The purpose of this paper is to highlight recent US nuclear power industry operating experience using high frequency acoustic emission (AE) valve leak detection technology to:
▸ Troubleshoot LLRT boundaries
▸ Identify internal through valve leakage
▸ Limit personnel exposure
▸ Limit outage schedule slippage
▸ Optimize & prioritize work scopes
▸ Eliminate unnecessary work orders
▸ Supplement existing troubleshooting methods
▸ Limit maintenance induced failures
Several examples where AE technology has been successfully utilized to make intelligent decisions related to the maintenance and testing of valves in nuclear power plants are examined including the resulting savings in time, personnel exposure and cost. The specific examples discussed herein represent the experiences of different plants, reactor types, systems and process mediums.
While utilizing acoustic or ultrasonic equipment as a troubleshooting tool for valves may not be considered groundbreaking, the acoustic emission system discussed in this paper was specifically designed for the early detection of leakage through a closed valve (sometimes known as “passing”). Because of the unique design of the AE sensor and associated electronics this new approach is essentially deaf to and thus unable to “hear” much of the background noise that has historically complicated use of existing general purpose acoustic or ultrasonic tools to reliably detect through valve leakage. As a consequence, it is now much easier for a novice technician to identify a leaking valve in a noisy operating plant environment. This new equipment was developed by a large UK based company as a result of experience with major oil and gas customers around the world where detection of through valve leakage in systems that contain explosive hydrocarbon products is a critical safety issue. This new technology has recently found a home in US nuclear power plants where it has been proven to quickly identify the location of leak paths during Appendix J leak rate testing, as a troubleshooting tool to identify or confirm suspected leaking valves and on the secondary side to identify costly steam losses.
