A food processing plant had installed a new variable speed drive compressor as extra capacity for their plant. Another variable speed unit of the same size had been running their system for a number of years. A compressed air auditor measured their system with data loggers and the readings showed that both compressors were unexpectedly required to run at peak flows, and further, than weekend non-production flows consumed what looked to be about 60% of the capacity of one compressor.
There was no flow meter installed in the plant, so the air flows initially needed to be estimated based on the compressor loading. The plant manager looked at the results with doubt, he was skeptical that the plant flow was that high, he knew their were plant leaks, but to add up to that much seemed impossible. So the local power utility offered to help pay for a new thermal mass flow meter which was installed on a Sunday non-production day. The meter immediately showed that 132 cfm was flowing into the plant, slightly less than 60 percent of the capacity of one compressor. This won over the plant manager, especially after special tests were done.
The flow meter was used to:
- Test the full flow of the new compressors
- Determine the weekend non-productive load
- Measure the compressed air used by some enclosure coolers
- Validate the flow reduction when some large leaks were turned off
- Determine the artificial demand reduction from dropping the pressure
- Estimate the peak requirement from an air crane
- Verify the flow reduction from leakage repair.
The flow meter turned out to be a very useful tool, based on the data generated the plant was able to identify changes that could greatly reduce their average compressed air flow and generate over $20,000 in utility incentives to help pay for improvements.