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.
How does VMOP work?
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.
Offline Testing – Safety Relief Valves
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.
In-Situ Testing and Online Monitoring
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