A Basic Compressed Air Problem 1

[FredGarvin]

OK, I hope I'm not coming off to brain dead, but this has been a thorn in my side for a bit and I want a liitle backing on this...

I have a storage tank that has to be filled to some pressure via a compressor with a known rated SCFM at the inlet and working pressure. Can I simply take the water volume and expand the air to standard conditions to get a standard cubic foot volume of the tank and then simply divide by the SCFM to get the time to recharge that tank to the pressure I want?

Does anyone have a general procedure for calculating time to fill a certain volume tank from one pressure to another?

Thanks All.

 

[Rich2001]

ESTIMATED TIME REQUIRED TO FILL A RECEIVER

The following formula can be used for this purpose.

T = (V * (P2-P1))/(PA*(Q*QE))

in which:

T = Time required to pump up receiver from pressure P1 to pressure P2 in minutes.
V = Volume of receiver in ft 3
P1 = Initial pressure in receiver psiA
P2 = Final or desired pressure in receiver psiA
PA = Atmospheric pressure, in psiA. Use the value 14.7 psiA pressure if at sea level. For other altitudes the correct
atmospheric pressure should be substituted.
Q = Output flow of compressor, in cfm (ft3 min.).
QE = Average volumetric efficiency of compressor, as a decimal. If QE is unknown, a value of 0.8 may be assumed.
The QE is not constant, but will decrease as the discharge pressure increases. Therefore, the average should be used.
(Q x QE) = Actual delivery of compressor, in cfm. If this value is known, it may be substituted in the formula for the two
terms Q and QE.

This formula will give only approximate results, since factors such as temperature changes are not considered in the formula and cannot be accurately measured without elaborate apparatus. In most cases, these factors would tend to slightly decrease the pump up time from that shown by the formula.

 

[FredGarvin]

Thanks for the help Rich. I'll use that against all of my other "estimates" and see how I fared.