The Shop > Tools
Compressor safety, or how do I make sure an old compressor is safe?
S. Heslop:
--- Quote from: awemawson on May 14, 2015, 03:40:26 PM ---That's why I always upload pictures to the forum rather than use a third party. That way the images are always there so long as the forum survives. Nothing worse than reading an interesting old thread where the pictures have all gone :scratch:
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I wish i'd done that sooner. I trusted iforce.nz since its been up and stable for a good few years now. I figured you wouldn't be able to embed attached pictures but it seems to be working fine. If iforce doesn't come back i'll probably go through my old threads and attach the pictures, i've kept them sort-of organized in folders.
S. Heslop:
--- Quote from: appletree on May 14, 2015, 03:59:08 PM ---Just had another look at your pictures, I think the vessel is better quality than suspected, the wall thickness of the inspection plug boss is of a good section and I would say the hole large enough to inspect through, after all that is what it is there for rather than a small pipe connection.
Any rust is likely to be at the lowest point a dentists type mirror would allow you to see, even if condensate has rested in the bottom it still needs oxygen for rusting to occur.
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I imagine in a compressor there's plenty of oxygen about. Corrosion might be a concern but i'm also worried about fatigue. Hydraulically testing it would put me more at ease than just checking for corrosion.
appletree:
Obviously when in use there is plenty of oxygen about in use but if the vessel is unused and the valves shut the oxygen will become depleted. I would inspect either way, going back to my earlier post as to what happens in industry, i do not see why the vessel would be fatigued, the vessel is designed in the first place even if the safety valve is not working which you can check, the maximum pressure achievable is determined by the compression ratio of the compressor.
vtsteam:
There's been plenty of oxygen and moisture condensation in most any compressor tank that's been used. That's why they put drains on the bottom. And likely rust, at least surface rust.
If your eyes can determine rust thickness under scale over every square millimeter of the inside of a tank through a borescope, and you know the thickness and composition of the metal and can then calculate the allowable stress left after deductions for the rust locations you've found, then that's the way to go.
Otherwise a pump you can make yourself and a reasonably priced gauge will actually tell you the strength of what you have to the degree you are interested in.
David Jupp:
In an industrial setting PSSR would apply - which requires a scheme of examination to be in place. Such schemes would be pretty similar for most compressors around this size - manufacturers often supply one with the machine (so may be worth asking).
Test pressure should be marked somewhere. For smaller vessels, the original plan could have been no routine test, but with a 'use by' date - though the label shown looks like it has space to record routine tests.
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