to post some pictures? is it just surface rust or is it actually pitting the tank? refrigerated dryers are always use downstream of the receiver, the air is too hot coming out of the compressor (up to 100degrees) for one to work between the compressor and the receiver. if you drain the water out of the receiver regularly you wont get the rust problem. we use an auto drain valve at work it opens for 3 seconds every 10 minutes.

Originally Posted by Theberylbloke

So.....

I decided to make some efforts to clean up my air compressor. It's an Atlas-Copco Aerman AE7, direct drive, about 25 CFM. The receiver is about 110 litres capacity. The compressor can run up to 10 bar or 145psi. I aim to run it at 125 psi or about 8.5 bar. It's been sitting on my verandah for about two years waiting on three phase.

I removed the inspection plate for the receiver tank and discovered loose flaking rust in the bottom and a water line about half way up the tank. Not impressed. The joys of second hand gear!

I doubt that anyone near me has the facilities to test the tank. I am thinking that I will strip the tank of fittings then get out as much of the rust as possible before filling the tank with water and 1 or 2 litres of "Evaporust". The aim being to get the tank back to clean bare metal. Should I spray the interior with spraycan of galmet paint ? Clearly I'll need to keep water out in the future and will probably go with a refrigerator dryer between the compressor and the tank.

I am concerned about the tank failing in service and don't have much experience with compressed air. A catastrophic tank failure would be way more experience than I require. So for those with some experience of compressors, is this a reasonable plan of attack or do I just buy another receiver?

Cheers

The Beryl Bloke
+

There may be someone locally that tests scuba tanks, they will likely have the ability to clean and check the tank. They use ball bearings in the tank and rotate it for an hour to get rid of rust before doing an inspection and pressure test. Check with the scuba filling stations, they will know who does it.

Pressure cleaners can be used to test the tank.. Fill tank with water, put a pressure gauge on it. connect pressure cleaner and pressurise.

Pressure cleaner, 1400psi or so?? Yoiks!
I have heard of using a grease gun to pressurize, after completely filling the tank with water; sounds a bit more controllable. Or get hold of a proper hydrostatic test pump.
At work our tanks are inspected and signed off annually by a boiler inspector. In places one tank has pitting which has reduced the steel below the original 5/16 thickness, but still OK for the pressure we run at. Measurement is by an ultrasonic gizmo; our tanks have not been hydro tested.
Neil

Bought myself a hydrostatic tester off ebay the other week.
150 clams, claims to pressurise up to 750psi.
I'm the sort to support the purchase of odd tools that might only get rare (but invaluable) usage.

Stustoys Thanks for the picture(s)

oops......fat fingers

Originally Posted by Theberylbloke

I am concerned about the tank failing in service and don't have much experience with compressed air. A catastrophic tank failure would be way more experience than I require. So for those with some experience of compressors, is this a reasonable plan of attack or do I just buy another receiver?

Cheers

The Beryl Bloke
+

If it fails in service due to a rust hole, it'll just leak slowly and not hold pressure. There is no way that you'll get a catastrophic failure causing an explosion.

We thrashed this to death recently on PM. The *only* verifiable accounts of catastrophic failure/explosion involved oil mist or similar and the thing basically 'dieseling' to rupture. This definitely can happen but is pretty rare.

Working pressure is 120 psi. Test to 250 psi, it doesn't need more than a 2X safety margin.

FWIW I know a fair bit about pressure vessel testing. I wrote the software used by a authorised & certified test station for SCUBA gear and it has to pass ISO audits.

PDW

Hi PDW,

Thanks for the info on tank failure mode.

I did look at taking some photos.. Ever tried to take a photo of the inside of a small black hole? Didn't work for me.... NASA say they have the same problem!

There are a number of dive facilities in the area and I have also discovered Atlas Copco have an office in Townsville which maybe handy.

LordBug, that's a dangerous idea. I have looked at ultrasonic metal thickness meters, tempting... I will not surrender to the temptation.

Also sorry to take so long to get back to this thread, been a bit of a busy Christmas.

Cheers

The Beryl Bloke