A compressed air system audit can show the actual cost of compressed air and identify simple ways to cut energy costs. Compressed air is a facility’s most expensive utility. By comparison, if a simple machine used 5 HP for 10 minutes to lift an object and the power could be provided by either electricity, natural gas or compressed air, the compressed air would be roughly 8 times more expensive than electricity and about 22 times more expensive than natural gas, to do the same work.
Compressed air system users should consider using an independent auditor to examine their compressed air system. Several firms exist that specialize in compressed air system audits. Audits are also performed by electric utilities, equipment distributors and manufacturers, energy service companies, and engineering firms. An informed consumer should be aware that the quality and comprehensiveness of audits can vary. Independent auditors should provide recommendations which are brand and systems-neutral.
A comprehensive compressed air system audit should include the following:
- Level of air treatment – Since increasing air treatment also increases energy usage, it is important to ensure that air treatment is optimal for the application.
- Air leaks – Only 5% of air leaks can be heard by the human ear. It takes special instrumentation to detect all air leaks in a system. An auditor is able to detect all leaks and tag them. Maintenance can then focus on repairing the largest leaks first by referring to the CFM level shown on the tag.
- Pressure levels – An auditor will determine the lowest pressure level required to satisfy all downstream requirements. In some cases, dedicated storage or deferential reduction may be needed.
- Controls – The existing control system is evaluated to determine if it is correct for the system demand profile. Gains in system performance are considered using alternative control strategies.
- Heat Recovery – An auditor will identify a potential use for waste heat recovery if not already in use.
- Air Distribution System – The auditor will examine the overall layout and size of the piping, including the placement and size of any receiver tanks. Pressure drops and condensate removal are also evaluated with recommendations. Large load “clusters” are also mapped.
- Load Profile – The compressed air load profile is determined based on CFM changes over time. A varying load profile may suggest a different control strategy while a short period of very high demand my suggest an alternative storage option.
- Compressor Motor – The motor should be checked as part of an audit. Abnormal thermal and vibration patterns may suggest imminent motor failure or shortened life.
- Equipment Review – Filters, dryer, aftercooler, automatic drains, tanks, solenoid valves, etc. are all checked for proper sizing and function during an audit.
Compressed air audits can substantially cut energy costs as well as improve system operation. If you haven’t had one in the past 3-years, it only makes sense to schedule one.