Subject: Time:2:28 PM
OFFICE MEMO Old air compressor Date:5/31/94
>I was given an old (1950s) 3/4 hp compressor by someone who wanted it out of
his garage.
Since I do engineering safety analyses of air compressors and other pressure
vessels here at work, the words "given" and "old" raise a red flag with me.
They indicate reasonable cause to suspect lack of maintenance by the PO. Did
you drain the water out of the tank? Did you even know it could have a couple
of gallons in there? It could be rusting away the tank from the inside until
its thin enough to blow apart at 120 psi. Not pretty.
We would do a hydraulic pressure test, which is to fill it almost full of
water, then from a safe distance pressurize it to 150% of the maximum allowable
working pressure MAWP, which should be stamped on the data plate, measuring the
circumference before and after the test to see if plastic deformation has
occurred (i.e. the tank stretched). If your data plate has a letter U within a
four leaf clover, that means this test was done on it when it was new. It
should be repeated if you have any cause to suspect significant degradation
inside the tank walls.
>flips open a bleed valve and turns the motor off, lets the air bleed down to
about 80 psi
>*supposed* to work this way?
Unusual, but I couldn't say whether its supposed to or not. Mine at home and
all the ones we have at work hold their pressure indefinitely. If the bleeder
is at the very bottom its purpose could be to bleed off the water I mentioned
above, but I would have thought it would close as it gets down to 100 or 110
psi. If its a brass safety relief valve I suspect its malfunctioning. You
should have at least one of these in the system, and it will be stamped with
its relief pressure, which will be somewhat higher than the 120psi shutoff
pressure you mentioned, but less than the MAWP.
>Besides pumping up tires, using the air to blow things dry, and maybe airbrush
painting, can I run any air tools with this?
Sure, if you have enough CFM (cubic feet per minute).
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