Clocking CNG Compressor for Gas Flow

Posted by on May 16, 2013 in Tips

Clocking CNG Compressor for Gas Flow

To clock a gas compressor you will need to identify the following:
That the only load on the gas meter is the compressor you are clocking.
What the gas pressure is at the meter while you are clocking.
What the smallest rotary dial on the meter measures in one revolution.

Next, record how long it takes for a given amount of gas to go through the meter and what pressure the meter was at when you clocked it.

Now the fun part; use the following formulas:

Correction Factor = 14.7 + P (pressure at meter in psi) / 14.7

Uncorrected Flow = Cubic feet clocked X 60 seconds / clocking time (seconds)

Corrected Flow (scfm) = Flow X Correction Factor

Example: You have determined that you need to know what the gas flow at your NGV station is. Pressure at the meter while running is 18 psig. It takes 25 seconds for the 10 cubic foot dial on the meter to rotate once. What is the corrected flow?

Correction Factor = 14.7 + 18 psig / 14.7 = 2.224

Uncorrected Flow = 10 scf X 60 / 25 sec = 24 scfm

Corrected Flow = 24 scfm X 2.224 = 53 scfm