Drain your compressors!

[timb]

Had one of those moments that in hindsight can cause a little bead of cold perspiration or two to break out.

I have an older small compressor (2hp, 20 gallon horizontal tank sort of thing). While it was a decent unit and was still running fine, it's a hand-me-down and must be over 25 years old. It's always had an auto-drain installed to drain off condensation.

However - despite the drain - rust happens. I hadn't had it up to pressure for a month or so and last night flipped on the switch to charge it up for some work I had to do. When it finally cut off at about 115 psi - I could just hear some faint hissing. Sometimes the auto-drain does that just before it will burp out some condensation - but this didn't stop. I gave the valve a few light taps to see if it had become stuck - no such luck. As I did this I realized the hiss was not coming from the drain valve, but nearby. Felt underneath the tank - and found a tiny pinhole squirting air. This as I'm leaning over the tank! /forums/images/graemlins/ooo.gif

Needless to say I shut off the power, grabbed the hose and backed off - draining the pressure through the tire chuck.

I have no idea if a pinhole leak from rust is more common than a catastrophic failure - but the latter would have given me quite a headache. This was an ASME tank, but despite reasonably good care - there is a limited lifetime.

I'm not sure how easy it would be for most homeowners to find somewhere to have at least a hydro test run periodically (if not something more sophisticated like a wall thickness analysys).

So - it's either new compressor time - or at least time for a new tank. Anyone know how to check out a single-stage compressor pump and judge it's condition? As I said - it seemed to be running fine - but I'd hate to buy a new tank just to have the compressor pump start to fail a year from now.

 

[slowrev]

I have seen a couple of air tanks with the same symptoms as you described. A pinhole. Never saw one blow up or directly heard of one, of course there are many horror stories out there about it, some are urban myths I think, but some are true. Worry more if you have a 175 lb or so system.

Ben

 

[shvl73]

In the 80's Bostitch had a portable made by Thomas that had some sudden tank failures. It was the unit with the pancake style tank. The style still lives on but, the tank has been changed, rolled edges with the welded seam centered on the side rather than at the corners.

 

[Darren]

I heard one blow up on a jobsite once. Very heavy sounding detonation. None of us knew what had happened and there were no explosives on site. I took off out of the trailer and found a tire service truck not far away. The tire guy had a gas powered compressor sitting between the tool boxes on the sides. When it blew a tool box was between him and the tank. The tank opened up and bloomed like a flower. The only thing that kept the unit in the truck was the compressor catching on the upper lip of the back window. The cab and the roof were bent and the diamond plate bed of the body was dished downwards.

It impressed the heck out of me.