CENTRIFIUGAL PUMPS Design & application. Second Edition

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2 CENTRIFIUGAL PUMPS Design & application Second Edition

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4 CENTRIFUGAL PUMPS Design & Application Second Edition Val S. Lobanoff Robert R. Ross

5 CENTRIFUGAL PUMPS Design & Application Second Edition Copyright 1985, 1992 by Butterworth-Heinemann. All rights reserved. Printed in the United States of America. This book, or parts thereof, may not be reproduced in any form without permission of the publisher. Originally published by Gulf Publishing Company, Houston, TX. For information, please contact: Manager of Special Sales Butterworth-Heinemann 225 Wildwood Avenue Woburn, MA ! Tel: Fax: For information on all Butterworth- Heinernann publications available, contact our World Wide Web home page at: Printed on Acid-Free Paper (oo) Library of Congress Cataloging-in-Publication Data Lobanoff, Val S., 1910 Centrifugal pumps: design & application/val S. Lobanoff, Robert R. Ross. 2nd ed. p. cm. Includes index. ISBN X 1. Centrifugal pumps. I. Ross, Robert R., II. Title. TJ919.L '7 dc CIP IV

6 Contents Preface xi Part 1: elements of pumps Design 1 Part1: 1 introduction Elements of Pump Design..,.,, 13 System Analysis for Pump Selection. Differential Head Required, NPSHA. Shape of Head Capacity Curve. Pump Speed. Liquid Characteristics. Viscosity. Specific Gravity. Construction. Pump Selection. 2 Specific Speed and Modeling Laws. 11 Definition of Pump Specific Speed and Suction Specific Speed. The Affinity Law. Specific Speed Charts. Correction for Impeller Trim. Model Law. Factoring Laws. Conclusion. 3 Impeller Design 28 Impeller Layout. Development of Impeller Profile (Plan View). Development of Impeller End View. Impeller Inlet Angles. Development of Impeller Vane. Design Suggestions. Notation. v

7 4 General Pump Design 45 Performance Chart. 5 Volute Design... SO Types of Volute Designs. Single-Volute Casing Designs. Double-Volute Casing Designs. Double-Volute Dividing Rib (Splitter). Triple-Volute Casings. Quad-Volute Casings, Circular-Volute Casings. General Design Considerations. The Use of Universal Volute Sections for Standard Volute Designs. The Design of Rectangular Double Volutes. The Design of Circular Volutes. General Considerations in Casing Design. Manufacturing Considerations. Casing Surface Finish. Casing Shrinkage. Conclusion, Notation. Reference, 6 Design of Multi-Stage Casing 6S General Considerations in Crossover Design. Specific Crossover Designs. Crossovers with Radial Diffusing Sections. Crossovers with Diagonal Diffusing Sections. Mechanical Suggestions. Notation. 7 Double-Suction Pumps and Side-Suction Design. 77 Double-Suction Pump Design. Pump Casing. Double-Suction Impeller. Side Suction and Suction Nozzle Layout. Suction Layout (End View). Suction Layout (Profile), 8 NPSH,, 15 Establishing NPSHA. Predicting NPSHR. Moderate Speed Pumps. Influence of Suction Specific Speed (Nss). High Speed Pumps. Cavitation-Free NPSHR. Influence of Suction Nozzle. Influence of Liquid. Suction Piping. Effect of Viscosity. Notation. References. Part2: Applications Vertical Pumps 113 by Erik B, Fiske Configurations. Well Pumps. Wet Pit Pumps. Barrel-Mounted or Can-Mounted Pumps. Applications. Well Pumps. Water Well Pumps. Incline-Mounted Pumps. Cavvi

8 ern Pumps, Mine Dewatering Pumps. Wet Pit Pumps. Water Supply Pumps. Condenser Cooling Water Pumps. Cooling Tower Pumps. Flood Control Pumps. Transfer Pumps. Barrel-Mounted or Can-Mounted Pumps. Condensate and Heater Drain Pumps. Process Pumps. Small Boiler Feed Pumps. Cryogenic Pumps. Loading Pumps. Pipeline Booster Pumps. Design Features. The Bowl Assembly. The Column Assembly. Outer Column. Column Shaft. Shaft Enclosing Tube. The Head Assembly, Pump Vibration, References. 10 Pipeline, Waterflood, anil CQ 2 Pumps,,...,., 139 Pipeline Pumps. Condition Changes. Destaging. Bi-rotors. Slurry Pipelines. Example of Pipeline Pump Selection. Series vs. Parallel. Waterflood Pumps. C0 2 Pumps, Mechanical Seals. Horsepower Considerations. Notation. References. 11 High Speed Pumps,,,...,.,,, 173 by Edward Gravelle History and Description of an Unconventional Pump Type. Terminology. Partial Emission Formulae. Specific Speed. Suction Specific Speed. Inducers. Partial Emission Design Evolution. Design Configuration Options. Other High-Speed Considerations. References, 12 Double-Case Pumps 206 by Erik B. Fiske Configurations. Pump Casing. Volute Casing with Opposed Impellers. Diffuser Cas ings with Balance Drum. Diffuser Casings with Balance Disk. Applications. Boiler Feed Pumps. Charge Pumps. Waterflood Pumps. Pipeline Pumps. Design Features. Removable Inner Case Subassembly. Auxiliary Take-off Nozzles. Double-Suction First- Stage Impellers. Mounting of the Impellers. Impeller Wear Rings. Shaft Seals. Radial Bearings. Thrust Bearings, Baseplates and Foundations. Mounting of the Barrel. Design Features for Pumping Hot Oil with Abrasives. Double-Case Pump Rotordynamic Analysis. The Effect of Stage Arrangement on Rotordynamics. The Effect of Impeller Growth from Centrifugal Forces. Comparison of Diffuser Casings with Volute Casings. Diffuser Casings. Volute Casings. References. 13 Slurry Pumps 226 by George Wilson Slurry Abrasivity. Pump Materials to Resist Abrasive Wear. Slurry Pump Types, Specific Speed and Wear. Areas of Wear. Casing. Impeller. Wear Plates. Bearing Frames, Sealing. Sump Design. Pump Drive. The Effect of Slurries on Pump Performance, vii

9 14 Hydraulic Power Recovery Turbines by Rolf Lmnetiurg and Richard M, Nelson Selection Process. Specific Speed. Net Positive Discharge Head. Power Output and Affinity Laws. Configuration. Turbine Performance Prediction. Prediction by Approximation. Prediction by Analysis. Optimizing and Adjusting Performance Characteristics. Design Features (Hydraulic and Mechanical). Reverse-Running Pump. Turbine Design with Fixed Guide Vanes. Turbine Design with Internally and Externally Adjustable Guide Vanes. Operating Considerations. Performance Testing. Applications. Operation and Control Equipment. Conclusion. References, 15 Chemical Pumps-Metallic and Nonmetatlic by Frederic W. Buse ANSI Pumps, Specifications. General Construction. Impeller. Casings. Volute. Gasketing. Flat Gasket. 0-Rings. Casing Covers. Stuffing Box. Frame. Support Head. Bearing Housing, Shaft. Impeller Attachment. Bearings. Lubrication of the Bearings, Mounting the Bearing. Clamping Between the Housing and End Cover. End Cover Mount. End Sealing. Bedplates. Standard Beds. Stiit-Mounted Beds. Springs- Mounted Beds. Noncorrosive Beds. Flinger. Other Types of Chemical Pumps. Sealless Pumps. Sump Pumps. Self Priming. Nonmetallic Pumps. Armored Pump. Reinforced Composite Material Pumps. Thermosetting Polymers. Thermoplastics. Manufacturing Techniques. Compression Molding. Resin Transfer. Design Stresses. Pressure vs. Temperature. NPSHR. General Construction of Nonmetallic Pumps. Nozzle Loading. Bolting. Gaskets. Back-up Support for Bolting. Stuffing Box Area. Mechanical Seals. Impellers. Nonmetaliic Immersion Sump Pumps. Driver. Level Controls. Stilling Tubes. Mounting Plates and Pit Covers. Processes. Pump Corrosion. Pump Materials. Chlorine. Sodium-Hypochtorite. Hydrochloric Acid HCL. Sulfuric Acid H 2 SQ 4. Ferrous and Ferric Chloride. Chlorinated Hydrocarbons. Ethylene and Propylene Glycol. Synthetic Glycerine. Corn Syrup. Dyes. Pesticides. Sodium Chlorite Na CI0 3. Pulp and Paper. Metal Finishing. Carbon Steel Pickling. Stainless Steel Pickling. Desalinization and Water Purification. Secondary Oil Recovery (Waterflood). Mining Copper Leaching and Uranium Solvent Extraction. Industrial Waste Treatment. Material Selection. References. Part3: 11 ( Shaft Design Mechanical and Axial Thrust... Design Shaft Design. Shaft Sizing Based on Peak Torsiona! Stress. Shaft Sizing Based on Fatigue Evaluation. Shaft Deflection. Key Stress. Axial Thrust. Double-Suction Singleviii

10 Stage Pumps. Single-Suction Single-Stage Overhung Pumps. Multi-Stage Pumps Notation. References. 17 Mechanical Seals 354 by James P. Netzel Theory of Operation. Design Fundamentals. Seal Leakage. Seal Wear. Classification of Seals by Arrangement. Classification of Seals by Design. Materials of Construction, Mating Ring Designs. Adaptive Hardware. Upstream Pumping. Mechanicai Seals for Chemical Service. Mechanical Seals for Refinery Service. Typical Applications. Light Hydrocarbon Service. Mechanical Seal Installation and Troubleshooting References. 48 Vibration and Noise in Pumps by Fred R. Szenasi Introduction. Sources of Pump Noise. Mechanical Noise Sources. Liquid Noise Sources. Causes of Vibrations. Installation/Maintenance Effects. Application. Hydraulic Effects. Half-Wave Resonance (Open-Open and Closed-Closed). Quarter-Wave Resonance (Open-Closed). Design/Manufacturing. Rotordynamic Analysis. Lateral Critical Speed Analysis. Seal Effects. Response to Unbalance. Acceptable Unbalance Levels. Allowable Vibration Criteria. Rotor Stability Analyses. Torsional Critical Speed Analysis. Variable Speed Drives. Diagnosis of Pump Vibration Problems. Measure ment Techniques. Impact Tests. Troubleshooting, Impact Tests. Appendix. Acoustic Velocity of Liquids. References. Part4: Extending Pump Life Alignment 497 by Malcolm G. Murray, Jr. Definitions. Why Bother With Precise Alignment? Causes of Misalignment. Management and Human Factors. Physical Factors. Pre-Alignment Steps. Methods of Primary Alignment Measurement. Methods of Calculating Alignment Movements. Jig Posts. Numerical Examples. Thermal Growth. References. 20 Rolling Element Bearings and Lubrication 524 by Heinz P. Bloch Friction Torque. Function of the Lubricant. Oil Versus Grease. Advantages. Disadvantages. Oil Characteristics. Viscosity. Viscosity Index. Pour Point. Flash and Fire Point. ix

11 Oxidation Resistance. Emulsification. Rust Prevention. Additives. General Lubricant Considerations. Application Limits for Greases. Life-Time Lubricated, "Sealed" Bearings. Oil Viscosity Selection. Applications of Liquid Lubricants in Pumps. Oil Bath Lubrication. Drip Feed Lubrication. Forced Feed Circulation. Oil Mist Lubrication. Selecting Rolling Element Bearings for Reduced Failure Risk. Magnetic Shaft Seals in the Lubrication Environment. References. 21 Mechanical Seal Reliability by Gordon S. Buck Failure Analysis. Seal Hardware Failures. Seal Failures from Installation Problems. Seal Failures Related to Pump Hardware. Seal Failures Caused by Pump Repair and installation Seal Failures Caused by Pump Operation. Reliability. Index,...,, x

12 Preface When Val and I decided to collaborate and write the first edition, our goal was to produce an easy-to-read, easy-to-understand, practical textbook stressing hydraulic design, that could be of hands-on use to the pump designer, student, and rotating equipment engineer. Although feedback from readers indicates that we achieved our desired goal, we did recognize that we had omitted several important topics. We had said little about the design of chemical pumps and touched only lightly on the extensive range of composite materials and the manufacturing techniques used in nonmetallic pump applications. We had totally ignored the subject of mechanical seals, yet we fully recognized that a knowledge of seal fundamentals and theory of operation is essential to the pump designer and rotating equipment engineer. Another major omission was the subject of vibration and noise in centrifugal pumps. With today's high energy pumps operating at ever increasing speeds, it is essential that we understand the sources of pump noise and causes of vibration that result from installation, application, cavitation, pulsation, or acoustic resonance. Although we had touched lightly on rotor dynamics, we felt this subject deserved to be expanded, particularly in the areas of bearing stiffness and damping, seal effects, and the evaluation of critical speed calculations. Finally, we had said nothing about the knowledge necessary to extend pump life during installation and operation, which requires a deep understanding of bearings, lubrication, mechanical seal reliability, and the external alignment of pump and driver. xi

13 This second edition was therefore written to incorporate these subjects, and in this regard, I have been fortunate in soliciting a number of Mends and colleagues, each expert in his chosen field to assist me. With the help of Heinz Bloch, Gordon Buck, Fred Buse, Erik Fiske, Malcolm Murray, Jim Netzel, and Fred Szenasi, I have expanded and improved the second edition in a manner I know would have made Val proud. Readers of the first edition will find this book of even greater practical value, and new readers will gain an in-depth practical knowledge from the extensive experience of the authors and contributors. Robert R, Ross xii

14 CENTRIFUGAL PUMPS Design & application Second Edition

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16 Part 1 Elements of Pump Design

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18 1 Introduction System Analysis for Pump Selection Before a pump can be selected or a prototype designed, the application must be clearly defined. Whether a simple recirculation line or a complex pipeline is needed, the common requirement of all applications is to move liquid from one point to another. As pump requirements must match system characteristics, analysis of the overall system is necessary to establish pump conditions. This is the responsibility of the user and includes review of system configuration, changes in elevation, pressure supply to the pump, and pressure required at the terminal. Relevant information from this analysis is passed on to the pump manufacturer in the form of a pump data sheet and specification. From the information given, the following will ultimately determine pump selection. Capacity range of liquid to be moved Differential head required NPSHA Shape of head capacity curve Pump speed Liquid characteristics Construction Differential Head Required The head to be generated by the pump is determined from the system head curve. This is a graphical plot of the total static head and friction 3

19 4 Centrifugal Pumps: Design and Application Figure 1-1. System head curve. losses for various flow rates. For any desired flow rate, the head to be generated by the pump or pumps, can be read directly (Figures 1-1 and 1-2), NPSHA Net positive suction head available (NPSHA) is of extreme importance for reliable pump operation. It is the total suction head in feet of liquid absolute, determined at the suction nozzle and referred to datum, less the vapor pressure of the liquid in feet absolute. This subject is discussed in detail in Chapter 9. Shape of Head Capacity Curve The desired shape of the head capacity (H-Q) curve is determined during analysis of the system. Most specifications call for a continuously rising curve (Figure 1-3) with the percentage rise from the best efficiency point (BEP) determined by system limits and mode of operation, Unsta-

20 Introduction 5 Figure 1-2. The system head curve establishes pump conditions. Figure 1-3. Continuously rising head capacity curve.