By Ron Marshall for the Compressed Air Challenge
A building products manufacturer installed a completely new compressed air system to increase reliability and reduce compressed air costs. A new two-stage VSD, externally heated dryer with dew point demand switching, and low differential filters all combined for excellent system energy performance.
The power utility installed a permanent monitoring system on the equipment as part of a new monitoring program. The system continuously monitored compressor power, pressure and flow and calculated Energy Performance Indicators to gauge the efficiency of the system. All looked good for the first few months … but then the system specific power started to fall off when the equipment was about a year old.
Analysis of the system data showed that despite a compressed air load that was only about 40% of its nameplate rating, the air dryer was purging at full cycle. An inspection of the unit did not show any issues, but dew point readings showed that the unit produced air at levels lower than -40° … therefore the dryer would not go into its standby mode, saving purge air.
After verifying all valves and heaters were working, a portable dewpoint monitor was connected to the dryer to validate the onboard reading. It was discovered that the onboard unit was 30° out of calibration—therefore, the control system never had a chance to operate in energy saver mode. The plant personnel learned that the dew point meters should be regularly checked for calibration and that continuous monitoring is valuable. The unit was sent out and the system specific power returned to normal.
Learn more about air dryers in our next Compressed Air Challenge seminar in your area. Visit www.compressedairchallenge.org for more information.
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