An automotive manufacturer had various paint booths in which they prepared their products. The painters working in the booths used compressed air for breathing inside pressurized suits to protect against fumes. When the facility was built, a large breathing air purifier was installed to condition against carbon monoxide poisoning, should the air compressors ingest the exhaust of an idling vehicle.
An auditor placed data loggers on the compressed air system to determine system efficiency. After a few hours, a strange pattern appeared on the pressure and flow profile. Every 10 minutes — sometimes at random — a huge compressed air demand would appear, consuming the full output of the installed 100-hp air compressor. This happened even when there was nobody in the building. But the facility was very simple, the auditor knew this demand could only be one thing.
He went to the breathing air purifier and found that one side of the desiccant dryer did not depressurize when the purge cycle started and blow off valve opened. The flow when this happed was 550 cfm, enough to overwhelm the installed compressor and cause pressure problems.
Further study found that the breathing air purifier ran continuously and consumed 90% of the compressed air demand in the facility. It ran 24 hours — 7 days a week, even though production happened only 8 hours a day — 5 days per week.
Repairs have been put on high priority, with measures being explored to turn off the breathing air when not required.