Estimating Compressor Capacity

[BenjaminM]

Hmm I made a post this morning, however it seems I forgot to hit submit. Here it is again. I think it is a rather simple problem but I'd been bashing my head on the wall over it.

I am currently looking into upgrading our nitrogen blanketing system. Currently we lose ALOT of nitrogen to atmosphere though leaks. I've put together a proposal but they have asked for a monitary justification based on saved compressed air consumption.

I know that in a year, our nitrogen generator has run 7400 hours and that it requires 27 SCFM @ 100 PSIG.

(7400 hr) x (27 SCFM) x (60 min/hr) = ~12,000,000 SCF/yr Easy!

Now here is where I do not think I am compairing apples to apples:

The compressor is rated for 102 CFM (NOT SCFM) @ 125 PSI.

Can I simiply say V1P1=V2P2?
(102 CFM)(125 PSI)=( x )(100 PSI)
x = 127 CFM @ 100PSI

And with that the required run time of the compressors for the year would be:
12,000,000 hr/ 127 CFM / 60 min/hr = 1575 hr

Also I have seen the equation
SCFM = CFM x (P/14.7)x(530/[T+460])

Using CFM=102, P=100PSI, and I measured the temperature on the compressor to be 440*F before the after cooler. I get SCFM = 408. That doesn't seem right either.

Thankyou all for any help or suggestions.

 

[dcasto]

the 102 cfm @ 125 psig means 125 cubic feet per minute at the compressor suction, so thats real close to scfm (standard cubic feet). At a lower discharge pressure the unit may be able to put out more volume, but the vendor needs to tell you this value.

even though your pv=pv is true, it doesn't apply and if it did, you need to use absolute pressures.


your scfm equation is correct, but you would substitue this P=atmospheric pressure at you altitude ,less drops through filters, and T is temperature of air intake.