By Ron Marshall for the Compressed Air Challenge
An equipment parts fabricator was concerned with their high utility costs, so they decided to bring in a compressed air auditor to study their compressed air system. An industry downturn had reduced their production demand considerably, so plant management was looking to significantly reduce operating costs.
The plant compressor is a 75-hp load/unload controlled unit. A few years ago, a similar compressed air study was done—it showed 24 hour x 5 day per week operation. The new audit showed that the plant compressed air system was now operating on a 24 x 7 basis. In addition to this, there appeared to be a high-flow, short-duration event occurring every 10 minutes that kept the compressor loaded at a level higher than previous.
The auditor questioned why the system was running full time; the plant maintenance supervisor indicated that there was a special requirement in the boiler room. On investigation, it was found that the plant boiler required a small amount of air, less than 1 cfm for controls. A small 1-hp reciprocating compressor had previously been installed to supply this requirement, but had been removed due to failure. This removal required the 75 hp to run to replace it, and while doing so all the plant leaks and transient demands had to be supplied too.
Calculations showed that running the compressor during the weekend consumed about $12,000 of electricity per year. Purchase of a $500 compressor for boiler control duty could save this consumption. Further to this, due to lower production, the main compressed air could be turned off at night, saving even more energy.
The transient demand was investigated and found to be a desiccant air dryer installed on a laser. This dryer had not been maintained for years and had developed a large leak between towers, due to a valve failure. There were four desiccant air dryers running on a 24 x 7 basis in the plant even though the associated lasers operated only during daytime hours, sometimes being shut down for extended periods.
Plans are to purchase a small compressor and maintain and the dryers. These will be turned off when not required. Leakage studies are ongoing and likely to result in significant additional savings. Management is pleased that these kinds of savings were identified.
Learn more about compressed air efficiency in our next Compressed Air Challenge seminar in your area. Visit www.compressedairchallenge.org for more information.
Filed Under: Pneumatic Tips