Curtiss-Wright offers a unique service for evaluation of critical valves in nuclear power plants. Our Valve Maintenance Optimization Program (VMOP) is backed by several current and former nuclear plant valve program owners with extensive experience in valve condition monitoring and maintenance.

A key element of VMOP is the application of the Curtiss-Wright StressWave product which uses advanced vibroacoustic sensors to detect leakage past valve seats and valve damage or wear. These StressWave values are critical to the VMOP’s ability to determine valve condition and justify extending maintenance cycles.

StressWave testing involves attaching sensors to the valve and performing valve cycling or lift testing. A Stress Wave Energy (SWE) value is measured and plotted and the post-lift SWE values are entered into algorithms to assess valve leakage and overall valve health. StressWave values are valuable in determining leakage increases that occurred during the time the valves were installed.

Valves, primarily safety relief valves, are removed from plants and sent to an off-site testing facility. Before returning the valves to the plant, a verification is performed to determine there is no excess leakage by performing a “cold bar” test. While the valve is under pressure, a cold bar is inserted downstream of the valve to see whether moisture forms on the surface. For well over a decade, VMOP has been supplementing the cold bar test by attaching StressWave sensors at strategic locations on valves being tested and has developed a high level of confidence in the correlation between the measured energy and future performance.

If high energy levels are detected during testing, the valves have additional maintenance such as seat lapping performed on them. Additionally, VMOP has been successfully applied to justify extending the testing and maintenance cycles at several plants.

VMOP provides a powerful benefit to the industry to avoid costly unplanned outages and possibly even reduce testing and maintenance costs.

Using VMOP for continuous monitoring of valves:

• Determines real-time status, i.e. leaking or not leaking valves
• Allows the customer to “see” the valve’s dynamic operational profile during the plant operational cycles
• Gives utilities a ranked order list of the valves in order to make well-informed maintenance decisions instead of relying on a scheduled time-in-operation maintenance method
• Assists in preventing poor operational procedure from causing mechanical damage to valves
• Performs effectively on valves that rarely open, ie. SRVs or gas storage blow-down valves
• Provides users with options to configure software to send alarms to the plant DCS or by email
• Includes StressWave testing which “listens” for check valve damage or wear, control valve cavitation, and other valve related problems

• Access to multiple current and former nuclear plant valve program owners and valve testing industry experts
• StressWave testing values compared to more than 800 historical tests
• Recommendations for program changes based on test results
• Access to industry best practices, such as lapping techniques, spring changes, seat plating, and more
• Assistance justifying extending maintenance cycles internally, and when applicable, to the NRC