Conference Proceedings Paper
Moving Valve Diagnostics Online – The Ormen Lange Example
9th International Conference on CANDU® Maintenance - 2011 December 04-06
Robert Greenlees (Score Atlanta Inc.)
Stan Hale (Score Atlanta Inc.)
The purpose of this abstract is to discuss replacing time and labor intensive nuclear outage activities with on line condition monitoring solutions, primarily the periodic verification of MOV functionality discussed in USNRC Generic Letter 96.05. This regulation requires that MOV age related performance degradations are properly identified and accounted for, causing utilities to have to retest valves periodically for the duration of the plants operating license.
AECL designed CANDU® reactors have a world class performance and safety record, with typical average annual capacity factors of 90%. The CANDU ® reactor design has the ability to refuel on line, as a result (a) it can be a challenge scheduling all required valve testing into limited duration outage work windows, (b) at multi unit sites, Unit 0 valves can be difficult to test because they are rarely ever out of service, (c) deuterium-oxide (heavy water) moderator is expensive to manufacture, as a result, effective through valve leakage monitoring is essential. These three factors alone make CANDU® sites the most suitable candidates for on line valve monitoring systems.
Nuclear industry regulations have been instrumental in the development of “at the valve” diagnostic systems, but diagnostic testing has not typically been utilized to the same degree in other less regulated industries. However, that trend is changing, and the move toward valve diagnostics and condition monitoring has moved fastest in the offshore oil & gas industry on the Norwegian side of the North Sea.
The Ormen Lange plant, located onNyhamnaIslandon the west coast ofNorway, operated by Shell, is one of the worlds most advanced gas processing plants. A stated maintenance goal for the plant is that 70% of the maintenance budget and spend should be based on the results of on line condition monitoring, utilizing monitoring systems equipped with switch sensing, strain gages, hydraulic and pneumatic pressure transducers and acoustic leakage detection. The valves test themselves during each operation and the Shell engineer responsible for valve condition monitoring is not even located at the site. The V-MAP on line valve monitoring system was one of the systems selected to meet the condition monitoring goals of the Project. The full paper on this topic and the accompanying presentation describes in detail how this plant achieved its goals, and how the same approach could be used to significantly reduce nuclear outage valve testing & personnel exposure, while improving plant efficiency and retrieving lost megawatts.
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