A rule of thumb used in the compressed air industry is a compressor consumes 1% more energy for every 2 psi in extra pressure at the discharge. When reducing the energy consumption of a compressed air system, we must pay detailed attention to pressure differentials at various points in the system. These pressure drops all add up to higher pressure at the compressor discharge — and higher energy costs.
Consider the pressure diagram in the graphic above; it appears the compressor is running at between 100 and 110 psi, yet the pressure at the critical load at the far end is only 70 psi. Some observations:
- There is 10-psi pressure drop across the air dryer and filters. Often, if the system is to be upgraded, choosing better system components can reduce this differential.
- The piping system shows a 5-psi pressure differential from end to end. This is not hugely significant, but best practices would allow only a maximum 2-psi differential at full system flow. This can be achieved by properly sizing pipes and looping piping runs.
- Pressure drop at end use components, caused by undersized and misapplied FRLs hoses, connectors and fittings adds up to 15 psi. This problem is very common, and is often the cause of high compressor discharge pressures, jacked up to compensate for all the various pressure loss. Proper design and upgrade of these supply components can greatly reduce pressure loss and provide better supply pressure for tools and equipment, often increasing the performance.
Once all the pressure differentials are addressed and reduced, the compressor pressure can be lowered, saving energy.
Try do some measurements on your system to see where your problems are. If your compressors are running above 100 psi, there is likely a problem.
If you want to know more about compressed air optimization, check out a Compressed Air Challenge Webinar coming soon: compressedairchallenge.org/calendar
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