Calculating air compressor FAD

http://en.wikipedia.org/wiki/FAD_%28disambiguation%29

Don't respond to questiosn you don't understand. Your link has nothing to do with compressor Free Air Delivery.

What is FAD. Install Air Flow Meter on each Compressor outlet. Check cfm / hr Vs Motor Kwh and you have your answer.

Thanks for that. But is there any other method to calculate the flow without using an air flow meter ? If so please mention.

the experiential formual:

displcement * RPM * 0.62 for 1stage @7bar;

displacement * RPM *0.72 for 2stage @7bar;

For the purpose of your application, FAD is short for Free Air Delivery. Free Air Delivery is a performance measurement of the air delivery by a compressor package at the discharge flange or outlet pipe of that package. It is expressed in terms of the inlet temperature and pressure of the compressor. In Europe and anywhere else that ISO sets the standards, free air delivery (FAD) is expressed as cubic meters per minute. In the United States, it is expressed as cubic feet per minute (CFM).

You could use the ASME PTC-9 test or ISO 1217 test, would would provide an accurate volumetric flow rate, but I doubt you have the instrumentation for these tests. Therefore, you can get a reasonable FAD by using pump-up time of the air receiver.

The formula for computing CFM based on pump-up time is as follows:

CFM = (Pf-Ps) Gallons/7.48 x atmos. press. (p.s.i.a.) x time (in mins.)

Where;

Pf = Air receiver final pressure

Ps = Air receiver starting pressure

Gallons = Air receiver capacity in terms of gallons

This will give you an approximate CFM for the collective FAD of all four compressors.

Thanks very much. This is what I was looking for. Great!!. This will really help me.

But can you further empasize on the following

1. Unit of measurement of Pf and Ps. Is it p.s.i.?

2. Air receiver capacity I suppost is US gallons and not UK. Is it ?

3. Is the formula like this

CFM = (Pf-Ps)x(Gallons/7.48)x atmos. press. (p.s.i.a.) x time (in mins.)

OR else please advise.

1. unit of measurement of Pf and Ps is PSIG. (example: 175 PSIG - 0 PSIG or whatever intial pressure you choose to use, it can be 100 PSIG - 50 PSIG)

2. Air receiver capacity is US Gallons.

3. No, the formula is (Pf-Ps) x Gallons divided by (7.48 x atmos. press. PSIA) x time in mins.

Thanks!!! Great !

All doubts cleared.

Standard compressors in a commercially competitive market usually have motors fitted with a power to exactly match the air output. The power can be read off the motor label.

You can expect an ordinary 100 psi compressor to deliver about 4 cu.ft per min per horsepower. That is, 100hp compressor will deliver about 400 scfm (standard cu ft per min).

A small single stage high speed compressor might just give 4 scfm/hp, whereas a large slow running 2-stage compressor (1,000hp at 100psig) with efficient inter-cooling could get nearer 5 scfm/hp.

The FAD of the Compressor can be calculated by volumetric calculation one by one or all of them together, to do this calculate the volume of receiver, feed time, and pressure (intiatial to final) and apply in pressure, volume time equation, it can be calculated (Aprox) the acuracy depends on datas taken by you.

Regards,

Sunil Nair,

Phone: 09826444358

e-mail: balajiispares@yahoo.com