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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

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

North Anna Power Station: MFW Pump Discharge Check Valve

drv b cutaway
DRV-B Cutaway

North Anna Power Station: MFW Pump Discharge Check Valve

nozzlecheck valve animation type drv b 18 900 rf
NozzleCheck Valve, Animation, Type DRV-B 18”-900# RF

North Anna Power Station: MFW Pump Discharge Check Valve

spring holder and spring
Spring Holder and Spring

North Anna Power Station: MFW Pump Discharge Check Valve

spring holder and spring1
Spring Holder and Spring

North Anna Power Station: MFW Pump Discharge Check Valve

Spring coil wear

Spring holder wear

spring holder and spring2
Spring Holder and Spring

North Anna Power Station: MFW Pump Discharge Check Valve

Spring coil wear

current status
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
status as of jan 2011
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
questions
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

[email protected]

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