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By J. Stanton McGroarty, CMfgE, CMRP, senior technical editor
Compressing air is a great way to store energy. Since the 1800s, compressed air has been used as a clean, sparkless alternative to electricity throughout industry.
|Learn how to use CAGI sheets to make better buying decisions about compressed air systems.|
Compressed air provides the energy to propel itself wherever piping is available. Once the air has arrived, the compression energy can be recaptured from it by devices as simple as nozzles or pneumatic cylinders. It is a simple, low-cost way to package, transport, and use energy over medium distances.
Compressed air accounts for 10% of electricity use and 16% of motor energy usage in all industrial plants, according to "United States Industrial Electric Motor Systems Market Opportunities Assessment," published by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy.
What is the most important thing to consider when buying a new compressed air system?
Drew Johnson, branch manager, Kaeser Compressors
John Brookshire, president, Atlas Copco
Michael O'Hanlon, sales manager, stationary air power, Sullair
Tim McDonald, national sales manager of compressor products, Gardner Denver
The exact percentages will vary widely from industry to industry, but it is safe to say that compressed air production is a very important part of the average factory’s energy bill. Add to that the fact that an air compressor system usually lasts 10 to 20 years and the purchase of a compressor becomes a significant milestone in a factory’s history. With electric rates climbing through $0.12/kWh, this is the kind of decision that can mark the difference between the Fred Jones Economical Air System and the Fred Jones Memorial Air System.
Whoever gets the assignment of creating or replacing compressor capacity for the plant should know there’s good news and bad news. The bad news is that this person has probably never bought a large compressor before. The good news is that, since these systems typically last so long, most people never buy a second. The market is expecting an inexperienced customer. A well-organized approach will be met with the needed information and support. If the purchaser takes care to create an internal team and an external team of suppliers and contractors, the experience is very survivable.
An orderly approach will help ensure that the new compressor won’t be a Memorial System.
First, the purchaser should have an air use survey done by a professional. The survey should run around the clock, even if production doesn’t. It should also identify large blocks of air use, like production departments. That way a variety of different production scenarios can be modeled without additional surveys. Then the purchaser should add a forecast of future needs. This survey becomes the basis for a 10-year needs forecast and the capacity specification for the system that will be purchased now. This information equips the buyer to specify the system. Reputable compressor vendors can provide specification formats that will help organize the data.
The next step will be development of system specifications, probably using both fixed- and variable-speed drives (VSDs), to determine investment and power usage estimates. Support is needed here, and great new resources are available, including OEM data sheets produced under Compressed Air and Gas Institute (CAGI) formats for accurate comparisons. Unless the compressors in a system will run most of the time at full capacity, it is appropriate to investigate the economics of investing in a VSD, which will add to the drive cost, but may reduce electrical consumption. Alternatively, fixed-output systems that use part-time compressor operation and buffer storage to provide partial capacity output economically may be explored. Here again, CAGI resources, often available through equipment dealers, may be helpful.
While obtaining information from dealers, the purchaser should remember to include the cost of appropriate spare parts in the purchase price. This will help avoid future surprises and will also help identify the true cost of purchasing systems from distant suppliers with poor local support.