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Compressor safety, or how do I make sure an old compressor is safe?
vtsteam:
I know of a guy who lost his hand inflating a wheelbarrow tire. He didn't set the regulator low enough, and it inflated so fast (being small) that it burst while he was holding it down on the bench.
A small vessel can actually be more dangerous than a large one. And a rubber tire is not necessarily "safe".
wgw:
OK I admit it was a bit of a stupid remark, re car tyre. It was meant to be tongue in cheek. Only excuse is I'd just put a hedge cutter into my leg and was in a bad mood. I've been hurt by tyre blowout, inflating a trailer tyre, that hurt but no damage to me. I knew a man killed by tractor tyre exploding, in the shop these have to be inflated in a cage for safety, but hard to do in the field.
RussellT:
I've often wondered whether the reason you don't hear of more accidents with small compressors is that the failure mode is pinholing as Pekka suggests.
LPG tanks are acceptable as air tanks (apparently even to HSE). I used a fire extinguisher - I was trying to find a couple of CO2 fire extinguishers as they're normally aluminium but couldn't find any at the time. Water fire extinguishers have an anti corrosion coating on the inside.
Russell
dawesy:
Yep I too have had this. Mine rusted a 5mm hole in it. I only noticed when I switched it on and heard a hissing noise. As with most things compressed as soon as a failure creates a relief the pressure drops.
The only thing I can imagine causing a tank to explode is weld fracture which would hopefully be found at the manufacture testing point.
petertheterrible:
I believe that although there are many valid points made here I believe that what MexicanJon said is as near to the truth and the best possible advice.
Most small compressor reservoirs are not destructively tested these days, factories get away with not a lot of testing, please take that in consideration.
If someone considers himself still inexperienced in compressors and pressure vessel workings I would not advice him in repairing safety valves but to throw away and buy new. Regulators and other valves although not to difficult to comprehend the workings of do present some difficulty for a novice. For one how do you test a valve setting safely without proprietary equipment of a working compressor and good regulator.
Something to take in consideration is that in the testing of pressure vessels like these the 'swelling' of the vessel is also taken into account and all data is compared to a perceived determined standard.
The other guy may be misconstrued about the power a bursting tire has, but it is still regular practice in some boilermaking circles to ping test a boiler by striking it and listening to the sound it makes. Burst discs and safety devices of regulated burst qualities are available but I reckon that that that is widely known to all informed members.
Although I have yet to see it in practice testing vessels, the non invasive electronic type testers used to test welds might be of use for the hobbyist to test pressure vessels. The neon ink I believe may not be a true indicator as it requires an existing crack or external bad spot.
I believe that the best safety device if the filling pipe. The greater the distance between yourself and the compressor, the better the chance that you won't get hurt. I have seen the aftermath a brand new industrial compressor left due to their being fiddled with it/ not installed properly. Just because it's new doesn't necessarily mean it's safe. I would after visual inspection when draining water (look for rust) probably take the unit out back as far as possible from anything that can be damaged and run it, while just peeping to see if it shuts of around a sturdy wall. (Just my personal method and I don't advice anyone to follow.)
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