Actually, two-stage compressors are not more efficient. Efficiency
decreases with increasing pressure (which generates increasing heat).
Two-stage compressors simply provide higher pressure. Most frequently, the
output of two cylinders is fed to a third (sometimes smaller) cylinder which
further compresses the air to a higher pressure than the two first-stage
cylinders can create.
All this is at the expense of air output per horsepower, but it's the way to
create higher pressures as required for some activities. If you don't ever
need over, say, 90 PSI, a single-stage is preferable and will actually
produce more volume at 90 PSI than a two-stage compressor using the same
motor.
One reason many guys prefer two-stage compressors even for lower-pressure
use is that the higher pressure in the tank lets you use air for a longer
time before the compressor kicks on - there's more air in the tank. Same
benefit as having a larger tank. I'm sure that under certain combinations
of conditions the less-frequent motor starting could offset the lower
efficiency of the two-stage, but I'll let Randall or another EE calculate
that ;-)
Karl
-----Original Message-----
From: Scott
Subject: Re: [Shop-talk] Air tank fittings
As far as I know, they deliver more air. Higher pressure attainable, more
volume, etc.
I'm curious about the 'how', somewhat, but hopefully someone will be along
shortly to fill us in. :-)
On 1/23/2012 2:40 PM, Mike Sinclair wrote:
> Can someone comment on the advantages of a two-stage compressor?
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