pump characteristics and applications

Pump Characteristicsand Applications

Second Edition

2005 by Taylor & Francis Group, LLC

MECHANICAL ENGINEERINGA Series of Textbooks and Reference Books

Founding Editor

L. L. Faulkner

Columbus Division, Battelle Memorial Instituteand Department of Mechanical Engineering

The Ohio State UniversityColumbus, Ohio

1. Spring Designers Handbook, Harold Carlson2. Computer-Aided Graphics and Design, Daniel L. Ryan3. Lubrication Fundamentals, J. George Wills4. Solar Engineering for Domestic Buildings, William A. Himmelman5. Applied Engineering Mechanics: Statics and Dynamics, G. Boothroyd

and C. Poli6. Centrifugal Pump Clinic, Igor J. Karassik7. Computer-Aided Kinetics for Machine Design, Daniel L. Ryan8. Plastics Products Design Handbook, Part A: Materials and Components;

Part B: Processes and Design for Processes, edited by Edward Miller9. Turbomachinery: Basic Theory and Applications, Earl Logan, Jr.10. Vibrations of Shells and Plates, Werner Soedel11. Flat and Corrugated Diaphragm Design Handbook, Mario Di Giovanni12. Practical Stress Analysis in Engineering Design, Alexander Blake13. An Introduction to the Design and Behavior of Bolted Joints,

John H. Bickford14. Optimal Engineering Design: Principles and Applications, James N. Siddall15. Spring Manufacturing Handbook, Harold Carlson16. Industrial Noise Control: Fundamentals and Applications, edited by

Lewis H. Bell17. Gears and Their Vibration: A Basic Approach to Understanding Gear Noise,

J. Derek Smith18. Chains for Power Transmission and Material Handling: Design

and Applications Handbook, American Chain Association19. Corrosion and Corrosion Protection Handbook, edited by

Philip A. Schweitzer20. Gear Drive Systems: Design and Application, Peter Lynwander21. Controlling In-Plant Airborne Contaminants: Systems Design

and Calculations, John D. Constance22. CAD/CAM Systems Planning and Implementation, Charles S. Knox23. Probabilistic Engineering Design: Principles and Applications,

James N. Siddall


24. Traction Drives: Selection and Application, Frederick W. Heilich III and Eugene E. Shube

25. Finite Element Methods: An Introduction, Ronald L. Huston and Chris E. Passerello

26. Mechanical Fastening of Plastics: An Engineering Handbook, Brayton Lincoln, Kenneth J. Gomes, and James F. Braden

27. Lubrication in Practice: Second Edition, edited by W. S. Robertson28. Principles of Automated Drafting, Daniel L. Ryan29. Practical Seal Design, edited by Leonard J. Martini30. Engineering Documentation for CAD/CAM Applications, Charles S. Knox31. Design Dimensioning with Computer Graphics Applications,

Jerome C. Lange32. Mechanism Analysis: Simplified Graphical and Analytical Techniques,

Lyndon O. Barton33. CAD/CAM Systems: Justification, Implementation, Productivity

Measurement, Edward J. Preston, George W. Crawford, and Mark E. Coticchia

34. Steam Plant Calculations Manual, V. Ganapathy35. Design Assurance for Engineers and Managers, John A. Burgess36. Heat Transfer Fluids and Systems for Process and Energy Applications,

Jasbir Singh37. Potential Flows: Computer Graphic Solutions, Robert H. Kirchhoff38. Computer-Aided Graphics and Design: Second Edition, Daniel L. Ryan39. Electronically Controlled Proportional Valves: Selection and Application,

Michael J. Tonyan, edited by Tobi Goldoftas40. Pressure Gauge Handbook, AMETEK, U.S. Gauge Division, edited by

Philip W. Harland41. Fabric Filtration for Combustion Sources: Fundamentals and Basic

Technology, R. P. Donovan42. Design of Mechanical Joints, Alexander Blake43. CAD/CAM Dictionary, Edward J. Preston, George W. Crawford,

and Mark E. Coticchia44. Machinery Adhesives for Locking, Retaining, and Sealing, Girard S. Haviland45. Couplings and Joints: Design, Selection, and Application, Jon R. Mancuso46. Shaft Alignment Handbook, John Piotrowski47. BASIC Programs for Steam Plant Engineers: Boilers, Combustion,

Fluid Flow, and Heat Transfer, V. Ganapathy48. Solving Mechanical Design Problems with Computer Graphics,

Jerome C. Lange49. Plastics Gearing: Selection and Application, Clifford E. Adams50. Clutches and Brakes: Design and Selection, William C. Orthwein51. Transducers in Mechanical and Electronic Design, Harry L. Trietley52. Metallurgical Applications of Shock-Wave and High-Strain-Rate Phenomena,

edited by Lawrence E. Murr, Karl P. Staudhammer, and Marc A. Meyers53. Magnesium Products Design, Robert S. Busk54. How to Integrate CAD/CAM Systems: Management and Technology,

William D. Engelke


55. Cam Design and Manufacture: Second Edition; with cam design software for the IBM PC and compatibles, disk included, Preben W. Jensen

56. Solid-State AC Motor Controls: Selection and Application, Sylvester Campbell

57. Fundamentals of Robotics, David D. Ardayfio58. Belt Selection and Application for Engineers, edited by Wallace D. Erickson59. Developing Three-Dimensional CAD Software with the IBM PC, C. Stan Wei60. Organizing Data for CIM Applications, Charles S. Knox, with contributions

by Thomas C. Boos, Ross S. Culverhouse, and Paul F. Muchnicki61. Computer-Aided Simulation in Railway Dynamics, by Rao V. Dukkipati

and Joseph R. Amyot62. Fiber-Reinforced Composites: Materials, Manufacturing, and Design,

P. K. Mallick63. Photoelectric Sensors and Controls: Selection and Application, Scott M. Juds64. Finite Element Analysis with Personal Computers, Edward R. Champion, Jr.

and J. Michael Ensminger65. Ultrasonics: Fundamentals, Technology, Applications: Second Edition,

Revised and Expanded, Dale Ensminger66. Applied Finite Element Modeling: Practical Problem Solving for Engineers,

Jeffrey M. Steele67. Measurement and Instrumentation in Engineering: Principles and Basic

Laboratory Experiments, Francis S. Tse and Ivan E. Morse68. Centrifugal Pump Clinic: Second Edition, Revised and Expanded,

Igor J. Karassik69. Practical Stress Analysis in Engineering Design: Second Edition,

Revised and Expanded, Alexander Blake70. An Introduction to the Design and Behavior of Bolted Joints: Second Edition,

Revised and Expanded, John H. Bickford71. High Vacuum Technology: A Practical Guide, Marsbed H. Hablanian72. Pressure Sensors: Selection and Application, Duane Tandeske73. Zinc Handbook: Properties, Processing, and Use in Design, Frank Porter74. Thermal Fatigue of Metals, Andrzej Weronski and Tadeusz Hejwowski75. Classical and Modern Mechanisms for Engineers and Inventors,

Preben W. Jensen76. Handbook of Electronic Package Design, edited by Michael Pecht77. Shock-Wave and High-Strain-Rate Phenomena in Materials, edited by

Marc A. Meyers, Lawrence E. Murr, and Karl P. Staudhammer78. Industrial Refrigeration: Principles, Design and Applications, P. C. Koelet79. Applied Combustion, Eugene L. Keating80. Engine Oils and Automotive Lubrication, edited by Wilfried J. Bartz81. Mechanism Analysis: Simplified and Graphical Techniques, Second Edition,

Revised and Expanded, Lyndon O. Barton82. Fundamental Fluid Mechanics for the Practicing Engineer,

James W. Murdock83. Fiber-Reinforced Composites: Materials, Manufacturing, and Design,

Second Edition, Revised and Expanded, P. K. Mallick84. Numerical Methods for Engineering Applications, Edward R. Champion, Jr.


85. Turbomachinery: Basic Theory and Applications, Second Edition, Revisedand Expanded, Earl Logan, Jr.

86. Vibrations of Shells and Plates: Second Edition, Revised and Expanded,Werner Soedel

87. Steam Plant Calculations Manual: Second Edition, Revised and Expanded,V. Ganapathy

88. Industrial Noise Control: Fundamentals and Applications, Second Edition,Revised and Expanded, Lewis H. Bell and Douglas H. Bell

89. Finite Elements: Their Design and Performance, Richard H. MacNeal90. Mechanical Properties of Polymers and Composites: Second Edition,

Revised and Expanded, Lawrence E. Nielsen and Robert F. Landel91. Mechanical Wear Prediction and Prevention, Raymond G. Bayer92. Mechanical Power Transmission Components, edited by David W. South

and Jon R. Mancuso93. Handbook of Turbomachinery, edited by Earl Logan, Jr.94. Engineering Documentation Control Practices and Procedures,

Ray E. Monahan95. Refractory Linings Thermomechanical Design and Applications,

Charles A. Schacht96. Geometric Dimensioning and Tolerancing: Applications and Techniques

for Use in Design, Manufacturing, and Inspection, James D. Meadows97. An Introduction to the Design and Behavior of Bolted Joints: Third Edition,

Revised and Expanded, John H. Bickford98. Shaft Alignment Handbook: Second Edition, Revised and Expanded,

John Piotrowski99. Computer-Aided Design of Polymer-Matrix Composite Structures, edited by

Suong Van Hoa100. Friction Science and Technology, Peter J. Blau101. Introduction to Plastics and Composites: Mechanical Properties

and Engineering Applications, Edward Miller102. Practical Fracture Mechanics in Design, Alexander Blake103. Pump Characteristics and Applications, Michael W. Volk104. Optical Principles and Technology for Engineers, James E. Stewart105. Optimizing the Shape of Mechanical Elements and Structures, A. A. Seireg

and Jorge Rodriguez106. Kinematics and Dynamics of Machinery, Vladimr Stejskal

and Michael Valsek107. Shaft Seals for Dynamic Applications, Les Horve108. Reliability-Based Mechanical Design, edited by Thomas A. Cruse109. Mechanical Fastening, Joining, and Assembly, James A. Speck110. Turbomachinery Fluid Dynamics and Heat Transfer, edited by Chunill Hah111. High-Vacuum Technology: A Practical Guide, Second Edition, Revised

and Expanded, Marsbed H. Hablanian112. Geometric Dimensioning and Tolerancing: Workbook and Answerbook,

James D. Meadows113. Handbook of Materials Selection for Engineering Applications, edited by

G. T. Murray


114. Handbook of Thermoplastic Piping System Design, Thomas Sixsmith and Reinhard Hanselka

115. Practical Guide to Finite Elements: A Solid Mechanics Approach, Steven M. Lepi

116. Applied Computational Fluid Dynamics, edited by Vijay K. Garg117. Fluid Sealing Technology, Heinz K. Muller and Bernard S. Nau118. Friction and Lubrication in Mechanical Design, A. A. Seireg119. Influence Functions and Matrices, Yuri A. Melnikov120. Mechanical Analysis of Electronic Packaging Systems, Stephen A. McKeown121. Couplings and Joints: Design, Selection, and Application, Second Edition,

Revised and Expanded, Jon R. Mancuso122. Thermodynamics: Processes and Applications, Earl Logan, Jr.123. Gear Noise and Vibration, J. Derek Smith124. Practical Fluid Mechanics for Engineering Applications, John J. Bloomer125. Handbook of Hydraulic Fluid Technology, edited by George E. Totten126. Heat Exchanger Design Handbook, T. Kuppan127. Designing for Product Sound Quality, Richard H. Lyon128. Probability Applications in Mechanical Design, Franklin E. Fisher

and Joy R. Fisher129. Nickel Alloys, edited by Ulrich Heubner130. Rotating Machinery Vibration: Problem Analysis and Troubleshooting,

Maurice L. Adams, Jr.131. Formulas for Dynamic Analysis, Ronald L. Huston and C. Q. Liu132. Handbook of Machinery Dynamics, Lynn L. Faulkner and Earl Logan, Jr.133. Rapid Prototyping Technology: Selection and Application,

Kenneth G. Cooper134. Reciprocating Machinery Dynamics: Design and Analysis,

Abdulla S. Rangwala135. Maintenance Excellence: Optimizing Equipment Life-Cycle Decisions,

edited by John D. Campbell and Andrew K. S. Jardine136. Practical Guide to Industrial Boiler Systems, Ralph L. Vandagriff137. Lubrication Fundamentals: Second Edition, Revised and Expanded,

D. M. Pirro and A. A. Wessol138. Mechanical Life Cycle Handbook: Good Environmental Design

and Manufacturing, edited by Mahendra S. Hundal139. Micromachining of Engineering Materials, edited by Joseph McGeough140. Control Strategies for Dynamic Systems: Design and Implementation,

John H. Lumkes, Jr.141. Practical Guide to Pressure Vessel Manufacturing, Sunil Pullarcot142. Nondestructive Evaluation: Theory, Techniques, and Applications,

edited by Peter J. Shull143. Diesel Engine Engineering: Thermodynamics, Dynamics, Design, and

Control, Andrei Makartchouk144. Handbook of Machine Tool Analysis, Ioan D. Marinescu, Constantin Ispas,

and Dan Boboc


145. Implementing Concurrent Engineering in Small Companies, Susan Carlson Skalak

146. Practical Guide to the Packaging of Electronics: Thermal and MechanicalDesign and Analysis, Ali Jamnia

147. Bearing Design in Machinery: Engineering Tribology and Lubrication,Avraham Harnoy

148. Mechanical Reliability Improvement: Probability and Statistics forExperimental Testing, R. E. Little

149. Industrial Boilers and Heat Recovery Steam Generators: Design, Applications, and Calculations, V. Ganapathy

150. The CAD Guidebook: A Basic Manual for Understanding and ImprovingComputer-Aided Design, Stephen J. Schoonmaker

151. Industrial Noise Control and Acoustics, Randall F. Barron152. Mechanical Properties of Engineered Materials, Wol Soboyejo153. Reliability Verification, Testing, and Analysis in Engineering Design,

Gary S. Wasserman154. Fundamental Mechanics of Fluids: Third Edition, I. G. Currie155. Intermediate Heat Transfer, Kau-Fui Vincent Wong156. HVAC Water Chillers and Cooling Towers: Fundamentals, Application,

and Operation, Herbert W. Stanford III157. Gear Noise and Vibration: Second Edition, Revised and Expanded,

J. Derek Smith 158. Handbook of Turbomachinery: Second Edition, Revised and Expanded,

edited by Earl Logan, Jr. and Ramendra Roy159. Piping and Pipeline Engineering: Design, Construction, Maintenance,

Integrity, and Repair, George A. Antaki160. Turbomachinery: Design and Theory, Rama S. R. Gorla

and Aijaz Ahmed Khan161. Target Costing: Market-Driven Product Design, M. Bradford Clifton,

Henry M. B. Bird, Robert E. Albano, and Wesley P. Townsend162. Fluidized Bed Combustion, Simeon N. Oka163. Theory of Dimensioning: An Introduction to Parameterizing Geometric

Models, Vijay Srinivasan164. Handbook of Mechanical Alloy Design, edited by George E. Totten,

Lin Xie, and Kiyoshi Funatani165. Structural Analysis of Polymeric Composite Materials, Mark E. Tuttle166. Modeling and Simulation for Material Selection and Mechanical Design,

edited by George E. Totten, Lin Xie, and Kiyoshi Funatani167. Handbook of Pneumatic Conveying Engineering, David Mills,

Mark G. Jones, and Vijay K. Agarwal168. Clutches and Brakes: Design and Selection, Second Edition,

William C. Orthwein169. Fundamentals of Fluid Film Lubrication: Second Edition,

Bernard J. Hamrock, Steven R. Schmid, and Bo O. Jacobson170. Handbook of Lead-Free Solder Technology for Microelectronic

Assemblies, edited by Karl J. Puttlitz and Kathleen A. Stalter171. Vehicle Stability, Dean Karnopp


172. Mechanical Wear Fundamentals and Testing: Second Edition, Revisedand Expanded, Raymond G. Bayer

173. Liquid Pipeline Hydraulics, E. Shashi Menon174. Solid Fuels Combustion and Gasification, Marcio L. de Souza-Santos175. Mechanical Tolerance Stackup and Analysis, Bryan R. Fischer176. Engineering Design for Wear, Raymond G. Bayer177. Vibrations of Shells and Plates: Third Edition, Revised and Expanded,

Werner Soedel178. Refractories Handbook, edited by Charles A. Schacht179. Practical Engineering Failure Analysis, Hani M. Tawancy,

Anwar Ul-Hamid, and Nureddin M. Abbas180. Mechanical Alloying and Milling, C. Suryanarayana181. Mechanical Vibration: Analysis, Uncertainties, and Control, Second

Edition, Revised and Expanded, Haym Benaroya182. Design of Automatic Machinery, Stephen J. Derby183. Practical Fracture Mechanics in Design: Second Edition, Revised

and Expanded, Arun Shukla184. Practical Guide to Designed Experiments, Paul D. Funkenbusch185. Gigacycle Fatigue in Mechanical Practive, Claude Bathias

and Paul C. Paris186. Selection of Engineering Materials and Adhesives, Lawrence W. Fisher187. Boundary Methods: Elements, Contours, and Nodes, Subrata Mukherjee

and Yu Xie Mukherjee188. Rotordynamics, Agnieszka Muszynska189. Pump Characteristics and Applications: Second Edition, Michael Volk


Pump Characteristicsand Applications

Second Edition

Michael VolkVolk and Associates, Inc.

Oakland, California, U.S.A.

Boca Raton London New York Singapore

A CRC title, part of the Taylor & Francis imprint, a member of theTaylor & Francis Group, the academic division of T&F Informa plc.


Published in 2005 byCRC PressTaylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300Boca Raton, FL 33487-2742

2005 by Taylor & Francis Group, LLCCRC Press is an imprint of Taylor & Francis Group

No claim to original U.S. Government worksPrinted in the United States of America on acid-free paper10 9 8 7 6 5 4 3 2 1

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xi

Preface to the Second Edition

Thankfully, the laws of physics have not changed since thefirst edition of this book was written in 1996. Therefore, vir-tually everything about pump selection, sizing, system anal-ysis, and other aspects of pump hydraulics remainsunchanged from the first edition. There have, however, beena number of innovations in the world of pumps, which areintroduced in this second edition. This edition also expandsthe material on many components of typical pump installa-tions that were only briefly covered in the first edition, if atall. Some of the most important new or expanded topics cov-ered in this second edition include:

ment (P.D.) pumps are introduced, while the infor-mation on other types of P.D. pumps has beenexpanded.

include NPSH analysis for closed systems, expansionof the discussion on NPSH margin, and system headcurve development for existing systems and for par-allel pumping systems.

eternity, and so the entire section of this chaptercovering software used to design and analyze pumppiping systems has been completely rewritten. A newCD is included with the second edition of the book,demonstrating one such software tool, including solv-ing some of the problems covered in the book.


Chapter 1 Several new types of positive displace-

Chapter 2 Important new topics in this chapter

Chapter 3 In the world of software, 9 years is an

xii Preface to the Second Edition

been added to provide in-depth coverage of two veryimportant and relevant topics: pump couplings andelectric motors. Additionally, several types of centrif-ugal pumps that were not included in the first editionare covered in this chapter.

on O-rings used in pumps, as well as additional infor-mation about sealless pumps.

included in this chapter. The first is an in-depth dis-cussion of variable-frequency drives. Second, thischapter includes a section covering pump life-cyclecost, an innovative approach to the study of the costof pumping equipment that looks way beyond thecapital cost of the pump.

sion of metallic corrosion in pumps, as well as dis-course on elastomers commonly used in pumps forsealing components.

include ten methods to prevent low flow damage inpumps, and a much more detailed discussion of vibra-tion, including a detailed vibration troubleshootingchart.


Chapter 4 Entire new sections of this chapter have

Chapter 5 This chapter has an entire new section

Chapter 6 Two major additions to the book are

Chapter 7 This chapter has added in-depth discus-

Chapter 8 New topics covered in this chapter

xiii

Acknowledgments

Thanks to my colleagues in the pump field who provided inputfor this second edition, or who reviewed particular sections ofit. Finally, I wish to thank my daughter Sarah, who typedmajor portions of the new material for this edition.


xv

Preface to the First Edition

This book is a practical introduction to the characteristics andapplications of pumps, with a primary focus on centrifugalpumps. Pumps are among the oldest machines still in useand, after electric motors, are probably the most widely usedmachines today in commercial and industrial activities.Despite the broad use of pumps, this subject is covered onlybriefly in many engineering curricula. Furthermore, compa-nies which use pumps are often unable to provide their engi-neers, operators, mechanics, and supervisors the kind oftraining in pump application, selection, and operation thatthis vital equipment merits.

The purpose of this book is to give engineers and tech-nicians a general understanding of pumps, and to provide thetools to allow them to properly select, size, operate, and main-tain pumps. There are numerous books on the market aoutpumps, but most of them are very, very technical, and aremainly design oriented, or else are directed to a specific nichemarket. I have attempted to provide practical information onpumps and systems to readers with with all levels of experi-ence, without getting so immersed in design details as tooverwhelm the reader.

This book begins with the basics of pump and systemhydraulics, working gradually to more complex concepts. Thetopics are covered in a clear and concise manner, and areaccompanied by examples along the way. Anyone reading thematerial, regardless of education and experience with pumps,will be able to achieve a better understanding of pump char-acteristics and applications.


xvi Preface to the First Edition

While it is not possible to cover pump hydraulics withoutgetting into some mathematics, this book covers the subjectwithout resorting to differential equations and other highlevel matchematics that most people forgot right after school.For the reader who is interested in a more complex or sophis-ticated approach to particular topics, or who wants additionalinformation in a given area, references are made to othersources which provide a more analytical approach.

A theme that is repeated throughout this book is that allaspects of pumps from system design, to pump selection,to piping design, to installation, to operation are interre-lated. Lack of attention to the sizing of a pump or improperdesign of the piping system can cause future problems withpump maintenance and operation. Even the most preciselysized pump will not perform properly if its installation andmaintenance are not performed carefully. A better under-standing of how these issues are related will help to solveproblems or to prevent them from occurring in the first place.

In addition to a thorough treatment of the fundamentals,this book also provides information on the current state ofthe art of various technologies in the pump field. Variablespeed pumping systems, sealless pumps, gas lubricating non-contacting mechanical seals, and nonmetallic pumps areexamples of recent technological trends in the pump industrywhich are introduced in this book. Computer software for

and a demonstration CD is included with this book. This isanother example of a powerful new technology related topumps that is covered in this book.

Because the book focuses on pump applications and char-acteristics, rather than on design, it is intended for a broaderaudience than typical books about pumps. The readership forthis book includes the following:

Engineers This book has broad appeal to mechan-ical, civil, chemical, industrial, and electrical engi-neers. Any engineer whose job it is to design or modifysystems; select, specify, purchase, or sell pumps; oroversee operation, testing, or maintenance of pump-ing equipment will find this book very helpful.


system design and pump selection is previewed in Chapter 3,

Preface to the First Edition xvii

Engineering Supervisors Because they have broadresponsibility for overseeing the design and operationof pumps and pump systems, engineering supervisorswill benefit from the integrated systems approachprovided in this book.

Plant Operators Employees of plants which utilizepumps are required to oversee the operation of thepumps, and often their maintenance, troubleshoot-ing, and repair. A better understanding of hydraulicsand applications will help these people do a betterjob of operating their pumps most efficiently whilereducing maintenance costs and downtime.

Maintenance Technicians Maintenance personeland their supervisors can do a much better job ofinstalling, maintaining, troubleshooting, and repair-ing pumps if they have a better understanding of howpumps are applied and operated in a system.

Engineering Students The real world problemswhich are presented in this book demonstrate to stu-dents that a pump is more than a black box. Manyuniversity engineering departments are expandingtheir technology program to better prepare studentsfor jobs in industry. This book can make an importantcontribution to a program in industrial machinery.

Formulae used in this book will generally be stated inUnited States Customary System (USCS) units, the systemmost widely used by the pump industry in the United States.Appendix B at the end of this book provides simple conversionformulae from USCS to SI (metric) units. The most commonterms mentioned in this book will be stated in both untis.

I wish to thank my colleagues in the pump field whoreviewed various sections of this book, or who assisted inobtaining materials and illustrations. Im especially gratefulto my friends Jim Johnston, Paul Lahr, and Buster League,who reviewed the entire manuscript and provided me withvaluable feedback. Final thanks go to my wife, Jody Lerner,for her word processing and editorial skills, as well as for herpatience and encouragement.


xix

About the Author

Michael W. Volk, P.E., is President of Volk & Associates, Inc.,

company specializing in pumps and pump systems. Volksservices include pump training seminars; pump equipmentevaluation, troubleshooting, and field testing; expert witnessfor pump litigation; witnessing of pump shop tests; pumpmarket research; and acquisition and divestiture consultationand brokerage. A member of the American Society of Mechan-ical Engineers (ASME), and a registered professional engi-neer, Volk received the B.S. degree (1973) in mechanicalengineering from the University of Illinois, Urbana, and theM.S. degree (1976) in mechanical engineering and the M.S.degree (1980) in management science from the University ofSouthern California, Los Angeles. He may be contacted at


Oakland, California, www.volkassociates.com, a consulting

[email protected].

http://www.volkassociates.commailto:[email protected]

xxi

Contents

1 Introduction to Pumps.............................................. 1

I. What Is a Pump?............................................................ 1II. Why Increase a Liquids Pressure?............................... 2

III. Pressure and Head......................................................... 3IV. Classification of Pumps.................................................. 5

A. Principle of Energy Addition ................................... 51. Kinetic ................................................................. 52. Positive Displacement ........................................ 5

B. How Energy Addition Is Accomplished .................. 7C. Geometry Used ......................................................... 7

V. How Centrifugal Pumps Work ...................................... 7VI. Positive Displacement Pumps ..................................... 14

A. General .................................................................... 14B. When to Choose a P.D. Pump................................ 15C. Major Types of P.D. Pumps.................................... 22

1. Sliding Vane Pump........................................... 242. Sinusoidal Rotor Pump .................................... 253. Flexible Impeller Pump ................................... 254. Flexible Tube (Peristaltic) Pump..................... 265. Progressing Cavity Pump ................................ 276. External Gear Pump ........................................ 297. Internal Gear Pump......................................... 338. Rotary Lobe Pump............................................ 339. Circumferential Piston and Bi-Wing

Lobe Pumps....................................................... 3510. Multiple-Screw Pump....................................... 3611. Piston Pump...................................................... 38


xxii Contents

12. Plunger Pump................................................... 4013. Diaphragm Pump ............................................. 4114. Miniature Positive Displacement Pumps ....... 47

2 Hydraulics, Selection, and Curves .......................51

I. Overview ....................................................................... 51II. Pump Capacity ............................................................. 54

III. Head .............................................................................. 54A. Static Head ............................................................. 56B. Friction Head.......................................................... 58C. Pressure Head ........................................................ 66D. Velocity Head .......................................................... 70

IV. Performance Curve....................................................... 71V. Horsepower and Efficiency .......................................... 80

A. Hydraulic Losses .................................................... 82B. Volumetric Losses................................................... 82C. Mechanical Losses .................................................. 83D. Disk Friction Losses............................................... 83

VI. NPSH and Cavitation .................................................. 89A. Cavitation and NPSH Defined .............................. 89

1. NPSHa ............................................................... 982. NPSHr................................................................ 99

B. Calculating NPSHa: Examples ............................ 101C. Remedies for Cavitation ...................................... 102D. More NPSHa Examples........................................ 106E. Safe Margin NPSHa vs. NPSHr........................... 109F. NPSH for Reciprocating Pumps.......................... 114

VII. Specific Speed and Suction Specific Speed............... 116VIII. Affinity Laws .............................................................. 122

IX. System Head Curves.................................................. 127X. Parallel Operation ...................................................... 139

XI. Series Operation......................................................... 146XII. Oversizing Pumps ...................................................... 152

XIII. Pump Speed Selection................................................ 155A. Suction Specific Speed ......................................... 156B. Shape of Pump Performance Curves .................. 156C. Maximum Attainable Efficiency.......................... 157


Contents xxiii

D. Speeds Offered by Manufacturers....................... 158E. Prior Experience................................................... 159

3 Special Hydraulic Considerations......................161

I. Overview ..................................................................... 161II. Viscosity ...................................................................... 162

III. Software to Size Pumps and Systems ...................... 185A. General .................................................................. 185B. Value of Piping Design Software......................... 186C. Evaluating Fluid Flow Software ......................... 186D. Building the System Model ................................. 187

1. Copy Command............................................... 1892. Customize Symbols......................................... 1903. CAD Drawing Features.................................. 1904. Naming Items ................................................. 1905. Displaying Results.......................................... 1906. The Look of the Piping Schematic ................ 191

E. Calculating the System Operation...................... 1911. Sizing Pipe Lines............................................ 1922. Calculating Speed........................................... 1923. Showing Problem Areas ................................. 1924. Equipment Selection ...................................... 1925. Alternate System Operational Modes........... 193

F. Communicating the Results ................................ 1931. Viewing Results within the Program............ 1932. Incorporating User-Defined Limits ............... 1943. Selecting the Results to Display ................... 1944. Plotting the Piping Schematic....................... 1945. Exporting the Results .................................... 1946. Sharing Results with Others......................... 1957. Sharing Results Using a Viewer Program ... 195

G. Conclusion............................................................. 195H. List of Software Vendors...................................... 196

IV. Piping Layout ............................................................. 196V. Sump Design............................................................... 200

VI. Field Testing ............................................................... 203A. General .................................................................. 203B. Measuring Flow.................................................... 205


xxiv Contents

1. Magnetic Flowmeter....................................... 2052. Mass Flowmeter ............................................. 2053. Nozzle .............................................................. 2054. Orifice Plate .................................................... 2065. Paddle Wheel .................................................. 2066. Pitot Tube........................................................ 2067. Segmental Wedge............................................ 2078. Turbine Meter................................................. 2079. Ultrasonic Flowmeter..................................... 207

10. Venturi............................................................. 20811. Volumetric Measurement............................... 20812. Vortex Flowmeter ........................................... 208

C. Measuring TH....................................................... 209D. Measuring Power.................................................. 211E. Measuring NPSH ................................................. 212

4 Centrifugal Pump Types and Applications......213

I. Overview ..................................................................... 213II. Impellers ..................................................................... 215

A. Open vs. Closed Impellers ................................... 215B. Single vs. Double Suction .................................... 223C. Suction Specific Speed ......................................... 225D. Axial Thrust and Thrust Balancing.................... 227E. Filing Impeller Vane Tips .................................... 230F. Solids Handling Impellers ................................... 232

III. End Suction Pumps.................................................... 233A. Close-Coupled Pumps........................................... 233B. Frame-Mounted Pumps ....................................... 237

IV. Inline Pumps .............................................................. 240V. Self-Priming Centrifugal Pumps............................... 242

VI. Split Case Double Suction Pumps ............................ 245VII. Multi-Stage Pumps .................................................... 250

A. General .................................................................. 250B. Axially Split Case Pumps .................................... 250C. Radially Split Case Pumps.................................. 254

VIII. Vertical Column Pumps............................................. 256IX. Submersible Pumps.................................................... 260X. Slurry Pumps.............................................................. 264


Contents xxv

XI. Vertical Turbine Pumps............................................. 268XII. Axial Flow Pumps ...................................................... 277

XIII. Regenerative Turbine Pumps.................................... 278XIV. Pump Specifications and Standards ......................... 279

A. General .................................................................. 2791. Liquid Properties............................................ 2802. Hydraulic Conditions ..................................... 2803. Installation Details......................................... 281

B. ANSI ...................................................................... 282C. API......................................................................... 284D. ISO......................................................................... 286

XV. Couplings .................................................................... 287XVI. Electric Motors ........................................................... 291

A. Glossary of Frequently Occurring Motor Terms..................................................................... 2941. Amps................................................................ 2942. Code Letter ..................................................... 2953. Design Letter .................................................. 2954. Efficiency ......................................................... 2965. Frame Size ...................................................... 2966. Frequency........................................................ 2967. Full Load Speed.............................................. 2978. High Inertial Load.......................................... 2979. Insulation Class.............................................. 297

10. Load Types ...................................................... 29711. Phase ............................................................... 29812. Poles................................................................. 29813. Power Factor ................................................... 29814. Service Factor ................................................. 29815. Slip................................................................... 29916. Synchronous Speed......................................... 29917. Temperature.................................................... 29918. Time Rating .................................................... 30019. Voltage ............................................................. 300

B. Motor Enclosures.................................................. 3001. Open Drip Proof.............................................. 3002. Totally Enclosed Fan Cooled.......................... 3013. Totally Enclosed Air Over.............................. 301


xxvi Contents

4. Totally Enclosed Non-Ventilated ................... 3015. Hazardous Location........................................ 302

C. Service Factor ....................................................... 302D. Insulation Classes ................................................ 303E. Motor Frame Size................................................. 303

1. Historical Perspective..................................... 3032. Rerating and Temperature ............................ 3073. Motor Frame Dimensions .............................. 3074. Fractional Horsepower Motors ...................... 3075. Integral Horsepower Motors.......................... 3126. Frame Designation Variations....................... 312

F. Single Phase Motors............................................. 314G. Motors Operating on Variable Frequency

Drives .................................................................... 319H. NEMA Locked Rotor Code................................... 321I. Amps, Watts, Power Factor, and Efficiency ........ 322

1. Introduction .................................................... 3222. Power Factor ................................................... 3223. Efficiency ......................................................... 3234. Amperes........................................................... 3255. Summary......................................................... 325

5 Sealing Systems and Sealless Pumps................327

I. Overview ..................................................................... 327II. O-Rings........................................................................ 328

A. What Is an O-Ring?.............................................. 328B. Basic Principals of the O-Ring Seal.................... 329C. The Function of the O-Ring................................. 329D. Static and Dynamic O-Ring Sealing

Applications .......................................................... 330E. Other Common O-Ring Seal Configurations...... 330F. Limitations of O-Ring Use................................... 333

III. Stuffing Box and Packing Assembly ......................... 333A. Stuffing Box .......................................................... 334B. Stuffing Box Bushing ........................................... 334C. Packing Rings ....................................................... 335D. Packing Gland....................................................... 336E. Lantern Ring......................................................... 337


Contents xxvii

IV. Mechanical Seals ........................................................ 338A. Mechanical Seal Advantages ............................... 338

1. Lower Mechanical Losses .............................. 3382. Less Sleeve Wear ............................................ 3383. Zero or Minimal Leakage............................... 3384. Reduced Maintenance .................................... 3395. Seal Higher Pressures.................................... 339

B. How Mechanical Seals Work ............................... 339C. Types of Mechanical Seals................................... 343

1. Single, Inside Seals ........................................ 3432. Single, Outside Seals...................................... 3453. Single, Balanced Seals ................................... 3464. Double Seals ................................................... 3475. Tandem Seals.................................................. 3496. Gas Lubricated Non-Contacting Seals.......... 351

V. Sealless Pumps........................................................... 352A. General .................................................................. 352B. Magnetic Drive Pumps ........................................ 354

1. Bearings in the Pumped Liquid .................... 3572. Dry Running ................................................... 3583. Inefficiency ...................................................... 3584. Temperature.................................................... 3585. Viscosity .......................................................... 359

C. Canned Motor Pumps .......................................... 3591. Fewer Bearings ............................................... 3602. More Compact................................................. 3613. Double Containment ...................................... 3614. Lower First Cost............................................. 361

6 Energy Conservation and Life-Cycle Costs .....363

I. Overview ..................................................................... 363II. Choosing the Most Efficient Pump ........................... 364

III. Operating with Minimal Energy............................... 372IV. Variable-Speed Pumping Systems ............................ 373V. Pump Life-Cycle Costs............................................... 395

A. Improving Pump System Performance: An Overlooked Opportunity?............................... 395

B. What Is Life-Cycle Cost? ..................................... 397


xxviii Contents

C. Why Should Organizations Care about Life-Cycle Cost? .................................................... 397

D. Getting Started..................................................... 399E. Life Cycle Cost Analysis ...................................... 399

1. Cic Initial Investment Costs...................... 4012. Cin Installation and Commissioning

(Start-up) Costs .............................................. 4023. Ce Energy Costs ......................................... 4034. Co Operation Costs..................................... 4045. Cm Maintenance and Repair Costs........... 4046. Cs Downtime and Loss of Production

Costs ................................................................ 4067. Cenv Environmental Costs, Including Disposal

of Parts and Contamination from Pumped Liquid ...................................... 407

8. Cd Decommissioning/Disposal Costs, Including Restoration of the Local Environment ................................................... 407

F. Total Life-Cycle Costs .......................................... 408G. Pumping System Design...................................... 408H. Methods for Analyzing Existing Pumping

Systems ................................................................. 413I. Example: Pumping System with a Problem

Control Valve ........................................................ 414J. For More Information........................................... 419

1. About the Hydraulic Institute....................... 4192. About Europump ............................................ 4193. About the U.S. Department of Energys

Office of Industrial Technologies ................... 421

7 Special Pump-Related Topics ..............................423

I. Overview ..................................................................... 423II. Variable-Speed Systems............................................. 424

III. Sealless Pumps........................................................... 425IV. Corrosion..................................................................... 426

1. Galvanic, or Two-Metal Corrosion................. 4282. Uniform, or General Corrosion...................... 4293. Pitting Corrosion ............................................ 430


Contents xxix

4. ................................. 4305. Erosion Corrosion ........................................... 4316. Stress Corrosion ............................................. 4317. Crevice Corrosion ........................................... 4328. Graphitization or Dezincification

Corrosion ......................................................... 432V. Nonmetallic Pumps .................................................... 432

VI. Materials Used for O-Rings in Pumps ..................... 435A. General .................................................................. 435B. Eight Basic O-Ring Elastomers .......................... 437

1. Nitrile (Buna N) ............................................. 4372. Neoprene ......................................................... 4373. Ethylene Propylene ........................................ 4384. Fluorocarbon (Viton) ...................................... 4385. Butyl ................................................................ 4396. Polyacrylate..................................................... 4397. Silicone ............................................................ 4398. Fluorosilicone .................................................. 440

VII. High-Speed Pumps..................................................... 441VIII. Bearings and Bearing Lubrication ........................... 446

IX. Precision Alignment Techniques ............................... 447X. Software to Size Pumps and Systems ...................... 449

8 Installation, Operation, and Maintenance .......451

I. Overview ..................................................................... 451II. Installation, Alignment, and Start-Up ..................... 452

A. General .................................................................. 452B. Installation Checklist........................................... 453

1. Tag and Lock Out........................................... 4532. Check Impeller Setting .................................. 4533. Install Packing or Seal................................... 4534. Mount Bedplate, Pump, and Motor............... 4545. Check Rough Alignment ................................ 4546. Place Grout in Bedplate................................. 4547. Check Alignment ............................................ 4568. Flush System Piping ...................................... 4579. Connect Piping to Pump ................................ 457

10. Check Alignment ............................................ 459


Intergranular Corrosion

xxx Contents

11. Turn Pump by Hand ...................................... 45912. Wire and Jog Motor........................................ 45913. Connect Coupling ........................................... 45914. Check Shaft Runout ....................................... 46015. Check Valve and Vent Positions .................... 46016. Check Lubrication/Cooling Systems.............. 46017. Prime Pump if Necessary .............................. 46018. Check Alignment ............................................ 46119. Check System Components Downstream ..... 46120. Start and Run Pump...................................... 46221. Stop Pump and Check Alignment................. 46222. Drill and Dowel Pump to Base...................... 46223. Run Benchmark Tests .................................... 462

III. Operation .................................................................... 462A. General .................................................................. 462B. Minimum Flow ..................................................... 463

1. Temperature Rise ........................................... 4642. Radial Bearing Loads..................................... 4653. Axial Thrust .................................................... 4654. Prerotation ...................................................... 4655. Recirculation and Separation ........................ 4666. Settling of Solids............................................. 4687. Noise and Vibration........................................ 4688. Power Savings, Motor Load ........................... 468

C. Ten Ways to Prevent Low Flow Damage in Pumps ............................................................... 4681. Continuous Bypass ......................................... 4702. Multi-Component Control Valve System ...... 4713. Variable Frequency Drive .............................. 4724. Automatic Recirculation Valve ...................... 4735. Relief Valve ..................................................... 4736. Pressure Sensor .............................................. 4757. Ammeter.......................................................... 4758. Power Monitor ................................................ 4759. Vibration Sensor ............................................. 476

10. Temperature Sensor ....................................... 476IV. Maintenance ............................................................... 477

A. Regular Maintenance ........................................... 4771. Lubrication...................................................... 477


Contents xxxi

2. Packing ............................................................ 4783. Seals ................................................................ 479

B. Preventive Maintenance ...................................... 4791. Regular Lubrication ....................................... 4802. Rechecking Alignment.................................... 4803. Rebalance Rotating Element ......................... 4804. Monitoring Benchmarks................................. 480

C. Benchmarks .......................................................... 4801. Hydraulic Performance .................................. 4802. Temperature.................................................... 4813. Vibration.......................................................... 482

V. Troubleshooting .......................................................... 489VI. Repair .......................................................................... 489

A. General .................................................................. 489B. Repair Tips............................................................ 492

1. Document the Disassembly ........................... 4922. Analyze Disassembled Pump......................... 4923. Bearing Replacement ..................................... 4934. Wear Ring Replacement................................. 4945. Guidelines for Fits and Clearances............... 4956. Always Replace Consumables........................ 4957. Balance Impellers and Couplings ................. 4958. Check Runout of Assembled Pump............... 4969. Tag Lubrication Status .................................. 497

10. Cover Openings Prior to Shipment............... 497

Appendix A: Major Suppliers of Pumps in the United States by Product Type ........................499

Appendix B: Conversion Formulae ..............................511

References ..........................................................................525


1

1

Introduction to Pumps

I. WHAT IS A PUMP?

Simply stated, a pump is a machine used to move liquidthrough a piping system and to raise the pressure of theliquid. A pump can be further defined as a machine that usesseveral energy transformations to increase the pressure of a

this definition. The energy input into the pump is typicallythe energy source used to power the driver. Most commonly,this is electricity used to power an electric motor. Alternativeforms of energy used to power the driver include high-pres-sure steam to drive a steam turbine, fuel oil to power a dieselengine, high-pressure hydraulic fluid to power a hydraulicmotor, and compressed air to drive an air motor. Regardlessof the driver type for a centrifugal pump, the input energy isconverted in the driver to a rotating mechanical energy, con-sisting of the driver output shaft, operating at a certain speed,and transmitting a certain torque, or horsepower.

The remaining energy transformations take place insidethe pump itself. The rotating pump shaft is attached to the

the liquid that has entered the pump to increase in velocity.This is the second energy transformation in the pump, wherethe input power is used to raise the kinetic energy of theliquid. Kinetic energy is a function of mass and velocity. Rais-ing a liquids velocity increases its kinetic energy.


liquid. The centrifugal pump shown in Figure 1.1 illustrates

pump impeller (see Figure 1.4). The rotating impeller causes

2 Pump Characteristics and Applications

After the liquid leaves the impeller, but before exitingthe pump, the final transformation of energy occurs in adiffusion process. An expansion of the flow area causes theliquids velocity to decrease to more than when it entered thepump, but well below its maximum velocity at the impellertip. This diffusion transforms some of the velocity energy topressure energy.

II. WHY INCREASE A LIQUIDS PRESSURE?

There are actually three distinct reasons for raising the pres-sure of a liquid with a pump, plus another related factor:

1. Static elevation. A liquids pressure must be increasedto raise the liquid from one elevation to a higherelevation. This might be necessary, for example, tomove liquid from one floor of a building to a higherfloor, or to pump liquid up a hill.

2. Friction. It is necessary to increase the pressure of aliquid to move the liquid through a piping systemand overcome frictional losses. Liquid movingthrough a system of pipes, valves, and fittings expe-riences frictional losses along the way. These lossesvary with the geometry and material of the pipe,valves, and fittings, with the viscosity and density ofthe liquid, and with the flow rate.

Figure 1.1 A centrifugal pump uses several energy transforma-tions to raise the pressure of a liquid.

Fuelsource

energy in:

Air, steam, electricity,hydraulic fluid, or diesel

engine oil

Driver Pump

Rotatingmechanical

energy

Liquid in:

Lowpressure

Liquid out:

High pressure


Introduction to Pumps 3

3. Pressure. In some systems it is necessary to increasethe pressure of the liquid for process reasons. Inaddition to moving the liquid over changes in eleva-tion and through a piping system, the pressure of aliquid must often be increased to move the liquid intoa pressurized vessel, such as a boiler or fractionatingtower, or into a pressurized pipeline. Or, it may benecessary to overcome a vacuum in the supply vessel.

4. Velocity. There is another factor to be considered here,namely that not all of the velocity energy in a pumpis converted to potential or pressure energy. The out-let or discharge connection of most pumps is smallerthan the inlet or suction connection. Because liquidsare, practically speaking, incompressible, the velocityof the liquid leaving the pump is higher than thatentering the pump. This velocity head may need tobe taken into account (depending on the point ofreference) when computing pump total head to meetsystem requirements. This is discussed further in

III. PRESSURE AND HEAD

It is important to understand the relationship between pres-sure and head. Most plant engineers and those involved inoperations tend to speak of the pressure of the liquid atvarious points in the process. Pressure is measured in psi(pounds per square inch, sometimes simply called pounds)if United States Customary System (USCS) units are used.In SI (metric) units, the equivalent units for pressure arekilopascal (kPa), bar, or kilograms per square centimeter(kg/cm2), while the equivalent units for head are meters (m).Most readers should be familiar with the difference betweengauge pressure and absolute pressure. Absolute pressure isgauge pressure plus atmospheric pressure. Atmospheric pres-sure is 14.7 psi (1 bar) at sea level.

In the study of pump hydraulics, it is important to realizethat any pressure expressed in psi (kPa) is equivalent to a


Chapter 2, Section III.


static column of liquid expressed in feet (meters) of head. Thisis not meant to imply that pressure and head are interchange-able terms, because conceptually head is a specific energyterm and pressure is a force applied to an area. However, theunits used in hydrodynamics for specific energy are ft-lb/lbf,which, in the gravitational field of the earth where the accel-eration of gravity is 32.2 ft/sec2, can be numerically reducedto (feet of) head. With this understanding (and because mostpumping applications occur under the earths gravitationalinfluence), the terms will be used interchangeably in thisbook.

The equivalence between pressure and head is illustratedin Figure 1.2, where the pressure in psi read on a gaugelocated at the bottom of a column of liquid is related to theheight of the column in feet and to the specific gravity of theliquid by the following formula (in USCS units):

(1.1)

where:psi = pounds per square inchs.g. = specific gravity

Figure 1.2 Pressure (in psi) is equivalent to a vertical column ofliquid with a certain specific gravity.

Water(S.G. = 1.0) 100 FT

43 PSI

Pressure (PSI) =Head (FT) S.G.2.31

= = 43 PSI100 FT 1.0 2.31

=psifeet s.g.

2.31



Specific gravity is the weight of a given volume of liquidcompared to the same volume of water. When applying cen-trifugal pumps, pressures should be expressed in units of feet(meters) of head rather than in psi (kPa).

As an example of the equivalency between psi and feetof head demonstrated by Equation 1.1, atmospheric pressureat sea level can be expressed as 14.7 psi, or as 34 feet of water.

For positive displacement pumps (discussed in SectionVI to follow), the conversion to feet of head is not made, andpressures are expressed in psi (kPa).

IV. CLASSIFICATION OF PUMPS

There are many ways to classify pumps: according to theirfunction, their conditions of service, materials of construction,etc. The pump industry trade association, the Hydraulic Insti-

sification divides pumps as follows:

A. Principle of Energy Addition

The first classification is according to the principle by whichenergy is added to the liquid. There are two broad classes ofpumps, defined below.

1. Kinetic

In a kinetic pump, energy is continuously added to the liquidto increase its velocity. When the liquid velocity is subse-quently reduced, this produces a pressure increase. Althoughthere are several special types of pumps that fall into thisclassification, for the most part this classification consists ofcentrifugal pumps.

2. Positive Displacement

In a positive displacement pump, energy is periodically addedto the liquid by the direct application of a force to one or moremovable volumes of liquid. This causes an increase in pressureup to the value required to move the liquid through ports in


tute, has classified pumps as shown in Figure 1.3. This clas-


Figure 1.3 Classification of pumps. (Courtesy of Hydraulic Insti-

Reciprocatingpumps

Airoperated

Diaphram

Bellows

Piston

Simplex

Duplex

SteamHorizontal

VerticalDouble-acting

Piston

Plunger

Simplex

Duplex

PowerHorizontal

Vertical Double-acting

Piston

Plunger

Simplex

DuplexSingle-acting

Multiplex

Horizontal

Vertical

Controlled volume

Packed plunger

Packed piston

DiaphramMechanically

coupled

Hydraulicallycoupled

Simplex

Duplex

Multiplex

Manualcontrol

Automaticcontrol

Blow case

Rotarypumps

VaneBlade, bucket roller or slipper

PistonAxialRadial

Flexiblemember

Flexible tubeFlexible vaneFlexible liner

Lobe

Single

Multiple

GearExternal

Internal

Circumferentialpiston

Screw Single

Multiple

Single

Multiple

Positive displacement

Overhung impller

Close-coupledsingle & two stage

Separately coupledsingle & two stage

End suction(including submersibles)In-line

In-lineFrame mountedCentering supportAPI 610Frame mountedANSI B73.1Wet pit volute

Axial flow impeller (propeller)volute type (horiz. or vert.)

Impeller betweenbearings

Separately coupledsingle stage

Separately coupledmultistage

Axial (horiz.) split case

Radial (vert.) split case

Axial (horiz.) split case

Radial (vert.) split case

Turbine type

Vertical typesingle & multistage

Deep well turbine(including submersibles)Barrel or can pumpShort setting or close-coupledAxial flow impeller (propeller)or mixed flow type (horizontalor vertical)

Centrifugal a

Regenerativeturbine

Overhung impeller

Impeller between bearings

Single stage

Two stage

Special effectReversible centrifugal

Rotating casing (pitot tube)

a Includes radial, mixed flow and axial flow designs.

Kinetic

Pumps

Double-acting

Single-acting


tute, Parsippany, NJ; www.pumps.org and www.pumplearning.org)

http://www.pumps.orghttp://www.pumplearning.org


the discharge line. The important points here are that theenergy addition is periodic (i.e., not continuous) and that thereis a direct application of force to the liquid. This is most easilyvisualized through the example of a reciprocating piston or

moves back and forth in the cylinder, it exerts a force directlyon the liquid, which causes an increase in the liquid pressure.

B. How Energy Addition Is Accomplished

The second level of pump classification has to do with themeans by which the energy addition is implemented. In thekinetic category, the most common arrangement is the cen-trifugal pump. Other arrangements include regenerative tur-bines (also called peripheral pumps), and special pumps suchas jet pumps that employ an eductor to bring water out of a well.

In the positive displacement category, the two most com-mon sub-categories are reciprocating and rotary pumps.

C. Geometry Used

The remaining levels of pump classification shown in

ugal pumps, the geometry variations have to do with thesupport of the impeller (overhung impeller vs. impellerbetween bearings), rotor orientation, the number of impellersor stages, how the pump is coupled to the motor, the pumpbearing system, how the pump casing is configured, and pumpmounting arrangements.

With positive displacement pumps, as is discussed inmore detail in Section VI, there are many different types ofrotary and reciprocating pumps, each with a unique geometry.

V. HOW CENTRIFUGAL PUMPS WORK

Stripped of all nonessential details, a centrifugal pump

with the shaft, and a casing that encloses the impeller. In acentrifugal pump, liquid is forced into the inlet side of the pumpcasing by atmospheric pressure or some upstream pressure. As


plunger pump (see Figure 1.23). As the piston or plunger

(Figure 1.4) consists of an impeller attached to and rotating

Figure 1.3 deal with the specific geometry used. With centrif-


the impeller rotates, liquid moves toward the discharge side ofthe pump. This creates a void or reduced pressure area at theimpeller inlet. The pressure at the pump casing inlet, whichis higher than this reduced pressure at the impeller inlet,forces additional liquid into the impeller to fill the void.

If the pipeline leading to the pump inlet contains a non-condensable gas such as air, then the pressure reduction atthe impeller inlet merely causes the gas to expand, and suc-tion pressure does not force liquid into the impeller inlet.Consequently, no pumping action can occur unless this non-condensable gas is first eliminated, a process known as prim-ing the pump.

With the exception of a particular type of centrifugalpump called a self-priming centrifugal pump, centrifugalpumps are not inherently self-priming if they are physicallylocated higher than the level of the liquid to be pumped. Thatis, the suction piping and inlet side of centrifugal pumps thatare not self-priming must be filled with noncompressible liq-uid and vented of air and other noncondensable gases beforethe pump can be started. Self-priming pumps are designed tofirst remove the air or other gas in the suction line, and tothen pump in a conventional manner.

Figure 1.4 Centrifugal pump with single volute casing. (FromPump Handbook, I.J. Karassik et al., 1986. Reproduced with per-mission of McGraw-Hill, Inc., New York, NY.)

TYPICAL PUMP SECTIONSECTION THROUGH IMPELLER AND

VOLUTE ALONG MEAN FLOW SURFACE

FLOWLINE

FLOWLINE

VOLUTE

IMPELLER

POINT OF ENTRANCETO IMPELLER VANES



If vapors of the liquid being pumped are present on thesuction side of the pump, this results in cavitation, which cancause serious damage to the pump. Discussed in greater detail

to lose prime.Once it reaches the rotating impeller, the liquid entering

the pump moves along the impeller vanes, increasing in veloc-ity as it progresses. The vanes in a centrifugal pump areusually curved backward to the direction of rotation. Some

vanes which are straight rather than curved. The degree ofcurvature of the vanes and number of vanes, along with otherfactors, determines the shape and characteristics of the pumpperformance curve, which is described in Chapter 2, SectionIV.

When the liquid leaves the impeller vane outlet tip, it isat its maximum velocity. Figure 1.5 illustrates typical velocity

Figure 1.5 Velocity and pressure levels vary as the fluid movesalong the flow path in a centrifugal pump.

Pressure(PSI)

Pressure

Velocity(FT/SEC)

Suction DischargeFlow path

Velocity

Outlet tipof impellervane

Inlet tip of impellervane


in Chapter 2, Section VI, cavitation may also cause the pump

special types of pump impellers (Chapter 7, Section VII) have


and pressure changes in a centrifugal pump as the liquidmoves through the flow path of the pump. After the liquidleaves the impeller tip, it enters the casing, where an expan-sion of cross-sectional area occurs. The casing design ensuresthat the cross-sectional area of the flow passages increasesas the liquid moves through the casing. Because the area isincreasing as the liquid moves through the path of the casing,a diffusion process occurs, causing the liquids velocity to

energy is transformed into increased potential energy, causingthe pressure of the liquid to increase as the velocity decreases.The increase of pressure while velocity is decreasing is alsoillustrated in Figure 1.5.

A centrifugal pump operating at a fixed speed and witha fixed impeller diameter produces a differential pressure, ordifferential head. Head is usually expressed in feet or meters,and abbreviated TH (total head). The amount of head pro-duced varies with the flow rate, or capacity delivered by thepump, as illustrated by the characteristic headcapacity

decreases, the capacity increases. Alternatively, as the pumphead increases, the flow decreases. Pump capacity is usuallyexpressed in gallons per minute (gpm) or, for larger pumps,in cubic feet per second (cfs). Metric equivalents, dependingon the size of the pump, are cubic meters per second, litersper second, or cubic meters per hour.

The centrifugal pump casing is one of several types. A

single volute casing has a single cutwater where the flow isseparated. As the flow leaves the impeller and moves aroundthe volute casing, the pressure increases. This increasingpressure as the liquid moves around the casing produces anincreasing radial force at each point on the periphery of theimpeller, due to the pressure acting on the projected area ofthe impeller. Summing all of these radial forces produces anet radial force that must be carried by the shaft and radialbearing system in the pump. The radial bearing must alsosupport the load created by the weight of the shaft and impeller.


decrease, as Figure 1.5 illustrates. By the Bernoulli equation(see Ref. [1] at the end of this book), the decreased kinetic

(HQ) curve shown in Figure 1.6. As the head of the pump

single volute casing is illustrated in Figure 1.4. Note that the


The radial bearing loads generated by a pump also varyas the pump operates at different points on the pump perfor-mance curve, with the minimum radial force being developed

points on the pump curve to the right or to the left of the BEPproduce higher radial loads than are produced when operatingat the BEP. This is especially true of single volute casingpumps, as Figure 1.7 illustrates.

Symptoms of excessive radial loads include excessiveshaft deflection and premature mechanical seal and bearingfailure. Continuous operation of the pump at too low a mini-mum flow is one of the most common causes of this type offailure. Because for rolling element bearings, bearing life isinversely proportional to the cube of the bearing load, oper-ating well away from the pump best efficiency point can causea reduction in bearing life by several orders of magnitude.

arrangement, consisting of multiple flow paths around the

Figure 1.6 Typical headcapacity relationship for centrifugal andpositive displacement pumps.

H(FT or PSI)

Q (GPM)

Slip

Centrifugal

Positivedisplacement


at the best efficiency point (BEP) of the pump (Figure 1.7). SeeChapter 2, Section V, for a discussion of BEP. Operation at

A diffuser casing (Figure 1.8) is a more complex casing


periphery of the impeller discharge. The liquid that leaves theimpeller vanes, rather than having to move completely aroundthe casing periphery as it does with the single volute casing,merely enters the nearest flow channel in the diffuser casing.The diffuser casing has multiple cutwaters, evenly spacedaround the impeller, as opposed to the one cutwater found ina single volute casing. The main advantage of the diffusercasing design is that this results in a near balancing of radialforces (Figure 1.7), thus reducing shaft deflection and elimi-nating the need for a heavy-duty radial bearing system. Thedead weight of the rotating element must still be carried bythe radial bearing, but overall the diffuser design minimizesradial bearing loads compared with other casing types.

Because the diffuser design produces minimal radial bear-ing loads, one might wonder why all pumps do not have diffusersrather than volute type casings. The reason is partially due to

Figure 1.7 Typical radial loads produced by single volute, doublevolute, and diffuser casings.

Singlevolute

Diffuser

Bestefficiency

point

Radialload (#)

H(FT)

Doublevolute

Q (GPM)



economics, as a pump with a diffuser casing generally hasmore parts or more complex parts to manufacture than apump with a volute casing. Depending on pump size andmaterials of construction, economics often do not justify theuse of diffuser casings except where significant savings canbe achieved in the size of shaft or radial bearing that is usedin the pump. This is usually only found to be the case in multi-stage, high-pressure pumps. However, with multi-stagepumps there are other considerations as well. Volute designsin multi-stage pumps allow, by the use of a cross-over, someof the impellers to be oriented in the opposite direction, provid-

pumps are themselves not in agreement on this subject.

have diffuser casings. Because the bearings for these verticalpumps are submerged in the liquid being pumped, it is notpractical to have a ball or roller type radial bearing for this typeof pump. Rather, the radial bearing loads must be accommo-dated by a sleeve type bearing, which is not an ideal bearing

Figure 1.8 Diffuser casing minimizes radial loads in a centrifugalpump. (From Pump Handbook, I.J. Karassik et al., 1986. Repro-duced with permission of McGraw-Hill, Inc., New York, NY.)

CASING

DIFFUSER

IMPELLER


ing balancing of axial thrust loads. (Refer to Chapter 4, SectionII.D and Section VII.) The leading manufacturers of multi-stage

Vertical turbine pumps (Chapter 4, Section XI) usually


system in this type of arrangement. Therefore, to minimizeradial bearing loads, diffuser type casings are used in thistype of pump.

A hybrid between a single volute casing and a diffusercasing is a double volute casing (Figure 1.9). With this casingdesign, the volute is divided, which creates a second cutwater,located 180 from the first cutwater. This design results inmuch lower radial loads than are present with single volute

by pump designers for larger, greater flow pumps (usually forflows higher than about 1500 gpm) to allow the use of smallershafts and radial bearings.

VI. POSITIVE DISPLACEMENT PUMPS

A. General

This book is primarily about centrifugal pumps. However, as

known as positive displacement (P.D.) pumps that deservessome attention. One of the earliest decisions that must be

Figure 1.9 Double volute casings are used in larger centrifugalpumps to reduce radial loads. (Courtesy of Goulds Pumps, Inc., ITTIndustries, Seneca Falls, NY.)


designs (Figure 1.7). Double volute casings are usually used

Figure 1.3 illustrates, there is an entire other class of pumps


made in designing a system and applying a pump is theselection of the type of pump to be used. The first issue is thegeneral decision whether the pump should be of the centrif-ugal or the positive displacement type. Surveys of equipmentengineers and pump users indicate that the majority of themhave a strong preference for centrifugal pumps over positivedisplacement pumps (if the hydraulic conditions are such thateither type can be considered). Many reasons are given forthis preference for centrifugals, but most are related to thebelief that centrifugal pumps are more reliable and result inlower maintenance expense. Centrifugal pumps usually havefewer moving parts, have no check valves associated with thepumps (as reciprocating positive displacement pumps do),produce minimal pressure pulsations, do not have rubbingcontact with the pump rotor, and are not subject to the fatigueloading of bearings and seals that the periodic aspect of manypositive displacement pumps produce. Centrifugals should beconsidered first when applying a pump, but they are notalways suited to the application.

B. When to Choose a P.D. Pump

This preference for centrifugal over P.D. pumps is certainlynot always the case, and, in fact, there are certain applicationcriteria that demand the use of a P.D. pump. The followingare some key application criteria that would lead to the selec-tion of a P.D. pump over a centrifugal pump:

High viscosity Self-priming High pressure Low flow High efficiency Low velocity Low shear Fragile solids handling capability Sealless pumping Accurate, repeatable flow measurement Constant flow/variable system pressure Two-phase flow



The ability to pump viscous liquids is one of the mostimport attributes of P.D. pumps. It is possible to handle low-viscosity liquids with centrifugal pumps. However, efficiencydegrades rapidly as viscosity increases and there is an upperlimit of viscosity above which it becomes impractical to con-sider centrifugal pumps due to the excessive waste of energy.Highly viscous liquids absolutely cannot be pumped with a

sion of viscosity and its effect on centrifugal pump perfor-mance.) For these liquids, some type of positive displacementpump may be the only practical solution.

Most positive displacement pump types are inherentlyself-priming, meaning they can be located above the surfaceof the liquid being pumped without the necessity of the suctionline being filled with liquid and the noncondensable gases inthe suction line being removed before starting the pump.Therefore, these pump types can be conveniently mounted ontop of transfer tanks with no special external priming devices.

The high pressure and low flow criteria above must beconsidered together. How high is high pressure, and how lowis low flow? It is possible to find, for instance, centrifugalpumps that produce pressures of several thousand psi. Andcertainly one can find very small centrifugal pumps whosecapacity is only a couple of gallons per minute. But what ifone has an application for 5 gpm at 2000 psi? In that case, apositive displacement pump is about the only solution.

range of centrifugal, rotary, and reciprocating pumps. Whilethere is a portion of this coverage chart that can be met byall three pump types, the one area that stands out as beingable to be met only by a positive displacement pump is lowflows in combination with very high pressures.

If energy efficiency were the only consideration in select-ing pumps, more positive displacement pumps would be con-sidered, since some positive displacement pumps are quiteenergy efficient. Energy is not the only consideration though,


of P.D. pumps in Section VI.C and Table 1.1 to follow.)

centrifugal pump. (See Chapter 3, Section II, for more discus-

Figure 1.10 shows in very broad terms the head and flow

(Refer to further discussion of the dry self-priming capability


and other factors such as installed cost and maintenanceexpense often outweigh the energy savings.

The criteria of low velocity, low shear, and fragile solidshandling capability often go hand-in-hand. Centrifugalpumps, because of the high velocities present at the impellerdischarge, and because of the close clearances inside thepump, often subject the pumped liquid to high shear stresses.Many liquids cannot tolerate these high velocities and highshear stresses. A good example of this is fruits and vegetablessuch as cherries and peas that are pumped in food processingplants. If these products were pumped using centrifugalpumps, they would produce cherry juice and pea juice! Thereis an entire class of centrifugal pump impellers of the nonclogtype, whose function is to pump sewage and other waste

trifugal pumps, however, are not concerned with maintainingthe integrity of the solids and often shred the solids as theypump them. Another centrifugal impeller type, known as arecessed, or vortex impeller (Chapter 4, Section II.F), is capable

Figure 1.10 Head vs. flow for centrifugal, rotary, and reciprocat-ing pumps.

100,000+

H(PSI)

6,500

4,500

1,800 15,000 200,000+

Q (GPM) = Scale change

Reciprocating

Centrifugal

Rotary


liquids containing solids (Chapter 4, Section II.F). These cen-


of pumping large solids with minimal degradation, but thedownside is that this impeller type is very, very inefficient.

Because of their unique design, several types of P.D.pumps, such as peristaltic (Section VI.C.4) and diaphragm(Section VI.C.13) pumps, are inherently sealless, requiring noshaft seals and having zero product leakage. While there areavailable today several types of sealless centrifugal pumps as

have their limitations and shortcomings. The inherent seal-less nature of some P.D. pumps may make them a simplersolution.

With positive displacement pumps, capacity varies directlywith speed and is independent of differential pressure or head.

ferential pressure for P.D. pumps, while being dependent ondifferential pressure (head) for centrifugal pumps.

Most positive displacement pumps exhibit slip, that is,leakage from the high pressure to the low pressure side ofthe pump. As shown in Figure 1.6, slip causes the pump todeliver a lower flow rate at higher differential pressures. Theamount of slip varies widely from one positive displacementpump to another, as well as varying with pump differentialpressure and with the liquid viscosity. Most positive displace-ment pumps are not nearly as subject to increased leakageback to suction because of wear as are centrifugal pumps.Some types exhibit very little slip. These factors make sometypes of P.D. pumps ideal for metering applications, where anaccurate, controllable flow rate of (usually) an expensivechemical must be dispensed, for example, to treat water withchlorine. Note that centrifugal pumps could also be used toaccurately control flow but they would have to rely on a controlloop that measures flow and then adjusts a system controlvalve. Reciprocating pumps are the most common type of P.D.pump used for metering pumps, although other types such asperistaltic pumps are also used for metering.

The requirement for a constant process flow rate wheresystem pressure varies widely can be met with a centrifugalpump. However, this usually requires a feedback control system,


Chapter 5, Section V, discusses, these centrifugal options also

Figure 1.6 illustrates that pump capacity is independent of dif-

pump characteristics and applications

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