Metering pump handbook PDF
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METERING PUMP HANDBOOK Robert E. McCabe Engineering Manager, Metering Philip G. Lanckton Product Manager, Metering William V. Dwyer Product Manager, Rotary PtlLSAFEEDER, INC. Industrial Press Inc. 200 Madison Avenue New York, New York 10016-4078 Library of Congress Cataloging in Publication Data McCabe, Robert E. Metering pump handbook. Bibliography: p. Includes index. 1. Metering pumps—Handbooks, manuals, etc. I. Lanckton, Philip G. II. Dwyer, William V. III. Title. TJ916.M37 1984 621.6'99 84-4465 ISBN 0-8311-1157-7 9 METERING PUMP HANDBOOK Copyright © 1984, by Industrial Press Inc., New York, New York. Printed in the united States of America. All rights reserved. This book, or parts thereof, may not be repro duced in any form without permission of the publishers. Preface RECENTLY, THERE HAS EVOLVED a great need for an authoritative engineering reference on the design, application, and maintenance of that class of positive displacement pumps known as metering, or controlled-volume, pumps. While a number of books have been published over the years, covering the subject of fluid transfer and their piping systems, no comprehensive publication until now has treated the special pumping problems associated with flow metering systems in the process industries. The use of metering pumps has expanded enormously since the 1960s, with the rapid growth of such industries as chemical, petrochemical, food processing, pharmaceuticals, and water treatment. But, despite the prolif eration of technical papers on metering pumps and systems, presented at meetings or published in journals, no significant attempt to consolidate this information and to present it in a systematic way has been made until now. This Handbook brings together information that was scattered among many technical reports, specialty journals, and manufacturers' catalogs pertaining to metering pumps. Although the process industries today use two types of positive displace ment pumps—rotary and reciprocating—to meter a wide variety of liquids, for purposes of this text only, the reciprocating type is considered a metering pump. In reality, a metering pump is simply a special type of reciprocating positive displacement pump, used to transfer liquids at an accurately con trolled rate, usually between a reservoir and a fluid process system. It is a controlled-volume device whose pumping rate can be varied by a simple adjustment of the effective stroking length of the piston or plunger alone, or perhaps stroking rate in addition, to produce controlled transfer of a pre determined volume of liquid over a specified period of time. At any fixed driven speed, the accuracy of true metering pumps is limited only by the design of the equipment, and is virtually unaffected by system discharge pressures. Other types of positive displacement pumps have fixed capacities at any single driven speed, hence their rate of output can only be changed by vary ing the speed of the driver. Losses in accuracy here arise not only from the limitations of the pump itself, but from the speed control system also— which, in many cases, is further distorted by changes in system discharge pressure. For these reasons, such groups as the Hydraulic Institute and the υ υί //// PREFACE American Petroleum Institute* do not classify these devices as metering pumps. There are two basic types of metering pumps: piston plunger and dia phragm. The piston or packed-plunger type contacts and directly pumps the actual process liquid. Diaphragm pumps were developed to provide positive isolation between the process liquid and the primary working components of the pump. Early style diaphragms were deflected by pure mechanical mo tion, while later designs added a hydraulic fluid to transmit the force of piston displacement more uniformly over the entire surface of the diaphragm, thus eliminating high stress points and giving maximum possible diaphragm life. The Metering Pump Handbook presents clearly and concisely the basic principles of the positive displacement pump; develops in-depth analysis of the design of reciprocating metering pumps and their piping systems; and demonstrates the practical implementation of these concepts through ex amples of actual metering pump application. 'Hydraulic Institute Standards, 13th e<±, Cleveland, Ohio, 1975. Positive Displacement Pumps— Controlled Volume, API Standard 675, 1 st ed. American Petroleum Institute, Washington, DC, March, 1980. Contents PART 1 Design Principles 1 What is a Metering Pump? 3 Introduction; The pump universe; Types of metering pumps; Summary 2 Power End Mechanisms 19 Introduction; Power end mechanisms; Adjustment mechanisms; Instantaneous liquid flow rate 3 Packings and Diaphragms 39 Introduction; Classes and styles of packings; Diaphragms 4 Valving 69 Introduction; Check valves; Compensator valves; Pressure-relief valve; Back-pressure valve 5 Lubrication 90 Introduction; Lubricant temperature; Gear lubrication; Bearing lubrication; Lubrication periods; Methods of lubrication; Lubrication of hydraulic diaphragm pumps; Classes of lubricating oils; Oil additives; Grease lubrication; Grease temperature; Packing lubrication 6 Control Mechanisms 105 Introduction; Types of control/adjustment; Pneumatic control devices; Electronic control devices; Hydraulic controllers; Variable-speed flow control 7 Multihead Pumps 114 8 Pump Drivers and Couplings 121 Introduction; Integral speed reduction; External speed reduction; Rotary induction motor; Driver couplings; Coupling guard PART £ Operating Principles 9 Metering Pump Characteristics and Performance 139 Introduction; Characteristics; Performance parameters 10 Noise 153 υϋί III I CONTENTS 11 Driver Power and Performance 157 12 Testing 162 Introduction; Standard production testing; Special customer testing; Engineering laboratory testing; Field testing PART 3 Selection 13 Fluid Analysis 177 Introduction; Chemical composition; Physical properties; Unique properties 14 Materials of Construction 184 Introduction; Forms of corrosion; Pump connections; Valve system; Seals; Liquid chamber; Piston, cylinder, and packing; Plunger, cylinder, and packing; Diaphragms; Power end 15 Environment 195 Introduction; Indoor environment; Outdoor environment; Noise; Service cycle; Storage; Enclosures 16 Safety 198 Introduction; Pump design; Motor design; Pumpage; System design; Instruction to personnel 17 Special Considerations 204 Introduction; Remote check valves and liquid chambers; Capacity loss due to compression 18 Process of Selection 212 Introduction; Primary selection; Final selection 19 Typical Applications 216 PART 4 System Design 20 Design of Metering Pump Systems 223 Introduction; Pump; Control; Driver; Accessories 21 The Piping System 232 Introduction; Source of supply; Suction piping; System hydraulics; Discharge piping; Special considerations PART D Maintenance 22 Maintenance 245 23 Troubleshooting 248 Appendix 252 Corrosion Guide 263 Bibliography 274 Index 276 PART 1 Design Principles CHAPTER 1 What is a Metering Pump? INTRODUCTION FOR A THOROUGH UNDERSTANDING of the principles bf metering pumps, one must first understand what a metering pump is and, of equal importance, what a metering pump is not. To best describe this difference, the following question may be asked: "What was the first metering pump?" Some would answer by pointing to a simple drinking cup and relating how it was invented to measure the volume of water that early humans required to quench their thirst. The drinking cup was, indeed, a unique device when first invented because it satisfied a need and gave additional benefits: It was more convenient for people to drink from a sitting or standing position instead of lying on their stomachs and sucking the water out of scooped hands into their mouths; it reduced the leakage of water between its source and its point of usage; it provided a better method of transferring a larger volume of liquid from one point to another than cupped hands; it also improved on the previous method, which needed suction, by requiring a more positive pressure condition to fill the system. Despite all the preceding features this "new" device possessed, it was not the first metering pump; however, its features do describe what a metering pump "is not": 1. Like today's common pump, the metering pump is a conven ience tool to accomplish work; however, this is not what the metering pump was designed to do. 2. Like today's common pump, the metering pump will effectively move liquid from one spot to another with minimum leakage; however, this is not what the metering pump was designed to do. 3. Like today's common pump, the metering pump will effectively provide a compression ratio through it, to provide a more pos itive pressure condition with which to work. If these features do not adequately describe the principles of a metering pump, what early device does? Fortunately, people weren't required to invent it, they were born with it beating inside their chests—it is the human heart. 3 4 //// METERING PUMP HANDBOOK When we compare the features of the heart to those of the modern me tering pump, we find many similarities: Sized to fit the system conditions. Positive displacement ability for repeatability, reproducibility, and lin earity. Flow rate adjustable for varying conditions. Adjustable for varying pressures. Pulsing or reciprocating action. Check valves. Leakproof. Built-in safety features. Relatively simple in construction compared to other parts of the system (liver, lungs, or brain). Rugged in construction, requiring little maintenance (2.5 billion pulses in average lifetime). Can meter two different liquids at the same time and maintain syn chronization. All parts of the system depend on it. Fig. 1-1. Early animal heart surgery using a metering pump to bypass the defective heart. WHAT IS A METERING PUMP? Illl 5 Although not necessary for a metering pump, the heart is electrically actuated. The vast majority of metering pumps are, but are capable of other types of actuation. In addition, we might add, the human heart and the modern metering pump are so closely related in job function that the metering pump can and has been used to replace the heart (Fig. 1-1). THE PUMP UNIVERSE To better understand the metering pump we must investigate its place within the universe of pumps. The pump universe could be organized in a variety of ways such as by their design, their materials of construction, or the liquids they pump. This book will organize the pump universe by classifying pumps based on the method by which the pump imparts energy to the liquid being pumped. This results in two basic classes of pumps: dynamic and displacement. Dynamic pumps encompass those shown on the left-hand side of Fig. 1 -2, and these impart energy to the liquid in a steady fashion. Displacement pumps encompass the remaining pumps in Fig .1 -2, and these impart energy to the liquid in a pulsating fashion. DISPLACEMENT -{" 1 CENTRIFUGAL RECIPROCATING ~ DOUBLE ACTING LD KS INGLE STAGE. ί-CLOSED IMPELLER SINGLE ACTING~-1 PLS DIMUPPLLEEXX MULTISTAGE -I L OPEN IMPELLER4- FIXED PITCH —{IP OWER1!— ΓL iD OUBLE ACTING -^ L TRIPLEX VARIABLE PITCH L MULTIPLEX J WXED FLOW 1 RADIAL FLOW r SELF PRIMING- OPEN PISTON.PLUNGER SIMPLEX r- DSOINUGBLLEE S SUUCCTTTItOtOoNIt Jτ --■M SNUINOLGNTLI PSERT SIAMTGIANEGG EJ-- ' IMSEPMEOLPLEENR IETERING}-) DIAPHRAGM -DTMURPUIPLLLETEXIPX L EX IMPELLER CLOSED "IMPELLER |— VAHE -MULTISTAGE EUSI 4 SINGLE ROTARY V . — FPLISETXOIBNL E SCREW PERISTALTIC . GEAR JET(EDUCTOR) A MULTIPLE ROTOR L -LOBE SPECIAL EFFECTh GAS LIFT - CIRCUMFERENTIAL PISTON HYDRAULIC RAM U- SCREW ELECTROMAGNETIC Fig. 1-2. Classification of the pump universe (Pump Handbook, Igor J. Karassik, William C. Krutzch, Warren H. Fraser, and Joseph P. Messina, ed„ Copyright 1976, Courtesy, McGraw-Hill Book Company).
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