> Dont think 8.5 cfm is enough for blasting.....my comp is 14 cfm and has a
> 200 ltr reciever (4 gallons I think is only 18.6 litres!!!) and what
> happens is after around two mins blasting on mine the pressure
> goes down too
> 55 psi.
> and I have to wait for it to build up again.
The problem here is that compressors are almost always rated in scfm or
"standard cubic feet per minute"; while tools like a blast gun are usually
rated only in cfm. The distinction is that scfm is measured after the air
has expanded back to room pressure (and temperature); while the cfm
consumption is measured with the air still compressed. Since 90psi is
roughly 7 atmospheres, there is a 7:1 difference in these two ways of
measuring flow at 90psi.
Thus, to keep up with a blast gun rated for 4 cfm at 90psi, you need a
compressor rated for 28 scfm @ 90psi. Of course, many people do as Mark has
suggested, use a smaller compressor to pump up a big tank and then blast
until the tank runs down.
Randall
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