The compressed air system is often ignored when it comes to maintenance. Under normal conditions, the system’s compressors, dryers, filters and pipes draw little attention, in part because they are often located in a far corner of the plant. Yet when there is trouble, the system can shut down production or, worse, cause the inadvertent production of defective or contaminated product.
A well-maintained system will provide an uninterrupted supply of cool, clean and dry compressed air at a stable and appropriate pressure in the most efficient manner possible. Poorly maintained systems have frequent system shutdowns, heat or moisture problems, exhibit system pressures that fluctuate wildly at levels that are too high to produce efficiently, and typically waste air due to leakage.
Following are several key maintenance-related points to consider for trouble-free compressed air system operation:
Compressors—The compressors are the heart of the compressed air system. Regular changing of inlet and lubricant filters is important to efficient and reliable operation. Ensuring the compressor lubricant does not fail or become saturated with water is important to guard against premature bearing and screw-element failure. Remember, lubricated air compressors mix inlet air with compressor lubricant as part of the normal compression process. Very few mechanical devices have this characteristic. The compressor lubricant should be monitored and tested regularly, especially when overheating is taking place, which accelerates lubricant aging.
Compressor Controls—Compressors must be properly controlled to maintain efficiency and pressure stability. Often, controls can become defective or misadjusted over time. Discharge pressures can inadvertently rise due to control problems or other random events. Proper system maintenance ensures the controls work as intended and that pressures are maintained as low as possible to save energy.
Dryers and Filters—These units should be maintained to manufacturers’ recommendations. Filters protect the dryers and downstream devices from contamination. The refrigerated air-dryer separator drain must work properly or moisture will pass through the dryer. Refrigerant pressures should be monitored and verified. Dryer controls should be checked to ensure energy-saving features work correctly.
Ventilation and Cooling—Excessive heat kills compressors and dryers. Cooling surfaces for air-cooled devices and/or the cooling medium for liquid-cooled units must be kept clean and free of restriction. This is a tough job because air compressors by their nature act like vacuum cleaners and suck the dirt and dust from the plant into the compressor room.
Drains—When there is a change in quality of compressed air, something is left behind: oil, water and/or dirt. That something must be removed from the system or it will carry over to downstream devices and processes. If the removal process is a drain, the drain must be tested and maintained to ensure correct operation.
Leakage—Regular leak-testing using ultrasonic detectors and timely repair can save significant operating costs.
More information about the benefits of system maintenance is available at the CAC Website (compressedairchallenge.org) and in CAC’s Best Practices for Compressed Air Systems Manual. While online, check out the CAC calendar for a schedule of upcoming training events. MT
The Compressed Air Challenge® is a partner of the U.S. Department of Energy’s Industrial Technology programs. To learn more about its many offerings, visit compressedairchallenge.org or email email@example.com.