Compressor Utilisation & Power Consumption

http://en.wikipedia.org/wiki/Overall_equipment_effectiveness

Yes, you can. The question is the payback period, considering the cost of individual compressors.

With only one compressor, if it fails, you have no air. Multiple compressors would allow one to be taken out of service for repair, and you could still have air.

Store gas at a higher pressure in the receiver. Make the compressor load and unload at defined pressures. If the compressor runs unloaded for quite sometime , say 20 minutes , it should shut down and start again when required. Else, increase the capacity of the receiver. you will be able to cut down power requirement.

Power required by reciprocating compressors= PLAN/4500 where p= Pressure, L=stroke length, A=cylinder area, N= RPM.

Also, if the current = I amp, Voltage= V volts, power consumed by motor = 1.732VICosø. This way also, you can calculate the power consumed by motor.

Sounds like the system you have may be oversized AND not correctly set for motor cut in pressure.

You can't store at above 7 Bar but you may be able to cut in at a lower pressure.

What is the minimum operating pressure (not delivery pressure) of your various shop tools? Can they operate if the delivery pressure drops down to say 3 or 4 Bar?

That 5.6/6.5 hysterisis seems a little narrow.....

You have had some good answers - particularly Sawmilleng.

Just to nit-pick, a 55kw compressor will only produce about 150 L/s at 7bar, but as 55kw is just a number on the nameplate, where motors usually have a 10% over-capacity, then you might be pulling 60kw at peak load.

Therefore use the line current x voltage x power factor to estimate power. Do this for both on-load and off-load. Then x the hours of each, and then x the price per kWhr to arrive at the running cost.

Whatever the cost, the average full load demand is only 25% of the time, a smaller compressor to match this demand would appear to be suitable. But be careful because it might not be big enough (even today) to cope with max demand.

On balance, if your original compressor was designed to match full load demand of full production, then a smaller compressor will not cope when you get busy again.

If the idea of one compressor per workshop is viable, then it might be better instead to replace you existing compressor with thee equal size smaller compressors with load sharing controls arranged with one running continuously on-load, the second on stop-start, and the third off-load (but selected in rotation for wear-and-tear and maintenance).

That would certainly save on running cost today and in future. Whether the capital outlay is viable in today's economic environment is another matter.

Back to the beginning. Have you talked with the folks who sold/service these units ?

They do this sort of analysis on a daily basis, and should already have the numbers you seek.

Air compressor efficiency is the ratio of energy input to energy output. Many air compressors may be running at efficiencies as low as 10 percent. Improving AC efficiency can yield significant savings to your facility. Thanks.