On 3 Oct 2003 19:57:58 -0700, (Daniel) wrote
something
.......and in reply I say!:

Jon Elson wrote ...

... 3/4 Hp is just too small for serious air tool work...


No argument in the context being discussed. However....

I've got three air conditioner compressors (one known good, two
unknown). Couldn't tell you the sizes, but I'm thinking it doesn't
matter much because I also have a 500 gallon propane tank that I'm
thinking of marrying one of them to. Now I may have to let the sucker
rung a day & a half to get up to pressure, but I'm thinking it would
take a LOT of serious air tool use to see much of a pressure drop from
a tank that size.

Not very much actually. There is no substitute for sheer input. The
only exception is where you have intermittent use and the compressor
_nearly_ meets the max requirement of the tool.

My figuring.

For a Random Orbital Sander

At 120 PSI in the tank (90 PSI at the regulator), you will have:

120 / 15 (pressure / atmos pressure) * 500 (gallons) / 6.4 (imperial
gallons per ft3) = 625 ft3

The tool will stop running properly below 90 PSI in the tank (and at
the regulator), at which stage you will have:

90 / 120 * 625 = 470 ft3

You get to use 156 ft3.

At, say 8 CFM (a kind estimate of the requirement for a ROS), you will
get twenty minutes continuous workable use out of the tank, absolute
max.

If it took a day and a half to get up from atmos pressure, then you
will take something over 156 / 625 * 1.5 days = 9 hours to get back up
to 120 PSI and start again.

A spraygun that could run down to say, 40PSI would be better, if it
used maybe 10CFM(???). You get to use 625 - ( 40 / 120 * 625) = 400
ft3, so you get 40 minutes continuous spraying, which would do a heck
of a lot.

You will then have the pump up time again, although you would only
have to go to 50PSI in the tank to get working again......but then you
would run out faster etc.

Give yourself 3/4 of these times if you mean 500 US Gallons.

Noise isn't an issue, the nearest neighbor is 1/2
mile & I can put the beast beyond the shop which is 100 yards from the
house. Any thoughts other than to pressure test it from a good
distance?

Pressure test with water, not air. Fill with water, until there is the
tiniest pocket left, then use air. Then the only air that can escape
explosively is the tiny bit you put in. You should also test to way
above what you intend to use it for.

************************************************** ****************************************
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The rest sit around and make snide comments.

Nick White --- HEAD:Hertz Music
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