Maintenance and Application Guide for Centrifugal Pump

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Deep Draft Vertical Centrifugal PumpMaintenance and Application Guide

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

Deep Draft Vertical Centrifugal Pump

Maintenance and Application GuideThis guide provides technical information on the understanding and

maintenance of deep draft vertical centrifugal pumps. It can help

utilities identify and address pump problems thus eliminating costly

downtime and improving plant availability.

BACKGROUND All nuclear power plants use a number of large verticalcentrifugal pumps in critical systems. Deep draft vertical centrifugal pumpsprovide maintenance personnel a particularly difficult challenge because of theiroperating environment and large size. Operability can be affected by pumpdesign, the effects of the intake structure, and water quality. A utility surveyconducted by the Nuclear Maintenance Applications Center (NMAC) identified aneed for a comprehensive guide providing a quick reference for deep draftvertical centrifugal pump predictive and preventive maintenance.

INTEREST CATEGORIES

Maintenance practicesNuclear plant operating andmaintenance

Engineering and technicalOBJECTIVE To provide guidance on the maintenance and troubleshooting ofdeep draft vertical centrifugal pumps.support

APPROACH A project team collected and compiled available industry data onthe maintenance and troubleshooting of deep draft vertical centrifugal pumps. Adocument review committee (DRC) of utility representatives and industryexperts reviewed and commented on the draft report. The final documentincorporates their comments and suggestions.

KEYWORDS

MaintenancePumps

RESULTS This guide presents technical information on the understanding andmaintenance of deep draft vertical centrifugal pumps. It provides an overview ofthe circulating water system including the specific components of the intakestructure and the deep draft vertical centrifugal pumps that provide the motiveforce for the circulating water system. It covers the troubleshooting of verticalcentrifugal pumps in the areas of high vibration, loss of performance, and highbearing temperatures. It also includes a discussion of the proper techniquesneeded to conduct a comprehensive inspection of vertical centrifugal pumps

and the corresponding repair activities.Appendix A to this guide provides an extensive discussion and illustrations ofthe design process for a new pump and sump installation. Other appendicesprovide a general introduction to vibration analysis, a summary of a methodol-ogy used to troubleshoot structural resonant vibration problems, and casehistories which are used to identify and modify a poor sump design.

EPRI PERSPECTIVE The scope of this guide covers the pump, its applicationin the circulating water system, and the intake structure design and mainte-nance. Although the guide primarily focuses on deep draft vertical centrifugal

Electric Power Research InstituteEPRI NP-7413s April 1994

EPRILeadership in Scienceand Technology


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pumps, many aspects of this guide can be applied to all verticalcentrifugal pumps. Related EPRI research includes TR-100855.

PROJECT

RP281 4-44

EPRI Project Manager: Kenneth F. Barry

Nuclear Power Division

Contractors: Hydro Engineering Services Incorporated

For further information on EPRI research programs, callEPRI Technical Information Specialists (415) 855-2411.


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Deep Draft Vertical Centrifugal Pump

Maintenance and Application Guide

NP-7413

Research Project 2814-44

Final ReportApril, 1994

Prepared by:

Hydro Engineering Services Incorporated3563 Driftwood PlaceBethlehem, PA 18017

Principal InvestigatorM. Mancini

Prepared for

Nuclear Maintenance Applications Center1300 Harris Boulevard

Charlotte, North Carolina 28262

Operated byElectric Power Research Institute

3412 Hillview AvenuePalo Alto, California 94304

EPRI Project ManagerK.F. Barry

Nuclear Power Division


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RESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM

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ORGANIZATION(S) THAT PREPARED THIS REPORT:

HYDRO ENGINEERING S ERVICES INCORP ORATED

Price: $10,000.00

ORDERING INFORMATION

Requests for copies of this report should be directed to the Nuclear Maintenance Applications Center (NMAC), 1300Harris Blvd., Charlotte, NC 28262, (800) 356-7448. There is no charge for reports requested by EPRI memberutilities.

Electr ic Power Research Ins t i tute and EPRI are regis tered service marks of Electr ic Power Research Ins t i tute , Inc .

Copyr igh t 1994 Electr ic Power Research Ins t i tute , Inc . All r ights reserved.


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Abstract

This comprehensive guide provides guidance on the understanding and maintenance of

deep draft vertical centrifugal pumps. It can be used to help utilities diagnose perceived

problems, limit deterioration, and prevent complete failure. It provides technical

information on all types and sizes of vertica l centrifugal pumps. The guide contains adiscussion of design and operating issues which influence pump/component performance,

reliability, and/or availability. It also addre sses issues which may force shutdown of pumps.

It can help utilities identify and address pump problems, thus improving plant availability.

The primary focus of this guide is on deep draft vertical centrif ugal pumps, but some

aspects of this guide are applicable to all vertical centrifugal pumps.

iii

EPRI Licensed Material

Deep Draft Vertical Centrifugal Pump Guide


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Acknowledgments

Special thanks are extended to the following companies and individuals:

Bently Nevada Corporation, especially Don Bently and Jim Sasso, for their input

towards the vibration monitoring and equipment section (Appendix B)

Structural Dynamics Research Corporation (SDRC), especially Paul Caito, f or

providing information on computer aided test and analysis for the determination and

elimination of structural resonance conditions (Appendix C)

ENSR Consulting and Engineering, especially Charles "Chick" Sweeney, for their

assistance on sump design and slump model testing (Appendix D)

Johnston Pump Company, especially Herman Gruetink, for providing past

experiences on vertical condenser cooling water applications

Hydro Incorporated, especially David Allard, George Harris, Diedrick Brinkman,

and Jim Shaffer for their contribution and support towards the repair andtroubleshooting sections

Charles Stauffer of Stauffer and Associate s and James Sottosanto of Hydro

Engineering Services for their support m all areas of the document preparation

Dr. Elemer Makay of Energy Research and Consultants Corporation for the years of

guidance and support

In addition, NMAC and Hydro Engineering would like to thank the following people for

their extensive review and comments on this report.

John Forsman Northern States Power

Southern NuclearWill Gates

Ted Johnson Northeast Utilities

Harry LeBlanc Entergy

v




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vii

Table of Contents

Section 1.0 Introduction 1-1

Section 2.0 Technical Descriptions 2-1

2.1 Introduction........................................................................................... 2-1

2.2 Circulating System Classfications...................................................... 2-1

2.2.1 Once-Through Systems............................................................... 2-1

2.2.2 Closed-Loop Systems.................................................................. 2-3

2.3 Circulating System Components ........................................................ 2-4

2.3.1 Intake System.............................................................................. 2-42.3.2 Circulating Water Pumps............................................................. 2-9

Section 3.0 Common Field Problems 3-1

3.1 Vibration................................................................................................ 3-1

3.1.1 Unbalance.................................................................................... 3-1

3.1.2 Misalignment................................................................................ 3-2

3.1.3 Mechanical Looseness ................................................................ 3-3

3.1.4 Insufficient Damping at the Bearings........................................... 3-3

3.1.5 Resonance................................................................................... 3-4

3.1.6 Hydraulic Instability...................................................................... 3-5

3.1.7 Sump Induced Vibration .............................................................. 3-6

3.1.8 Vibration Testing and Analysis .................................................... 3-7

3.2 Loss of Performance............................................................................ 3-7

3.2.1 Head Variation............................................................................. 3-7

3.2.2 High Motor Amps ......................................................................... 3-9

3.2.3 Performance Testing Techniques................................................ 3-9


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Table of Contents (continued)

3.3 High Bearing Temperatures............................................................... 3-13

3.3.1 High Axial Thrust Loads............................................................. 3-13

3.3.2 Misalignment.............................................................................. 3-14

3.3.3 High Vibration ............................................................................ 3-15

Section 4.0 Component Inspection and Repair 4-1

4.1 Shaft ..................................................................................................... 4-1

4.1.1 Surface/Subsurface Cracks ......................................................... 4-1

4.1.2 Shaft Bow..................................................................................... 4-2

4.1.3 Damage to Threads..................................................................... 4-4

4.1.4 Loss of Integrity of Material Deposition ....................................... 4-5

4.1.5 Fretting ........................................................................................ 4-5

4.1.6 Damage to Keyways .................................................................... 4-6

4.1.7 Perpendicularity of Shaft End Faces ........................................... 4-6

4.2 Bearings................................................................................................ 4-7

4.3 Wear Components................................................................................ 4-8

4.4 Impellers.............................................................................................. 4-10

4.4.1 Surface and/or Subsurface Cracks............................................ 4-11

4.4.2 Cavitation Damage .................................................................... 4-11

4.4.3 Separation Damage...................................................................4-12

4.4.4 Inspection .................................................................................. 4-13

4.4.5 Suction Recirculation Damage .................................................. 4-14

4.4.6 Fretting/Galling of Bores............................................................ 4-14

4.4.7 Broken Shrouds or Vanes.......................................................... 4-14

4.5 Stationary Parts .................................................................................. 4-15


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4.5.1 Surface Cracks .......................................................................... 4-15

4.5.2 Erosion....................................................................................... 4-15

4.5.3 Alignment Fits ............................................................................ 4-16

4.6 Hardware ............................................................................................. 4-17

Appendix A General Pump Design and ApplicationGuide A-1

A.1 General Overview .................................................................................A-1

A.2 System Curve........................................................................................A-1

A.3 Pump Selection.....................................................................................A-4

A.3.1 Hydraulic Requirements ..............................................................A-4

A.3.2 Pump Length................................................................................A-5

A.3.3 Specific Speed...........................................................................A-12

A.3.4 Modelling Equations ..................................................................A-12

A.3.5 Affinity Laws...............................................................................A-14

A.3.6 Moody Equation.........................................................................A-17

A.4 Pump Curves.......................................................................................A-19

A.4.1 Performance ..............................................................................A-19

A.5 Motors..................................................................................................A-23

A.5.1 Horsepower ...............................................................................A-23

A.5.2 Speed-Torque Diagram .............................................................A-23

A.5.3 Reduced Voltage Starting..........................................................A-24

A.5.4 Axial Thrust................................................................................A-25

A.5.5 Starting and Stopping Procedures.............................................A-26

A.5.6 Karman-Knapp Diagrams (Reverse Runaway Speed) ..............A-27


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A.6 Pump Configuration ...........................................................................A-30

A.6.1 Above Ground vs. Below Ground Discharge ..........................A-30

A.6.2 Pull-out vs Non-Pull-out Construction.....................................A-31

A.7 Component Design.............................................................................A-33

A.7.1 Suction Bell .............................................................................A-34

A.7.2 Impeller ...................................................................................A-38

A.7.3 Back Wear Rings....................................................................A-40

A.7.4 Impeller Attachment ................................................................A-41

A.7.5 Bowl ........................................................................................A-43

A.7.6 Shaft/Bearing System .............................................................A-43

A.7.7 Line Shaft/Line Shaft Couplings..............................................A-49

A.7.8 Bearings..................................................................................A-51

A.7.9 Bearing Lubrication System....................................................A-53

A.7.10 Shaft Enclosing Tube..............................................................A-54

A.7.11 Column....................................................................................A-55

A.7.12 Discharge Elbow.....................................................................A-58

A.7.13 Stuffing Box.............................................................................A-59

A.7.14 Drive Coupling ........................................................................A-60

A.8 Materials of Construction ..................................................................A-61A.8.1 Erosion and Cavitation Resistance.........................................A-61

A.8.2 Corrosion ................................................................................A-63

A.8.3 First, Repair, and Replacement Costs ....................................A-65

Appendix B - Vibration Analysis and Mounting B-1

B.1 General Overview .................................................................................B-1


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B.2 Typical Malfunctions and Failure Modes............................................B-3

B.3 Basic Vibration Principles ...................................................................B-5

B.3.1 Basic Parameters.........................................................................B-5

B.3.2 Vibration Measurements..............................................................B-7

B.4 Vibration Transducer Selection.........................................................B-13

B.4.1 Selection Factors.......................................................................B-13

B.4.2 Transducer Types......................................................................B-13

B.4.3 Advantages and Disadvantages of Specific Transducers .........B-16

B.5 Monitoring Recommendations..........................................................B-18

B.5.1 Special Considerations..............................................................B-18

B.6 Evaluation and Diagnostics Information ..........................................B-19

B.7 Data Display, Presentation and Analysis .........................................B-20

B.7.1 Cascade and Waterfall Plots .....................................................B-20

B.7.2 Bode and Polar Plots.................................................................B-21

B.7.3 Shaft Centerline Position Plot....................................................B-23

B.7.4 Overall Amplitude Plot ...............................................................B-23

B.8 System Inspection and Maintenance................................................B-24

B.8.1 Visual Inspection .......................................................................B-25

B.8.2 Verification of Transducer Operation.........................................B-25

B.8.3 Instrument Calibration................................................................B-25

B.9 Case History - Dynamic of a Vertical Pump .....................................B-25

B.9.1 Introduction................................................................................B-25

B.9.2 Machine Description ..................................................................B-26

B.9.3 Transducer Selection.................................................................B-27


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B.9.4 Static Testing.............................................................................B-27

B.9.5 Field Testing ..............................................................................B-28

B.9.6 Imbalance ..................................................................................B-28

B.9.7 Misaligned Response Testing ...................................................B-30

B.9.8 Hydraulic Response Testing......................................................B-32

B.9.9 Summary....................................................................................B-32

Appendix C Troubleshooting of Vibration Problems in VerticalCondenser Cooling Water Pumps Using Computer-Aided Test, Analysis, and Design Techniques C-1

C.1 General Overview .................................................................................C-1

C.2 Background...........................................................................................C-2

C.3 Creating an Analytical Model.............................................................C-10

C.3.1 Testing.......................................................................................C-12

C.3.2 Analytical Modeling....................................................................C-13

C.3.3 Correlation .................................................................................C-14

C.3.4 Evaluating Design Modifications Using the CorrelationAnalytical Model ........................................................................C-16

C.4 Case History........................................................................................C-17C.4.1 Background................................................................................C-17

C.4.2 Modal Testing ............................................................................C-18

C.4.3 FEM Model Construction and Correlation..................................C-19

C.4.4 Design Modifications .................................................................C-22

C.4.5 Summary....................................................................................C-25

Appendix D Sump Design D-1

D.1 General Overview .................................................................................D-1


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D.2 Detrimental Effects of Poor Sump Design .........................................D-2

D.2.1 Approach Flow.............................................................................D-2

D.2.2 Effects of Approach Flow on Impeller Performance.....................D-3

D.2.3 Vortex Formation .........................................................................D-4

D.2.4 Debris Loading in Screen Systems..............................................D-4

D.2.5 Fish Protection.............................................................................D-5

D.2.6 Sediment Loading........................................................................D-5

D.3 Identifying Poor Sump Design.............................................................D-5

D.3.1 Field Testing ................................................................................D-5

D.3.2 Visual Observation ......................................................................D-6

D.3.3 Aural Observation........................................................................D-6

D.3.4 Vibration Measurements..............................................................D-6

D.3.5 Performance Measurements........................................................D-7

D.3.6 Laboratory Testing.......................................................................D-7

D.3.7 Model Scaling ..............................................................................D-8

D.3.8 Selection of Model Limits.............................................................D-8

D.3.9 Testing Program ........................................................................D-10

D.3.10Testing Procedures and Techniques.........................................D-10

D.3.11Acceptance Criteria ...................................................................D-11D.4 Remedying Poor Sump Design .........................................................D-12

D.4.1 Introduction................................................................................D-12

D.4.2 Modifying Approach Flow ..........................................................D-12

D.4.3 Changing Sump Relative Geometries........................................D-15

D.4.4 Sump Width ...............................................................................D-16


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D.4.5 Back Wall Clearance................................................................D-17

D.4.6 Bell to Floor Clearance.............................................................D-17

D.4.7 Minimum Vortex Submergence.................................................D-18

D.4.8 Localized Flow Guidance .........................................................D-20

D.4.9 Cones.......................................................................................D-20

D.4.10 Splitters ....................................................................................D-21

D.4.11 Fillets........................................................................................D-21

D.4.12 Formed Inlets ...........................................................................D-23

D.4.13 Grating Cages ..........................................................................D-23

D.4.14 Pump Design Modifications......................................................D-23

D.4.15 Operational Constraints ...........................................................D-23

D.5 The Sump Design Process ................................................................D-24

D.5.1 Introduction...............................................................................D-24

D.5.2 Design Responsibility...............................................................D-24

D.5.3 Design Sequence.....................................................................D-24

D.5.4 Preliminary Selection of Pumps................................................D-25

D.5.5 Selection of Screens ................................................................D-25

D.5.6 Conceptual Layout of the Station .............................................D-25

D.5.7 Hydraulic Model Testing...........................................................D-26

D.6 Case History........................................................................................D-26

D.6.1 Case History No. 1 ...................................................................D-26





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Appendix E References E-1


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xvii

List of Figures

2.1 Once-Through System.......................................................................................... 2-2

2.2 Closed-Loop System ............................................................................................ 2-3

2.3 Typical Trash Rack ............................................................................................... 2-5

2.4 Typical Traveling Water Screen............................................................................ 2-6

2.5 Modified Through-Flow Traveling Water Screen................................................... 2-7

2.6 Fish-Bucket-Type Screen Basket Assembly ......................................................... 2-8

3.1 Gap B ................................................................................................................... 3-6

3.2 Rigid Adjustable Motor Drive Coupling ................................................................. 3-8

4.1 Shaft End Machined with Relief............................................................................ 4-7

4.2 Areas of Cavitation Damage................................................................................. 4-12

4.3 Cavitation Damage to Vane.................................................................................. 4-134.4 Anti-Stall Hump..................................................................................................... 4-13

A.1 Low-Head Siphon System .................................................................................... A-2

A.2 Medium-Head Siphon System .............................................................................. A-3

A.3 High-Head Siphon System.................................................................................... A-3

A.4 Above and Below Ground Discharge Piping......................................................... A-5

A.5 Oscillation of an Overhanging Ruler ..................................................................... A-6

A.6 NPSH Corrections for Elevation and Temperature ............................................... A-8

A.7 Individual, System, and Combined Pump Curves................................................. A-10A.8 Efficiency vs. Specific Speed (Impeller Shape) .................................................... A-13

A.9 Pump Curve for Example 5................................................................................... A-17

A.10 Curve Shape vs. Specific Speed .......................................................................... A-19

A.11 Regions of Stable Operation................................................................................. A-20

A.12 Three Paralleling Pump vs. System Curve ........................................................... A-20


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List of Figures (continued)

A.13 Pump vs. System Curve ....................................................................................... A-22

A.14 Typical Speed vs. Torque Diagram....................................................................... A-24

A.15 Karman Knapp Diagram ....................................................................................... A-27

A.16 Reverse Speed vs. Specific Speed ...................................................................... A-28

A.17 Above Ground Discharge vs. Below Ground Discharge ....................................... A-30

A.18 Pull Out vs. Non-Pull Out...................................................................................... A-31

A.19 Bottom, Mid, and Top Seat Construction .............................................................. A-32

A.20 Pump Assembly.................................................................................................... A-33

A.21 Pump Bell profile................................................................................................... A-34

A.22 Suction Bell Umbrella............................................................................................ A-35

A.23 Recommended Sump Dimension Outlines ........................................................... A-37

A.24 Suction Bell with and w/o Bottom Bearing ............................................................ A-38

A.25 Open and Enclosed Impeller Design .................................................................... A-39

A.26 Back Wear Rings.................................................................................................. A-40

A.27 Impeller to Shaft Attachment Methods.................................................................. A-42

A.28 Shaft Coupling Designs ........................................................................................ A-50

A.29 Discharge Elbow Types ........................................................................................ A-58

A.30 Galvanic Series in Seawater................................................................................. A-66

B.1 Freedom System Motion....................................................................................... B-5

B.2 Mass Position at Any Point in Time....................................................................... B-6

B.3 Velocity Frequency ............................................................................................... B-8

B.4 In-Phase Vibration ................................................................................................ B-9

B.5 Out-of-Phase Vibration ......................................................................................... B-9

B.6 Amplitude vs. Time Plot ........................................................................................ B-10


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B.7 Orbital Presentation.............................................................................................. B-11

B.8 Frequency Domain ............................................................................................... B-12

B.9 Proximity Probe .................................................................................................... B-14

B.10 Velocity Transducer .............................................................................................. B-15

B.11 Accelerometer....................................................................................................... B-16

B.12 Cascade Plot ........................................................................................................ B-20

B.13 Waterfall Plot ........................................................................................................ B-21

B.14 Bode Plot .............................................................................................................. B-22

B.15 Polar Representation of Bode Plot ....................................................................... B-22

B.16 Shaft Centerline Position Plot ............................................................................... B-23

B.17 Overall Amplitude Plot .......................................................................................... B-24

B.18 Outline Drawing of Case History Pump................................................................. B-26

B.19 Submersible Proximity Probe Design.................................................................... B-27

B.20 Results of Case History Testing............................................................................ B-28

B.21 Case History Orbit Plots........................................................................................ B-29

B.22 Case History Time Base Plots .............................................................................. B-30

B.23 Case History Orbit Plots (in B Location) ............................................................. B-31

B.24 Case History Time Base Plots (in B Location) .................................................... B-31

C.1 Simple Single Degree of Freedom System........................................................... C-3

C.2 Transfer Function Plot .......................................................................................... C-4

C.3 Graphical Relation of Stiffness, Mass and Damping withRespect of Stiffness Modification.......................................................................... C-6

C.4 Effects of Stiffness Modification............................................................................ C-9

C.5 Effects of Mass Modification................................................................................. C-9C.6 Effects of Damping Modification........................................................................... C-10


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List of Figures (Continued)

C.7 Methodology Flow Chart....................................................................................... C-11

C.8 Modes Shapes of Simply Supported Shaft........................................................... C-12

C.9 Transfer Function.................................................................................................. C-13

C.10 1st Mode Shape of Case History Model................................................................ C-18

C.11 2nd Mode Shape of Case History Model .............................................................. C-18

C.12 Drive Point Transfer Function at Top of Motor ...................................................... C-19

C.13 Isometric View of Model........................................................................................ C-20

C.14 Analysis Mode Shape 1 ........................................................................................ C-20




C.18 Drive Point Transfer Functions ............................................................................. C-22

C.19 Design Modifications............................................................................................. C-23

C.20 Design Modifications............................................................................................. C-23

C.21 Analysis Mode Shape 1, Modified Design............................................................. C-24

C.22 Analysis Mode Shape 2, Modified Design............................................................. C-24

C.23 Drive Point Transfer Function - Modified Design .................................................. C-25

D.1 Impact of Pre-rotation on Impeller Approach Velocity Vectors.............................. D-2

D.2 Velocity and Energy Profile at a Section Through a Vortex.................................. D-3

D.3 Example of Circulation Pattern in a Sump Due to Approach Channel andTraining Wall Layout............................................................................................. D-13

D.4 Example of Guide Wall and Piers Improving Approach Flow VelocityDistribution............................................................................................................ D-13

D.5 T Shaped Flow Diffusers Used to Straighten Flow Entering a Sump orPump Bay ............................................................................................................. D-14

D.6 Perforated Plate Flow Baffling at the Entrance to Individual Pump Bays.............. D-15


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xxi


D.7 Relative Geometry of A Sump .............................................................................. D-17

D.8 Example of a Curtain Wall Used to Dissipate Surface Vortices............................ D-19

D.9 Example of Grating Used to Dissipate Surface Vortices....................................... D-19

D.10 Layout of Flow Guidance Near a Pump................................................................ D-20

D.11 Example of a Formed Inlet.................................................................................... D-22

D.12 Example of a Formed Inlet.................................................................................... D-22

D.13 Sump Design Process Case History - Site Plan ................................................... D-27

D.14 Sump Design Process Case History - Initial Conceptual Design .......................... D-29

D.15 Sump Design Process Case History - Final Conceptual Design........................... D-30

D.16 Case History No. 1 - Initial Sump Layout .............................................................. D-31

D.17 Case History No. 1 - Cone Profiles....................................................................... D-32


D.19 Case History No. 2 - Propose Sump Modifications............................................... D-35

D.20 Case History No. 2 - Baffle Plate Cone Modifications........................................... D-36

D.21 Case History No. 3 - Initial Intake Design ............................................................. D-37


D.23 Case History No. 3 - Sump Modification Details ................................................... D-39

D.24 Case History No. 3 - Intake Plan........................................................................... D-40


D.26 Case History No. 4 - Sump Modifications ............................................................. D-42

D.27 Case History No. 4 - Sump Modification Details ................................................... D-43


D.29 Case History No. 5 - Sump Modifications ............................................................. D-45

D.30 Case History No. 6 - Site Modifications................................................................. D-46


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xxiii

List of Tables

Table A.1 Frequency Ranges of Mechanical and Hydraulic Forces ................................ A-6

Table A.2 Shaft Material Properties................................................................................. A-45

Table A.3 Typical Bearing Diametrical Clearance............................................................ A-52

Table A.4 Typical Bearing L/D Ratios .............................................................................. A-52

Table A.5 Typical Shaft Enclosing Tube Data ................................................................. A-54

Table A.6 Discharge Elbow Head Loss ........................................................................... A-59

Table A.7 Material Erosion Properties ............................................................................. A-62

Table A.8 Typical Velocities Through Pump Components............................................... A-63

Table A.9 Typical Pump Materials of Construction .......................................................... A-67

Table B.1 Transducer Advantages and Disadvantages................................................... B-17

Table B.2 Monitoring Recommendations......................................................................... B-18

Table B.3 Monitoring Recommendations - Scaled Down................................................. B-18

Table B.4 Rotor Natural Frequencies .............................................................................. B-29

Table D.1 Basic Sump Dimension Based on Pump Bell Diameter................................... D-16


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1.0 Introduction

Deep draft vertical centrifugal pumps (also referred to as circulating water pumps and

condenser cooling water pumps) provide many challenges to maintenance personnel. In

developing a guide for these pumps it became clear that the pump design, the effects of the

intake structure, and water quality can all significantly influence the overall operability ofthe pumps. Hence the scope of this guide covers the pump, its application in the circulating

water system and the intake structure design and maintenance. While the primary focus

has been on deep draft vertical centrifugal pumps, some aspects of this guide can be applied

to all vertical centrifugal pumps.

Chapter 2.0, Technical Descriptions, covers an overview of the circulating water system.

This includes the specific components of the intake structure and the deep draft ver tical

centrifugal pumps that provide the motive force for the circulating water system. This

chapter provides a comprehensive background for the new system engineer and an excellent

review for those with system experience.

Chapter 3.0, Common Field Problems, covers the troubleshooting of these pumps in threebasic areas; high vibration, loss of performance, and high bearing temperatures. This

chapter can be applied to many other c entrifugal pumps and should be considere d as a

general vertical centrifugal pump troubleshooting guide.

Chapter 4.0, Component Inspection and Repair, c overs the proper techniques to conduct acomprehensive inspection and the corresponding repair activities. While this section waswritten for deep draft vertical centrifugal pumps in circulating water service, the scope ca nbe applied to other centrifugal pumps. This section cover s shafts, bearings, wearcomponents, impellers, stationary components, and other hardware.

Appendix A, General Pump Design and Application Guide, covers the design process for a

new pump and sump installation. This process will be very informative to both the systemengineer and maintenance engineer in providing a better understanding of the factors that

can affect the pump performance and reliability.

Appendix B, Vibration Analysis and Monitoring, provides a general introduction to

vibration analysis. The appendix also provides recommendations for prope r probe type

selection and placement. These recommendations are applicable to most vertical

centrifugal pump applications.

Appendix C, Troubleshooting Vibration Problems in Vertical Condenser Cooling Water

Pumps Using Computer Aided Test, Analysis, and Design Techniques, provide s a summary

of a methodology used to troubleshoot structural resonant vibra tion problems in deep draft

vertical centrifugal pumps.

Appendix D, Sump Design and Analysis, covers the detrimental effects of poor sump design,

how to identify a poor design, and finally ways to modify an existing sump to alleviate these

problems.

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2.0 Technical Descriptions

This maintenance guide covers the maintenance, troubleshooting, and application of deep

draft vertical centrifugal pumps. These pumps are typically used in circulating water

systems as the primary cooling source for the power plant's main condensers. Because

these pumps are susceptible to detrimental affects from other components in the circulating

water system, this technical description section will cover those components that may affect

the operation and maintenance of deep draft vertical centrifugal pumps.

2.1 Introduction

The circulating-water system supplies cooling water to the turbine condensers and thus

rejects heat from the steam cycle to the environment. The system may also provide lesser

amounts of auxiliary cooling water for various f unctions throughout the plant.

The circulating system must effectively reject heat from the plant to the environment but

at the same time conform to thermal-discharge regulations. The circulating water system

performance is vital to the power plant's efficie ncy. A condenser operating at the lowesttemperature possible results in maximum turbine work, maximum cycle efficiency and

minimum heat rejection. Hence a good heat-rejection system makes its own job easier.

2.2 Circulating System Classifications

2.2.1 Once-through Systems

A once-through system takes its suction from a natural body of water such as a lake, riveror ocean and pumps it through the condenser where it removes heat from the condensing

steam and then discharges back to the sour ce. A once through cooling system is,thermodynamically, the most efficient means of heat rejection. It typically uses the lowest-

temperature heat sink available to the power plant.

Figure 2-1 shows the basic layout of this type of system. The intake structure provides a

controlled flow of water to the circulating water pumps. The circulating water pumps

provide the motive power for the circulating water to pass through the condenser. The size

and number of circulating water pumps depends on the heat rejection requirements of the

plant.

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2.2.2 Closed-Loop Systems

In some instances the use of a once-through system is not possible and a closed-loop system

is used. This will typically occur when water is scarce or when environmental regulations

limit the utilization of surface waters or its temperature rise.

A closed-loop system typically consists of a cooling device, circulating water pumps, and the

condenser. This is shown in Figure 2-2. A source for makeup water is still needed for this

system, but the overall water requirements a re much less than that of a once-through

system.

Figure 2.2

Closed-Loop System

There are several types of cooling devices available for a closed loop system:

2.2.2.1 Cooling Towers

Cooling towers can be a wet-type, dry-type or a combination of the two. The majority of

those in use are wet-type. Wet-cooling towers dissipate plant rejected heat to the

environment by the addition of sensible heat to the air and the evaporation of a portion ofthe recirculation water itself.

The basic operation of a cooling tower provides heat transfer between the circulating water

and the atmosphere. This is done by showering or spraying the circulating water into the

path of a moving air mass. The water's surface area is increased through the use of a

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lattice work of slats called fill or packing. The water cascades down through the fill driven

by gravity and collects in a basin at the bottom of the cooling tower.

The air is driven by mechanical or natural means. In a mechanical draft cooling tower the

air is moved by forced or induced draft fans. Natural draft air flow uses no fans but relies

upon the natural driving pressure caused by the difference m density between the cool

outside air and the hot, humid air inside. In order to achieve the desired air flow, naturaldraft towers are typically very tall. Natural draft cooling towers are typically built with a

hyperbolic vertical profile and hence, are called hyperbolic towers. The hyperbolic profile

has been found to offer superior strength and the greatest resistance to outside wind

loading and has little to do with inside air flow.

The direction that the air flows through the fill determines whether the tower is classified

as counter-flow (water moves down and air moves up through the fill) or cross-flow (water

moves down and air moves horizontally through the fill).

2.2.2.2 Spray Ponds

Spray ponds rely upon the winds that blow across the ponds to cool fine sprays of water byevaporation.

2.2.2.3 Spray Canals

Spray canals operate similarly to spray ponds except that the water is sprayed into larger

droplets to minimize the drift loss that occurs when water droplets are carried beyond the

pond surface by the wind.

2.2.2.4 Cooling Lakes

Cooling lakes depend upon being cooled naturally by evaporation and radiation of the

thermal energy. They are the least efficient and he nce require the greatest acreage, butthey also require the least mechanical equipment.

2.2.2.5 Combination Systems

Any of the above systems can be combined to deal with certain situations. A cooling tower

can be used with an open system to minimize the temperature differential before

discharging back to the environment.

2.3 Circulating System Components

The intake structure's sole purpose is to provide clean water with proper hydraulic

properties to the circulating water pumps. If it fails in this purpose, due to either design

problems or unforeseen environmental issues, the result can be pump failure. A large

number of circulating water pump failures can be attributed to problems with the sump

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2.3.1 Intake System

2.3.1.1 Intake Structure


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and not the fault of the pump's design or manufacture. This is discussed in more detail in

Appendix D.

The intake system starts with a skimmer wall that assists on obtaining cooler water fromthe water source in a once-through system. The intake structure is located on the land end

of the intake channel and is constructed of reinforced concrete.

2.3.1.2 Trash Racks

Trash Racks are typically the first line of defense to prevent debris from entering the

circulating water system. Trash Racks (F igure 2-3) consist of vertical bars mounted close

together with a raking mechanism that removes the debris as it accumulates.

The spacing of the bars should be such that items which may damage the pump will not

pass through. This is generally dictated by the size of the circulating pump. A general rule

is to space the bars at 50% of the largest sphere that the pump can handle.

The arrangement of the bars and the rate of the raking mechanism both affect the head

loss that occurs across the rack. During times of heavy trash load, the velocity of the water

that does pass will be higher and can affect the turbulence and velocity in the intake

structure itself.

Figu r e 2 . 3

Typical Trash Rack

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2.3.1.3 Traveling Water Screens

Traveling water screens are typically located downstream from the bar racks and filter out

trash of a much smaller size. This is accomplished by using a smaller mesh size than the

bar racks and by continuously moving and cleaning the screens. This allows the removal of

trash that is smaller than the pump's requirements and takes into consideration the size of

other components in the circulating system such as condenser tubes or spray nozzles.

Figure 2-4 shows a typical traveling water screen. A traveling water screen consists of

multiple assemblies with screen panels. The screen has a typical opening of 3/8 in. x 3/8

in., which is cleaned by jet spray nozzles into a trash trough at the top of the screen

mechanism.

F i g u r e 2 . 4

Typical Traveling Water Screen

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Modified designs include mechanisms for the protection of fish life. Figure 2-5 shows the

general layout of a traveling water screen that has been modified to provide a safe travel

path for fish small enough to pass thro ugh the bar rack but too big for the scr een mesh size

of the traveling screen. Figure 2-6 shows a c loseup of the individual screen assemblies.

Figure 2.5

Modified Through-Flow Traveling Water Screen

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Figure 2.6

Fish-Bucket-Type Screen Basket Assembly, Salem CWS

(Source: Public Service Electric and Gas Company, 1984)

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2.3.2 Circulating Water Pumps

The circulating water pumps deliver a large volume of water at relatively low head. The

pumps are typically single-stage, mixed flow designs and can be oriented either vertically or

horizontally.

Vertical designs are designated wet-pit pumps since these models take suction directly froman open pit. The pump impeller is over hung and the pump thrust is usually taken by the

motor thrust bearings through a rigid coupling.

Please refer to Appendix A for a more de tailed explanation on application guidelines and

helpful examples.

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3.0 Common Field Problems

When attempting to "cure" a field problem, it is important to ascertain its root cause(s).

This requires a dialogue between "the pump" and "the analyst" to define the nature and

severity of the problem. Pumps have their own language to communicate normal or

abnormal operation. It is the analyst's responsibility to understand the subtle nuances ofthis foreign language so that the information is processed correctly in establishing the

proper conclusions. The principal dialects of the pump language are:

Vibration Waveforms Performance Bearing Temperature

Common field problems result in a change f rom standard in one or more of the above

categories leading to high vibration, increase or decrease in performance, and/or a rise in

bearing temperature. Proper investigative work in curing the problem requires:

Obtaining complete dataUnderstanding correlation between data and probable causes

Continued exploration to precipitate the root cause( s)

Modifying design or operation to remove or mitigate the root cause(s)

This section discusses common field problems of condenser cooling water pumps as theyrelate to the measurable parameters provided by the equipment - vibration, performance,and bearing temperature; provides guidance on how to pinpoint the actual root cause( s) ofthe problem; and suggests solutions for its remedy.

3.1 Vibration

Vibration analysis provides the greatest diagnostic information to the analyst. It is the

"blood work" in the pumps physical exam. A complete discussion of vibration diagnostics

and monitoring is provided in Appendix B.

Various factors affect both the occurrence and severity of vibration. These include:

Unbalance

Misalignment

Mechanical Looseness

Resonance

Hydraulic Instability

Sump Induced Vibration

3.1.1 Unbalance

Some degree of unbalance is always present in pump parts. Normally all major rotating

parts are dynamically balanced during manufacture or repair. Little vibration should be

experienced in new or recently repaired pumps unless the work was not properly

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accomplished. Unbalance can, however, increase as the pump is operated, usually as aresult of:

Component material loss or damage

Bowing of the shaft

Material loss or damage can be due to several factors including:

Abrasive solids m the liquid

Corrosive attack by contaminants m the liquid

Cavitation/separation damage of hydraulic components

Foreign objects passing through the pump

Regardless of the cause, vibration due to unbalance occurs at a frequency corresponding to1x (one times rotational speed) with the primary amplitude in the radial direction.

In order to correct rotor unbalance, the pump must be removed and the major rotating

parts balanced to acceptable limits. MIL-S-167 (Military specification) and API-610

(American Petroleum Institute specification) generally concur that the maximumacceptable residual unbalance is 4xW/N; where W is the rotor weight (lbs), and N is the

rotor speed (rpm). For high energy pumps such as the vertical condenser cooling water

pump, it is recommended that the impeller be statically and dynamically balanced so that

the maximum residual unbalance does not exceed 1xW/N.

If the fundamental cause of the unbalance is from damage during operation, the problem

will continue to return unless the source of the problem is removed.

3.1.2 Misalignment

Some small amount of misalignment will always be present in a system. Provided the

alignment is within normal limits, little vibration should be experienced due to initialmisalignment. If, however, the proper alignment at the various shaft couplings is not

accomplished during assembly and installation, significant vibrations may be experienced.

Vibrations due to misalignment exhibit themselves in the frequency domain at 1x and its

harmonics (2x, 3x, etc.). The harmonics are not really vibrations at those frequencies, but a

response of the digital signal process when motion is restricted.

Vibrations due to misalignment can only be cured by removing the pump and inspecting:

Dimensional clearance and concentricity of alignment fitsPerpendicu lar i ty o f a l ignment faces to the shaf t ax i s

Parallelism of the alignment faces to each other

Attention should be paid to the rabbet fits locating the shaft bearings. Parts which do not

assist in alignment based on the results of the inspection must either be repaired, replaced

or redesigned as required.

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3.1.3 Mechanical Looseness

Another cause of vibration in condenser cooling pumps is mechanical looseness. This can

result from:

Rabbet fits being or becoming loose

Loose or inadequate bolting at one or more connections Looseness at the pump foundation joint (due to improper or broken grouting)Lack of crush between the bearing and its support

Increased clearance between the bearing and journal

Looseness of the rotating element with respect to stationary components exhibits itself as

harmonics of running speed (1x, 2x, 3x, etc.) when lightly loaded. I t is not uncommon to

also see harmonics at running speed; i.e., 1x, 2x, etc. The harmonics are once again

due to digital signal processing of the sine wave being "clipped" when the loose parts hit

against the limit of their movement. In addition to harmonics, looseness can be detected by

a decrease in amplitude at higher load.

Highest amplitudes are normally found at 1x and 2x when caused by looseness between thepump and foundation. The vibration may be high in both radial and axial directions.

In order to reduce or eliminate vibra tion due to mechanical looseness, the looseness must be

eliminated. To accomplish this the pump must be removed and all fits inspected to ensure

proper fit. All bolting must be checked to ensure tightness. Parts which are loose must

either be repaired, replaced or redesigned as required. If the vibration after rework

remains unchanged, it is an indicatio n that the bolting design is inadequate. In this case

the bolting must be redesigned to provide additional strength.

3.1.4 Insufficient Damping at the Bearings

Insufficient damping can result from:

Improper bearing designExcessive bearing clearance

Vertical condenser cooling water pump radial bearings are lightly loaded. A decrease in thedamping will aggravate this situation and result in a vibra tion at approximately x. It iscaused by the bearing riding up on its high pressure wed ge and falling to the other side.This phenomenon is worsened with increased bearing clearance.

A reduction in damping will also affect the shaft critical speed. In the extreme, the effectwould be the same as having no bearing present since with extreme wear the bearing

provides no support for the shaft.

The first inspection should be to check the bearing clearance. If the clearances are withindesign tolerances, then a new bearing design may be appropriate. An upgraded design mayconsider:

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Closer bearing clearanceAxial groovesPressure damLobed journalsTilting pads

If the high vibration is a result of bearing wear, a simple r eplacement of the bearing may be

sufficient. If the bearing wear recurs too quickly, replacement bearings of different

material may be required. Also, the addition of, or modification to, a clean water flush

system may be needed to increase bearing life.

3.1.5 Resonance

If any pump internal or external forcing freque ncy approximately coincides with the

natural frequenc y of the rotor or any component/assembly, the vibra tion amplitude will

increase. The magnitude of this increase is dependent on the pump or rotor damping. The.

coincidence of forcing and natural frequency is called resonance. Under resonant

conditions, a very small exciting input force can, and most often will, result in a very large

and potentially damaging vibration amplitude which requires immediate action to correct.

The correction of resonance problems is seldom easy and frequently requires sophisticated

techniques (See Appendix C). There are only two ways to eliminate a resonant condition:

change the exciting frequency or alter the natural frequency. Usually the exciting

frequency cannot be eliminated, so the resonant natural frequency must be changed.

In order to reduce vibration amplitude to suitable levels the natural frequency should be atleast 25% above or below the exciting frequency. As noted in Appendix A, the shaft criticalspeed should be at least 60% above the operating speed. Methods used to modify theresonant frequency vary with the component design.

For example, there are several ways to increase the natural frequency of the line shaft:

Increase the shaft diameterDecrease the bearing spacingChange the shaft material (incre ase Young's Modulus, E)

Naturally, any combination of the above may be used concurrently.

The modifications required for a column pipe are totally different. The natural frequency of

this component can be altered by:

Changing the wall thickness of the pipe

Adding full length ribsChanging the length

Again, a combination of these corrections can be used to effe ct the change to the naturalfrequency. Note that adding ribs can only increase the natural frequency. Changing thethickness and length can either increase or decrease the natural frequency (increasedthickness and decreased length will increase the natural frequency).

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3.1.6 Hydraulic Instability

Any hydraulic instability in the pump or system will be reflected in the operating vibration

levels of the pump. These include

Cavitation due to insufficient NPSHAFlow separation at the impeller inletRecirculation at the impeller outlet and casing inlet

Impact loading of the exiting impeller flow on the stationary casing vanes

Flow separation at the discharge elbowOperation in the unstable portion of the pump curve

Hydraulic resonances in the piping system

The frequency range for hydraulic insta bility varies with the cause and is categorized

below:

Cavitation:

Flow separation/recirculation:

Impact loading:Hydraulic resonance:

Broadband vibration in the 3-5kHz range4-10 Hz and 0.55x to 0.90x

Vane pass frequencyDischarge pipe natural frequency

Hydraulic instability due to flow separation/recirculation results in subsynchronous

vibrations which can be extremely damaging to the pump and must be identified and

corrected. Unfortunately, this type of hydraulic instability is often confused with the

conditions previously described for insufficiently damped bearings since both events are

closely associated on the frequency spectrum.

Flow separation in the impeller eye results in cavitation damage to either the visible(suction) or non-visible (pressure) side of the blade. This phenomenon can be lessened oreliminated by redesigning the inlet vane profile to include an Anti-stall hump (see S ection

4.4.4).

Impact loading is a result of having a too-tight Gap "B" (F igure 3.1). Gap B is defined by:

D3 - D2Gap B = 3.1

D2

D 2 = Impel ler ex i t d iameter

D 3 = Bowl in le t d iameterwhere:

The remedy is to increase Gap B to an acce ptable design without affecting the hea d

recovery of the bowl.

Flow separation damage at the discharge elbow can be fixed by including flow splitter(s) in

the elbow to remove the stall condition at the turn.

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Figure 3.1

Gap B

3.1.7 Sump Induced Vibration

Sump induced vibrations can result from many factors. This subject is covered in depth in

Appendix D. Normally, sump induced vibrations result from the improper relationship of

pump position and sump geometry, and/or poor sump inlet condit ions (including trash rack

and/or screen design).

Sump problems frequently result in the formation of surface and/or subsurface vortices.

The vibrations caused by vortices will appear at vane passing frequency and multiples

thereof. Other random vibrations will be prevalent due to other sump induced hydraulic

instabilities.

Since vibrations due to vortexing can be damaging, it is imperative that the cause beidentified and corrected . The best way to achieve stable flow in the sump for all operating

conditions is to perfor m a sump model test. Models of this type permit many inexpensive

modifications to be made to determine the most effective correction at the lowest possible

cost.

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3.1.8 Vibration Testing and Analysis

In order to properly qualify and quantify pump vibrations, it is necessary to use one of the

various vibration analyzers that are on the market. New or recently repa ired pumps

should be vibration tested as soon after installation as possible. It is important during this

testing that the pump be operating in a normal fashion; without cavitation or separation;

with uniform, non-vortexing flow in the sump; and with the pump producing a total headequal to the specified design head.

This initial test record should be retained as a reference to trend all future readings. The

cause of any abnormally high vibration readings found during this initial testing should be

identified and corrected as necessary. Frequently, the change of vibration levels with time

is more significant than the initial levels. Higher vibrations can be accommodated if there

is no increase in levels over a long period of time and there is no other indication of damage

to bearings or increase in noise level.

For further discussion of vibration testing and analysis, refer to Appendix B.

3.2 Loss of Performance

3.2.1 Head Variation

Pump performance may indicate either pump or system problems. As shown in Figure A.7,

pumps always operate at the intersection of the pump and system resistance curves. If a

new pump does not provide the proper flow rate, either the pump furnished or the hydraulic

conditions specified were incorrect.

Frequently, incorrectly specified hydraulic conditions result from extreme conservatism in

the determination of the system head. Use of friction factors for old pipe and safe ty factors

are the most common culprits. This is compounded by the fact that Hydraulic Institute

standards do not allow a negative tolerance on delivered performance ; but allow up to 10%higher flow or 5% higher head, whichever is greater.

If the actual flow is too high, the impeller can be remachined to obtain design conditions.

Depending on the specific speed (Ns) of the design, this remachining may be a decrease in

the outside diameter for lower Ns designs or a change in the vane length on higher Ns

designs.

Far less often, the pump has too little flow at initial start-up as a result of the system headbeing higher than specified. Increased output of the pump can be achieved by:

Underfiling the impeller vane (the amount of flow increase depends on the specific

speed of the pump and impeller exit angle, 2 )Reducing system friction losses

Purchasing a new impeller

Purchasing a new pump

Care must be taken so that any changes to the pump hydraulics will not result in a pump

horsepower requirement which exceeds the motor rating.

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The top half coupling hub mounted on the motor shaftThe bottom half coupling hub mounted on the pump shaftA nut used to adjust the vertical position of the rotor, mounted on the pump shaftThrough bolts and nuts to connect the coup ling halves

When checking the pump setting ,most of the through bolts are disassembled. A few bolts

are left in place to ease the pump rotor down onto the impeller shroud. A feeler gage isemployed between the adjustable nut and the top half coupling hub to determine what therunning clearance is between the impeller and shroud. If the recorded clearance is notwithin design standards, the vertical position of the rotor may be adjusted by turning thecoupling nut in the appropriate direction to either lift or lower the rotor the calculateddistance. The coupling halves are then re-connected by installing and tightening allthrough bolts.

Poor inlet conditions can sometimes be visually observed; however, more often than not,

this situation requires model testing. All other inspections require pump removal and

disassembly.

3.2.2 High Motor Amps

Higher specific speed pump designs have different shaped curves than the other centrifugalpumps used in power plants. Higher Ns pump curves have several distinct features:

The head vs. capacity curve is steepThe head vs. capacity curve usually contains an unstable regionThe horsepower vs capacity curve rises to shut-off

Rising motor amps is directly related to increased pump horsepower, and can result from:

Operation at lower flow rates

Increased motor thrust bearing friction due to higher a xial loads at lower flow rates

Internal rubbingPacking adjusted too tightly

If any, or a combination of these items is sufficiently large, the current drawn by the motor

will exceed the nameplate rating and may cause the motor to trip offline due to overload.

3.2.3 Performance Testing Techniques

Soon after installation, any new pump should be performance tested to provide a base line

for comparison with future tests. If this is to be used for acceptance of the pump(s), the

testing must be performed in accordance with a recognized standard such as Hydraulic

Institute Standards.

Various items of data must be recorded using calibrated instruments. The readings to betaken are:

The setting is defined as the vertical lift (or clearance) of the impeller off of the shroud.

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Discharge pressureSump liquid level below dischargeFlow in GPM using a venturi, nozzle or orificeLiquid temperatureHorsepower draw of the motor

Discharge pressure must be recorded using a calibrated pressure gage or transducer. It isimportant that steady flow conditions exist at the point of measurement. It is also

important that the connection to the pipe does not affect the flow past the connection. Refer

to the Hydraulic Institute Standards for proper pipe taps.

The pressure reading must be converted to feet of cold (60 F) water with a specific gravity

of 1.0 referred to the centerline of the pump discharge.

During operation the liquid level in the sump must be determined and referred to the

centerline of the discharge.

Total head is defined as the rea ding of the discharge gauge in feet, plus the velocity head in

the pipe at the gauge connection in feet, plus the vertic al distance from the gauge center to

the free water level in the sump in ft.

Pd x 2.31TH =

V3.2+ + (Z -Z )

2gS. G

Gravitational constant (32.2 ft/sec )where:= Discharge pressure reading (psig)Pd

Specific gravity of the liquid, (1.0 for fresh water and cool

Documents

Maintenance and Application Guide for Centrifugal Pump