A full compressed air audit at Motor Coach Industries in Winnipeg showed that the company’s compressed air system was annually costing \$170,000 to operate and maintain. An improvement project, costing \$250,000, has lowered the company’s operating and maintenance costs by \$116,000 a year. Payback for the projects is 1.5 years, with the help of a Manitoba Hydro incentive under the Performance Optimization Program.
Motor Coach Industries, headquartered in Schaumburg, Illinois, is the largest manufacturer of intercity tour coaches for the tour, charter, line-haul, scheduled service, commuter transit and conversion markets in the U.S. and Canada. The company operates a four screw-type air compressor system at its Clarence Avenue plant in Winnipeg. To maintain adequate system pressure at the plant, Motor Coach was forced to run all four compressors 24 hours a day, seven days a week.
|Total annual electrical savings to date are an estimated 1,650,000 kW/h|
In the face of high operating costs, staff tried to control the compressors with timers that often turned the compressors on and off at the wrong times, causing pressure drops during critical operations, such as bus painting. The pressure would drop below the lower limit of 65 psi required by the paint guns, marring paintwork. Oil, water, and dust in the compressed air lines would also cause “fisheyes” and other paint defects. Because of detailed customer specifications, reworking a bus paint job can prove extremely costly. On the recommendation of their compressed air service provider Motor Coach asked Manitoba Hydro to perform an audit to find solutions.
Manitoba Hydro installed data loggers at critical points in the compressed air system to monitor pressure, temperature, current, and dewpoint. Readings recorded by the loggers showed exactly what was happening throughout the system. Pressure drops were caused mainly by incorrect timer settings and manual operation of the compressors.
Another factor was heat build-up in rooms housing the compressors. Temperatures would soar as high as 50_C, forcing the compressors to shut down. In addition, leak tests with an ultrasonic leak detector identified air leakage serious enough to keep a 125 HP compressor running continuously.
The audit recommended the following solutions:
- upgrading ventilation in the compressor rooms to prevent overheating of the compressors
- installing heat recovery systems in the compressor rooms so that hot exhaust air could be used to warm parts of the plant during the winter months
- installing an 8,200-gallon receiver tank and flow controller to cushion the compressors from large air events, and keep the minimum number of compressors on line
- running the compressors in efficient load/unload mode, rather than in less efficient modulation mode
- coordinating operation of all four compressors for maximum efficiency
- installing a 2,400 cfm duplex cycling dryer to prevent moisture build-ups in the lines
- installing a high efficiency, low differential, coalescing air filter to eliminate oil and other contaminants in the lines
- installing air saver drains that automatically eliminate condensate without losing compressed air
- replacing aging hoses and other sources of air leaks, and introducing a regular system of leak testing.
|“With this project Motor Coach was able to get a double whammy—excellent power savings and much increased compressed air quality. “ – Ron Marshall, Manitoba Hydro|
Seminar Inspires Action
Following the audit, Manitoba Hydro sponsored a compressed air seminar by Scot Foss, world-class expert in compressed air system efficiency. Inspired by ideas from the seminar, Motor Coach staff selected a proposal by a local mechanical contractor, to perform a turnkey project that would act on the results of Hydro’s audit. Ron Marshall, the Manitoba Hydro Industrial Systems Officer who performed the audit at Motor Coach, reports that to date, the improvement projects have reaped the following savings:
- $50,000 in lower operating costs
- $13,000 in reduced maintenance
- $8,500 in lower gas heating costs through heat recovery
Motor Coach is also saving an estimated \$20,000 a year in increased productivity from improved air quality and system pressure. Total annual electrical savings to date are an estimated 1,650,000 kW/h.
“Saving power through increased efficiency was on their management’s hit list,” says Ron Marshall. “With this project Motor Coach was able to get a double whammy—excellent power savings and much increased compressed air quality. “And they report their equipment runs a lot smoother,” he says. “Some say they can even hear the difference when they’re out in the plant!”
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