A newspaper printing plant had several printing presses that used low pressure air to help direct and manipulate the web of paper being printed. After years of operation, the small vane blowers that generated the low pressure air wore out. To save money on maintenance, rather than repairing the vane pumps, the maintenance personnel simply tied the low pressure blowers to the main compressed 125 psi air system.
After a while, the plant noticed that two of their main air compressors were operating when only one ran before. The second spare compressor was old and unreliable and its frequent shutdowns caused production problems. A compressed air auditor was called in to investigate. It was found that due to high pressure air being used for a low pressure purpose, the air loading had exceeded the capacity of only one compressor. Furthermore, since two compressors now had to run, the plant piping system was overloaded—causing low pressure in other areas of the plant.
The auditor found that the original high pressure air was consuming 34 kW per 100 cfm produced. The original vane compressors produced low pressure air at a rate of 10 kW per 100 cfm or at about 30% of the cost. Using high pressure air was costing about $10,000 per year. The cost of completely new low pressure vane compressors was $15,000, but a utility incentive program was available to reduce this cost by 50%.
The low pressure blowers were replaced, which reduced the air loading enough so that the plant could again operate on only one compressor. While improving the system, since a substantial utility incentive was available for the project, the plant personnel also replaced the ailing spare compressor with a variable speed drive controlled unit, installed an energy savings cycling dryer, low differential filters and large storage receiver. Total savings gained were $22,300 per year for a 1.7 year payback.
Learn more about compressed air efficiency in our next Compressed Air Challenge seminar in your area. Visit www.compressedairchallenge.org for more information.
By Ron Marshall for the Compressed Air Challenge