Second hand air compressor safety

[Dinkum]

Hi all,

I just bought a used 3 phase air compressor, the guy reckons it puts out about 30 cfm. My question is this: I have heard that old air compressors occasionally blow up if the tank hasn't been drained after use everytime (the water rusts the bottom out). Is this true?

Many thanks.

 

[John Rudd]

Dinkum,

It would pay you to get the tank inspected and tested (hydraulicly)...If it has a relief valve( and I'd be surprised if it didnt..) have that re certified too...

 

[Ken I]

I don't know your location so I can't comment on your local regulations - but there is almost certainly a requirement that it be tested before putting it into service - thereafter every 2 to 4 years.

Typically a test is 1.1 x rated specified max. pressure (filled with water so if it blows up is goes bump not BANG !) and a test of the safety valve lifting pressure - normally a log book should be kept (does it have one ?).

Usually an internal inspection every 12 months and a pressure test every 2 - 4 years - the pressure test being performed if a visual inspection is not possible / practical.

As a certified engineer I used to sign off pressure vessels as part of my duties - I have never had one fail (although I once had a tiebar fail in a boiler which scared the crap out of me with the bang).

My own compressor is well overdue - must pull my finger out and test it.

If there is a mishap - the first thing you are going to be asked to produce is its certification and test history. If you can't you are generally in trouble.

Like I say - generally not a problem but these things can and do fail - so rather be safe and have it checked out / documented.

Ken

 

[Tin Falcon]

dink here in the US some fuel dealers also provide the service of inspecting fuel tanks. . IIRC ultrasonic testing they check the bottoms for thin spots cased by corrosion from moisture sitting on the bottom of the tank. IIRC a low end tester is about US $250 the last time i looked.

Tin

 

[kwoodhands]

Hi all,

I just bought a used 3 phase air compressor, the guy reckons it puts out about 30 cfm. My question is this: I have heard that old air compressors occasionally blow up if the tank hasn't been drained after use everytime (the water rusts the bottom out). Is this true?

Many thanks


If the tank leaks from water rusting the tank out I would think this would be at the bottom.I have had and seen tanks that rusted out.I have reservations about a compressor blowing up from a leak.I don't see how myself. The motor and pump can burn out if the leak happens when there is no one around to shut the compressor off.
As far as an actual explosion, I would like to hear from others if they have seen or heard of this.Five years ago I had a pinhole leak in a Quincy 20 gallon compressor. I cleaned the area up and drilled and tapped a 10/32 screw with JB Weld as a thread lock.Hasn't leaked since.
Get the the tank tested if you have any concerns.
mike

 

[Dinkum]

Thanks for the replies. I'll see if I can find someone to test it.

 

[Ken I]

Corrosion will normally produce a pinhole leak before catastropic failure - but if there is a nice line of corrosion pits AND your pressure control switch welds shut AND in the meantime your safety valve has gunged itself up - then expect an almighty bang.

Don't laugh - these are the kind of strings of failures that lead to major catastophes.

Hence inspections and tests - at the very least periodically lift your safety valve to check it is still clear.

Ken