Compressed Air Best Practices - February 2009 - (Page 24)

| 02/09 Focus Industry POWER PLANTS | INSTRUMENT AIR IN NUCLEAR POWER PLANTS The Service Air System was tied in to the Instrument Air System as a backup. This proved advantageous as well as problematic. The Worthington’s were high maintenance and Service Air was often used to supplement Instrument Air. Since the Service Air system was supported by oil-flooded compressors, the Instrument Air System was frequently contaminated by oil causing operational problems. The oil problem was eliminated with the installation of Deltech Color Change filters at the Service Air to Instrument Air crossover. By the mid 1980s, the Nuclear Regulatory Commission (NRC) had gathered quite a bit of data concerning problems experienced at nuclear power plants that resulted from poor instrument air quality and reliability. The NRC issued Generic Letter 88-14 (INSTRUMENT AIR SUPPLY SYSTEM PROBLEMS AFFECTING SAFETY-RELATED EQUIPMENT). This report referenced NUREG-1275, Volume 2, “Operating experience Feedback Report — Air Systems Problems,” which indicated “that the performance of the air-operated, safety-related components may not be in accordance with their intended safety function because of inadequacies in the design, installation and maintenance of the instrument air system.” In addition to Generic Letter 88-14 (4), the Institute of Nuclear Power Operations (INPO) issued Supplemental Operating Experience Report (SOER) 88-1 (Instrument Air System Failures), written to address system failures that had been initiated by poor quality instrument air (IA). It noted at that time, “system failures, caused by instrument air failures, are occurring at a rate that indicates greater attention to instrument air systems is warranted.” (5) “ In order to use nuclear energy safely, the nuclear industry needs to work together.” Addressing Issues with Instrument Air ONS, as well as the rest of the Nuclear Industry, addressed these issues. At ONS, an additional air compressor was installed; Sullair 32/25 400, a 2,200 cfm, oil-flooded tandem rotary screw compressor. Dual two-stage pre-filters and two SAHARA heatless desiccant dryers (each rated at 1,400 scfm) were installed in parallel downstream of the new compressor. This configuration, now the primary source of instrument air, operates approximately 340 days per year and is taken out of service each quarter for preventive maintenance. The Worthington compressors have become the backup source of air and the supporting refrigerant dryers were replaced with two 750 scfm heatless SAHARA desiccant dryers installed in parallel. This arrangement has worked well, providing a much more reliable source of dry, clean compressed air (6). Oconee Nuclear Station is unique with its Instrument Air System configuration, using an oilflooded compressor as well as having one central source supply for all three nuclear units. A majority of the nuclear industry use oil-free compressors, rotary screw or centrifugals. Most of their systems are configured such that each nuclear unit has its own air source. Though each unit has its own source, most sites have cross connects between the units instrument air supplies. The cross-connects are kept isolated except during emergencies, ensuring that a problem on one air system does not affect the operation of multiple units. 24 www.airbestpractices.com 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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