Compressed Air Best Practices - September 2008 - (Page 14) | 09/08 Focus Industry FOOD PACKAGING & PROCESSING | COMPRESSED AIR AUDIT OF THE MONTH Auditing a Food Packager & Processor The average cfm usage of the system was recorded at 349.5 and the maximum cfm usage was 459. These numbers are far below the rated capacity of these machines. In actuality, the 100-hp air compressor should have been able to carry the load by itself for the entire audit period. The air compressor did in fact carry the plant load at the end of the audit period when the other compressors were turned off. With the maximum-recorded hp of 193.9, this would mean that there is approximately 90+ hp being wasted. This audit will recommend how to reduce the use of air compressor hp. Contaminant Removal System (CRS): Plant management has asked that a review be done to evaluate the potential of oil carryover into the air system. The audit has discovered the potential for oil carryover to exist as well as dew point and pressure drop concerns. The 50-hp air compressor ran just barely above the loaded point for the majority of the audit week. When a rotary screw air compressor runs unloaded, for extended periods of time, it is very common for them to pass oil from the separator. In looking at the moisture separator and the area around it, there seems to have been a large amount of oil being carried over. The moisture separator may not have been functioning correctly, based on visual observation only. This excessive oil carryover from the air compressors will greatly reduce the life span of an in-line oil coalescing filter. In addition to causing premature failure of the filter elements, there is an increased risk of oil contamination in the regenerative dryer. Oil contamination of a regenerative air dryer is a death sentence for the dryer. The principle of a regenerative dryer is the adsorptive properties of the desiccant. The moisture in the air system is not absorbed into the desiccant but instead is adsorbed onto the surface of the beads. When oil enters the dryer, the desiccant beads are coated over and lose all adsorptive abilities and require replacement. As seen by the following graph, there is a definite problem in the pressure delivery across the CRS. The pressure drop across a regenerative dryer and filter system should be seen in the 5–7 psig range, rather than the 12–20 psig range seen in this installation, as indicated by the yellow line. Mr. Lane Hollar, of Air Flow, Inc., programming a data logger. 14 http://www.teseoair.com
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