Cleaning old compressor tank

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Hi guys,I've recently picked up a 60-gallon compressor for my shop.  The inside of the tank appears to be covered in oil film and gritty particles that feel like sand.  The air pump had failed on the unit, and I don't know the environment in which it was run, but I don't want that crap in the air system.  Any thoughts or recommendations on suitable cleaning procedures?Thanks!Edit:  Added welding content! Also picked up a Lincoln 175HD Mig machine recently.  I've only run some flux core through it so far, but it looks to be a well-built machine, certainly a good step up from the import units I've looked at.Last edited by renns; 09-25-2008 at 09:01 PM.
Reply:Dawn dish washing liquid and hot water and a couple of friends to help you slosh the watery mixture around in that 60 gal tank. then fill it with hot water and Dawn and let it sit over night, then repete first step. Then let it dry for a good 12hrs and go from there.Miller Thunderbolt 225Millermatic 130 XPLincoln HD 100 Forney C-5bt Arc welderPlasma Cutter Gianteach Cut40ACent Machinery Bandsaw Cent Machinery 16Speed Drill PressChicago Electric 130amp tig/90 ArcHobart 190 Mig spoolgun ready
Reply:A previous thread discussed old tanks, pressure testing and danger from their bursting; it might be good to search for that and related threads before you put the tank back in service.A tank that size should have large inspection ports through which you can use a high pressure washer or even a steam cleaner to get the oily and loose material out. The material called Gunk which is sold as both an aerosol or in gallon cans also works well as an emulsifier to remove oil and grease. However, if there is no appreciable rust on the inside walls, it may be better to leave any protective oil in the surface pores. If there is much rust, the tank should have a subsequent and thorough inspection for defects. Some would say it needs it in any case.
Reply:I'd definitely hydrostatically test the tank. It's relatively easy to do yourself and safe if you take the right precautions. A co2 tank and regulator, some hose, and to fill the tank with water is really all you need.
Reply:Thanks for the help guys.  I managed to wash it out pretty well with hot water and laundry detergent.  The grit that came out looked like sand, rather than rust flakes.  I don't know what kind of service this machine had prior, but the whole unit is not more than about 15 yrs old.  Perhaps it was run without an inlet filter, which may be why the compressor unit itself failed.Regarding those big access ports, there are two on my tank, one at the bottom, and the other part way up the side.  I couldn't budge either of those with a pipe wrench and 3 ft pipe.  I ended up using the 3/4" outlet port for filling and draining.Is the hydrostatic testing process outlined somewhere?  I'd imagine, fill with water, cap all ports, introduce inert gas via regulator to top port, and pressurize to 'X'?Thanks,Roger.
Reply:Doing your own hydrostatic test on a tank is just for your own exercise and maybe peace of mind.In other words, it is not official and doesn't count.Basic idea - fill tank with non-compressible fluid, pressurize the tank to a desired proof-pressure (higher than the rated/working pressure rating of the tank), check for leaks or failure.  The reason for the non-compressible fluid instead of a (compressible) gas is so that in the event of a failure there should just be leakage or a pfffft instead of a KA-BOOM.Also check regulations in your area for required official retesting of pressure vessels in use in commercial/industrial settings, as opposed to an air compressor in your home garage for hobby/personal use.  The best laid schemes ... Gang oft agley ...
Reply:As stated above, you don't want any compressible gas inside when it is tested. A good, cheap, non-messy, non-compressible liquid is, of course, water. To get the pressure you want, an old grease gun works fairly well once all the old grease is cleaned out. I understand the industrial testing is done with the tanks also submerged in a pool of water to contain any 'blast' which might occur.
Reply:Thanks for the info.  I'll fill it up and try the grease gun trick to test.
Reply:I've had several 2nd hand compressor tanks hydrostatically tested for about $15 each at my local fire extinguisher service company.  For one tank that was too large for their test rig they sent me to another fire extinguisher service company across town that had a larger test setupI haven't seen their test setups, so don't know why size matters.  I think it has to do with the bath they put the tank in for testing.  I believe that one criterion for passing the test (in addition to not bursting) is how much the tank expands at test pressure.  That is determined by the displacement of water from the vessel in which the tank under test is placed.While it is certainly possible to safely apply some arbitrary hydrostatic test pressure to an air compressor tank "at home," I think an official test by a neutral third party with proper certifications is well worth the price.  They know what the appropriate test pressures and procedures and passage criteria are.  Do you?  Don't get me wrong.  I am an enthusiastic do-it-yourselfer.  But some things are best left to the pros who can put an official test tag on your tank.By the way, I think it is always desirable to use a tank that has an ASME certification tag welded to it.  An ASME (American Society of Mechanical Engineers) tank is fabricated by certified pressure vessel welders with certified materials and inspection.awrightLast edited by awright; 10-04-2008 at 03:04 AM.