How to Test Air Compressors

The compressor must feed a receiver or tank of a known volume. (stamped tag)
To conduct the test, close the valve that isolates the receiver from the plant's distribution system and turn off the compressor. Vent the receiver down to approximately 30 psi and turn the compressor back on. Study the pressure gauge on the receiver and use the stopwatch to time how long it takes for the pressure to build from 50 to 100 psi. Use the following formula to calculate the flow (scfm) of your compressor:
0.45 V_R t = O_C
where:
V_R is receiver volume, gal
t is time, minutes
O_C is Compressor output, scfm
Dividing the results of the test by the manufacturer's flow specification will indicate what percentage of the original capacity the compressor is operating at.
As an example, lets say a 712-hp compressor has a factory rating of 28 scfm and an 80-gal receiver. It takes 2 min and 6 sec to build the pressure from 50 to 100 psi. Then:
0.45 80 2.1 = 17.1 scfm, and
17.1 28 = 0.61
So the compressor is operating at only 61% of its original capacity. This indicates that the compressor is operating at a severely diminished capacity. This information should be carefully considered before replacing the unit.

I hope this helps you.

How would I test an air compressor tank, concerning inside rusting if the unit is about 30 years old, and it is a large compressor with 15hp wisconsin engine? I have ran it up to 120lb no leaks. would like to run it a 150 to 180 lb. Should I be concerned, just trying to be safe, any comments. does anyone do this?

Hi,

To do this safely you will hydro-test the vessel (tank) to 1.5 times its rated pressure. DO NOT use air or any other gas to do this, use clean fresh water. If it ruptures, your floor only gets wet.

Regards,

Tim