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MFW Pump Discharge Check Valve OE Follow Up

MFW Pump Discharge Check Valve OE Follow Up. Dominion North Anna Power Station. Gary W. Liffick FW System Engineer FSRUG, Feb 21-24, 2011. Outline. North Anna Power Station: MFW Pump Discharge Check Valve. Application Overview Background of OE31369 (update of OE29594)

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MFW Pump Discharge Check Valve OE Follow Up

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  1. MFW Pump Discharge Check ValveOE Follow Up Dominion North Anna Power Station Gary W. Liffick FW System Engineer FSRUG, Feb 21-24, 2011

  2. Outline North Anna Power Station: MFW Pump Discharge Check Valve • Application Overview • Background of OE31369 (update of OE29594) • Corrective Action • Current Status

  3. Application Overview North Anna Power Station: MFW Pump Discharge Check Valve • PWR, 963 MWe, Westinghouse NSSS Operational Since: • June 1978 Unit 1 • Dec 1980 Unit 2 • Application is Main Feedwater Pump Discharge • 3 Pump Circuit, 2 Active, 1 Standby • NozzleCheck Replaced the Tilting Disk Check • October 2007 at 1-FW-19 • Feedwater Normal Conditions: • 390 F, 1,180 psi, 15,000 GPM per Feedwater Pump • Enertech Supplied: • type DRV-B,18”-900#, RF Flanges, Commercial Grade

  4. Application Overview North Anna Power Station: MFW Pump Discharge Check Valve Enertech Supplied Type DRV-B: • 18”-900# • RF Flanges • Commercial Grade • WC6 body • ASTM A351 CF8M Diffuser and Disk • Inconel X-750 Spring

  5. OE31369, MFW Pump Discharge check valve failed to fully close. Original OE29594. North Anna Power Station: MFW Pump Discharge Check Valve • During March 2009 Outage, backflow detected through check valve. • Disassembly showed 1 broken spring and 2 with visible wear of spring coils due to friction. • Remaining Components indicate normal wear. • Factory installed new springs, radial guide assembly, performed seat leak test. • Returned to site as spare

  6. Corrective Action North Anna Power Station: MFW Pump Discharge Check Valve • Increased clearance of spring holder and spring cavity. • Eliminate possible solid height of spring • No change to spring design • Improve check valve reliability without changing Vmin or disk closure force with zero flow

  7. NozzleCheck Valve, Type DRV-B 18”-900# RF North Anna Power Station: MFW Pump Discharge Check Valve

  8. DRV-B Cutaway North Anna Power Station: MFW Pump Discharge Check Valve

  9. NozzleCheck Valve, Animation, Type DRV-B 18”-900# RF North Anna Power Station: MFW Pump Discharge Check Valve

  10. Spring Holder and Spring North Anna Power Station: MFW Pump Discharge Check Valve

  11. Spring Holder and Spring North Anna Power Station: MFW Pump Discharge Check Valve Spring coil wear Spring holder wear

  12. Spring Holder and Spring North Anna Power Station: MFW Pump Discharge Check Valve Spring coil wear

  13. Current Status North Anna Power Station: MFW Pump Discharge Check Valve • Valves incorporating design changes were installed in all six check valve locations (3 per unit) during 2010 • Two valves removed for modification & refurbishment Sept. 2010 • Factory evaluation shows spring wear after 12 months and 18 months of service • Valves with the modification are operating per design

  14. Status as of Jan 2011 North Anna Power Station: MFW Pump Discharge Check Valve Conclusion • Final conclusion is pending the removal of the check valves from service to confirm spring wear has been eliminated • Current PM frequency is 4.5 years • Next valve scheduled for removal/PM is during Spring 2012

  15. Questions? North Anna Power Station: MFW Pump Discharge Check Valve Gary W. Liffick, FW System Engineer Dominion – North Anna Power Station PH 540 894-2429 Gary.Liffick@dom.com

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