Volume 1
TR-105852v1
Final Report, February 1999
EPRI Project Manager V. Varma
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 notices embedded in the document prior to publication.
(EPRI). NEITHER EPRI, ANY MEMBER OF EPRI, ANY COSPONSOR, THE ORGANIZATION(S) NAMED 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 PACKAGE, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, OR (II) THAT SUCH USE DOES NOT INFRINGE ON OR INTERFERE WITH PRIVATELY OWNED RIGHTS, INCLUDING ANY PARTY'S INTELLECTUAL PROPERTY, OR (III) THAT THIS PACKAGE 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 PACKAGE OR ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS 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.
This report was prepared by Kalsi Engineering, Inc. 745 Park Two Dr. Sugarland, TX 77478 Principal Investigators Bahir H. Eldiwany Daniel 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.
The Valve Application, Maintenance, and Repair Guide is a two-volume series that provides a generic overview of valve application, selection, maintenance, and repair. Volume 1 of the series is a comprehensive reference on the application and use of valves that provides 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). Extensive illustrations and sample calculations make the guide useful to a wide range of personnel. This volume has been expanded to include general maintenance requirements and diagnostics for different valve types.
Information on valves and valve operators, where other comprehensive NMAC
documents are available (such as Air Operated Valves, Solenoid Valves, Check Valves, Safety
and 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 in power plant systems cause significant losses in plant availability. Over the last several years, EPRI, the U.S. NRC, and the electric utilities have conducted many valve and actuator research projects to improve plant safety and availability by reducing valve and actuator problems. These projects resulted in many proprietary and
non-proprietary documents that deal with the various specialized areas of valve/actuator sizing, performance characteristics, maintenance, repair, testing, and diagnostic
techniques. However, information to aid plant personnel in resolving these problems is difficult 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, and maintenance of valves, in which information is readily accessible and understandable by a wide range of plant personnel.
recent 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 to eliminate topics that were either irrelevant or covered in greater depth elsewhere. The scope of this guide was expanded to include maintenance, troubleshooting, and diagnostic equipment. An overview of other key documents is provided to assist the reader in quickly finding sources of additional information. Numerous illustrations and examples of applications, valve sizing, and strategies for use and maintenance were 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 diaphragm valves and manual, hydraulic, and electro-hydraulic actuators, including their
installation, operation, maintenance, and most common problems. For other types of valves and actuators not covered in this guide, references to pertinent EPRI/NMAC documents are given. The guide presents information in a clear and understandable manner to those with little knowledge of the factors involved in successful valve applications. For those who have extensive experience with valves and actuators, this guide provides easy access to specific information that is pertinent to specific needs with references.
EPRI Perspective
Although the information contained in the guide focuses on the application and maintenance of valves in power plant systems, it is also directly applicable to comparable system applications in the chemical, petroleum, marine, and similar industries. The intended audience of the guide includes system designers; engineers who 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 new and replacement valves/actuators, and developing/updating valve maintenance programs and procedures.
Interest Categories Valves
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 Engineering Corporation of Massachusetts and Kalsi Engineering, Inc., of Texas. They received wide cooperation from experienced nuclear utility personnel and service industries. This revision was created on the solid framework of the earlier publication.
We wish to extend our thanks to the individuals who spent many hours performing detailed reviews of this revision, so necessary to produce a quality document. In particular, we thank Kenneth Hart of Pennsylvania Power & Light for his extensive comments and input on valve packing and maintenance program issues. Other reviewers include Chris Hansen of Vermont Yankee, Greg Harttraft of GPU, John Holstrom of Duke Engineering Services, Eric Cartwright of PECO, and Jim Wilson and Eugene Phillips of Wisconsin Electric Co.
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... 1-3 1.2.3 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... 1-7 1.2.11 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
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
4.1 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
5.1 Introduction and Application ... 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 Introduction and Application ... 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
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 6.3 Installation Practices ... 6-30 6.4 Operation Practices and Precautions ... 6-30 6.5 Common Problems ... 6-31 6.6 Maintenance Methods ... 6-31
7 BUTTERFLY VALVES—ISOLATION FUNCTION ... 7-1
7.1 Introduction and Application ... 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 Installation Practices ... 7-19 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 7.4 Operation Practices and Precautions ... 7-22 7.5 Common Problems ... 7-22
7.6 Maintenance Methods ... 7-24
8 BUTTERFLY VALVES—MODULATING/THROTTLING FUNCTION... 8-1
8.1 Introduction and Application ... 8-1 8.2 Hydrodynamic Torque Characteristics ... 8-2 8.3 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 8.6 Maintenance Methods ... 8-7
9 BALL VALVES—ISOLATION FUNCTION... 9-1
9.1 Introduction and Application ... 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 9.6 Maintenance Methods ... 9-9
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
11.1 Introduction and Application ... 11-1 11.2 Design... 11-1 11.3 Installation Practices ... 11-4 11.4 Operation Practices and Precautions ... 11-4
11.5 Common Problems ... 11-4 11.6 Maintenance Methods ... 11-5
12 DIAPHRAGM VALVES—ISOLATION FUNCTION ... 12-1
12.1 Introduction and Application ... 12-1 12.2 Design... 12-1 12.3 Installation Practices ... 12-4 12.4 Operation Practices and Precautions ... 12-4 12.5 Common Problems ... 12-4 12.6 Maintenance Methods ... 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
14.1 Introduction and Application ... 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... 14-4 14.2.5 Gear Operators ... 14-4 14.3 Installation Practices ... 14-4 14.4 Operation Practices and Precautions ... 14-5 14.5 Common Problems ... 14-5 14.6 Maintenance Methods ... 14-5
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
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 ... 16-23 16.5.4 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
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
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 ... 19-1 19.2.1 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
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 and
Torque 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
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
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
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 ... 4-2 Figure 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 Wedge
Gate 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 Maximum
System Flows... 6-2 Figure 6-2 Control Valve Sizing Example ... 6-5 Figure 6-3 Single-Port Control Valve ... 6-9 Figure 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 Across
the 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
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 ... 7-5 Figure 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 ... 7-17 Figure 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 and
Pumped Systems ... 8-4 Figure 8-3 Typical Opening Torque Characteristics of a Symmetric Disc Butterfly Valve
under High Flow Conditions ... 8-6 Figure 9-1 Floating Ball... 9-4 Figure 9-2 Trunnion-Mounted Ball ... 9-5 Figure 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 ... 12-3 Figure 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
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 ... 16-24 Figure 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 outboard
seat. 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 back
cover of this report.) ... 21-1 Figure 23-1 Tilted Disc Contact Mode Resulting in Point Contact with the Downstream
Seat... 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... 24-5 Figure 24-4 Globe Valve FL 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 ... 24-44 Figure 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 24-17 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 ... 25-13 Figure 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
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 Operating
Conditions, and Minimum Design Seating Stress y... 2-79 Table 3-1 Control Valve Seat Leakage Classifications (In Accordance with ANSI/FCI
70-2-1976... 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 ... 16-2 Table 16-2 Typical Valve Standards ... 16-3 Table 16-3 Safety Classes and Applicable Standards ... 16-5 Table 164 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 (Fi) . 24-10 Table 24-2 Typical Critical Pressure Values ... 24-14
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
1
INTRODUCTION/SUMMARY HOW TO USE THE
GUIDEBOOK
1.1 Introduction
The purpose of this guide is to present, in a comprehensive manner, information and methods that have been successfully utilized in the application, use, maintenance, and repair of valves in power plant systems. The information presented in this guide provides 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 significant
improvements in valve reliability and plant availability
• Recent regulatory issues concerning the performance of valves and actuators in nuclear power plant applications
Over the last several years, EPRI, the U.S. NRC, and electric utilities have conducted many research projects to improve plant safety and availability by reducing valve and actuator 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 testing and diagnostic technologies. However, information to aid plant personnel in resolving these 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 additional sources of information.
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 diaphragm valves in power plant applications. Volume 1 is a revision of NMAC NP-6516, issued in August 1990. Apart from the technical update (which is very extensive), several topics were 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 this revision 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 in References 1.2 and 1.7 respectively. Only minimum discussions of motor operators are included 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 valve repair techniques both in situ and off-line for gate, globe, and check valves. The discussions in Volume 2 cover component repair, flaw removal techniques, material selection, machining, welding, heat treatment guidelines, final inspection and testing requirements, which are also applicable to other valve types.
This guide was developed for persons who prepare valve specifications, install and operate valves in various applications, and perform required valve maintenance and repairs. The guide will also be useful to system designers, plant management,
engineers, and others who need in-depth understanding of the capabilities and
limitations of valves that affect performance and system availability. For readers with little valve background, the guide is intended to provide basic understanding of valve technology. 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 this guide and to facilitate easy access to it. The Table of Contents provides a fairly
descriptive 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 are discussed in Section 2. Figures are used extensively to illustrate the different types of valves and specific component details and features.
1
1.2.2 Valve Functions
Section 3 provides the basic valve functions and the features necessary to perform these functions. 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 other
systems, or a given piece of equipment (such as a heat exchanger) within a system. To achieve isolation, the valve is typically closed and is expected to exhibit a very low seat leakage.
Modulating/Throttling. In performing a modulating function, the position of the valve
closure element (gate, plug, disc, or ball) is varied between the fully open and the fully closed positions. The position of the closure element is controlled by an actuator that is an integral part of the valve or is attached to the valve stem. The position of the valve closure element is automatically controlled by a feedback signal to the actuator to achieve a desired condition (for example, flow rate, fluid level, temperature, pressure) within the system. Modulating valves are used where automatic, repeatable, and accurate 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 a power source to the actuator). The valve closure element is positioned at a fixed percentage of valve opening to satisfy a specific system flow requirement. The valve then provides a constant hydraulic resistance to achieve a fixed pressure drop at a given system flow rate. When the system flow requirement changes, the valve is
manually 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 a minimum because these valves are discussed in great detail in References 1.2 and 1.7 respectively.
Check (Non-Return). Check valves are located in a hydraulic system to ensure that the
process medium flows in one direction only. A common application for check valves is at the discharge of multiple pumps in parallel that provide flow and pressure head to a common manifold. In the event that one of the pumps ceases to produce flow and pressure head, a check valve located in its discharge line prevents a flow reversal through the non-operating pump caused by the pressure head produced by the
operating pump(s). Another typical application is at system interfaces where the intent is to allow flow in one direction only from one system into another. Check valves are not normally considered isolation valves because they may exhibit higher leakage rates than usually required for isolation applications.
In this volume of the guide, the discussion of check valve application, use and
maintenance is kept to a minimum because these subjects are discussed in great detail in References 1.20 and 1.21. Volume 2 of this guide provides detailed guidance for check valve repair.
Pressure-Relief. Pressure-relief valves are used to protect piping systems and
components from overpressurization by dissipating excess system pressure to a pressure suppression system or to the atmosphere. Pressure relief is performed in a number of ways including:
• The valve opens automatically to discharge system media when pressure at valve inlet (acting directly on valve disc) exceeds a predetermined level. No external power 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 opens the 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 valve inlet pressure exceeds a predetermined level.
• The valve opens when the actuator’s power source receives a signal that other system conditions or events have occurred that will cause a pressure rise to occur (for example, power failure to a pump or the sub-normal pressure preceding a pressure surge or water hammer).
In this guide, the discussions of pressure relief valves are eliminated because these valves are discussed in great detail in Reference 1.4.
1.2.3 Specific Valve Types by Function
Sections 4 through 12 provide information on specific types of valves commonly used to perform isolation and modulating/throttling functions. The specific types addressed are gate, globe, butterfly, ball, plug, and diaphragm valves. The information provided focuses on a number of areas pertinent to the application of each specific valve type. These are as follows:
Introduction and Application. Performance features and capabilities of the specific valve
type are discussed with respect to the stated function, together with other application considerations. For example, for flow isolation, fully open gate valves offer minimal flow resistances and pressure drops (thus reducing pumping costs). However, gate valves require a relatively long stem travel to open and close. Therefore, stroke times
for gate valves are relatively longer than for globe valves, which could adversely affect the system performance. On the other hand, globe valves, while satisfying stroke time requirements, introduce high flow resistances and pressure drops, which may be unacceptable in some applications.
Design. Using a valve cross-sectional drawing, the design features of the specific valve
type are discussed.
The effect of different variants of the valve type (for example, solid wedge versus flexible wedge gate valves) on valve performance is noted. The advantages and disadvantages of the variants are discussed.
Installation Practices. The proximity of other components (pumps, piping connections,
etc.) may affect valve performance. Installation configuration, direction of flow, forces, and moments applied to the valve by the connecting pipe, orientation to vertical, and accumulation of debris/biological growth inside the valve are typical installation considerations. These are discussed as they apply to each specific valve type and function, and an assessment is provided where a particular sensitivity to any of these exists. General guidelines for valve installation are given in Section 19.
Operation Practices and Precautions. Methods to improve the functional reliability of
valves through correct operational practices are discussed. Practices that may adversely affect the performance of valves are presented. Such practices include applying
excessive actuator loading thrust to reduce seat leakage and using of valves for other than the intended function (for example, long-term throttling with a gate valve).
Common Problems. For each valve type, a section is devoted to provide a concise list of
the common valve problems and malfunctions. Wherever possible, suggested corrective and preventive actions are given. Detailed repair procedures are given in Volume 2 [1.1].
Maintenance. General discussions of maintenance methods and practices for specific
valves are provided. The focus is on areas that are considered critical to achieve
satisfactory valve performance. General discussions of other valve maintenance issues including programmatic consideration, troubleshooting, corrective action, maintenance requirements, and diagnostic equipment are given in Sections 17 through 20.
1.2.4 Actuator Types
Section 13 provides a general introduction to the different types of valve actuators. Section 14 is dedicated to manual actuators. For other types of actuators, the reader is referred to other EPRI documents [1.2, 1.4, 1.7, and 1.22 through 1.26].
1.2.5 General Design Requirements for Valves and Actuators
Deficient performance and valve failures result from the use of valves under operating conditions for which they were not intended. A complete knowledge of all of the conditions to which the valve will be subjected is extremely valuable in avoiding problems. This includes system start-up, shutdown, and anticipated transient conditions. All verified pertinent valve data should be recorded and filed for future reference. Section 15 provides detailed discussion of general design requirements that need to be defined and applied to valves during the original or replacement
procurement cycle.
1.2.6 Valve Pressure Boundary and Structural Integrity
The valve is an integral part of the system pressure boundary and must be designed so that the integrity of the system is maintained. Section 16 discusses pressure boundary and structural integrity requirements including:
• Applicable codes and standards • Pressure temperature ratings
• Materials and material compatibility
• Pressure boundary materials and their proper selection • Corrosion allowance
• Valve end connections
• Pipeline loads and vibrations
• Leakage, and shop hydrostatic testing • Structural integrity and valve operability
1.2.7 Valve Maintenance and Inspection Programs
In the last few years, there has been ever-increasing pressure on the electric power industry to improve plant efficiency, shorten plant outages, and cut costs. Under this environment, valve maintenance groups are required to improve the efficiency of valve repairs and reliability. Section 17 discusses the different factors that affect valve
maintenance and have direct impact on valve reliability and plant availability.
Recommendations to enhance maintenance programs and procedures are also included in Section 17.
1.2.8 Troubleshooting and Recommended Corrective Actions
One of the most important responsibilities of plant maintenance and operation
personnel is to quickly identify valve problems and determine the necessary corrective actions. In many cases, the root cause is simple but not obvious. Section 18 provides guidance on troubleshooting and recommended corrective actions for gate, globe, butterfly, ball, plug, and diaphragm valves. The use of checklists can improve the quality and the effectiveness of the maintenance activities and are recommended in this guide (see Section 18 for sample checklists).
1.2.9 Installation, Testing, and Maintenance Requirements
Valve installation, testing, and maintenance must meet certain code and regulatory requirements. For nuclear power plants, these requirements are more stringent than in any other application. Section 19 provides a detailed discussion of these requirements and identifies the governing codes that should be reviewed for additional information. 1.2.10 Diagnostic Equipment and Methods
Recent advances in computers and measurement equipment coupled with innovative solutions for measurement problems resulted in a surge in valve diagnostic equipment and methods. Section 20 provides a summary of the state of the art of valve and
actuator diagnostic equipment and methods. It is expected that these advances will continue and new equipment will be developed while existing equipment will be further refined. Thus, the reader is encouraged to continue to obtain new information from diagnostic equipment vendors and service companies that develop and maintain the equipment. However, the information provided in Section 20 can be used as a starting point to identify the specific plant needs.
1.2.11 Valve Selection Chart
Section 21 provides information on using the Valve Selection Chart shown in Figure 21-1. The chart is in the form of an algorithm and is provided for use as a wall chart. It provides a structured path of the mental process of selecting a new valve or evaluating an existing valve. Caution should be exercised in using the chart because it is not a “go/no-go” device, but rather one that suggests options to be evaluated and points to the direction of needed additional investigation. Some of the options shown may not always be available to the user. Decisions such as the type of valve end connections, valve body/bonnet material, etc., may be mandated by overall system considerations. Several typical valve applications are presented in the text to assist the reader in the use of the Valve Selection Chart.
1.2.12 References and Bibliography
As mentioned above, the vast amount of information/documents developed over the last few years makes it difficult for plant personnel to locate the applicable documents for a particular need. In this guide, a listing of the key references, codes, and standards are provided to enable the reader to locate additional documents for further study. In Section 22, the references and bibliography are listed according to their categories in six different groups. Proprietary documents (available only to certain program
participants) are included in separate sections and clearly identified. Most of these references provide additional references for specific information such as valve test reports and friction coefficient data.
1.2.13 Appendices
Appendices are provided to broaden the scope of knowledge presented in the text. References in the text are made to specific appendices where additional information is given on the subject being discussed.
Section 23 provides a brief discussion of recent advances in the valve and actuators technology along with latest regulatory requirements. Section 23 also provides a brief summary of some key EPRI/NMAC documents that are believed to be of particular interest to the reader.
Section 24 provides a brief discussion of control valve sizing methods based on the Instrument Society of America (ISA) approach. Several examples are provided to
further clarify the methods used and to understand their limitations. It should be noted that several computer programs have been developed by valve manufacturers and others to perform control valve sizing calculations. Evaluation and discussion of these computer programs are outside the scope of this guide. It is recommended, however, that the reader seek information about such software from the developing
organizations.
Section 25 provides valve procurement specifications. Suggested data sheets for use by the purchaser and bidder/seller are included for convenience.
Finally, complete reading of the entire guide, including the appendices, should provide the reader with an overall view of the current state of the art of valve and actuator technology.
2
GENERAL VALVE DESIGN
2.1 Nomenclature/Glossary of Terms
2.1.1 Introduction
This section covers commonly used valve terminology and nomenclature. As an example, Figures 2-1 and 2-2 show a globe and a gate valve along with typical nomenclature used for these valve types. Reference is given, where appropriate, to figures found in later sections which depict the term being defined. Many terms used in this document are defined in the following standards and technical textbooks.
• Glossary of Valves Terms, Grove Valve Regulator Company, Oakland, CA, 1980.
• ASME Standard 112, Diaphragm Actuated Control Valve Terminology, American Society of Mechanical Engineers, New York, NY.
• ISA Handbook of Control Valves, Second Edition, Instrument Society of America, 1976.
• Control Valve Handbook, Second Edition, Fisher Control Company, Marshalltown,
Iowa, 1977.
• ANSI B95.1, Terminology for Pressure Relief Devices. 2.1.2 Glossary of Terms
Active Valve
A valve that is required to change obturator position to accomplish its required function(s).
Actual Discharge Area
Actuator Spring (Diaphragm Actuator) (Figure 2-1)
A spring that moves the actuator stem in a direction opposite to the direction created by diaphragm pressure.
Actuator Stem (Diaphragm Actuator) (Figure 2-1)
A rod-like extension of the diaphragm plate to permit convenient external connection (usually to the valve stem).
Figure 2-1
Figure 2-2
Gate Valve Typical Valve Nomenclature Backpressure
Pressure on the downstream side of the valve. Backseat (Figure 2-1)
A shoulder on the stem disc of a valve that seals against a mating surface inside the bonnet to act as a back-up seal to the packing to limit stem seal leakage.
Belleville Spring
A cone-shaped washer/disc spring used where small deflections and relatively high loads are required.
Bellows Seal Bonnet (Figure 2-24)
A bonnet that uses metal bellows for sealing against leakage of controlled fluid around the valve stem.
Block and Bleed
The capability of obtaining a pressure seal across the upstream and downstream seats of a valve, usually a gate valve, when the body pressure is bled off to the atmosphere through blowdown valves or vent plugs. This is useful in testing the integrity of seat shut-off and in accomplishing minor repairs under line pressure. It is also useful in keeping different process fluids separated. See Double Block and Bleed.
Body (Figures 2-1 and 2-2)
The principal pressure-containing part of a valve where the closure element and seats are located.
Bonnet (Figures 2-1 and 2-2)
• The separable portion of the valve pressure boundary that permits access to the internals.
• The major part of the bonnet assembly, excluding the sealing means.
• The top pressure-containing part of a valve, attached to the body, that guides the stem and adapts to extensions or operators.
Bonnet Assembly
An assembly that includes the part through which a valve plug stem moves and a means for sealing against leakage around the stem. It usually provides a means for mounting the actuator.
Bore (or Port)
The inside diameter, or other control configuration, of the flow passage through a valve (for example, the diameter of the hole in the ball of a ball valve, the inside diameter of
seat rings). The bore is usually the minimum flow area when the disc is in the fully open position.
Boss (Figure 2-1)
A localized projection on a valve surface provided for various purposes, such as attachment of drain connections or other accessories.
Breaking Pin See Shear Pin. Breaking Pin Device See Shear Pin Device. Breaking Pressure
The value of inlet static pressure at which a breaking pin or shear pin device functions. Terms such as “breaking pressure,” “force,” “load,” or “torque” are used to identify the load for which the intentional section of weakness is designed to fail.
Bubble-Tight Shut-Off
A phrase used in describing the sealing ability of a valve. During air pressure testing of a valve in the closed position, leakage past the seats is bubbled through water. To qualify as “bubble-tight,” no bubbles should be observed in a prescribed time span. Burst Pressure
The value of inlet static pressure at which a rupture disc functions. Bypass (Figure 2-21)
A system of pipes and valves intended to permit the diversion of flow or pressure around a line valve or to communicate the body cavity to either the upstream or downstream side.
Cage. (Figure 6-9A)
A hollow cylindrical trim element that is a guide to align the movement of a valve disc with a seat ring and also to retain the seat ring in the valve body. Often the walls of the cage contain openings that determine the flow characteristics of a control valve.
Capacity
Rate of flow through a valve under stated conditions of pressure drop and fluid density.
Chatter
Rapid reciprocating or vibrating motion of the valve disc during which the disc contacts the seat. In mid-stroke, a valve may chatter on its guides or cage without touching the seat.
Closing Pressure
The value of the decreasing inlet static pressure at which the valve disc of a safety valve re-established contact with the seat or at which lift becomes zero.
Closure Element (Figures 2-1 and 2-2)
The moving part of a valve, positioned in the flow stream, that controls flow through the valve. Ball, gate, plug, clapper, disc, etc., are specific names for closure elements. Coefficient of Discharge
The ratio of the measured flow capacity to the theoretical flow capacity. Control Valve
A power-operated device that modifies the fluid flow rate in a process control system. It consists of a valve connected to an actuator mechanism that is capable of changing the position of a flow-controlling element in the valve in response to a signal from the controlling system.
Cv (Valve Flow Coefficient)
The number of gallons of water at 60°F (15.6°C) that will flow through a given valve within 1 minute, with a pressure drop (loss) of 1 psi (6.9 kPa).
Dead Band (Diaphragm Actuator)
The amount that the actuating pressure on the diaphragm can be varied without initiating valve disc motion.
Design Pressure
The pressure used in the design of a valve and other pressure-retaining components for the purpose of determining the minimum permissible wall thickness. When applicable, static head should be added to the design pressure to determine the thickness of the pressure-retaining components. There are slight differences in the exact definition of the design pressure used by different codes; therefore, the definition from the
applicable code, such as ASME, must be used. Design Temperature
The temperature that is used to determine allowable stresses for the purpose of design calculations. Generally, the design temperature is set at a value higher (or further from ambient) than the operating temperature and includes allowances for upsets and variation in operating conditions.
Diaphragm (Figure 2-1)
A flexible pressure responsive element that transmits force to the diaphragm plate. Diaphragm Actuator (Figure 2-1)
An assembly utilizing fluid pressure acting on a diaphragm to develop a force to move the actuator stem. It may or may not have a spring for positioning and return of the actuator stem.
Diaphragm Pressure Span (or Range)
Difference between the high and low values of the diaphragm pressure range. This may be stated as an inherent or installed characteristic.
Direct Acting Actuator (Figure 6-19)
A diaphragm actuator in which the actuator stem extends with increasing diaphragm pressure.
Disc (Figure 2-1 and 2-2)
The closure element of a gate, globe, check, butterfly, safety, or relief valve. The disc in different valve designs may be referred to as gate, wedge, poppet, or plug.
Discharge Area
Double Block and Bleed
The capability of a valve to isolate the body cavity from line pressure when the valve is in either the fully closed or fully open position. (See Block and Bleed for this operation with the valve in only the closed position.) In open position, pressure energized seat-ball valves and through-conduct gate valves can effectively shut off the system pressure from entering the valve body cavity from either the upstream or downstream side, permitting the integrity of the seats to be checked with the closure member in the open position.
Dynamic Unbalance
The net force produced on the valve disc in any stated open position by the fluid pressure acting upon it.
Effective Area
In a diaphragm actuator, the effective area is that part of the diaphragm area that is effective in producing a stem force. (The effective area of a diaphragm may change as it is stroked, usually being maximum at the start and minimum at the end of the travel range. Molded diaphragms that incorporate convolutions have less change in effective area than flat sheet diaphragms.)
Equal Percentage Flow Characteristic
An inherent flow characteristic that, for an equal increment of rated travel, will ideally give an equal percentage change of the flow coefficient.
Explosion Rupture Disc Device
A type of rupture disc device designed for use at high rates of pressure rise. Extension Bonnet (Figure 2-22)
A bonnet with an extension between the packing box assembly and bonnet flange to thermally isolate the stem packing from the process fluid.
Fail-As-Is1
A characteristic of a particular type of actuator that, upon loss of power supply, will cause the valve plug, ball, or disc to remain in the position attained at the time of the loss of external actuating power.
Fail-Closed1
A condition wherein the valve disc will move to the closed position upon loss of external actuating power.
Fail-Indeterminate1
A characteristic of a particular type of actuator that, upon loss of power supply, can move to any undefined position.
Fail-Open1
A condition wherein the valve disc will move to the open position upon loss of external actuating power.
Fail-Safe1
The selection of fail-as-is, fail-closed, or fail-open action that avoids an undesirable consequence in a fluid system.
Field Serviceable
A statement indicating that normal repair of the valve or replacement of operating parts can be accomplished in the field without return to the manufacturer.
Fire Safe
A statement associated with a valve design that is capable of passing certain specified leakage and operational tests during and after exposure to fire of specified conditions.
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Flow Characteristic
Relationship between flow through the valve and percent rated travel as the latter is varied from 0 to 100%. This is a special term. It should always be designated as either inherent flow characteristic or installed flow characteristic.
Flow Coefficient See Cv.
Flow Rating Pressure
The inlet static pressure at which the relieving capacity of a pressure relief device is measured for rating purposes.
Flutter
Rapid reciprocating motions of the valve disc during which the disc does not contact the seat or body.
Fusible Plug Device
A type of non-reclosing pressure relief device designed to function by yielding or melting a plug of suitable melting temperature material.
Gate (Figure 2-2)
The closure element of a gate valve. Globe Valve (Figure 2-1)
A basic control valve type that gets its name from the globular shape of its body. It normally uses the basic valve disc as its valve closure member.
Hard Facing
A surface preparation in which an alloy is deposited on a critical valve surface (for example, seat, guide, disc), usually by weld overlay or spray coating techniques, to increase resistance to wear, galling, abrasion, and corrosion.
High-Recovery Valve
A valve design that dissipates relatively little flow stream energy due to streamlined internal contours and minimal flow turbulence. Therefore, pressure downstream of the
valve vena contracta recovers to a high percentage of its inlet value. (Straight-through flow valves, such as rotary-shaft ball valves, are typically high-recovery valves.) Inherent Diaphragm Pressure Span (or Range)
The high and low values of pressure applied to the diaphragm to produce rated valve plug travel with atmospheric pressure in the valve body. (This range is often referred to as a “bench set” range since it is the range over which the valve will stroke when it is set on the work bench.)
Inherent Flow Characteristic
Flow characteristic when constant pressure drop is maintained across the valve. Inherent Rangeability
Ratio of maximum to minimum flow coefficient within which deviation from the specified inherent characteristic does not exceed some stated limit.
Inlet Size
The nominal pipe size of the inlet of a valve, unless otherwise designated. Installed Diaphragm Pressure Span (or Range)
The high and low values of pressure applied to the diaphragm to produce rated valve plug travel with stated conditions in the valve body. (It is because of forces acting on the valve plug that the installed diaphragm pressure range can differ from the inherent diaphragm pressure range.)
Installed Flow Characteristic
Flow characteristic, when pressure drop across the valve varies, as dictated by flow and related conditions in the system in which the valve is installed.
Lantern Ring (Figure 2-20)
A spacer installed between packing sets to permit injection of sealant or lubricant into the packing area, or as a leak-off collection chamber from which leakage past the first set is piped to a safe location.
Leak Test Pressure
The specified inlet static pressure at which a quantitative seat leakage test is performed in accordance with a standard procedure.
Leakage
Quantity of fluid passing through an assembled valve when the valve is in the closed position under stated closure forces with pressure differential [6.12].
Linear Flow Characteristic
An inherent flow characteristic that can be represented ideally by a straight line on a rectangular plot of percent of related flow coefficient (Cv) versus percent rated travel.
(Equal increments of travel yield equal increments of flow at a constant pressure drop.) Live Loading (Figure 2-30)
A term used in reference to stem packing stuffing box arrangements to denote that the packing gland follower is loaded through springs in order to minimize loss of packing load due to packing consolidation and wear.
Lock-Up Valves
A device used to retain air pressure on a pneumatic actuator or chamber upon loss of air supply, causing the valve to fail as is.
Low-Recovery Valve
A valve design that dissipates a considerable amount of flow stream energy due to turbulence created by the contours of the flow path. Consequently, pressure
downstream of the valve vena contracta recovers to a lesser percentage of its inlet value than is the case with a valve having more streamline flow path. (Although individual designs vary, conventional globe-style valves generally have low pressure recovery capability.)
Lower Valve Body
A half housing for internal valve parts having one flow connection. For example, the half housing of a split body valve.
Maximum Allowable Working Pressure (MAWP)
The maximum pressure permissible in a pressure-retaining component at a designated temperature. This pressure is based on the nominal thickness of the component,
exclusive of allowances for corrosion and thickness required for loadings other than pressure. Maximum allowable working pressure is also used as the basis for the pressure setting of the pressure relieving devices protecting the component. Maximum Allowable Pressure Drop
The maximum flowing or shutoff pressure drop that a valve can withstand. While the maximum inlet pressure is commonly dictated by the valve body, maximum allowable pressure drop is generally limited by the internal controlling components (plug, stem, disc, shaft, bearings, and seals).
Non-Rising Stem Gate Valves (Figure 4-1B)
A gate valve having its stem threaded into the gate. As the stem turns, the gate moves (for example, from the closed to the opened position), but the stem does not rise. Stem threads are exposed to line fluids.
Outlet Size
The nominal pipe size of the outlet of a valve, unless otherwise designated. Outside Screw And Yoke (OS&Y) (Figure 4-2)
A valve in which the fluid does not come in contact with the stem threads. The stem sealing element is between the valve body and the stem threads.
Packing (Stuffing) Box Assembly (Figure 2-28)
The part of the bonnet assembly used to seal against leakage around the valve stem, including various combinations of all or part of the following: packing gland, packing nut, gland follower, lantern ring, packing spring, packing flange, packing flange studs or bolts, packing flange nuts, packing ring, packing wiper ring, and felt wiper ring. Packing Gland (Figure 2-28)
Passive Valve
A valve that maintains obturator position and is not required to change obturator position to accomplish its intended function(s).
Piston Actuator
A fluid pressure operated piston and cylinder assembly for positioning the actuator stem in relation to the operating fluid pressure or pressures.
Pilot Valve
An auxiliary valve that, when actuated, causes the actuation of a main valve. Plug
See Closure Element. Port
The flow control orifice of a control valve. It is also used to refer to the inlet or outlet openings of a valve.
Port Guided (Figures 5-1, 5-2)
A design in which the valve plug is aligned by the body port or ports only. Pressure-Containing Member
A part of the component that is in actual contact with the pressure media. Pressure-Retaining Member
A part of the component that is stressed due to its function in holding one or more pressure-containing members in position.
Push-Down-to-Close Construction
A globe-style valve construction in which the valve plug is located between the
actuator and the seat ring, so that extension of the actuator stem moves the valve plug toward the seat ring, finally closing the valve.