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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

MFW Pump Discharge Check ValveOE Follow Up

Dominion

North Anna Power Station

Gary W. Liffick

FW System Engineer

FSRUG,

Feb 21-24, 2011


Outline
Outline

North Anna Power Station: MFW Pump Discharge Check Valve

  • Application Overview

  • Background of OE31369 (update of OE29594)

  • Corrective Action

  • Current Status


Application overview
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


Application overview1
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


Oe31369 mfw pump discharge check valve failed to fully close original oe29594
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


Corrective action
Corrective Action close. Original OE29594.

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


Nozzlecheck valve type drv b 18 900 rf
NozzleCheck Valve, Type DRV-B 18”-900# RF close. Original OE29594.

North Anna Power Station: MFW Pump Discharge Check Valve


Drv b cutaway
DRV-B Cutaway close. Original OE29594.

North Anna Power Station: MFW Pump Discharge Check Valve


Nozzlecheck valve animation type drv b 18 900 rf
NozzleCheck Valve, Animation, close. Original OE29594.Type DRV-B 18”-900# RF

North Anna Power Station: MFW Pump Discharge Check Valve


Spring holder and spring
Spring Holder and Spring close. Original OE29594.

North Anna Power Station: MFW Pump Discharge Check Valve


Spring holder and spring1
Spring Holder and Spring close. Original OE29594.

North Anna Power Station: MFW Pump Discharge Check Valve

Spring coil wear

Spring holder wear


Spring holder and spring2
Spring Holder and Spring close. Original OE29594.

North Anna Power Station: MFW Pump Discharge Check Valve

Spring coil wear


Current status
Current Status close. Original OE29594.

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


Status as of jan 2011
Status as of Jan 2011 close. Original OE29594.

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


Questions
Questions? close. Original OE29594.

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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