Location: Southeastern, United States
Plant: Boiling water reactor
Application: Steam jet air ejector
Product: V1-4 with gear operator
Overview: In 2016, a boiling water nuclear reactor plant (BWR) located in the Southeastern United States experienced repetitive seat leakage problems with its steam jet air ejector (SJAE) suction butterfly valves. The defective valves encountered reverse flow through the standby off-gas preheater/recombiner during critical plant operation, costing the customer millions of dollars in ongoing outage maintenance repairs. In addition, the plant experienced SJAE intercondenser loop seal high-level alarms with subsequent operator burden. The valve’s seat leakage issue caused major complications during plant and off-gas system startups, resulting in unplanned shutdowns and operational delays.
Requirement: During the past several operating cycles, seat leakage of SJAE suction butterfly valves have complicated plant startups
and caused operator finessing and work-arounds. Field troubleshooting during outages routinely found that manual, “sweet spotting”
of SJAE suction valves improved the circumstance temporarily but did not correct the situation. Maintenance on the incumbent unreliable
valves, including pressure testing of the seat and proper actuator setup during refuel or forced outages, proved to be costly and
time consuming. The plant required a technology change and selected metal seated ball valves with absolute zero-leakage seating
characteristics at the expected process design conditions of 2,380 psi (164 bar) at a temperature of 500˚F (260°C).
Solution: ValvTechnologies sought to provide a dependable, high-performance valve that would resolve leakage concerns and eliminate
startup and operational risk. ValvTechnologies supplied an 8” full port metal seated, zero-leakage ball valve as required per SJAE outlet.
This valve would be closed for the standby SJAE and open for the in-service SJAE. A ball valve design in this case would provide full
flow characteristics, unencumbered by butterfly valve disc and shaft when open to support SJAE operation and positive metal seated
isolation when closed eliminating the reliance on the butterfly design to thwart reverse flow when closed. The unique, custom-engineered
valve solution was explosion proof and spark resistant. It was supplied with dissimilar butt weld end schedules and a custom packing
and lantern ring configuration to protect against hydrogen emissions.
Result: The ValvTechnologies’ ball valves installed to combat the operation issues experienced due to the repetitive seat-leaking
butterfly valves, performed as intended and eliminated startup risk and operational issues. “Our operations team appreciates the
lack of reverse flow while the plant is operating and the absence of startup headaches when placing the steam jet air ejectors in
service. Additionally, startup complications once a vacuum is established in the main condensers are eliminated,” said the customer.
“ValvTechnologies valves are doing exactly what we intended and hoped for.”
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