Compressed Air Best Practices - February 2008 - (Page 15)

Compressed Air Industry BULK HANDLING | 02/08 | Periodic Pressure Decay in Instrument Air System. With the dryer repaired, Brian tried lowering pressure again. This time pressure was lowered to 80 psig where it was held until a problem with a group of dust collectors surfaced and pressure again had to be increased, although only to 90 psi. When Brian investigated the dust collector situation, he observed a pressure gauge indicating a drop greater than 40 psi. At high supply pressure, this situation went unnoticed. But at 80 psig, a pressure more appropriate for the plant, air delivered for back-pulsing the filter bags was not sufficient to cause the cake to be shed. High pressure had been compensating for a deficiency in the system. Regulators that had been installed to lower pressure for the dust collectors were restricting the flow needed to back-pulse. The dust collectors actually represented another instance of a high flow intermittent demand, and the resulting pressure fluctuations would be resolved with local storage. In the interim, the regulators, which were set at line pressure anyway, were removed and pressure was again lowered to 80 psig. After successfully operating the plant at 80 psig for some time, pressure was reduced even further. It was lowered to 70 psig and held there until an issue with one of the transport systems surfaced. Again pressure was increased to 80 psig and the problem with the transport system will have to be investigated. When the demand side pressure requirement is finally determined the compressor control set points will be adjusted appropriately. For the time being they are set at 94 and 108 psig. Compressor Controls When the plant was running at 80 psig, compressors were unloading and turning off. Unfortunately, they would not stay off. The local compressor controls (provided as part of the compressor package), which were designed to communicate with each other and control the group as a system, kept restarting compressors when they weren’t needed. At times, all six ran with two or more unloaded. We needed to be able to control the group so that that only one of them would run at part-load, and unnecessary starts would be eliminated. The factory-provided controls were failing to accomplish these tasks and needed to be “re-tuned.” www.airbestpractices.com 15 http://www.mikroporamerica.com http://www.mikroporamerica.com http://www.airbestpractices.com

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Compressed Air Best Practices - February 2008 Contents From the Editor Utility-Air News February Audit of the Month: Dense-Phase Transport System Wreaks Havoc on Compressed Air System Real World Best Practices: Material Conveying with Pneumatic and Vacuum Systems Industrial Vacuum Cleaners Use Compressed Air in Portland Cement Manufacturing Processes The Numatics Air Preparation Group The Ins and Outs of Vacuum Generators Dekker Vacuum Technologies Do Your Meetings Sabotage Your Profits? Resources for Energy Engineers Wall Street Watch Advertiser Index Job Market

Compressed Air Best Practices - February 2008

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