In a December 2000 report by the US Department of Energy1, compressed air is cited as “one of the most expensive utilities in an industrial facility.”  The DOE advises that “users should always consider other cost-effective forms of power to accomplish the required tasks and eliminate unproductive demands.  Inappropriate uses of compressed air include any application that can be done more effectively or more efficiently by a method other than compressed air.”  Not surprisingly, air-operated diaphragm pumps are among the possible inappropriate uses of compressed air cited by the DOE report.

Air-operated diaphragm pumps use compressed air to drive diaphragms to force liquid out of a pumping chamber.  An air shifter typically is used to alternate between two opposing diaphragms and check valves prevent the backflow of liquid.  These pumps are typically easy to install and have a relatively low purchase price making them popular in a wide range of applications.  Unfortunately, this also drives users to misapplication of these pumps and higher overall costs due to the hidden costs of electrical energy.

For Example:

An existing air-operated diaphragm pump is used to transfer 20cP paint from tank to tank at 50 GPM against 50 PSI.  On average the pump runs 4 hours a day, 5 days a week throughout the year.

By switching this pump out with an electric motor driven internal gear pump, this hypothetical customer could save around $680 by the end of the first year in energy savings alone2. That's just one pump - How many do you have operating in your facility?



Energy costs continue to rise so this value will continue to appreciate year over year.  Even a modest 3% increase in industrial electricity rates would yield a $760 savings by year 5 for a cumulative energy savings of over $3,600.

Rising energy costs and environmental concerns are forcing many to reevaluate their pump installations with special attention to those using compressed air.  Here are some tips to help identify potentially misapplied air-operated diaphragm pumps to target for replacement.

• High Duty Cycle – Air-operated diaphragm pumps are not ideal process pumps.  The longer they run, the higher the energy costs.
• High Viscosity Applications – Air-operated diaphragm pumps are capable of handling a wide range of viscosities, but become even more inefficient when handling viscous liquids.
• High Flow Rates – It may seem obvious, but there are many 3” and even 4” air-operated diaphragm pumps on the market today.  Larger pumps replaced with high efficiency alternatives yield the highest savings benefit.
• High Speed Applications – Air-operated diaphragm pumps are most efficient when sized large and slow.  This also increases the life of the diaphragms by reducing the number of total cycles.

*  Conversions are based upon 125 PSI plant air using a screw compressor at 92% loading. No adjustment is made for air leaks or other system losses.  Actual energy cost will be higher than listed. Pump efficiencies are based on an average value for air operated diaphragm pumps.  Average Industrial electricity price for US at $0.0706 based on Nov. 2008 EIA report.

1  DOE/GO “Compressed Air Tip Sheet #2”    December 2000

2  Energy Information Administration “Average Retail Price of Electricity to Ultimate Customers by End-Use, by State”    February 13, 2009