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Practical Centrifugal Pumps Design, Operation and Maintenance Other titles in the series Practical Cleanrooms: Technologies and Facilities (David Conway) Practical Data Acquisition for Instrumentation and Control Systems (John Park, Steve Mackay) Practical Data Communications for Instrumentation and Control (Steve Mackay, Edwin Wright, John Park) Practical Digital Signal Processing for Engineers and Technicians (Edmund Lai) Practical Electrical Network Automation and Communication Systems (Cobus Strauss) Practical Embedded Controllers (John Park) Practical Fiber Optics (David Bailey, Edwin Wright) Practical Industrial Data Networks: Design, Installation and Troubleshooting (Steve Mackay, Edwin Wright, John Park, Deon Reynders) Practical Industrial Safety, Risk Assessment and Shutdown Systems for Instrumentation and Control (Dave Macdonald) Practical Modern SCADA Protocols: DNP3, 60870.5 and Related Systems (Gordon Clarke, Deon Reynders) Practical Radio Engineering and Telemetry for Industry (David Bailey) Practical SCADA for Industry (David Bailey, Edwin Wright) Practical TCP/IP and Ethernet Networking (Deon Reynders, Edwin Wright) Practical Variable Speed Drives and Power Electronics (Malcolm Barnes) Practical Electrical Equipment and Installations in Hazardous Areas (Geoffrey Bottrill and G. Vijayaraghavan) Practical E-Manufacturing and Supply Chain Management (Gerhard Greef and Ranjan Ghoshal) Practical Grounding, Bonding, Shielding and Surge Protection (G. Vijayaraghavan, Mark Brown and Malcolm Barnes) Practical Hazops, Trips and Alarms (David Macdonald) Practical Industrial Data Communications: Best Practice Techniques (Deon Reynders, Steve Mackay and Edwin Wright) Practical Machinery Safety (David Macdonald) Practical Machinery Vibration Analysis and Predictive Maintenance (Cornelius Scheffer and Paresh Girdhar) Practical Power Distribution for Industry (Jan de Kock and Cobus Strauss) Practical Process Control for Engineers and Technicians (Wolfgang Altmann) Practical Power Systems Protection (Les Hewitson, Mark Brown and Ben. Ramesh) Practical Telecommunications and Wireless Communications (Edwin Wright and Deon Reynders) Practical Troubleshooting of Electrical Equipment and Control Circuits (Mark Brown, Jawahar Rawtani and Dinesh Patil) Practical Hydraulics (Ravi Doddannavar, Andries Barnard) Practical Batch Process Management (Mike Barker and Jawahar Rawtani) Practical Centrifugal Pumps Design, Operation and Maintenance Paresh Girdhar B. Eng (Mech Eng), Senior Engineer for Girdhar and Associates Octo Moniz CEng, MBA (Tech Mgmt), Senior Hospital Engineer based in Perth, Western Australia specialising in Mechanical Plant and Services Series editor: Steve Mackay FIE (Aust), CPEng, BSc (ElecEng), BSc (Hons), MBA, Gov.Cert.Comp., Technical Director – IDC Technologies AMSTERDAM • BOSTON • HEIDELBERG • LONDON NEW YORK • OXFORD • PARIS • SAN DIEGO SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Newnes is an imprint of Elsevier Newnes An imprint of Elsevier Linacre House, Jordan Hill, Oxford OX2 8DP 30 Corporate Drive, Burlington, MA 01803 First published 2005 Copyright © 2005, IDC Technologies. All rights reserved No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1T 4LP. Applications for the copyright holder’s written permission to reproduce any part of this publication should be addressed to the publishers British Library Cataloguing in Publication Data Girdhar, Paresh Practical centrifugal pumps: design, operation and maintenance 1. Centrifugal pumps I. Title II. Moniz, Octo 621. 6’7 Library of Congress Cataloguing in Publication Data A catalogue record for this book is available from the Library of Congress ISBN 0 7506 6273 5 For information on all Newnes Publications visit our website at www.newnespress.com Typeset by Integra Software Services Pvt. Ltd, Pondicherry, India www.integra-india.com Printed and bound in The Netherlands Working together to grow libraries in developing countries www.elsevier.com | www.bookaid.org | www.sabre.org Contents Preface................................................................................................................................ viii 1 Introduction................................................................................................................. 1 1.1 Applications.................................................................................................. 3 1.2 Pump types ................................................................................................. 4 1.3 Reciprocating pumps ................................................................................... 4 1.4 Rotary pumps .............................................................................................. 6 1.5 Centrifugal pumps ..................................................................................... 10 2 Centrifugal pump design and construction ............................................................... 18 2.1 Impellers .................................................................................................... 18 2.2 Pump casings ............................................................................................ 24 2.3 Wearing rings ............................................................................................ 29 2.4 Shaft .......................................................................................................... 32 2.5 Stuffing boxes ............................................................................................ 33 2.6 Mechanical seals and seal housings .......................................................... 36 2.7 Bearing housing/bearing isolators .............................................................. 39 2.8 Couplings .................................................................................................. 43 3 Pump hydraulics ...................................................................................................... 48 3.1 Specific gravity .......................................................................................... 48 3.2 Viscosity .................................................................................................... 48 3.3 Vapor pressure .......................................................................................... 49 3.4 Flow .......................................................................................................... 50 3.5 Head ......................................................................................................... 50 3.6 System resistance ..................................................................................... 50 3.7 Pump efficiency ......................................................................................... 53 3.8 Hydraulic power ......................................................................................... 53 3.9 Pump characteristic curve ......................................................................... 53 3.10 Curve corrections ...................................................................................... 56 3.11 Specific speed ........................................................................................... 59 3.12 Cavitation, recirculation, and Net Positive Suction Head (NPSH) .............. 62 3.13 Suction-specific speed ............................................................................... 73 3.14 Performance calculation procedure ........................................................... 74 4 Forces in centrifugal pumps ..................................................................................... 76 4.1 Axial thrust ................................................................................................ 76 4.2 Radial loads .............................................................................................. 82 vi Contents 5 Centrifugal pump operation and characteristics ....................................................... 89 5.1 Behavior of hydraulic properties of pumps ................................................. 90 5.2 Non-dimensional characteristics ................................................................ 95 5.3 The cause of the H–Q curve ...................................................................... 96 5.4 The inlet velocity triangle ........................................................................... 97 5.5 The cause of the P–Q curve ...................................................................... 98 5.6 The effect of speed changes on characteristic curves ................................ 99 5.7 The complete characteristic curve ........................................................... 100 5.8 Multiple pump operation .......................................................................... 102 5.9 Pump characteristics – viscous liquids, liquids with considerable solids ... 105 5.10 Pump characteristics – abnormal operation ............................................. 106 5.11 Pump characteristics – speed–torque curves ........................................... 108 5.12 Discharge regulation of pumps ................................................................ 111 5.13 Range of pump operation ........................................................................ 117 6 Pump specification and selection ........................................................................... 121 6.1 System analysis ....................................................................................... 122 6.2 Data sheet – the pump specification document ........................................ 128 6.3 Bid request .............................................................................................. 129 6.4 Bid review/analysis .................................................................................. 130 6.5 Conclusion ............................................................................................... 131 7 Pump testing and inspection .................................................................................. 132 7.1 Material inspection requirements ............................................................. 133 7.2 Shop tests ............................................................................................... 135 7.3 Performance test procedure .................................................................... 137 8 Pump installation and commissioning .................................................................... 144 8.1 Site location ............................................................................................. 144 8.2 Receipts and physical inspection ............................................................. 144 8.3 Pre-alignment checks .............................................................................. 145 8.4 Location of pump foundation .................................................................... 145 8.5 Design and dimensions of pump foundation ............................................ 145 8.6 Excavation and forms for pump foundation .............................................. 146 8.7 Rebar and anchor bolts ........................................................................... 147 8.8 Pouring .................................................................................................... 148 8.9 Base plate and sole plate preparation ...................................................... 149 8.10 Grouting ................................................................................................... 150 8.11 Installation of pump and driver ................................................................. 153 8.12 Associated piping and fittings .................................................................. 153 8.13 On-site installation and commissioning of the pump set ........................... 157 8.14 Pre-operational checks ............................................................................ 158 8.15 Preparation for start-up ............................................................................ 159 8.16 Pump in operation ................................................................................... 159 9 Centrifugal pump maintenance .............................................................................. 160 9.1 Introduction .............................................................................................. 160 9.2 Pump breakdown and removal ................................................................ 164 9.3 Single-stage pump dismantling and repair ............................................... 165 Contents 9.4 9.5 9.6 9.7 9.8 vii Preparation for reassembly .......................................................................170 Pump assembly ........................................................................................175 Vertical pump repair .................................................................................180 Multistage pump repair .............................................................................186 Optimum time to maintain pumps .............................................................190 Appendix A: Pump types ...................................................................................................195 References ........................................................................................................................243 Index ...............................................................................................................................246 Preface This books covers the essentials of pump construction, design applications, operations, maintenance and management issues and the authors have tried to provide you with the most up-to-date information and best practice in dealing with the subject. Key topics which the book homes in on are: the various types of centrifugal pumps; relevant pump terminology; pump characteristics and pump curves; pump calculations; auxiliary equipment associated with pumping circuits; operating pump systems – drafting the correct operations, controls and procedures; pump reliability definition in terms of availability, criticality and wear characteristics; pump efficiency – capital, maintenance and life cycle costs. From the reader’s perspective the following is offered: • If you are an engineer or technician you will learn the inside information on why and how pumps are designed. No longer will you be specifying pumps you don’t understand. • If you are working in the plant and maintenance area you will learn how pumps work, what the main causes of pump problems are and how to fix them quickly and effectively. • Also if you are a design engineer or technician, you will gain a global picture in designing pumps from the authors’ many years of experience. We would hope that you will gain the following knowledge from this book: • • • • • • • • • • • • Pump terminology Real pump classifications, types and criteria for selection How to read pump curves and cross referencing issues Pump efficiency determination and cost analysis Critical elements in pump system design Shaft seal selection and failure determination How to install and commission a pump Condition monitoring and trouble-shooting of pumps What makes up a pump’s total discharge head requirement How to install pumps How to look after pump bearings Precautions when starting up a new pump or after strip-down for maintenance. Typical people who will find this book useful include: • Plant Operations & Maintenance Personnel • Plant Engineer, Managers & Supervisors • Process Control Engineers & Supervisors • Consulting Engineers • Maintenance Engineers & Technicians • Pump Sales and Applications Personnel • Pump Users • Pump Service Contractors. You should have a modicum of mechanical knowledge and some exposure to pumping systems to derive maximum benefit from this book. 1 Introduction The transfer of liquids against gravity existed from time immemorial. A pump is one such device that expends energy to raise, transport, or compress liquids. The earliest known pump devices go back a few thousand years. One such early pump device was called ‘Noria’, similar to the Persian and the Roman water wheels. Noria was used for irrigating fields (Figure 1.1). Figure 1.1 Noria water wheel (From the Ripley’s believe it not) The ancient Egyptians invented water wheels with buckets mounted on them to transfer water for irrigation. More than 2000 years ago, a Greek inventor, Ctesibius, made a similar type of pump for pumping water (Figure 1.2). During the same period, Archimedes, a Greek mathematician, invented what is now known as the ‘Archimedes’ screw’ – a pump designed like a screw rotating within a cylinder (Figure 1.3). The spiraled tube was set at an incline and was hand operated. This type of pump was used to drain and irrigate the Nile valley. In 4th century Rome, Archimedes’ screw was used for the Roman water supply systems, highly advanced for that time. The Romans also used screw pumps for irrigation and drainage work.