Rather than skill and experience, sometimes serendipity comes into play when optimizing a compressed air system.
An auditor was just finishing up a system assessment and was ready to leave the site when he spotted a previously installed flow meter. He had located it on a previous audit a few years before. The device measured the flow of various blowing nozzles installed in the grain distribution pipework of a food products plant.
The readings of the flow meter had been used to justify the installation of shut off solenoids and restrictors on some older blowing nozzles. The nozzles had been needed to help prevent grain products from clogging up feed lines to some mixers and cookers. The previous blowing devices had all be optimized to reduce the flow to the lowest possible.
Having some extra time to spend, the auditor powered up the flow meter to see what it would read; all the previously optimized nozzles were shut off, so he expected no flow, but was surprised to see 43 cfm flowing! One by one, the old nozzles were inspected, and the compressed air feed turned off to isolate in case there was a problem with the solenoid control, nothing. But after careful inspection a newly installed nozzle was found.
Operations staff had been having trouble with one duct frequently clogging and causing long production outages, so staff decided to add a compressed air input to an existing inspection port by hooking it up to a rubber hose. They didn’t realize the 40 cfm continuous flow was costing about $8,000 per year to operate — and consumed 12% of the average compressed air flow in the entire plant!
The auditor had found a nice additional item to optimize, with enough savings to pay for a significant part of his audit fee. Plans are in the works for a correction of this problem.