In January 2012, Bridge City Steel, a precision steel cutting shop and steel wholesaler purchased a new laser cutting table for their Portland, Oregon facility. Their 25 hp shop air compressor was able to supply ample compressed air to maintain pressure to the new state of the art cutting table. It was noted through periodic observation of the percent capacity gauge, the air compressor was very lightly loaded, which is an indication of the potential for energy savings.
Rogers Machinery was selected to perform a streamlined energy audit of the existing baseline system. The power (kW) consumed by the compressor as well as the flow (cfm) was calculated by using a current transducer collecting amperage data every 15 seconds for a seven day period.
The data showed significant periods of low compressed air demands; however, high demands were seen when the new laser machine was in operation. These events made it obvious the larger
25 hp compressor was sized properly. It did, however present an opportunity for energy savings by installing a VFD to be able to slow down the air compressor and save energy during significant amount of time when the system was running at less than full capacity.
After the new system was properly installed and tuned, Rogers Machinery returned to verify the savings through the same process as before, by calculating power and flow using the same current transducer method over a typical week-long period.