Compressed Air Best Practices - February 2009 - (Page 27)

Focus Industry POWER PLANTS | 02/09 | The compressors should be sized to carry approximately 75% load to allow for growth or changes in system dynamics. Their suction sources should be in areas not subject to high temperatures, sources of contaminants or highly moisturized air. The compressor controls should be such that a failure on one controller will not affect the capabilities of the other two compressors. The piping between the compressor and the dryer should be stainless steel so as to minimize the corrosive effects of highly moisturized air. This will also minimize the corrosion brought on by other atmospheric contaminants that could be initiated by the discharge from other industries in the area. Likewise, the wet receiver should be either stainless steel or coated such as to prevent corrosion. The pre-filter should be a high-quality, coalescing filter supported by automatic drain traps. A “mist eliminator” should also be used depending upon the type of compressor used and the expected contaminants in the area of the suction of the compressor. Drain traps (supporting the after-cooler/inter-cooler moisture separators, the wet receiver and the pre-filters) should be “Zero-Loss” drain traps with at least 3/8” ports to prevent blockage. Each of the drain traps should have their own individualized drain discharging to a sump. They should also be supported by a bypass line and valve that allows the drain trap to be removed from service for maintenance and yet allow the supported component to remain in service. The CANUG discussed the type of desiccant air dryer to be used in this system and decided upon a heatless desiccant dryer. The reason was a simpler design and operation than the internally heated or blower purge dryers. We understand that in the long run this is more costly, but reliability was considered over cost. This may still be up for discussion. Both wet and dry receivers should be installed. The wet receivers provide a surge volume for dryer purges as well as another opportunity to collect and condense moisture in the compressed air. The dry receivers prevent over rating the dryers on sudden surges in the instrument air header as well as an accumulator volume to support operation of downstream components. The CANUG also considered installing dual-parallel pre-filters and after-filters to increase the margin of reliability. This allows the removal of a filter from service without taking the whole train out of service. In addition to the monitors provided with the equipment installed, there needs to be additional monitoring capabilities in order to observe the health of the instrument air system. Dew point monitors should be installed at the outlets of each air dryer if they do not come as part of the air dryer package. There should also be sample taps throughout the system to allow periodic monitoring of air quality, downstream of each of the pre-filter/mist eliminators (oil and hydrocarbons) and the dryer after-filters (particulate and moisture) as well as strategic locations throughout the system. Moisture can enter the Instrument Air System through leaks and thus periodic moisture monitoring at locations downstream of the after-filters might prove advantageous (Fick’s law). Flow and pressure indications should be available at strategic locations to provide an indication of use (trending) as well as assist in diagnosing problems. www.airbestpractices.com “ The Institute of . Nuclear Power Operations provides an operating experience database of problems experienced throughout the nuclear industry that is regularly reviewed for applicability.” 27 http://www.airbestpractices.com

Table of Contents Feed for the Digital Edition of Compressed Air Best Practices - February 2009

Compressed Air Best Practices - February 2009 Contents From the Editor Utility-Air News Compressed Air Audit of the Month Air Standards Instrument Air in Nuclear Power Plants Seven Sustainability Projects for Industrial Energy Savings The Pneumatic Advantage Personal Productivity Resources for Energy Engineers Wall Street Watch Advertiser Index Classifieds

Compressed Air Best Practices - February 2009

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