Compressed-air calculator
Compressor flow test (load/unload)
A compressor’s actual in-service flow often differs from its datasheet: wear, fouling, intake conditions. The load/unload test measures it on site, without a flow meter, from a known volume and a stopwatch.
Enter the system volume, the pressures and the pump-up time: the calculator derives the delivered flow (isothermal compression assumption).
Flow test
Compressor flow from a load/unload test (isothermal compression in a receiver).
How do you run the test?
- Close the isolation valve downstream of the receiver, then bleed it down to the load pressure (the compressor restarts).
- Time the rise between the load pressure and the unload pressure (the compressor stops).
- Enter the receiver volume, both pressures and the duration: the flow shows on the right.
Result
- Total volume
- —ft³
- ΔP measured
- —psi
- Time
- —s
Compressor flow—SCFM
≈ roughly a — HP compressor at 100 psig
To calculate, still needed: the receiver volume, both pressures, the duration.
SCFM = (V · ΔPabs · 60) / (Pstd · t)
Isothermal compression. P_std = 14.5 psia (1 bar abs).
Indicative estimates — validate all results before any technical decision.