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Valve Application Maintenance

nd Repair Guide

EPI2

Volume

Effective March 21, 2008, this report has been made publicly available in accordance with Section734.3(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 anylicense agreement from EPRI. This notice supersedes the export control restrictions and any proprietarylicensed material notices embedded in the document prior to publication.

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EPRI • 3412 Hillview Avenue, Palo Alto, California 94304 • PO Box 10412, Palo Alto, California 94303 • USA800.313.3774 • 650.855.2121 • [email protected] • www.epri.com

Valve Application, Maintenance, andRepair Guide

Volume 1TR-105852v1

Final Report, February 1999

EPRI Project ManagerV. Varma

Effective March 21, 2008, this report has been made publicly available in accordance with Section734.3(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 anylicense agreement from EPRI. This notice supersedes the export control restrictions and any proprietarylicensed material notices embedded in the document prior to publication.

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DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIES

THIS PACKAGE WAS PREPARED BY THE ORGANIZATION(S) NAMED BELOW AS AN ACCOUNT OFWORK SPONSORED OR COSPONSORED BY THE ELECTRIC POWER RESEARCH INSTITUTE, INC.(EPRI). NEITHER EPRI, ANY MEMBER OF EPRI, ANY COSPONSOR, THE ORGANIZATION(S) NAMEDBELOW, NOR ANY PERSON ACTING ON BEHALF OF ANY OF THEM:

(A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLIED, (I) WITHRESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEMDISCLOSED IN THIS PACKAGE, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULARPURPOSE, OR (II) THAT SUCH USE DOES NOT INFRINGE ON OR INTERFERE WITH PRIVATELY OWNEDRIGHTS, INCLUDING ANY PARTY'S INTELLECTUAL PROPERTY, OR (III) THAT THIS PACKAGE ISSUITABLE TO ANY PARTICULAR USER'S CIRCUMSTANCE; OR

(B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER (INCLUDINGANY CONSEQUENTIAL DAMAGES, EVEN IF EPRI OR ANY EPRI REPRESENTATIVE HAS BEEN ADVISEDOF THE POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOUR SELECTION OR USE OF THISPACKAGE OR ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED INTHIS PACKAGE.

ORGANIZATION(S) THAT PREPARED THIS PACKAGE

Kalsi Engineering, Inc.

ORDERING INFORMATION

Requests for copies of this package should be directed to the EPRI Distribution Center, 207 Coggins Drive, P.O.Box 23205, Pleasant Hill, CA 94523, (925) 934-4212.

Electric Power Research Institute and EPRI are registered service marks of the Electric Power Research Institute, Inc.EPRI. POWERING PROGRESS is a service mark of the Electric Power Research Institute, Inc.

Copyright © 1999 EPRI, Inc. All rights reserved.

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iii

CITATION

This report was prepared by

Kalsi Engineering, Inc.745 Park Two Dr.Sugarland, TX 77478

Principal InvestigatorsBahir H. EldiwanyDaniel Alvarez

and

EPRI Nuclear Maintenance Applications Center (NMAC)1300 W.T. Harris Blvd.Charlotte, NC 28262

This report describes research sponsored by EPRI. The report is a corporate document

that should be cited in the literature in the following manner:

Valve Application, Maintenance, and Repair Guide, Volume 1, EPRI, Palo Alto, CA: 1998.TR-105852-V1.

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v

REPORT SUMMARY

The Valve Application, Maintenance, and Repair Guide is a two-volume series that providesa generic overview of valve application, selection, maintenance, and repair. Volume 1of the series is a comprehensive reference on the application and use of valves thatprovides guidance on the selection of specific types of valves on the basis of functional

and system requirements. This document is based on an earlier EPRI document (NP-6516, Guide for the Application and Use of Valves in Power Plant Systems). Extensiveillustrations and sample calculations make the guide useful to a wide range of personnel. This volume has been expanded to include general maintenancerequirements and diagnostics for different valve types.

Information on valves and valve operators, where other comprehensive NMACdocuments are available (such as Air Operated Valves, Solenoid Valves, Check Valves, Safetyand Relief Valves, and the Technical Repair Guide series on Limitorque operators), have been referenced without duplicating the contents in this volume.

Background

The improper application, incorrect use, and ineffective maintenance of valves inpower plant systems cause significant losses in plant availability. Over the last severalyears, EPRI, the U.S. NRC, and the electric utilities have conducted many valve andactuator research projects to improve plant safety and availability by reducing valveand actuator problems. These projects resulted in many proprietary and non-proprietary documents that deal with the various specialized areas of valve/actuatorsizing, performance characteristics, maintenance, repair, testing, and diagnostictechniques. However, information to aid plant personnel in resolving these problems isdifficult to glean from scattered sources, and access may be restricted by proprietary

considerations.

Objective

To provide a comprehensive and authoritative guidebook on the application, use, andmaintenance of valves, in which information is readily accessible and understandable by a wide range of plant personnel.

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Approach

The project team was selected from a group of specialists who were heavily involved inrecent valve and actuator research projects. The project team determined the scope of this project using the initial release of this guide (EPRI NP-6516) and all of the

significant reports from the recent research projects. This guide outline was revised toeliminate topics that were either irrelevant or covered in greater depth elsewhere. Thescope of this guide was expanded to include maintenance, troubleshooting, anddiagnostic equipment. An overview of other key documents is provided to assist thereader in quickly finding sources of additional information. Numerous illustrationsand examples of applications, valve sizing, and strategies for use and maintenancewere incorporated to make the guide easier to use.

Results

The guide contains a thorough treatment of the application of valves on the basis of

their functional requirements. It covers gate, globe, butterfly, ball, plug, and diaphragmvalves and manual, hydraulic, and electro-hydraulic actuators, including theirinstallation, operation, maintenance, and most common problems. For other types of valves and actuators not covered in this guide, references to pertinent EPRI/NMACdocuments are given. The guide presents information in a clear and understandablemanner to those with little knowledge of the factors involved in successful valveapplications. For those who have extensive experience with valves and actuators, thisguide provides easy access to specific information that is pertinent to specific needswith references.

EPRI Perspective

Although the information contained in the guide focuses on the application andmaintenance of valves in power plant systems, it is also directly applicable tocomparable system applications in the chemical, petroleum, marine, and similarindustries. The intended audience of the guide includes system designers; engineerswho establish specification requirements for valves; personnel who install, operate,maintain, and repair valves; plant training instructors; and others for whom a more in-depth knowledge of valves could lead to improved valve performance. The guide will be helpful in evaluating valve/actuator applications in existing systems, selecting newand replacement valves/actuators, and developing/updating valve maintenanceprograms and procedures.

Interest Categories

ValvesPlant Support Engineering

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EPRI Li censed Mat eri al

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ACKNOWLEDGMENTS

The original Guide for the Application and Use of Valves in Nuclear Power Plant Systems(NP-6516), published by EPRI in 1990, was developed by Stone & Webster EngineeringCorporation of Massachusetts and Kalsi Engineering, Inc., of Texas. They received widecooperation from experienced nuclear utility personnel and service industries. Thisrevision was created on the solid framework of the earlier publication.

We wish to extend our thanks to the individuals who spent many hours performingdetailed reviews of this revision, so necessary to produce a quality document. Inparticular, we thank Kenneth Hart of Pennsylvania Power & Light for his extensivecomments and input on valve packing and maintenance program issues. Otherreviewers include Chris Hansen of Vermont Yankee, Greg Harttraft of GPU, JohnHolstrom of Duke Engineering Services, Eric Cartwright of PECO, and Jim Wilson andEugene Phillips of Wisconsin Electric Co.

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CONTENTS

1 INTRODUCTION/SUMMARY HOW TO USE THE GUIDEBOOK ....................................... 1-1

1.1 Introduction................................................................................................................... 1-1

1.2 Summary/How to Use the Guidebook........................................................................... 1-2

1.2.1 General .................................................................................................................. 1-2

1.2.2 Valve Functions...................................................................................................... 1-31.2.3 Specific Valve Types by Function .......................................................................... 1-4

1.2.4 Actuator Types....................................................................................................... 1-5

1.2.5 General Design Requirements for Valves and Actuators ....................................... 1-6

1.2.6 Valve Pressure Boundary and Structural Integrity.................................................. 1-6

1.2.7 Valve Maintenance and Inspection Programs........................................................ 1-6

1.2.8 Troubleshooting and Recommended Corrective Actions ....................................... 1-7

1.2.9 Installation, Testing, and Maintenance Requirements............................................ 1-7

1.2.10 Diagnostic Equipment and Methods..................................................................... 1-71.2.11 Valve Selection Chart........................................................................................... 1-7

1.2.12 References and Bibliography ............................................................................... 1-8

1.2.13 Appendices .......................................................................................................... 1-8

2 GENERAL VALVE DESIGN................................................................................................ 2-1

2.1 Nomenclature/Glossary of Terms ................................................................................. 2-1

2.1.1 Introduction ............................................................................................................ 2-1

2.1.2 Glossary of Terms.................................................................................................. 2-1

2.2 Common Valve Construction Features ....................................................................... 2-19

2.2.1 Body-to-Bonnet Connections ............................................................................... 2-20

2.2.2 Seat and Seat Rings ............................................................................................ 2-23

2.2.3 Disc-to-Stem Connection ..................................................................................... 2-34

2.2.4 Disc/Stem Guide Arrangements........................................................................... 2-35

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2.3 Accessories and Special Features.............................................................................. 2-37

2.3.1 Manual Override Handwheels or Levers .............................................................. 2-37

2.3.2 Stem Leak-Off Connection................................................................................... 2-39

2.3.3 Limit Switch.......................................................................................................... 2-40

2.3.4 Internal and External Bypass ............................................................................... 2-40

2.3.5 Remote Position Sensor ...................................................................................... 2-41

2.3.6 Bonnet Extension................................................................................................. 2-41

2.3.7 Impact, Hammerblow, and Chain-Operated Handwheels .................................... 2-42

2.3.8 Stem Backseating Feature................................................................................... 2-42

2.3.9 Fire Safety Feature .............................................................................................. 2-43

2.4 Valve Trim................................................................................................................... 2-43

2.4.1 Trim Components and Materials .......................................................................... 2-43

2.4.2 Design Practices to Minimize Corrosion............................................................... 2-45

2.4.3 Design Practices to Minimize Erosion .................................................................. 2-47

2.4.4 Design Practices to Minimize Wear and Galling................................................... 2-49

2.4.5 Cobalt-Free Alloys for Hard-Surfacing of Trim...................................................... 2-52

2.4.6 Design Practices to Minimize the Effects of Temperature .................................... 2-54

2.5 Valve Stem Seals ....................................................................................................... 2-55

2.5.1 Flexible Metal Seals ............................................................................................. 2-56

2.5.2 Valve Stem Packings ........................................................................................... 2-59

2.6 Gasket Types and Materials ....................................................................................... 2-77

2.6.1 Gasket Types....................................................................................................... 2-77

2.6.2 Flat Metal Gaskets ............................................................................................... 2-81

2.6.3 Flat Non-Metallic and Metal Clad Gaskets ........................................................... 2-81

2.6.4 Spiral Wound Gaskets ......................................................................................... 2-81

3 FUNCTIONAL REQUIREMENTS OF VALVES................................................................... 3-1

3.1 General......................................................................................................................... 3-1

3.2 Isolation Valves............................................................................................................. 3-3

3.3 Modulating/Throttling Valves......................................................................................... 3-5

3.4 Pressure Relief Valves.................................................................................................. 3-8

3.5 Check Valves.............................................................................................................. 3-10

4 GATE VALVES ................................................................................................................... 4-1

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4.1 Introduction and Application ......................................................................................... 4-1

4.2 Design........................................................................................................................... 4-1

4.2.1 General .................................................................................................................. 4-1

4.2.2 Solid Wedge........................................................................................................... 4-3

4.2.3 Flexible Wedge ...................................................................................................... 4-5

4.2.4 Split Wedge............................................................................................................ 4-6

4.2.5 Parallel-Expanding Gate ........................................................................................ 4-8

4.2.6 Parallel Slide Double-Disc.................................................................................... 4-11

4.2.7 Westinghouse Flexible Wedge............................................................................. 4-13

4.2.8 Slab Gate............................................................................................................. 4-15

4.2.9 Pressure Locking in Gate Valves ......................................................................... 4-17

4.2.10 Options to Mitigate Pressure Locking in Gate Valves ........................................ 4-21

4.2.11 Thermal Binding in Wedge Gate Valves ............................................................ 4-21

4.3 Installation Practices................................................................................................... 4-23

4.4 Operation Practices and Precautions ......................................................................... 4-24

4.5 Common Problems ..................................................................................................... 4-24

4.6 Maintenance Methods ................................................................................................ 4-27

4.7 Recent Improvements in Flexible Wedge Gate Valve Designs................................... 4-28

5 GLOBE VALVES—ISOLATION FUNCTION....................................................................... 5-1


5.2 Design........................................................................................................................... 5-1

5.3 Installation Practices..................................................................................................... 5-5

5.4 Operation Practices and Precautions ........................................................................... 5-5

5.5 Common Problems ....................................................................................................... 5-5

5.6 Maintenance Methods .................................................................................................. 5-6

6 GLOBE VALVES—MODULATING/THROTTLING FUNCTION .......................................... 6-1


6.1.1 General .................................................................................................................. 6-1

6.1.2 System Differential Pressure versus Control Valve Differential Pressure............... 6-2

6.1.3 High Pressure Drop Applications ........................................................................... 6-8

6.2 Design........................................................................................................................... 6-8

6.2.1 General .................................................................................................................. 6-8

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6.2.2 Single-Port (Single-Seated) Valves........................................................................ 6-8

6.2.3 Double-Port (Double-Seated) Valves ................................................................... 6-10

6.2.4 Cage-Style Valves: Balanced and Unbalanced.................................................... 6-12

6.2.5 Angle Valves ........................................................................................................ 6-13

6.2.6 Y-Style Valves...................................................................................................... 6-13

6.2.7 Three-Way Valves................................................................................................ 6-14

6.2.8 High Pressure Drop Service Control Valves......................................................... 6-15

6.2.9 Flow Characteristics ............................................................................................. 6-18

6.2.10 Rangeability ....................................................................................................... 6-27

6.2.11 Stability .............................................................................................................. 6-28



6.5 Common Problems ..................................................................................................... 6-31


7 BUTTERFLY VALVES—ISOLATION FUNCTION .............................................................. 7-1


7.2 Design........................................................................................................................... 7-4

7.2.1 General .................................................................................................................. 7-4

7.2.2 Symmetric (Lens Type) Disc with Concentric Shaft................................................ 7-7

7.2.3 Nonsymmetric Disc with Single Offset Shaft .......................................................... 7-9

7.2.4 Nonsymmetric Disc with Double Offset Shaft....................................................... 7-11

7.2.5 Nonsymmetric Disc with Triple Offset Design....................................................... 7-11

7.2.6 Special Disc ......................................................................................................... 7-12

7.2.7 Valve Shaft, Shaft Connections, and Seal ........................................................... 7-13

7.2.8 Valve Bearings..................................................................................................... 7-14

7.2.9 Valve Seats.......................................................................................................... 7-15


7.3.1 Valve-to-Pipe Connections................................................................................... 7-19

7.3.2 Valve Orientation.................................................................................................. 7-19

7.3.3 Valve Location ..................................................................................................... 7-19

7.3.4 Shaft Orientation .................................................................................................. 7-21


7.5 Common Problems ..................................................................................................... 7-22

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8 BUTTERFLY VALVES—MODULATING/THROTTLING FUNCTION.................................. 8-1


8.2 Hydrodynamic Torque Characteristics .......................................................................... 8-28.3 Effect of Hydraulic System Characteristics on Peak Hydrodynamic Torque ................ 8-3

8.4 Torque Characteristics of Butterfly Valves.................................................................... 8-5

8.5 Common Problems ....................................................................................................... 8-7


9 BALL VALVES—ISOLATION FUNCTION.......................................................................... 9-1


9.2 Design and Materials .................................................................................................... 9-1

9.2.1 General .................................................................................................................. 9-1

9.2.2 Floating Ball ........................................................................................................... 9-2

9.2.3 Trunnion Mounted Ball ........................................................................................... 9-4

9.2.4 Wedged Ball........................................................................................................... 9-6

9.3 Installation Practices..................................................................................................... 9-8

9.4 Operation Practices and Precautions ........................................................................... 9-8

9.5 Common Problems ....................................................................................................... 9-8


10 BALL VALVES—MODULATING/THROTTLING FUNCTION ......................................... 10-1

10.1 Introduction and Application ..................................................................................... 10-1

10.2 Design....................................................................................................................... 10-1

10.3 Installation Practices................................................................................................. 10-4

10.4 Operation Practices and Precautions ....................................................................... 10-4

10.5 Common Problems ................................................................................................... 10-5

10.6 Maintenance Methods .............................................................................................. 10-5

11 PLUG VALVES ............................................................................................................... 11-1


11.2 Design....................................................................................................................... 11-1



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11.5 Common Problems ................................................................................................... 11-4


12 DIAPHRAGM VALVES—ISOLATION FUNCTION ......................................................... 12-1

12.1 Introduction and Application ..................................................................................... 12-112.2 Design....................................................................................................................... 12-1



12.5 Common Problems ................................................................................................... 12-4


13 VALVE ACTUATORS—GENERAL INFORMATION....................................................... 13-1

13.1 General..................................................................................................................... 13-1

13.2 Actuator Types.......................................................................................................... 13-4

13.2.1 Manual Actuators ............................................................................................... 13-4

13.2.2 Motorized Actuators ........................................................................................... 13-4

13.2.3 Pneumatic Actuator............................................................................................ 13-7

13.2.4 Hydraulic Actuators ............................................................................................ 13-8

13.2.5 Electrohydraulic Actuators................................................................................ 13-11

13.2.6 Solenoid Actuator............................................................................................. 13-11

13.2.7 Process Medium Actuators .............................................................................. 13-13

13.3 Considerations in Actuator Selection ...................................................................... 13-13

14 MANUAL ACTUATORS .................................................................................................. 14-1


14.2 Design Considerations.............................................................................................. 14-3

14.2.1 Operating Force ................................................................................................. 14-3

14.2.2 Lever Position Control........................................................................................ 14-3

14.2.3 Chain-Wheel Operators...................................................................................... 14-3

14.2.4 Hammerblow or Impact Handwheels.................................................................. 14-414.2.5 Gear Operators .................................................................................................. 14-4



14.5 Common Problems ................................................................................................... 14-5


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15 GENERAL DESIGN REQUIREMENTS FOR VALVES AND ACTUATORS.................... 15-1

15.1 Introduction............................................................................................................... 15-1

15.2 Fluid Parameters....................................................................................................... 15-2

15.2.1 Introduction ........................................................................................................ 15-2

15.2.2 Flow Media......................................................................................................... 15-2

15.2.3 Pressure/Temperature ....................................................................................... 15-3

15.2.4 Velocity .............................................................................................................. 15-3

15.2.5 Viscosity............................................................................................................. 15-4

15.2.6 Density, Specific Gravity .................................................................................... 15-4

15.2.7 Radiation............................................................................................................ 15-4

15.2.8 System Contaminants ........................................................................................ 15-4

15.3 Operating Modes and Transients.............................................................................. 15-5

15.3.1 Introduction ........................................................................................................ 15-5

15.3.2 Plant Condition................................................................................................... 15-5

15.3.3 System Condition ............................................................................................... 15-7

15.4 Fluid Transients ........................................................................................................ 15-9

15.4.1 General .............................................................................................................. 15-9

15.4.2 System Fluid Transients..................................................................................... 15-9

15.4.3 Fluid Transients Caused by Valves.................................................................. 15-11

15.5 Environmental Considerations and Natural Hazards .............................................. 15-13

15.5.1 Introduction ...................................................................................................... 15-13

15.5.2 Environmental Conditions ................................................................................ 15-14

15.6 Valve Performance Requirements .......................................................................... 15-17

15.6.1 Introduction ...................................................................................................... 15-17

15.6.2 Speed of Operation or Stroke Time.................................................................. 15-17

15.6.3 Flow Rate and Pressure Drop.......................................................................... 15-18

15.6.4 Leak Rate......................................................................................................... 15-18

15.6.5 Frequency of Operation ................................................................................... 15-19

15.6.6 Nuclear Valve Qualification .............................................................................. 15-19

16 PRESSURE CONTAINMENT AND STRUCTURAL INTEGRITY REQUIREMENTS....... 16-1

16.1 Introduction............................................................................................................... 16-1

16.2 Codes and Standards ............................................................................................... 16-1

16.2.1 General .............................................................................................................. 16-1

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16.2.2 Pressure/Temperature Ratings .......................................................................... 16-5

16.2.3 Codes and Standards for Pressure Relief Valves............................................ 16-11

16.3 Materials ................................................................................................................. 16-12

16.3.1 Material Compatibility ....................................................................................... 16-12

16.3.2 General Discussion of Pressure Boundary Materials ....................................... 16-12

16.3.3 Body Materials ................................................................................................. 16-15

16.3.4 Special Considerations for Material Selection for Valves in Raw Water,Especially Seawater.................................................................................................... 16-17

16.4 Corrosion Allowance............................................................................................... 16-19

16.5 Valve End Connections .......................................................................................... 16-22

16.5.1 General ............................................................................................................ 16-22

16.5.2 Threaded Ends ................................................................................................ 16-22

16.5.3 Welding Ends................................................................................................... 16-2316.5.4 Brazing Ends.................................................................................................... 16-25

16.5.5 Solder Ends ..................................................................................................... 16-25

16.5.6 Flanged Ends................................................................................................... 16-25

16.5.7 Flared Ends...................................................................................................... 16-27

16.5.8 Hub Ends (Bell and Spigot).............................................................................. 16-27

16.6 System/Valve Interactions ...................................................................................... 16-27

16.6.1 General ............................................................................................................ 16-27

16.6.2 Pipeline End Loads .......................................................................................... 16-27

16.6.3 Leakage ........................................................................................................... 16-28

16.6.4 Vibration........................................................................................................... 16-28

16.7 Shop Tests.............................................................................................................. 16-29

16.8 Structural Integrity and Valve Operability................................................................ 16-30

17 VALVE MAINTENANCE AND INSPECTION PROGRAMS ............................................ 17-1

17.1 Introduction............................................................................................................... 17-1

17.2 Definitions................................................................................................................. 17-2

17.3 Objective and Scope of Valve Maintenance Programs............................................. 17-2

17.3.1 Objective and Maintenance Philosophy ............................................................. 17-3

17.3.2 The Maintenance Rule (MR) .............................................................................. 17-3

Methodology to Select Plant SCCs to Be in the MR Scope ...................................... 17-4

Establishing Criteria and Goals ................................................................................. 17-4

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Maintenance Preventable Functional Failures (MPFFs)............................................ 17-5

Controlling Equipment Removal of Service ............................................................... 17-5

Periodic Effectiveness Assessment........................................................................... 17-5

17.3.3 Scope................................................................................................................. 17-5

17.4 Valve Maintenance Group ........................................................................................ 17-6

17.5 Valve Categorization and Prioritization ..................................................................... 17-7

17.6 Coordination between Maintenance Group and Other Groups................................. 17-9

17.7 Involvement of Valve Maintenance Group with Other Activities................................ 17-9

17.8 Inspection Frequency and Scope ........................................................................... 17-10

17.9 Maintenance Schedule ........................................................................................... 17-10

17.10 Spare Parts Inventory and Control........................................................................ 17-11

18 TROUBLESHOOTING AND RECOMMENDED CORRECTIVE ACTIONS ..................... 18-1

18.1 Introduction............................................................................................................... 18-1

18.2 Gate Valve Problems................................................................................................ 18-3

18.2.1 Solid, Flex, and Split Wedge Gate Valve Problems ........................................... 18-3

18.2.1.1 Excessive Packing Leaks............................................................................ 18-3

18.2.1.2 Valve Will Not Respond to the Actuation Signal.......................................... 18-4

18.2.1.3 Valve Will Not Fully Open............................................................................ 18-6

18.2.1.4 Valve Will Not Fully Close or Properly Seat................................................. 18-6

18.2.1.5 Excessive Flange Leaks.............................................................................. 18-7

18.2.2 Double-Disc Gate Valve Problems..................................................................... 18-8

18.2.2.1 Excessive Packing Leaks............................................................................ 18-8

18.2.2.2 Valve Will Not Respond to the Actuation Signal.......................................... 18-8

18.2.2.3 Valve Will Not Fully Open............................................................................ 18-9

18.2.2.4 Valve Will Not Fully Close or Properly Seat................................................. 18-9

18.2.2.5 Excessive Flange Leaks.............................................................................. 18-9

18.2.3 Westinghouse Gate Valve Problems.................................................................. 18-9

18.3 Globe Valve Problems ............................................................................................ 18-10

18.3.1 Excessive Packing Leaks................................................................................. 18-10

18.3.2 Valve Will Not Respond to the Actuation Signal............................................... 18-10

18.3.3 Valve Will Not Fully Open................................................................................. 18-10

18.3.4 Valve Will Not Fully Close or Properly Seat...................................................... 18-11

18.3.5 Excessive Flange Leaks .................................................................................. 18-11

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18.4 Butterfly and Ball Valve Problems........................................................................... 18-11

18.4.1 Excessive Packing Leaks................................................................................. 18-11

18.4.2 Valve Will Not Respond to the Actuation Signal............................................... 18-12

18.4.3 Valve Will Not Fully Open................................................................................. 18-13

18.4.4 Valve Will Not Fully Close or Properly Seat...................................................... 18-13

18.4.5 Excessive Flange Leaks .................................................................................. 18-14

18.5 Plug Valve Problems............................................................................................... 18-14

18.6 Diaphragm Valve Problems .................................................................................... 18-15

18.7 Inspection and Repair Checklists:........................................................................... 18-15

19 INSTALLATION, TESTING, AND MAINTENANCE REQUIREMENTS........................... 19-1

19.1 Introduction............................................................................................................... 19-1

19.2 Installation Requirements ......................................................................................... 19-119.2.1 General Valve Installation Requirements ........................................................... 19-1

19.2.2 Bypasses ........................................................................................................... 19-3

19.3 Testing and Inspection Considerations..................................................................... 19-5

19.3.1 Shop Performance Testing ................................................................................ 19-5

19.3.2 Pre-Operational Tests ........................................................................................ 19-6

19.3.3 In-Service Test Requirements............................................................................ 19-6

19.4 Maintenance Requirements.................................................................................... 19-15

19.4.1 Separation and Maintenance ........................................................................... 19-15

19.4.2 General Good Maintenance Practices ............................................................. 19-22

20 DIAGNOSTIC EQUIPMENT AND METHODS................................................................. 20-1

20.1 Introduction............................................................................................................... 20-1

20.2 Equipment................................................................................................................. 20-2

20.2.1 Boroscopes ........................................................................................................ 20-2

20.2.2 Radiography....................................................................................................... 20-2

20.2.3 Acoustics............................................................................................................ 20-2

20.2.4 Temperature Monitoring..................................................................................... 20-3

20.2.5 Ultrasonics ......................................................................................................... 20-3

20.2.6 Stem Thrust/Torque Measurement Devices....................................................... 20-4

20.3 Methods for Measuring Stem Thrust/Torque ............................................................ 20-4

20.3.1 Spring Pack Displacement ................................................................................. 20-4

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20.3.2 Strain Measurement of the Yoke Legs............................................................... 20-5

20.3.3 Strain Measurement of the Stem........................................................................ 20-5

20.3.4 Load Measurement at the Actuator Base........................................................... 20-6

20.3.5 Electric Motor Power Monitor ............................................................................. 20-7

20.3.6 Diaphragm/Piston Pressure ............................................................................... 20-7

20.3.7 Data Acquisition ................................................................................................. 20-7

20.4 Summary .................................................................................................................. 20-8

21 VALVE SELECTION GUIDELINE CHARTS ................................................................... 21-1

22 REFERENCES AND BIBLIOGRAPHY............................................................................ 22-1

22.1 EPRI / NMAC Reports .............................................................................................. 22-1

22.2 Proprietary Documents Developed under EPRI MOV Performance Prediction

Program............................................................................................................................ 22-3

22.3 Proprietary Documents Developed under Utility-Sponsored Generic Thrust andTorque Overload Qualification Program for Limitorque Actuators.................................... 22-4

22.4 NRC Generic Letters, Information Notices, and Related References ....................... 22-6

22.5 Books, Magazines, Technical Meetings, and Journal Articles .................................. 22-8

22.6 Codes and Standards ............................................................................................. 22-13

23 APPENDIX A: RECENT ADVANCES IN VALVE AND ACTUATOR TECHNOLOGY..... 23-1

23.1 Introduction............................................................................................................... 23-1

23.2 Background............................................................................................................... 23-1

23.3 Motor-Operated Valve Performance Prediction Methodology................................... 23-2

23.3.1 System Flow Model............................................................................................ 23-3

23.3.2 Solid and Flex Wedge Gate Valve Model........................................................... 23-3

23.3.3 Methodologies for Special Design Gate Valves ................................................. 23-6

23.3.4 Butterfly Valve Model ......................................................................................... 23-6

23.3.5 Globe Valve Model............................................................................................. 23-7

23.4 EPRI/NMAC Application and Maintenance Guides................................................... 23-7

23.5 Generic Thrust and Torque Qualification Program for Limitorque Actuators.......... 23-14

23.5.1 Background...................................................................................................... 23-14

23.5.2 Technical Approach ......................................................................................... 23-15

23.5.3 Highlights of Results and Conclusions ............................................................. 23-16

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24 APPENDIX B: CONTROL VALVE SIZING METHODS AND EXAMPLES...................... 24-1

24.1 General Methods, Definitions, and Evaluation.......................................................... 24-1

24.1.1 Introduction to Control Valve Specification, Sizing, and Selection ..................... 24-1

24.1.2 Definitions .......................................................................................................... 24-2

24.1.3 Sizing Formulas and Procedures for Liquid Flow ............................................... 24-9

24.1.4 Sizing Formulas and Procedures for Gas Flow................................................ 24-29

24.2 Examples of Sizing for Special High Pressure Drop Applications ........................... 24-42

24.2.1 Feedwater Recirculation................................................................................... 24-42

24.2.2 Atmospheric Steam Dump and Turbine Bypass............................................... 24-47

24.2.3 Attemperator Spray Control.............................................................................. 24-50

24.2.4 Deaerator Level Control ................................................................................... 24-52

24.2.5 Feedwater Pump Flow Control......................................................................... 24-56

25 APPENDIX C: VALVE PROCUREMENT SPECIFICATION............................................ 25-1

25.1 General..................................................................................................................... 25-1

25.2 Specific Elements ..................................................................................................... 25-2

25.3 Data Sheets.............................................................................................................. 25-6

26 APPENDIX D: TRANSLATED TABLE OF CONTENTS................................................... 26-1

26.1 Français (French)....................................................................................................... 26-2

26.2 (Japanese)............................................................................................................... 26-14

26.3 Español (Spanish).................................................................................................... 26-24

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LIST OF FIGURES

Figure 2-1 Globe Valve Typical Valve Nomenclature.............................................................. 2-2

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

Figure 2-3 Screwed Bonnet .................................................................................................. 2-20

Figure 2-4 Flanged (Bolted) Bonnet...................................................................................... 2-21

Figure 2-5 Welded Bonnet.................................................................................................... 2-22

Figure 2-6 Pressure-Sealed Bonnet ..................................................................................... 2-22

Figure 2-7 Seat Joint Mating Surfaces (Lay of Roughness Concentric) ............................... 2-23

Figure 2-8 Seat Plane Distortion under Vertical and Horizontal Bending Moments .............. 2-24

Figure 2-9 Typical Globe Valve Seating Configurations ....................................................... 2-27

Figure 2-10 Cross Ring Indentation ...................................................................................... 2-28

Figure 2-11 Soft Seat Retention Methods............................................................................. 2-29

Figure 2-12 Methods for Attaching Seat to Body.................................................................. 2-31

Figure 2-13 Flexible Seat...................................................................................................... 2-32

Figure 2-14 Floating Seat ..................................................................................................... 2-32

Figure 2-15 Spring-Loaded Packing Seals ........................................................................... 2-33

Figure 2-16 Stem Connections ............................................................................................. 2-34

Figure 2-17 Gate Valve Gate Guide ..................................................................................... 2-36

Figure 2-18 Manual Override Lever on Pressure-Relief Valve.............................................. 2-38

Figure 2-19 Manual Override Handwheel on Motor-Operated Valve .................................... 2-38

Figure 2-20 Steam Leak-Off Connection .............................................................................. 2-39

Figure 2-21 External Bypass................................................................................................. 2-41

Figure 2-22 Bonnet Extension .............................................................................................. 2-42

Figure 2-23 Trim Components .............................................................................................. 2-44

Figure 2-24 Bellows Seal...................................................................................................... 2-56

Figure 2-25 Bellows on Butterfly Valve ................................................................................. 2-57

Figure 2-26 Metal Diaphragm Stem Seal.............................................................................. 2-58

Figure 2-27 Basic Types of Stem Seals................................................................................ 2-60

Figure 2-28 Packing Gland Details ....................................................................................... 2-62

Figure 2-29 Distribution of Stresses in the Packing and Location of Actual Sealing Point.... 2-63

Figure 2-30 Live Loading of Valve Packing Using Disc Springs ........................................... 2-73

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Figure 2-31 Packing Compressive Stress Versus Consolidation .......................................... 2-74

Figure 2-32 Lantern Ring / Stem Leakoff Connection........................................................... 2-76

Figure 3-1 Valve Classification by Function ............................................................................ 3-2

Figure 4-1 Inside Screw Stem Thread Configurations ............................................................ 4-2

Figure 4-2 Rising Stem Design, Outside Screw...................................................................... 4-2Figure 4-3 Wedge Gate Valve ................................................................................................ 4-4

Figure 4-4 Anchor/Darling Double-Disc Gate Valve ................................................................ 4-8

Figure 4-5 W-K-M Through-Conduit Double-Wedge Parallel Expanding Gate Valve ............. 4-9

Figure 4-6 Parallel Slide Double-Disc Gate Valve................................................................. 4-11

Figure 4-7 Through-Conduit Parallel Slide Double-Disc Gate Valve..................................... 4-12

Figure 4-8 Westinghouse Flexible Wedge Gate Valve ......................................................... 4-14

Figure 4-9 Slab Gate Valve .................................................................................................. 4-16

Figure 4-10 Gate Valve Bonnet Overpressurization ............................................................. 4-18

Figure 4-11 Typical Seat and Guide Damage Locations in Conventional Flexible WedgeGate Valves Under High Flow Conditions..................................................................... 4-25

Figure 5-1 T-Pattern Globe Valve ........................................................................................... 5-2

Figure 5-2 Angle-Pattern Globe Valve .................................................................................... 5-2

Figure 5-3 Y-Pattern Globe Valve........................................................................................... 5-3

Figure 5-4 Velan 2" (5.1 cm), 1500# Globe Valve (Guide-Based) Model: Figure No.137132............................................................................................................................ 5-4

Figure 6-1 Pressure Drop Through a Control Valve at Minimum, Design, and MaximumSystem Flows.................................................................................................................. 6-2

Figure 6-2 Control Valve Sizing Example ............................................................................... 6-5

Figure 6-3 Single-Port Control Valve ...................................................................................... 6-9Figure 6-4 Double-Seated Globe Valve................................................................................ 6-11

Figure 6-5 Balanced Disc Cage Style Valve ......................................................................... 6-13

Figure 6-6 Y-Style Body Valve.............................................................................................. 6-14

Figure 6-7 Three-Way Valve for Flow Diverting Service Unbalanced Disc ........................... 6-14

Figure 6-8 Three-Way Valve, Balanced Plug........................................................................ 6-15

Figure 6-9 Low Noise, Anti-Cavitation Trim........................................................................... 6-16

Figure 6-10 High Pressure Drop Multiple Step Plug and Cage............................................. 6-17

Figure 6-11 High Pressure Drop Control Valve, Labyrinth Design........................................ 6-18

Figure 6-12 Inherent Flow Curves for Various Valve Plugs with Constant Delta P Acrossthe Valve....................................................................................................................... 6-19

Figure 6-13 Comparison of Installed Characteristics versus Inherent Characteristics .......... 6-20

Figure 6-14 Typical Pump Characteristics ............................................................................ 6-22

Figure 6-15 Flow Schematic without Piping Losses.............................................................. 6-22

Figure 6-16 Installed Characteristics without Piping Losses................................................. 6-24

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Figure 6-17 Flow Schematic with Piping Losses................................................................... 6-25

Figure 6-18 Installed Characteristics with Piping Losses ...................................................... 6-27

Figure 6-19 Force Balance Diagram for Control Valves........................................................ 6-29

Figure 7-1 Typical Motor-Operated Butterfly Valve................................................................. 7-2

Figure 7-2 Most Common Butterfly Valve Disc Shapes Used in Nuclear Power Plants.......... 7-5Figure 7-3 Typical Variations in Butterfly Disc Designs........................................................... 7-6

Figure 7-4 Typical Symmetric Disc Design with Elastomer Lined Body .................................. 7-8

Figure 7-5 Cross-Section of a Typical Nonsymmetric Butterfly Valve ................................... 7-10

Figure 7-6 Valve Disc Flow Orientation Terminology............................................................ 7-11

Figure 7-7 Triple Offset Butterfly Valve................................................................................. 7-12

Figure 7-8 Fishtail Disc ......................................................................................................... 7-13

Figure 7-9 Special Disc Design for Noise and Cavitation Reduction..................................... 7-13

Figure 7-10 Typical Seat Designs ......................................................................................... 7-16

Figure 7-11 Inflatable Seat Butterfly Valve ........................................................................... 7-17Figure 7-12 Effect of Upstream Disturbance, Shaft Orientation, and Disc Opening

Direction on Hydrodynamic Torque............................................................................... 7-20

Figure 7-13 Hydrostatic Torque Component in a Horizontal Shaft Installation...................... 7-21

Figure 8-1 Flow Through a Symmetric Disc Butterfly Valve .................................................... 8-2

Figure 8-2 Variation in Location of Peak Hydrodynamic Torque for Constant Head andPumped Systems ............................................................................................................ 8-4

Figure 8-3 Typical Opening Torque Characteristics of a Symmetric Disc Butterfly Valveunder High Flow Conditions ............................................................................................ 8-6

Figure 9-1 Floating Ball........................................................................................................... 9-4

Figure 9-2 Trunnion-Mounted Ball .......................................................................................... 9-5Figure 9-3 Wedged Ball Design .............................................................................................. 9-7

Figure 10-1 Eccentric Rotating Plug/Ball Control Valve........................................................ 10-2

Figure 10-2 Segmented Ball with Tubular Resistance Trim .................................................. 10-3

Figure 10-3 Multistage Anticavitation Ball Valve ................................................................... 10-4

Figure 11-1 Nonlubricated Plug Valve .................................................................................. 11-2

Figure 11-2 Lubricated Plug Valve........................................................................................ 11-2

Figure 11-3 Lubricated Tapered Plug Valve ......................................................................... 11-3

Figure 12-1 Saunders Pattern Flexible Diaphragm Valve..................................................... 12-2

Figure 12-2 Straightway Flexible Diaphragm Valve.............................................................. 12-3Figure 12-3 Full Bore Body Flexible Diaphragm Valve ......................................................... 12-3

Figure 13-1 Types of Valve Actuators................................................................................... 13-2

Figure 13-2 Limitorque SMB-0 Motor Operator Cutaway View ............................................. 13-5

Figure 13-3 Simplified Motor Operator.................................................................................. 13-6

Figure 13-4 Hydraulic Actuator with Fail-Safe Operation Using a Mechanical Spring........... 13-9

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Figure 13-5 Hydraulic Actuator with Fail-Safe Operation Using a Gas Spring .................... 13-10

Figure 13-6 Solenoid Actuator ............................................................................................ 13-12

Figure 14-1 Manual Lever..................................................................................................... 14-1

Figure 14-2 Worm Gear Actuator.......................................................................................... 14-2

Figure 16-1 Butt Weld End Connection .............................................................................. 16-24Figure 16-2 Socket Weld End Connection.......................................................................... 16-24

Figure 16-3 Butterfly Valve End Connections ..................................................................... 16-26

Figure 19-1 Test Valve Arrangement for Maintained Flowrate Test...................................... 19-9

Figure 19-2 Globe Valve Reverse Air Test (Test Pressure Under Seat)............................. 19-10

Figure 19-3 Globe Valve Reverse Air Test (Test Pressure Above Seat) ............................ 19-11

Figure 19-4 Gate Valve Reverse Air Test (With Body Vent Test Connection) .................... 19-12

Figure 19-5 Gate Valve Through Body Air Test (LOCA pushes disc toward outboardseat. Through body pressurization measures leakage by both seats.) ....................... 19-12

Figure 19-6 Required Valve Maintenance Clearance for Typical Installation...................... 19-19

Figure 19-7 Required Maintenance Clearance for Chain-Operated Valve.......................... 19-20

Figure 19-8 Human Factors Clearance-General................................................................. 19-21

Figure 21-1 Valve Selection Chart (This figure is located in a pouch inside the backcover of this report.) ...................................................................................................... 21-1

Figure 23-1 Tilted Disc Contact Mode Resulting in Point Contact with the DownstreamSeat............................................................................................................................... 23-5

Figure 23-2 Limitorque Actuator Test Fixture...................................................................... 23-15

Figure 24-1 Pressure Profile of Fluid Passing through a Valve............................................. 24-3

Figure 24-2 Pressure Profile through Restriction.................................................................. 24-4

Figure 24-3 Effects of Vaporization....................................................................................... 24-5Figure 24-4 Globe Valve F

L Values..................................................................................... 24-11

Figure 24-5 High Performance Butterfly/Ball FL Values....................................................... 24-12

Figure 24-6 Liquid Critical Pressure Ratio Factor Curve..................................................... 24-13

Figure 24-7 Globe Valve Liquid Incipient Cavitation Factor (Fi) Values .............................. 24-17

Figure 24-8 Reynolds Number Factor ................................................................................. 24-18

Figure 24-9 Compressibility Factors for Gases with Reduced Pressures from 0 to 40 ....... 24-34

Figure 24-10 Compressibility Factors for Gases with Reduced Pressures from 0 to 6 ....... 24-35

Figure 24-11 Conventional Method of Recirculation Control: Control Valve (On-Off) in

Series with a Breakdown Orifice ................................................................................. 24-44Figure 24-12 Method of Recirculation Control Using High Pressure, Modulating Anti-

Cavitation Valve .......................................................................................................... 24-44

Figure 24-13 Globe Angle Control Valve with Anti-Cavitation Trim..................................... 24-45

Figure 24-14 Globe Control Valve with Low Noise Trim ..................................................... 24-48

Figure 24-15 Typical Condensate System.......................................................................... 24-53

Figure 24-16 Typical Condensate System Curve ............................................................... 24-54

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Figure 24-17 Globe Control Valve with Anti-Cavitation Variable Resistance Trim .............. 24-54

Figure 24-18 Main Feedwater System................................................................................ 24-57

Figure 25-1 Suggested Manual Valve Data Sheet by Purchaser.......................................... 25-8

Figure 25-2 Suggested Manual Valve Data Sheet by Bidder/Seller ................................... 25-11

Figure 25-3 Suggested Motor-Operated Valve Data Sheet by Purchaser .......................... 25-13Figure 25-4 Suggested Motor-Operated Valve Data Sheet by Bidder/Seller...................... 25-17

Figure 25-5 Control Valve Data Sheet................................................................................ 25-20

Figure 25-6 Relief Valve Data Sheet .................................................................................. 25-24

Figure 25-7 Rupture Disc Data Sheet................................................................................. 25-26

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LIST OF TABLES

Table 2-1 Corrosion Ranking for Materials Selection............................................................ 2-46

Table 2-2 Critical Variables for Accelerated Erosion-Corrosion ............................................ 2-49

Table 2-3 Chart of Wear and Galling Resistance of Material Combinations ......................... 2-52

Table 2-4 Typical Properties of Plastics and Elastomers Used in Valves for Soft Seats,Seals, and Gaskets...................................................................................................... 2-68

Table 2-5 Typical Radiation Resistance of Plastics .............................................................. 2-70

Table 2-6 Gasket Materials and Contact Facings, Gasket Factors M for OperatingConditions, and Minimum Design Seating Stress y...................................................... 2-79

Table 3-1 Control Valve Seat Leakage Classifications (In Accordance with ANSI/FCI70-2-1976........................................................................................................................ 3-6

Table 3-2 Seat Leakage Criteria............................................................................................. 3-7

Table 6-1 Valve Cv and Pressure as a Function of Flow Rate without Line Losses .............. 6-23

Table 6-2 Valve Cv and Pressure as a Function of Flow Rate with Line Losses ................... 6-26

Table 13-1 Normal Application of Power Actuators for Valves.............................................. 13-3

Table 14-1 Maximum Recommended Rim Pull as a Function of Handwheel Diameter ........ 14-3

Table 16-1 Valve Design Codes........................................................................................... 16-2Table 16-2 Typical Valve Standards ..................................................................................... 16-3

Table 16-3 Safety Classes and Applicable Standards.......................................................... 16-5

Table 16-4 Pressure/Temperature Ratings for Steel Valves. Source: ANSI B 16.34 -1981.............................................................................................................................. 16-6

Table 16-5 Cast Iron Gate Valve Ratings Source: MSS-SP-70 ............................................ 16-8

Table 16-6 Bronze Gate, Globe, and Check Valve Ratings Source: MSS-SP-80................. 16-9

Table 16-7 Commonly Used Pressure Boundary Materials ................................................ 16-13

Table 18-1 Inspection Checklist for Solid and Flexible Wedge Gate Valves....................... 18-17

Table 18-2 Inspection Checklist for Butterfly Valves........................................................... 18-25

Table 19-1 Valve Maintenance Clearance Data ................................................................. 19-16

Table 20-1 Comparison of Selected Diagnostic Methods..................................................... 20-9

Table 21-1 Valve Selection Matrix ........................................................................................ 21-2

Table 24-1 Typical Valve Recovery Coefficients (FL) and Incipient Cavitation Factors (F

i) . 24-10

Table 24-2 Typical Critical Pressure Values ....................................................................... 24-14

Table 24-3 Typical Values of Cv: Globe Valve, Flow over the Seat..................................... 24-20

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Table 24-4 Typical Values of Cv: Globe Valve, Flow under the Seat .................................. 24-21

Table 24-5 Typical Piping Geometry Factors, Fp : Valve with both Reducer and

Expander..................................................................................................................... 24-22

Table 24-6 Typical Piping Geometry Factors, Fp: Valve with Outlet Expander Only ........... 24-23

Table 24-7 Terminal Pressure Drop Ratios (xT)................................................................... 24-31

Table 24-8 Gas Physical Data ............................................................................................ 24-32

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1-1

1INTRODUCTION/SUMMARY HOW TO USE THE

GUIDEBOOK

1.1 Introduction

The purpose of this guide is to present, in a comprehensive manner, information andmethods that have been successfully utilized in the application, use, maintenance, andrepair of valves in power plant systems. The information presented in this guideprovides state-of-the-art valve and actuator technology in use in U.S. power plants,including:

• The latest advances in the application, use, and maintenance of valves and actuators

• Current techniques used for both in situ and off-line repairs

• Guidelines for troubleshooting valve and actuator problems

•New and emerging technologies for diagnostic systems and equipment

• Requirements for valve maintenance programs that provide significantimprovements in valve reliability and plant availability

• Recent regulatory issues concerning the performance of valves and actuators innuclear power plant applications

Over the last several years, EPRI, the U.S. NRC, and electric utilities have conductedmany research projects to improve plant safety and availability by reducing valve andactuator problems. These projects resulted in many proprietary and nonproprietary

documents, which deal with various specialized areas of valve/actuator sizing,performance characteristics, valve and actuator maintenance/repair as well as testingand diagnostic technologies. However, information to aid plant personnel in resolvingthese problems is difficult to glean from scattered sources, and access may be restricted by proprietary consideration. Brief summaries along with a comprehensive listing of key documents are included in this guide to assist the reader to quickly find additionalsources of information.

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Introduction/Summary How to Use the Guidebook

1-2

This is Volume 1 of a two-volume guide. In this volume, the focus is on the application,use, maintenance, and troubleshooting of gate, globe, butterfly, plug, and diaphragmvalves in power plant applications. Volume 1 is a revision of NMAC NP-6516, issued inAugust 1990. Apart from the technical update (which is very extensive), several topicswere eliminated from this revision because they are covered in great depth in other

recent EPRI/NMAC publications. For example, check valves are not discussed in thisrevision because they are covered in two very detailed documents [1.20,

1 1.21]. Air-

operated valves and solenoid valves are also omitted because they are covered inReferences 1.2 and 1.7 respectively. Only minimum discussions of motor operators areincluded because detailed discussions are given in other EPRI documents [1.22, 1.23,1.24, 1.25, and 1.26].

Volume 2 of this guide [1.1] provides detailed discussions about most current valverepair techniques both in situ and off-line for gate, globe, and check valves. Thediscussions in Volume 2 cover component repair, flaw removal techniques, materialselection, machining, welding, heat treatment guidelines, final inspection and testingrequirements, which are also applicable to other valve types.

This guide was developed for persons who prepare valve specifications, install andoperate valves in various applications, and perform required valve maintenance andrepairs. The guide will also be useful to system designers, plant management,engineers, and others who need in-depth understanding of the capabilities andlimitations of valves that affect performance and system availability. For readers withlittle valve background, the guide is intended to provide basic understanding of valvetechnology. For readers with extensive valve experience, the guide is a reference book,which provides easy access to specific valve information as well as guidance to other

sources of specialized areas.

1.2 Summary/How to Use the Guidebook

1.2.1 General

This section provides the reader with a “road map” to the information presented in thisguide and to facilitate easy access to it. The Table of Contents provides a fairlydescriptive title for each section. Section 2 provides the nomenclature and glossary of terms that are common in the industry and used throughout the text. Aspects of component construction common to several different types of valves and actuators arediscussed in Section 2. Figures are used extensively to illustrate the different types of valves and specific component details and features.

1 Numbers in brackets denote technical references given in Section 22.

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1-3

1.2.2 Valve Functions

Section 3 provides the basic valve functions and the features necessary to perform thesefunctions. These functions generally fall into one of the following four categories:

Isolation. The valve is used to isolate portions of a system, an entire system from othersystems, or a given piece of equipment (such as a heat exchanger) within a system. Toachieve isolation, the valve is typically closed and is expected to exhibit a very low seatleakage.

Modulating/Throttling. In performing a modulating function, the position of the valveclosure element (gate, plug, disc, or ball) is varied between the fully open and the fullyclosed positions. The position of the closure element is controlled by an actuator that isan integral part of the valve or is attached to the valve stem. The position of the valveclosure element is automatically controlled by a feedback signal to the actuator toachieve a desired condition (for example, flow rate, fluid level, temperature, pressure)within the system. Modulating valves are used where automatic, repeatable, andaccurate control of a system fluid parameter is required.

A throttling function is similar to the modulating function except that the position of the valve closure element is manually controlled either locally or remotely (using apower source to the actuator). The valve closure element is positioned at a fixedpercentage of valve opening to satisfy a specific system flow requirement. The valvethen provides a constant hydraulic resistance to achieve a fixed pressure drop at agiven system flow rate. When the system flow requirement changes, the valve ismanually repositioned to provide the necessary hydraulic resistance and pressure drop.

In this guide, the discussions of air-operated valves and solenoid valves are kept to aminimum because these valves are discussed in great detail in References 1.2 and 1.7respectively.

Check (Non-Return). Check valves are located in a hydraulic system to ensure that theprocess medium flows in one direction only. A common application for check valves isat the discharge of multiple pumps in parallel that provide flow and pressure head to acommon manifold. In the event that one of the pumps ceases to produce flow andpressure head, a check valve located in its discharge line prevents a flow reversalthrough the non-operating pump caused by the pressure head produced by theoperating pump(s). Another typical application is at system interfaces where the intentis to allow flow in one direction only from one system into another. Check valves arenot normally considered isolation valves because they may exhibit higher leakage ratesthan usually required for isolation applications.

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1-4

In this volume of the guide, the discussion of check valve application, use andmaintenance is kept to a minimum because these subjects are discussed in great detailin References 1.20 and 1.21. Volume 2 of this guide provides detailed guidance forcheck valve repair.

Pressure-Relief. Pressure-relief valves are used to protect piping systems andcomponents from overpressurization by dissipating excess system pressure to apressure suppression system or to the atmosphere. Pressure relief is performed in anumber of ways including:

• The valve opens automatically to discharge system media when pressure at valveinlet (acting directly on valve disc) exceeds a predetermined level. No externalpower source is needed.

• A pilot valve opens automatically when pressure at the inlet of the pilot valve

exceeds a predetermined level. The opening of the pilot valve subsequently opensthe main valve. Alternatively, the pilot valve may be opened at any inlet pressure by the application of an external power source.

• The valve opens when the actuator power source receives a signal that the valveinlet pressure exceeds a predetermined level.

• The valve opens when the actuator’s power source receives a signal that othersystem conditions or events have occurred that will cause a pressure rise to occur(for example, power failure to a pump or the