Air loss calculation

[dkhayes117]

Hi all, I'm trying to determine CFM loss from change in PSI and known storage. We have an Ingersoll rand r75n screw compressor rated at a maximum of 457 CFM, 75kw/100hp. The compressor runs at approximately 114psi. The compressor is tankless, the only storage is the piping, which comes out to about 6000 cubic feet volume. The pressure drops from 114 psi to 84 psi in 1.55 minutes with compressor off. How much CFM is being lost?
What I've tried so far....
114psi/14.7psi = 7.755 atmospheres x 6000 cubic feet = 46530 cubic feet
84psi/14.7psi = 5.714 atmospheres x 6000 cubic feet = 34284 cubic feet

46530-34284 = 12246 cubic feet difference/1.55 minutes = 7900CFM which cannot be right, what am I missing?

also tried
leakage rate = (volume x (Pressure intial - Pressure final))/14.7 x time

(6000cuft x 30psi)/14.7psi x 1.55min = approx. 7900CFM???

there must be a difference between the compressor's cfm rating and the cfm I'm calculating???

 

[dkhayes117]

Just noticed that I typed 140 SCFM, actually it was 104 SCFM. FYI proof reading helps before posting.

ENGINEER"S MOTTO
If it isn't broken, take it apart and fix it!!

 

[berkshire]

dkhayes117 (Electrical)
Having determined that you have 104 SCFM leaking , your next job is to track the source of the leaks, if you can get the plant maintenance personnel on your side. It should be noted that worn o rings in hose quick disconnects are notorious for air leaks and that one such hose fitting can leak up to 6 SCFM .
B.E,

You are judged not by what you know, but by what you can do.