valve application, maintenance and repair guide

8/18/2019 Valve Application, Maintenance and Repair Guide

1/397

Valve Application, Maintenance and Repair Guide

(In Situ State-of-the-Art Valve W

elding Repair )

(Gate, Globe, & Check Valves), Volume 2

Technical Report L

I

C

E N

S E D

M A T

E R

I

A

L

WARNING:Please read the Export Control

and License Agreement on theback cover before removing the Wrapping Material.

Effective December 6, 2006, this report has been made publicly available in accordance

with Section 734.3(b)(3) and published in accordance with Section 734.7 of the U.S. Export

Administration Regulations. As a result of this publication, this report is subject to only

copyright protection and does not require any license agreement from EPRI. This notice

supersedes the export control restrictions and any proprietary licensed material noticesembedded in the document prior to publication.


2/397


3/397

EPRI TR-105852v2s Electric Power Research Institute December 1996

R E P O R T S U M M A R Y

INTEREST CATEGORIES

ValvesRepair WeldingHardfacing RepairNuclear Valve Repair

KEYWORDS

MaintenanceRepairValvesWeldingHardfacing

Valve Application, Maintenance,and Repair GuideIn Situ State-of-the-Art Valve Welding Repair(Gate, Globe, & Check Valves), Volume 2

The Valve Application, Maintenance, and Repair Guide is a threevolume series that provides a generic overview of valve application,selection, maintenance, and repair. Volume 2 of this series is a com-prehensive guide for in situ weld repair of gate, globe, and checkvalve components such as bodies, bonnets, discs, and seats. Theinformation in this guide, though directed toward nuclear plant person-nel, will assist all power plant engineers, planners, and maintenance

personnel responsible for valve maintenance and repair. Volume 1 ofthis report will contain information on valve design, application, andsizing; while Volume 3 will provide information on welding repair ofbutterfly, ball, and plug-type valves.

BACKGROUND Several EPRI-sponsored studies and surveys have concludedthat valve failures are the single largest contributor to unscheduled shutdownsand lost plant availability. While a majority of these failures are maintenancerelated and can be addressed in short order, the more time consuming prob-

lems are typically related to cracks or wear of the valve body or critical internalcomponents. Replacing a valve or part especially those which are large orsafety related, can take in excess of 26 weeks to obtain, if it is available at all.Today with the major emphasis on shorter outages and downtime, utilities areopting for innovative repair techniques which keep the valve either in-line or atthe plant site. This guide has been developed to provide utility personnel withthe information necessary to identify and evaluate the problem, select theappropriate repair option, establish the repair criteria and procedures, and carryout a successful repair.

OBJECTIVES

• To provide general design and operating criteria for gate, globe, and checkvalves.

• To present wear and degradation problems that are unacceptable for plantperformance and/or safety, and provide repair options.

• To provide the most current and effective welding repair techniques andtechnology to successfully repair valve components in accordance with therequirements of the governing code body.

APPROACH EPRI surveyed the industry leaders associated with valve manu-facturing, maintenance, repair, and operations to gain a thorough understandingof common valve failures, materials, manufacturing methods, and repair meth-ods typically employed. The survey was also used to identify qualified repair

EPRIPowering Progress


4/397

vendors, their in situ repair capabilities, and their experience. TheNuclear Plant Reliability Data System (NPRDS) and License EventReport (LER) databases provided information on failures and theircauses by valve type. Plant visits were made to manufacturing andrepair centers to gather in-depth knowledge on specific componentrepair techniques and how remote welding and machining technologywas utilized in these repairs. All of this data was then broken down byvalve type and component, repair options and procedures, and repair

operations (machining, welding, heat treating, and so on).

RESULTS This guide presents nuclear utilities with the backgroundinformation necessary to understand why their valve is not meetingeither internal or external leak requirements, and provides detailedrepair options and procedures to address the problem with soundengineering practices meeting the requirements of the ASME Boiler &Pressure Vessel Code. The guide is written in such a manner to allowthe responsible engineer to understand each step in the repair pro-cess, to write repair procedures and specifications, and to follow thework as it is performed by in-house or contractor personnel. Experi-enced valve repair personnel looking for specific information shouldrefer to specific topical sections or appendices for detailed information.

EPRI PERSPECTIVE Since 1980, EPRI has been engaged in thedevelopment and evaluation of welding and machining equipment andpractices related to in situ valve repair. An extensive effort has beenmade by valve repair service vendors and equipment manufacturers tospecifically address the repair of main steam isolation valve seats andguide ribs. An equal effort has been made to develop hardfacingmaterials welding techniques for in situ application. This documentdraws on the results of these efforts and presents alternative repairsolutions which are known to, or practiced by few. The repair methodspresented in this guide have provided considerable cost savings andplant availability to those utilities which have chosen to look forward.

PROJECT

Work Order 3887 and 3814

EPRI Project Managers:

Michael K. Phillips, Repair and Replacement Applications Center

Vic Varma, Nuclear Maintenance Applications Center

Nuclear Power Group

For ordering information about this report, call the Nuclear

Maintenance Applications Center, 800/356-7448.

For membership information, call 415/855-2514.


5/397

Valve Application, Maintenance, and Repair GuideIn Situ State-of-the-Art Valve Welding Repair

(Gate, Globe, & Check Valves), Volume 2

TR-105852v2

Final ReportDecember 1996

Prepared byEPRI Repair & Replacement Applications Center (RRAC)

Principal InvestigatorsMichael K. Phillips

Shane J. Findlan

Contributing Author

William F. Newell, Jr.W. F. Newell & Associates

Prepared for

Nuclear Maintenance Applications CenterRepair & Replacement Applications Program1300 W.T. Harris Boulevard, Charlotte, NC 28262

(P.O. Box 217097, Charlotte, NC 28221)

Operated byElectric Power Research Institute

3412 Hillview Avenue, Palo Alto, CA 94304(P.O. Box 10412, Palo Alto, CA 94303)

EPRI Project ManagersVic VarmaMichael K. Phillips

Nuclear Power Group


6/397

DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIES

THIS REPORT WAS PREPARED BY THE ORGANIZATION(S) NAMED BELOW AS AN ACCOUNT OF WORK

SPONSORED OR COSPONSORED BY THE ELECTRIC POWER RESEARCH INSTITUTE, INC. (EPRI). NEITHER

EPRI, ANY MEMBER OF EPRI, ANY COSPONSOR, THE ORGANIZATION(S) BELOW, NOR ANY PERSON ACTING

ON BEHALF OF ANY OF THEM:

A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLIED, (I) WITH RESPECT

TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS

REPORT, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, OR (II) THAT SUCHUSE DOES NOT INFRINGE ON OR INTERFERE WITH PRIVATELY OWNED RIGHTS, INCLUDING ANY PARTY’S

INTELLECTUAL PROPERTY, OR (III) THAT THIS REPORT IS SUITABLE TO ANY PARTICULAR USER’S

CIRCUMSTANCE; OR

(B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER (INCLUDING ANY

CONSEQUENTIAL DAMAGES, EVEN IF EPRI OR ANY EPRI REPRESENTATIVE HAS BEEN ADVISED OF THE

POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOUR SELECTION OR USE OF THIS REPORT OR ANY

INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS REPORT.

ORDERING INFORMATIONPRICE: $35,000

Requests for copies of this report should be directed to the Repair & Replacement Applications Center orthe Nuclear Maintenance Applications Center (NMAC), 1300 W.T. Harris Boulevard, Charlotte, NC 28262,800/356-7448. There is no charge for reports requested by RRAP and NMAC member utilities.

Electric Power Research Institute and EPRI are registered service marks of Electric Power Research Institute, Inc.

Copyright © 1996 Electric Power Research Institute, Inc. All rights reserved.


7/397

iii

EPRI L icensed Mat eri al

Valve Application, Maintenance, and Repair Guide: In Situ State-of-the-Art Valve Welding Repair

ACKNOWLEDGEMENTS

Volume 2 of the EPRI RRAC/NMAC Maintenance and Repair Guide, In-Situ State-of-the-ArtValve Welding Repair has been developed with the support of numerous organizations andindividuals dedicated to the advancement of new repair technology and methods. Theauthors want to thank the steering committee members of the Repair and ReplacementApplications Program and the Nuclear Maintenance Applications Center for their visionto recognize the problems associated with valve repair and support this much neededguide. We want to especially recognize the following utility personnel, valve manufactur-

ers, and repair service vendors who made a contribution by way of technical input, repairexperience, or advice that supported the development of this product:

Pedro Amador Welding Services, IncorporatedRafiq Bandukwala Edward Valves, IncorporatedPat Brennan VR-TESCO, Incorporated James Cobb Edward Valves, IncorporatedBill Fingrudt GE Nuclear Services, IncorporatedBill Knect Anchor Darling Valve CompanyRay Luda Anchor Darling Valve CompanyGarland Mahan Entergy/River Bend

John Polacheck PCI Energy ServicesTim Satterfield Anchor Darling Valve CompanyAl Silvia Northeast UtilitiesTerry Weigel Climax Portable Machine Tools, Incorporated

Our thanks also goes to the following companies who hosted on-site visits and pro-vided detailed information on their valves and repair practices:

Anchor Darling Valve CompanyEdward Valves, IncorporatedVR-TESCO, IncorporatedEntergy/Grand Gulf

Finally, we would like to extend a word of special thanks to those who reviewed thefinal draft:

Greg Hartraft GPU Nuclear John Aikin AECLBill Pratt TVABill Knect Anchor Darling Valve CompanyRichard Smith Altran John Hosler EPRI


8/397

iv



Let it be known that the various alloys or hardfacing materials referred to throughoutthe document have trademarked names. The following is a list of trademarked alloys orhardfacing:

Colmonoy Wall Colmonoy IncorporatedDelchrome Deloro Stellite Limited

Deloro Stoody Deloro Stellite IncorporatedHastelloy Haynes International IncorporatedIncoloy Inco Alloys International IncorporatedInconel Inco Alloys International IncorporatedMonel Inco Alloys International IncorporatedNOREM EPRINucalloy Stoody Deloro Stellite IncorporatedStellite Stoody Deloro Stellite IncorporatedTristelle Stoody Deloro Stellite Incorporated


9/397

v



CONTENTS

1.0 PROJECT DESCRIPTION .............................................................................................................. 1-1

1.1 Introduction and Application ............................................................................................. 1-1

1.2 Summary ............................................................................................................................. 1-3

2.0 CODES AND STANDARDS ............................................................................................................ 2-1

2.1 General ................................................................................................................................ 2-1

2.2 Pressure/Temperature Ratings .......................................................................................... 2-42.2.1 General .................................................................................................................... 2-4

2.2.2 Special Class Valves (Weld-End Valve) ................................................................... 2-62.2.3 Intermediate Rating Valves (Weld-End and Threaded Valves) ................................ 2-7

2.3 General Discussion of Pressure Boundary Materials ..................................................... 2-7

2.4 Required Minimum Wall and Corrosion Allowance ......................................................... 2-9

3.0 GENERAL VALVE DESIGN ............................................................................................................ 3-1

3.1 Nomenclature/Glossary of Terms ...................................................................................... 3-13.1.1 Introduction .............................................................................................................. 3-1

3.1.2 Glossary of Terms .................................................................................................... 3-1

3.2 Common Valve Construction Features ........................................................................... 3-10

3.2.1 Body-to-Bonnet Connections ................................................................................. 3-103.2.2 Seat and Seat Rings .............................................................................................. 3-14

3.2.3 Disc-to-Stem Connection ....................................................................................... 3-233.2.4 Disc/Stem Guide Arrangements ............................................................................ 3-26

4.0 VALVE MATERIALS ........................................................................................................................ 4-1

4.1 Trim Components and Materials ....................................................................................... 4-1

4.2 Material Selection Practices .............................................................................................. 4-34.2.1 Design Practices to Minimize Corrosion .................................................................. 4-34.2.2 Design Practices to Minimize Erosion ..................................................................... 4-6

4.2.3 Design Practices to Minimize Wear and Galling ...................................................... 4-8

4.3 Hardfacing ........................................................................................................................... 4-94.3.1 Cobalt-Base Alloys (Stellites™) ............................................................................... 4-94.3.2 Cobalt-Free Alloys ................................................................................................. 4-10

4.4 Resilient (Soft) Seating .................................................................................................... 4-11

4.5 Pressure-Retaining Materials .......................................................................................... 4-14


10/397

vi



5.0 GATE VALVES ................................................................................................................................ 5-1


5.2 Design .................................................................................................................................. 5-15.2.1 General .................................................................................................................... 5-1

5.2.2 Solid-Wedge Gate ................................................................................................... 5-3

5.2.3 Split-Wedge Gate .................................................................................................... 5-55.2.4 Flexible-Wedge Gate ............................................................................................... 5-75.2.5 Double-Disc Gate .................................................................................................... 5-95.2.6 Parallel-Slide Gate ................................................................................................. 5-12

5.2.7 Slab Gate ............................................................................................................... 5-155.2.8 Knife Gate .............................................................................................................. 5-17

5.3 Repair Issues .................................................................................................................... 5-195.3.1 Leakage Past the In-Body Seat ............................................................................. 5-19

5.3.2 Leakage Past the Pressure Seal Ring ................................................................... 5-245.3.3 Valve Stem Leaks .................................................................................................. 5-26

5.3.4 Valve Body Damage .............................................................................................. 5-285.3.5 Valve Bonnet Leaks ............................................................................................... 5-31

5.3.6 Wedge Guides ....................................................................................................... 5-33

6.0 GLOBE VALVES ............................................................................................................................. 6-1


6.2 Design .................................................................................................................................. 6-26.2.1 General .................................................................................................................... 6-2

6.2.2 Horizontal Globe ...................................................................................................... 6-36.2.3 Y-Globe .................................................................................................................... 6-56.2.4 Angle Globe ............................................................................................................. 6-6

6.2.5 Y-Angle Globe .......................................................................................................... 6-76.2.6 Control Valves .......................................................................................................... 6-8

6.3 Repair Issues .................................................................................................................... 6-11

6.3.1 Leakage Past the In-Body Seats ........................................................................... 6-116.3.2 Leakage Past the Pressure Seal Ring ................................................................... 6-146.3.3 Valve Stem Leaks .................................................................................................. 6-14


6.3.6 Poppet (Disc) Guide Ribs ...................................................................................... 6-16

7.0 CHECK VALVES ............................................................................................................................. 7-1


7.2 Design .................................................................................................................................. 7-27.2.1 General .................................................................................................................... 7-2

7.2.2 Swing Check ............................................................................................................ 7-27.2.3 Lift Check ................................................................................................................. 7-57.2.4 Tilting Disc ............................................................................................................... 7-8

7.3 Repair Issues .................................................................................................................... 7-107.3.1 Leakage Past the In-Body Seats ........................................................................... 7-107.3.2 Leakage Past the Pressure Seal Ring ................................................................... 7-137.3.3 Valve Stem Leaks .................................................................................................. 7-14


7.3.6 Poppet (Disc) Guide Ribs ...................................................................................... 7-147.3.7 Leakage Past the Hinge Pin Cover ........................................................................ 7-15


11/397

vii



8.0 VALVE COMPONENT REPAIRS .................................................................................................... 8-1

8.1 Valve Body Repair .............................................................................................................. 8-18.1.1 Repair Strategy ........................................................................................................ 8-28.1.2 Repair Prerequisites ................................................................................................ 8-3

8.1.3 Flaw Removal .......................................................................................................... 8-48.1.4 Filler Material Selection ........................................................................................... 8-4

8.1.5 Preheat and Post-Weld Heat Treatment (PWHT) Requirements ............................. 8-48.1.6 Welding Repair ........................................................................................................ 8-58.1.7 Final Machining ........................................................................................................ 8-7

8.1.8 Inspection ................................................................................................................ 8-78.1.9 Testing ..................................................................................................................... 8-8

8.2 Pressure Seal Area Repair ................................................................................................. 8-88.2.1 Repair Strategy ........................................................................................................ 8-9

8.2.2 Repair Prerequisites .............................................................................................. 8-108.2.3 Flaw Removal ........................................................................................................ 8-118.2.4 Filler Material Selection ......................................................................................... 8-12

8.2.5 Preheat and Post-Weld Heat Treatment Requirements ......................................... 8-128.2.6 Welding Repair ...................................................................................................... 8-13

8.2.7 Final Machining ...................................................................................................... 8-148.2.8 Inspection .............................................................................................................. 8-14

8.2.9 Testing ................................................................................................................... 8-14

8.3 Seat Ring Repair ............................................................................................................... 8-148.3.1 Repair Assessment and Strategy .......................................................................... 8-168.3.2 Repair Prerequisites .............................................................................................. 8-16

8.3.3 Defect Removal ..................................................................................................... 8-278.3.4 Filler Material Selection ......................................................................................... 8-288.3.5 Preheat and Post-Weld Heat Treatment Requirements ......................................... 8-29

8.3.6 Repair Welding ...................................................................................................... 8-298.3.7 Final Machining ...................................................................................................... 8-32

8.3.8 Inspection .............................................................................................................. 8-34

8.3.9 Testing ................................................................................................................... 8-348.4 Seat Ring Replacement .................................................................................................... 8-35

8.4.1 Repair Assessment and Strategy .......................................................................... 8-39

8.4.2 Repair Prerequisites .............................................................................................. 8-408.4.3 Seat Ring Removal ................................................................................................ 8-42

8.4.4 Filler Material Selection ......................................................................................... 8-458.4.5 Preheat and Post-Weld Heat Treatment Requirements ......................................... 8-458.4.6 Seat Ring Installation and Welding ........................................................................ 8-45

8.4.7 Machining .............................................................................................................. 8-508.4.8 Inspection .............................................................................................................. 8-52

8.4.9 Testing ................................................................................................................... 8-52

8.5 Integral Seat Repair .......................................................................................................... 8-52

8.5.1 Repair Assessment and Strategy .......................................................................... 8-538.5.2 Repair Prerequisites .............................................................................................. 8-54

8.5.3 Defect Removal ..................................................................................................... 8-558.5.4 Filler Material Selection ......................................................................................... 8-55

8.5.5 Preheat and Post-Weld Heat Treatment Requirements ......................................... 8-558.5.6 Repair Welding ...................................................................................................... 8-568.5.7 Machining .............................................................................................................. 8-57

8.5.8 Inspection .............................................................................................................. 8-598.5.9 Testing ................................................................................................................... 8-59


12/397

viii



8.6 Integral Seat Replacement ............................................................................................... 8-598.6.1 Repair Assessment and Strategy .......................................................................... 8-608.6.2 Seat Hardfacing Replacement Prerequisites ......................................................... 8-61

8.6.3 Seat Removal and Weld Preparation ..................................................................... 8-618.6.4 Filler Material Selection ......................................................................................... 8-63

8.6.5 Preheat and Post-Weld Heat Treatment Requirements ......................................... 8-64

8.6.6 Welding Repair ...................................................................................................... 8-648.6.7 Machining .............................................................................................................. 8-658.6.8 Inspection .............................................................................................................. 8-668.6.9 Testing ................................................................................................................... 8-67

8.7 Bonnet Backseat Repair and Replacement .................................................................... 8-678.7.1 Repair Strategy ...................................................................................................... 8-678.7.2 Repair Prerequisites .............................................................................................. 8-688.7.3 Flaw Removal ........................................................................................................ 8-69

8.7.4 Filler Material Selection ......................................................................................... 8-718.7.5 Preheat and Post-Weld Heat Treatment Requirements ......................................... 8-71

8.7.6 Welding Repair ...................................................................................................... 8-728.7.7 Final Machining ...................................................................................................... 8-72


8.8 Guide Repair and Replacement....................................................................................... 8-758.8.1 Repair Strategy ...................................................................................................... 8-76



8.8.7 Final Machining ...................................................................................................... 8-808.8.8 Inspection .............................................................................................................. 8-80

8.8.9 Testing ................................................................................................................... 8-80

8.9 Guide Rib Repair ............................................................................................................... 8-818.9.1 Repair Strategy ...................................................................................................... 8-828.9.2 Repair Prerequisites .............................................................................................. 8-838.9.3 Flaw Removal ........................................................................................................ 8-83

8.9.4 Filler Material Selection ......................................................................................... 8-848.9.5 Preheat and Post-Weld Heat Treatment Requirements ......................................... 8-84

8.9.6 Welding Repair ...................................................................................................... 8-858.9.7 Final Machining ...................................................................................................... 8-88


8.10 Hinge Pin Repair ............................................................................................................... 8-888.10.1 Repair Strategy ...................................................................................................... 8-95



8.10.7 Final Machining ...................................................................................................... 8-998.10.8 Inspection ............................................................................................................ 8-100

8.10.9 Testing ................................................................................................................. 8-100


13/397

ix



8.11 Wedge/Disc Repair (Gate, Swing Check, and TDC) ..................................................... 8-1008.11.1 Repair Strategy .................................................................................................... 8-1028.11.2 Repair Prerequisites ............................................................................................ 8-103

8.11.3 Flaw Removal ...................................................................................................... 8-1058.11.4 Filler Material Selection ....................................................................................... 8-107

8.11.5 Preheat and Post-Weld Heat Treatment Requirements ....................................... 8-107

8.11.6 Welding Repair .................................................................................................... 8-1088.11.7 Final Machining .................................................................................................... 8-1108.11.8 Inspection ............................................................................................................ 8-1128.11.9 Testing ................................................................................................................. 8-113

8.12 Poppet Hardfacing Repair .............................................................................................. 8-1138.12.1 Repair Strategy .................................................................................................... 8-1148.12.2 Repair Prerequisites ............................................................................................ 8-1158.12.3 Flaw Removal ...................................................................................................... 8-116

8.12.4 Filler Material Selection ....................................................................................... 8-1178.12.5 Preheat and Post-Weld Heat Treatment Requirements ....................................... 8-117

8.12.6 Welding Repair .................................................................................................... 8-1178.12.7 Final Machining .................................................................................................... 8-118

8.12.8 Inspection ............................................................................................................ 8-1198.12.9 Testing ................................................................................................................. 8-120

8.13 Valve Stem Repair........................................................................................................... 8-120

9.0 DEFECT REMOVAL........................................................................................................................ 9-1

9.1 Grinding ............................................................................................................................... 9-5

9.2 Machining ............................................................................................................................ 9-6

9.3 Lapping ................................................................................................................................ 9-8

9.4 Honing ............................................................................................................................... 9-10

10.0 WELDING PROCESS SELECTION ............................................................................................. 10-1

10.1 Gas Tungsten Arc Welding (GTAW) ................................................................................. 10-2

10.2 Gas Metal Arc Welding (GMAW) ...................................................................................... 10-3

10.3 GMAW-P ............................................................................................................................. 10-4

10.4 FCAW ................................................................................................................................. 10-4

10.5 Shielded Metal Arc Welding (SMAW) .............................................................................. 10-5

10.6 Machine Welding ............................................................................................................... 10-6

10.7 GTAW-P-AU ........................................................................................................................ 10-6

10.8 Efficiency/Cost Comparisons .......................................................................................... 10-6

11.0 WELDING FILLER MATERIAL ..................................................................................................... 11-1

11.1 Types of Filler Metals ....................................................................................................... 11-1

11.2 Filler Metal Requirements ................................................................................................ 11-2

11.3 Filler Metal Selection ........................................................................................................ 11-411.3.1 A-Numbers............................................................................................................. 11-8

11.3.2 F-Numbers ............................................................................................................. 11-9


14/397

x



11.4 Storage of Welding Filler Materials ............................................................................... 11-11

11.5 Handling of Welding Filler Materials ............................................................................. 11-11

11.6 Dissimilar Weldments ..................................................................................................... 11-12

11.7 Filler Metals for Hardfacing Applications ..................................................................... 11-15

11.8 Typical Weld Filler Metal Specifications ....................................................................... 11-15

12.0 SHIELDING AND PURGING GASES ........................................................................................... 12-1

12.1 Purging .............................................................................................................................. 12-1

12.2 Shielding ............................................................................................................................ 12-2

13.0 PREHEAT/POST-WELD HEAT TREATMENT REQUIREMENTS................................................. 13-1

13.1 Preheat ............................................................................................................................... 13-3

13.2 Interpass Temperature ..................................................................................................... 13-4

13.3 Post-Weld Heat Treatment ................................................................................................ 13-5

13.4 Guide to Selection of Heating Methods .......................................................................... 13-713.4.1 Gas Torch Heating ................................................................................................. 13-7

13.4.2 Electrical Resistance Heating ................................................................................ 13-713.4.3 Furnace Heating .................................................................................................... 13-7

13.4.4 Induction Heating ................................................................................................... 13-7

13.5 Guide for Selection of Preheat and PWHT ..................................................................... 13-7

13.6 Preheat and PWHT Procedures ....................................................................................... 13-813.6.1 General .................................................................................................................. 13-8

13.6.2 Temperature Measurement.................................................................................... 13-813.6.3 Thermocouples ...................................................................................................... 13-9

13.6.4 Minimum Controlled Band Width ......................................................................... 13-1413.6.5 Heat Treatment Records ...................................................................................... 13-14

13.7 Preheat and Post-Weld Heat Treatment Considerations—Hardfacing ....................... 13-1613.7.1 Preheat ................................................................................................................ 13-1613.7.2 Post-Weld Heat Treatment—Hardfacing .............................................................. 13-16

13.8 Contracted PWHT ........................................................................................................... 13-16

14.0 WELDING METHODS AND PROCEDURES ............................................................................... 14-1

14.1 Manual Base Metal Welding Procedure Guidelines ....................................................... 14-114.1.1 Manual SMAW ....................................................................................................... 14-114.1.2 Manual GTAW ........................................................................................................ 14-2

14.2 Machine Base Metal Welding Procedure Guidelines ..................................................... 14-214.2.1 Machine GTAW ...................................................................................................... 14-2

14.3 Hardfacing Welding Procedure Guidelines .................................................................... 14-314.3.1 General Requirements—Hardfacing ...................................................................... 14-314.3.2 Suggested Welding Practices ................................................................................ 14-5

14.3.3 Manual GTAW ........................................................................................................ 14-514.3.4 Localized Hardfacing Repair Practices .................................................................. 14-6


15/397

xi



14.4 Machine Hardfacing Welding Procedure Guidelines ..................................................... 14-814.4.1 Machine GTAW ...................................................................................................... 14-814.4.2 Machine PTAW ...................................................................................................... 14-9

14.5 Temperbead Welding Repair Guidelines ........................................................................ 14-914.5.1 Temperbead Qualification and Demonstration....................................................... 14-914.5.2 Implementation .................................................................................................... 14-13

15.0 INSPECTION AND TESTING METHODS .................................................................................... 15-1

15.1 Nondestructive Examination ........................................................................................... 15-1

15.2 Post-Repair Testing .......................................................................................................... 15-315.2.1 Exercise Test .......................................................................................................... 15-3

15.3 Blue Check ........................................................................................................................ 15-4

APPENDIX A: GATE VALVE WEDGE FITTING TECHNIQUES ............................................................. A-1

APPENDIX B: IN SITU WELDING EQUIPMENT ................................................................................... B-1

APPENDIX C: IN SITU VALVE MACHINING EQUIPMENT ...................................................................C-1

APPENDIX D: VALVE MANUFACTURERS ...........................................................................................D-1

APPENDIX E: IN SITU VALVE REPAIR VENDORS .............................................................................. E-1

APPENDIX F: REFERENCES AND ADDITIONAL BIBLIOGRAPHY ................................................... F-1

Additional Bibliography ................................................................................................................ F-6

APPENDIX G: ACRONYMS AND ABBREVIATIONS ............................................................................G-1


16/397


17/397

xiii



LIST OF FIGURES

Figure No. Page No.

Section 3 ____________________________________________________________________________

3-1 Globe Valve—Typical Valve Nomenclature .................................................................................. 3-2

3-2 Gate Valve—Typical Valve Nomenclature ................................................................................... 3-3

3-3 Screwed Bonnet ........................................................................................................................ 3-11

3-4 Flanged (Bolted) Bonnet ........................................................................................................... 3-12

3-5 Welded Bonnet .......................................................................................................................... 3-12

3-6 Pressure-Sealed Bonnet ........................................................................................................... 3-13

3-7 Seat Joint Mating Surfaces ....................................................................................................... 3-14

3-8 Seat Plane Distortion under Vertical and Horizontal Bending Moments ................................... 3-15

3-9 Typical Globe Valve Seating Configurations .............................................................................. 3-17

3-10 Cross Ring Indentation.............................................................................................................. 3-18

3-11 Soft Seat Retention Methods .................................................................................................... 3-19

3-12 Methods for Attaching Seat to Body .......................................................................................... 3-21

3-13 Flexible Seat .............................................................................................................................. 3-22

3-14 Floating Seat ............................................................................................................................. 3-22

3-15 Spring-Loaded Packing Seals ................................................................................................... 3-23

3-16 Stem Connections ..................................................................................................................... 3-24

3-17 Gate Valve Gate Guide.............................................................................................................. 3-27

Section 4 ____________________________________________________________________________

4-1 Double-Seated Globe Valve Trim Components ........................................................................... 4-2

4-2 Balanced Disc Cage-Style Valve ................................................................................................. 4-2


18/397

xiv



Figure No. Page No.

Section 5 ____________________________________________________________________________

5-1 Inside Screw Stem Thread Configurations .................................................................................. 5-2

5-2 Rising Stem Design, Outside Screw ........................................................................................... 5-2

5-3 Solid-Wedge Gate Valve ............................................................................................................. 5-4

5-4 Split-Wedge Gate Valve .............................................................................................................. 5-6

5-5 Flex-Wedge Gate Valve ............................................................................................................... 5-8

5-6 Double-Disc Gate Valve ............................................................................................................ 5-10

5-7 Through-Conduit, Double-Disc Gate Valve ............................................................................... 5-11

5-8 Parallel-Slide Gate Valve ........................................................................................................... 5-13

5-9 Through-Conduit, Parallel-Slide Gate Valve .............................................................................. 5-15

5-10 Slab Gate Valve ......................................................................................................................... 5-16

5-11 Knife-Gate Valve ........................................................................................................................ 5-18

5-12 Welded-In Gate Valve Seat Ring ............................................................................................... 5-20

5-13 Gate Valve Wedge Seating Too Low in Seats ........................................................................... 5-21

5-14 Split-Wedge Gate with Spacer Ring .......................................................................................... 5-22

5-15 Typical Pressure Seal Bonnet Configuration ............................................................................. 5-24

5-16 Pressure Seal Bonnet ............................................................................................................... 5-26

5-17 Typical Valve Stem/Bonnet Backseat ........................................................................................ 5-27

5-18 Typical Gate Valve Body ............................................................................................................ 5-29

5-19 Typical Bolted Bonnet Components .......................................................................................... 5-31

5-20 Single Guide Design for Gate Valves ........................................................................................ 5-34

5-21 Parallel Guide Design for Gate Valves ...................................................................................... 5-35


19/397

xv



Figure No. Page No.

Section 6 ____________________________________________________________________________

6-1 Plug-Type Disc ............................................................................................................................ 6-2

6-2 Cage-Type Disc ........................................................................................................................... 6-3

6-3 Horizontal Globe Valve ................................................................................................................ 6-4

6-4 Y-Globe Valve .............................................................................................................................. 6-5

6-5 Angle Globe Valve ....................................................................................................................... 6-6

6-6 Y-Angle Globe Valve .................................................................................................................... 6-7

6-7 Single-Port Control Valve ............................................................................................................ 6-8

6-8 Double-Port Control Valve ......................................................................................................... 6-10

6-9 Three-Way Valve ....................................................................................................................... 6-11

6-10 Disc Seating Too Low in Seat .................................................................................................... 6-13

6-11 Valve Body ................................................................................................................................ 6-15

Section 7 ____________________________________________________________________________

7-1 Swing Check Valve ...................................................................................................................... 7-3

7-2 Lift Check Valve, T-Pattern........................................................................................................... 7-5

7-3 Lift Check Valve, Y-Pattern........................................................................................................... 7-6

7-4 Lift Check Valve, Angle Configuration ......................................................................................... 7-6

7-5 Disc-Type Lift Check Valve .......................................................................................................... 7-7

7-6 Piston-Type Lift Check Valve ....................................................................................................... 7-7

7-7 Tilting Disc Check Valve .............................................................................................................. 7-9

7-8 Disc Seating Too Low in Seats .................................................................................................. 7-12

7-9 Swing Check and Tilting Disc Check Valve, Standard CompressionFlange and Gasket Joints ......................................................................................................... 7-16

7-10 Swing Check and Tilting Disc Check Valve, Pressure Seal Joints ............................................ 7-17


20/397

xvi



Figure No. Page No.

Section 8 ____________________________________________________________________________

8-1a Typical Body Repair Locations .................................................................................................... 8-1

8-1b Recommended First Layer Weld Repair Bead Placement forValve Body Base Material Repairs .............................................................................................. 8-6

8-1c Recommended Second Layer Weld Repair Bead Placement for

Valve Body Base Material Repairs .............................................................................................. 8-6

8-1d Recommended Cavity Fill Weld Repair Bead Placement forValve Body Base Material Repairs .............................................................................................. 8-7

8-2a Pressure Seal Repair Location ................................................................................................... 8-9

8-2b Example of Pressure Seal Area Boring..................................................................................... 8-12

8-3a Seat Ring Configuration ............................................................................................................ 8-15

8-3b Blue Check for Seating Location ............................................................................................... 8-17

8-3c Typical Wedge Dimensions ....................................................................................................... 8-18

8-3d Gate Valve Seat Measurements ................................................................................................ 8-19

8-3e Reference Dimensions for Gate/Check Valve Seat Width ......................................................... 8-20

8-3f Reference Points on the Seat Ring of Swing Check Valve ........................................................ 8-21

8-3g Seating Location on Tilting Disc ................................................................................................ 8-22

8-3h Reference Mark Locations on Tilting Disc ................................................................................. 8-23

8-3i Seat Location on Poppet ........................................................................................................... 8-24

8-3j Typical Body Dimensions, Globe Valve ..................................................................................... 8-25

8-3k Typical Body Dimensions, Y-Type Globe and Lift Check Valve .................................................. 8-26

8-3l Gate Valve Seat Machining ....................................................................................................... 8-27

8-3m Globe Valve Seat Machining ..................................................................................................... 8-28

8-3n Gate Valve Hardfacing Application, Machine GTAW ................................................................. 8-30

8-3o Globe Valve Hardfacing Application, Machine GTAW ............................................................... 8-31

8-3p Globe Valve Seat Final Machining ............................................................................................ 8-33

8-3q Typical Globe Valve Seat Angle Differential .............................................................................. 8-34

8-4a Typical Gate Valve Seat Ring Seal Weld ................................................................................... 8-35


21/397

xvii



Figure No. Page No.

Section 8 ____________________________________________________________________________

8-4b Typical Seal Weld Locations for Globe-Type Seat Rings ........................................................... 8-36

8-4c Seat Ring Angle Generated by the Angle in the Seat Pocket ................................................... 8-37

8-4d Example of Globe Valve with a Threaded Seat Ring ................................................................. 8-38

8-4e Split View of Valve Body (In-Line) Exhibiting the Seal Weld Fixture .......................................... 8-43

8-4f Valve Body Preparation for Replacement Seat Ring ................................................................. 8-44

8-4g Typical Weld Buildup for Repair of Threaded Globe Valve Seat Ring Pocket ............................ 8-46

8-4h Valve Boring System with Thread Attachment for Restoration

of Threads in the Seat Ring Pocket ........................................................................................... 8-47

8-4i Example of Tapered Seat Ring .................................................................................................. 8-48

8-4j Split View of Valve Body (In-Line) Exhibiting Seal Weld Head Setup ........................................ 8-49

8-4k Gate Valve Seat Narrowing ....................................................................................................... 8-51

8-4l Typical Lapping Fixture for Globe-Type Seat Ring .................................................................... 8-52

8-5a Turbine Throttle Valve ................................................................................................................ 8-56

8-5b Swing Check Valve Lapping Machine ....................................................................................... 8-58

8-6a Seat Removal with Automatic Grinding System ........................................................................ 8-62

8-6b Base Material Restoration for Seat Ring ................................................................................... 8-65

8-6c In Situ Machining of MSIV Seat ................................................................................................ 8-66

8-7a Typical Bonnet Backseat/Stem Configuration for Blueing ......................................................... 8-69

8-7b Proper Stem to Backseat Seating Configuration ....................................................................... 8-73

8-7c Lapping Bonnet Backseat to Stem ............................................................................................ 8-74

8-8a Typical Single Guide Configuration for Gate-Type Valves ......................................................... 8-75

8-8b Double-Guided Gate Configuration ........................................................................................... 8-76

8-9a Globe Valve Configuration Showing Guide Rib ......................................................................... 8-81

8-9b Y-Type MSIV .............................................................................................................................. 8-85

8-9c Guide Rib Hardfacing Refurbishment Sequence ...................................................................... 8-87


22/397

xviii



Figure No. Page No.

Section 8 ____________________________________________________________________________

8-10a Swing Check and Tilting Disc Check Valves ............................................................................. 8-89

8-10b Swing Check Valve, Pin Supported in Cast Journals ................................................................ 8-90

8-10c Swing Check Valve, Bracket Mounted on Two Pads.................................................................. 8-91

8-10d Swing Check Valve, Pin Supported in Bracket Attached to Bonnet .......................................... 8-91

8-10e Hinge Pins and Covers Inserted into Disc Assembly Bushings ................................................ 8-92

8-10f Pipe Plug Seal Cover ................................................................................................................ 8-93

8-10g Blind Flange Cover.................................................................................................................... 8-94

8-10h Pressure Seal Cover ................................................................................................................. 8-95

8-10i Boring Bar with Flange Facing Capabilities ............................................................................. 8-100

8-11a Typical Wedge ......................................................................................................................... 8-101

8-11b Removable Valve Disc/Wedges............................................................................................... 8-101

8-11c Seat Angle Determinations for Tilting Disc Check Valve ......................................................... 8-105

8-11d Wedge or Disc Mounted in Fixture .......................................................................................... 8-106

8-11e Hardfacing Refurbishment Sequence ..................................................................................... 8-109

8-11f Lapping Table and Portable Lapping Adapter ......................................................................... 8-110

8-11g Seat Angle Determination for Tilting Disc Check Valve ........................................................... 8-111

8-11h Lapping Fixture for In-Body Tilting Disc Check Valve Seat and Disc ...................................... 8-112

8-12a Poppets with Hardfaced Wear Rings....................................................................................... 8-113

8-12b Poppet Seat and Wear Ring Dimensions ................................................................................ 8-116

8-12c Typical Globe Valve Seat Angle Differential ............................................................................ 8-119

Section 9 ____________________________________________________________________________

9-1 Removal of Surface Indications Where No Weld Repair Is Required .......................................... 9-2

9-2 Excavation for Defect Type Verification and Local Weld Repair .................................................. 9-4

9-3 Gate Valve Seat Machining ......................................................................................................... 9-7

9-4 Milling Machine Removing Hardfacing from Guide Ribs ............................................................. 9-8

9-5 Gate Valve Lapping Machine ...................................................................................................... 9-9


23/397

xix



Figure No. Page No.

Section 10 ___________________________________________________________________________

10-1 Welding Process Versus Deposition Rate at 100% Duty Cycle ................................................ 10-2

10-2 Process Diagram (GTAW) ......................................................................................................... 10-2

10-3 Circuit Diagram (GTAW) ............................................................................................................ 10-3

10-4 Process Diagram (GMAW) ........................................................................................................ 10-3

10-5 Block Diagram (GMAW) ............................................................................................................ 10-4

10-6 Shielded Metal Arc Welding Process ........................................................................................ 10-5

10-7 Circuit Diagram (SMAW) ........................................................................................................... 10-5

Section 11 ___________________________________________________________________________

11-1 Styles of Consumable Inserts ................................................................................................... 11-7

Section 12 ___________________________________________________________________________

12-1 Sample Fixtures for Purging the Inside Diameter of Pipe Weldments....................................... 12-2

Section 13 ___________________________________________________________________________

13-1 Typical Setup for Preheating Pipe Welds with Electrical Resistance Equipment ...................... 13-2

13-2 Typical Setup for Flexible Pad Heating Elements ...................................................................... 13-4

13-3 Thermocouple Attachment for PWHT Using the Capacitor Discharge Method ...................... 13-10

13-4 Thermocouple Attachment for PWHT Using Clips and a Flattened Tube ............................... 13-11

13-5 Minimum Controlled Band Width (CBW) for Post-Weld Heat Treatment ................................. 13-12

13-6 Required Thermocouple Locations and Minimum Heated Band Width (HBW)for Post-Weld Heat Treatment ................................................................................................. 13-13

13-7a Heat Treatment Quality Control Specification.......................................................................... 13-15

13-7b Heat Treatment Quality Control Record .................................................................................. 13-17

Section 14 ___________________________________________________________________________

14-1 Temperbead Groove Preparation, Geometry, and Weld Bead Sequence ............................... 14-11


24/397

Figure No. Page No.

Appendix A _________________________________________________________________________

A-1 Blue Check Illustration ................................................................................................................ A-4





A-6 Heel and Toe Measurement Parameters..................................................................................... A-7

A-7 Gauges Used to Determine Seat and Wedge Angles ................................................................. A-8


25/397

xxi



LIST OF TABLES

Table No. Page No.

Section 2 ____________________________________________________________________________

2-1 Valve Design Codes .................................................................................................................... 2-2

2-2 Typical Valve Standards .............................................................................................................. 2-3

2-3 Safety Classes and Applicable Standards .................................................................................. 2-4

2-4 Pressure/Temperature Ratings for Steel Valves .......................................................................... 2-5

2-5 Materials Commonly Used for Pressure Boundary Parts............................................................ 2-8

Section 4 ____________________________________________________________________________

4-1 Chart of Wear and Galling Resistance of Material Combinations ............................................... 4-4

4-2 Metals in Order of Corrosion Rate .............................................................................................. 4-5

4-3 Critical Variables for Accelerated Erosion-Corrosion................................................................... 4-7

4-4 Properties of Plastics and Elastomers Used for Soft Seats ...................................................... 4-13

Section 11 ___________________________________________________________________________

11-1 P-Number, Composition, and Specifications for Selected Valve Materials ................................ 11-1

11-2 Welding Filler Material Use by Process..................................................................................... 11-2

11-3 Weld Filler Metal Specifications ................................................................................................ 11-3

11-4 Typical Filler Metals for Various Base Metals ............................................................................ 11-5

11-5 Weld Metal for Joining Selected Stainless Steel Base Materials .............................................. 11-6

11-6 Popular Electrode Product Forms and Available Sizes ............................................................. 11-8

11-7 A-Numbers—Classification of Ferrous Weld Metal Analysis for Procedure Qualification ......... 11-9

11-8 F-Number Grouping of Welding Electrodes and Rods ............................................................ 11-10

11-9 Filler Metal Selection for Different P-Number Combinations ................................................... 11-13

11-10 Selected Weld Filler Metals Used for Hardfacing and Valve Seat Applications....................... 11-14


26/397

xxii



Table No. Page No.

Section 13 ___________________________________________________________________________

13-1 Preheat, Interpass, and PWHT Guidelines ............................................................................... 13-1

13-2 Mandatory Requirements for Post-Weld Heat Treatment of Welds ........................................... 13-5

13-3 AWS Post-Weld Heat Treatment Temperatures for Selected Base Metal .................................. 13-6

13-4 Code References for Preheat & PWHT Requirements ........................................................... 13-16

Section 15 ___________________________________________________________________________

15-1 ASTM and ASME Standards for Nondestructive Examination Methods ................................... 15-2


27/397

1-1



1

PROJECT DESCRIPTION

1.1 Introduction and Application

Valves play a key role in the operation and performance of power plants. Maintenanceand repair of valves have been a leading concern of plant operators as they seek tomaximize plant availability and the return on their capital investment.

EPRI has initiated numerous studies and surveys aimed at understanding the impact of valve-related problems on plant availability. The results of these studies indicate thatvalve failures are the single largest contributor to unscheduled shutdowns and lostpower generation [1]. EPRI responded positively to the results of these studies by initi-ating several projects that addressed basic maintenance needs, such as bolting practices,valve stem packing, and motor-operated valve (MOV) training.

A costly issue that has not been adequately addressed involves the repair of the valve bodies, bonnets, and internal trim components, which generally requires some degreeof welding and machining. Damage to critical valve parts due to wear, erosion, corro-

sion, cracking, and other destructive mechanisms typically leads to lengthy forced orextended outages when welding is required. Welded repairs to valves have tradition-ally been performed by the valve manufacturer who attempts a lengthy repair in theirmanufacturing facility or a “hot” shop facility if the valve is contaminated. Anothertypical approach has been to replace the valve with a new one. This also has manyshortcomings, especially in today’s market when replacement stock is not readily avail-able for most larger valves.

Today, with the emphasis on shorter refueling outages and tighter radiation exposurelimits, utilities are looking for a faster and more cost-effective approach to getting backon-line quickly. In situ repair of welded-in valves and on-site repair for flanged valves

have become the preferred or required approach. Performing the repair in situ avoidscutting the valve out of line and shipping it to the repair facility, eliminates the systemhydro testing after reinstallation, and keeps the owner in control of the repair and itsimpact on the outage schedule.

Major in situ repairs are currently being performed by original equipment manufacturers(OEMs), service vendors, and utility maintenance personnel with varied levels of success.The welding and machining technology currently available to make field repairs is


28/397

1-2



limited, focusing primarily on some large nuclear valves (main steam isolation valves orMSIVs) of the globe-type configuration. In the early 1980s, EPRI sponsored a program todevelop in situ machining and welding equipment to address the boiling water reactor(BWR) MSIV seating problems. Several equipment manufacturers and service organiza-tions designed and built MSIV repair systems. These systems were demonstrated at the

EPRI NDE Center in 1987 and several are being utilized today [2]. The result of that EPRI-sponsored program was a better understanding of the valve repair issues that the nuclearindustry faces, which has further influenced the development of repair systems forsmaller globe-type valves.

In 1994, the subscribing members of the EPRI Repair and Replacement ApplicationsProgram (RRAP) initiated a study to identify the capabilities and qualifications of orga-nizations performing in situ valve repair. Three separate surveys were sent out to fieldservice vendors, valve manufacturers, and RRAP utility members. The purpose of thesurveys were to:

• Identify the most common valve repair issues

• Determine the types and sizes of valves that contribute to down time

• Determine the capabilities of the manufacturers and service vendors to performwelded in situ repairs

• Develop contacts and obtain case histories for these guidelines

The results of that survey indicated that the number of utilities and service vendorsperforming in situ valve repairs was less than ten, and repair capabilities were quitelimited. It was also apparent from the survey that there had been very little transfer of information on repair cases and capabilities across the industry. In fact, many utilitycontacts were unaware of in situ repair capabilities, other than general maintenance

grinding/lapping of valve seats.

In 1996, the Nuclear Maintenance Applications Center (NMAC) and its member utilities joined with RRAC to develop a comprehensive valve application, repair, and mainte-nance series. Volume 1 addresses the selection of valves and maintenance issues. Thisdocument, Volume 2, addresses the repair of gate, globe, and check valves. Volume 3will address the repair of ball, butterfly, and plug-type valves.

The purpose of the guidelines in this document is to present information on valve prob-lems that require repair practices and applications beyond those typically recognized asmaintenance. These guidelines specifically address machining to remove defects in valve

components and restoring those materials by welding. These guidelines are aimed at thesystem, maintenance, and welding engineers responsible for maintaining valves. Second-ary audiences are the design engineers and others interested in understanding the typesof valves and the techniques needed to repair them. Most important, these guidelines leadthe engineer down a path to resolving problems associated with valve base material andtrim by offering guidance in understanding the work scope and developing resourcerequirements. Finally, the guidelines will assist in writing a repair specification and pro-vide the basic knowledge for the engineer to understand the operations he will oversee.


29/397

1-3



1.2 Summary

Numerous EPRI-sponsored studies and development efforts have been performed sincethe early 1980s to address valve reliability issues in nuclear power plants. The majority of these programs have resulted in applicable products or guidelines aimed at valve mainte-nance and diagnostics. Some of the more familiar products addressed bolting, on-line leaksealing, motor-operated valve (MOV) diagnostics and maintenance, and several valve-specific maintenance guidelines [3, 4, 5, 6, 7, 8, 9]. This study moves beyond the generalmaintenance of valves and addresses the repair of valve bodies and internal components,and more specifically, in situ repair. For the purpose of this program, “repair” refers tooperations that incorporate welding and/or machining of base materials.

Valves that require repair due to cracking, erosion, corrosion, or wear have had signifi-cant impact on plant availability, extending outages by days or even weeks. Most of these repairs are unique due to repair location, size, type, and configuration of thevalve. In addition to being unique, most of the failures are identified well into the out-age or during start up, which adds to the scheduling impact on start up.

When a problem is identified, the real challenge begins. Utilities must first search out aqualified in-house staff repair vendor or team of vendors. Together, they must thendevelop a repair strategy and implement it. The repair program typically requiresdeveloping or adapting welding and machining systems, developing a mock-up, dem-onstrating the repair, qualifying welders and procedures, and finally implementing therepair. Any one of these steps can be a great challenge that results in significant delays.Only recently have cost-effective repair techniques been demonstrated for the repair of large globe-type valves such as the Y-type Atwood Morrill MSIV found in BWR plants[26, 27]. Repairs to smaller globe valves and all gate- and check-type valves have beenperformed but with varying degrees of success.

This guide provides extensive guidance to the user in identifying a specific repair issue,understanding the repair options, walking through the spe

valve application, maintenance and repair guide

Documents