Compressed Air Challenge: Re-commission Your System

landscape photo of a measurement of pressure

By Ron Marshall, CET, CEM for the Compressed Air Challenge (CAC)

Once upon a time, your compressed air system was shiny and new. You proudly inspected the final installation, knowing that the supplier and installer had set things up so that the compressors and dryers would coordinate with each other and work properly.

Over time, however, things can change. Components wear and fail. Relays and sensors burn out and clog. Eventually, the system requires repairs and adjustment. Then, along comes Mr. Fixit, your handy compressor-repair guy. His tool chest includes a handy-dandy adjustment screwdriver that he promptly uses to “optimize” the settings of your system.

The bad news is that Mr. Fixit may not have been around when your equipment was new and set up correctly. He may never have attended a compressor-repair class, much less clearly understand the important aspects—and intricacies—of compressor control. That doesn’t stop him, though, as he happily twists an adjustment screw here and there, hoping to get your compressor purring like a kitten.

While your plant may not have dealt with this type of Mr. Fixit, data from many compressed-air assessments of relatively young, upgraded systems show that the situation is not uncommon. Often, the efficiency of a system depends on the careful adjustment of critical equipment settings. That said, adjustments must be made by qualified personnel who know how compressed-air systems should work.

It pays to have somebody look at your system from time to time to re-commission it, i.e., ensure nothing has happened that might be causing efficiency issues. Regular compressed-air assessments can pay for themselves quickly in energy savings. Items to examine include:

Compressor-pressure settings. Because it’s rather easy (physically) to adjust compressor settings, it’s also easy to misadjust them. Although adjustments may have been made since the system was installed, they could have been in response to a one-time, low-pressure event or other temporary system problem. Consequently, the pressure may be too high or pressure bands too narrow. Reviewing the appropriateness of your compressor settings is an important exercise.

Selection of lead compressor. Some compressors are more efficient than others. Some are more appropriate as lead compressors, others should trim, taking partial load. Efficiency can be maintained by choosing the correct order of operation.

Air-dryer settings. If you have desiccant dryers with dewpoint controls, they could have been bypassed, or might not be working due to a fouled sensor. Reviewing the operation of your dryers and repairing as needed could save a bundle.

Automatic drains. Airless drains, purchased to prevent wasted air, can wear out and fail (undetected). This situation affects dryer operation and the quality of the compressed air. Proper testing is important.

Monitoring systems. It’s important to monitor the efficiency of your system, especially if compressed air is a major part of your electric bill. Permanent monitoring of the system helps you assess the system on a daily basis to maintain efficiency.

Find more information about compressor efficiency on the CAC website (compressedairchallenge.org) or in the organization’s Best Practices for Compressed Air Systems Manual. Check the website calendar for scheduled training. MT

rcmarshall@hydro.mb.ca