Water pumps and pumping systems

Digital Electronics and Water Pumps and Systems 1.3 Introduction I 1.3 Computer-Aided Calculations of Water Loads and Pipe Friction I 1.3 Hydraulic Gradient Diagrams I 1.4 Speed and Accu

WATER PUMPS AND PUMPING SYSTEMS

James B (Burt) Rishel, P.E.

McGRAW-HILL

New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul

Sydney Toronto

McGraw-Hill ZZ

A Division of The McGraw-HiU Companies

Copyright © 2002 by The McGraw-Hili Companies, Inc All rights reserved Printed

in the United States of America Except as permitted under the United States

Copyright Act of 1976, no part of this publication may be reproduced or distributed

in any form or by any means, or stored in a data base or retrieval system, without the

prior written permission of the publisher.

I 2 3 4 5 6 7 890 AGM/AGM o 9 8 7 6 5 4 3 2

ISBN 0-07-137491-4

The sponsoring editor for this book was Larry Hager, the editing supervisor was

Steven Melvin, and the production supervisor was Sherri Souffrance It was set in

the HBI design in Times Roman by Kim Sheran and Wayne Palmer of

McGraw-Hill's Professional's Hightstown, N J., composition unit.

Printed and bound by QuebecorlMartinsburg.

*This book was printed on recycled, acid-free paper containing

a minimum of 50% recycled, de-inked fiber.

McGraw-Hili books are available at special quantity discounts to use as premiums

and sales promotions, or for use in corporate training programs For more

information, please write to the Director of Special Sales, Professional Publishing,

McGraw-Hili, Two Penn Plaza, New York, NY 10121-2298 Or contact your local

bookstore.

Information contained in this work has been obtained by The McGraw-Hili

Companies, Inc ("McGraw-Hili") from sources believed to be reliable However,

neither McGraw-Hili nor its authors guarantee the accuracy or completeness of any

information published herein, and neither McGraw-Hili nor its authors shall be

responsible for any errors, omissions, or damages arising out of use of this

informa-tion This work is published with the understanding that McGraw-Hili and its authors

are supplying information but are not attempting to render engineering or other

pro-fessional services If such services are required, the assistance of an appropriate

This book is dedicated to my wife Alice for her patience during the time required for its completion.

Preface xix

Table of Symbols and Terminology xxiii

Location of Figures xxv

PART 1 The Basic Tools of Design

CHAPTER 1 Digital Electronics and Water Pumps and Systems 1.3

Introduction I 1.3

Computer-Aided Calculations of Water Loads and Pipe Friction I 1.3

Hydraulic Gradient Diagrams I 1.4

Speed and Accuracy of Electronic Design of Water Systems I 1.5

Equation Solutions by Computer I 1.5

Databasing I 1.5

Electronic Communication I 1.6

Electronic Design of the Piping and Accessories I 1.6

Electronic Selection of Water Pumping Equipment I 1.6

Electronic Control of Water Pumping Systems I 1.6

Electronics and Water Pumping Systems I 1.7

Electronics and Variable-Speed Pumping Systems I 1.7

Electronic Commissioning I 1.7

Purpose of This Book I 1.8

CHAPTER 2 Physical Data for Water Pumping Systems 2.1Introduction I 2.1

Standard Operating Conditions I 2.1

Standard Air Conditions I 2.2

Operating Pressures I 2.2

Thermal Equivalents I 2.4

Water Data I 2.4

Viscosity of Water I 2.6

Vapor Pressure and Specific Weight for Water, 32 to 2l2"F I 2.6

Velocity of Sound in Water I 2.10

Areas and Volumes of Steel Pipe and Tanks I 2.10

Electrical Data I 2.10

Total Owning Cost I 3.1

Maximum Capacities and Velocities of Actual Piping I 3.3

Pipe Velocity is Designer's Responsibility I 3.4

Pipe and Fitting Specifications I 3.5

General Pipe Friction Analysis I 3.5

Pipe friction formulas I 3.7

Reynolds number and Moody diagrams / 3.8

Use of the Darcy-Weisbach equation I 3.11

Use of the Hazen-Williams formula I 3.35

Pipe Friction Tables / 3.35

Asphalt-Coated Cast Iron and New Steel Pipe Friction Tables I 3.36

Plastic Pipe I 3.36

PVC and CPVC plastic pipe I 3.37

HDPE pipe I 3.37

Copper Pipe and Tubing / 3.42

Pipe Fitting Losses I 3.42

Steel and cast iron pipe fittings / 3.79

Results of Recent Laboratory Testing of Fittings I 3.83

Effect of Fabrication on Steel Fitting Loss / 3.86

Copper Fittings I 3.88

Plastic Pipe Fittings I 3.88

Hydraulic Gradient Diagrams I 3.90

Piping Network Analyses / 3.91

Summary I 3.95

References I 3.98

PART 2 Pumps and Their Performance

CHAPTER 4 Basic Design of Centrifugal Pumps 4.3

Introduction I 4.3

General Design of Centrifugal Pumps I 4.4

General Performance of a Centrifugal Pump I 4.7

Centrifugal Pump Impeller Design I 4.10

Specific Speed of a Centrifugal Pump I 4.12

Critical Speed of a Centrifugal Pump I 4.17

Minimum Speed for a Variable-Speed Pump / 4.21

Minimum Flow for Centrifugal Pumps I 4.22

Pump Suction Limitations / 4.22

Net positive suction head I 4.23

Submergence in open tanks, wet wells, and open pits / 4.27

Sizing Centrifugal Pumps I 4.27

General Pump Design Information I 4.28

Books for Further Reading I 4.29

CHAPTER 5 The Physical Design of Centrifugal Pumps for Water 5.1

Introduction I 5.1

Basic Elements of Physical Design I 5.1

Forces on centrifugal pumps I 5.2

Leakage control in centrifugal pumps I 5.7

Physical Description of Centrifugal Pumps I 5.11

Two Basic Types of Centrifugal Pumps I 5.16

Volute Type Pumps I 5.16

Single-suction pumps I 5.17

Double-suction pumps I 5.27

Axial Flow Type Pumps I 5.32

Axial flow pump heads I 5.37

Column assemblies for axial flow pumps I 5.43

Axial flow type bowls and impellers I 5.47

Regenerative Turbine Pumps I 5.57

Typical constant-speed pump head-flow curves I 6.12

Brake horsepower required curves I 6.17

"Steep" versus "flat" head-flow curves I 6.17

Series and Parallel Operation of Centrifugal Pumps I 6.19

Variable-Speed Pump Head-Flow Curves I 6.22

Air Entrainment and Vortexing I 6.26

Flexible member pumps / 7.2

Lobe type pumps / 7.3

Gear pumps / 7.5

Screw pumps / 7.5

High volume screw pumps (Archimedes principle) / 7.7

Progressive cavity pumps / 7.8

Definitions for Rotary Pumps / 7.11

Reciprocating Power Pumps / 7.11

Electric motor power characteristics / 8.2

Motor output ratings / 8.3

Motor speed / 8.3

Types of polyphase motors and code letters / 8.3

Electric motor torque and horsepower / 8.4

Motor currents / 8.6

Electric motor output horsepower / 8.7

Electric motor power factor / 8.7

Electric motor efficiency / 8.7

Electric motor construction / 8.8

Motor siZing for pumps / 8.9

Vanable-Speed Drives for Pumps / 8.10

Variable-Frequency Drives / 8.10

Early Variable-Frequency Drives / 8.12

PWM Drives / 8.12

Drives with multipulse input circuits / 8.15

Clean POWervariable-speed drives / 8.15

Medium Voltage drives / 8.]5

Harrnonics and Variable-Frequency Drives / 8.29

Advantages of Variable-Frequency Drives / 8.32

Sizing of Variable-Frequency Drives / 8.32

Efficiency of Variable-Frequency Drives / 8.33

Application of Variable-Speed Drives / 8.35

Variable Frequency-Drive Accessories and Requirements / 8.37

Engine-Driven Pumps / 8.39

SUIT1lnary / 8.42

Sources of Technical Information / 8.42

PART 3 The Pumping World

Introduction / 9.3 Determination of Useful Energy / 9.3 Useful consumption of pumping energy / 9.3 Inefficient use of energy / 9.4

Calculation of System Efficiency / 9.4 kW/MGD / 9.6

Energy Lost to Mechanical Flow Control Devices / 9.7 Evaluation of Piping Design / 9.8

Load Range for a Water System / 9.8 Energy Consumption and Water Use / 9 /0

Categorization of Water Systems / 9./0

Suggested Design Rules / 9.10

CHAPTER 10 Configuring a Pumped Water System 10.1

Introduction / /0.1

Modeling a Water System / 10.2

System Head Curve Components / 10.3

Pumping System Losses / 10.5

System Head Areas / 10.9

Static Pressure / 10.13

Configuration of Typical Water Systems / /0.13

All friction system / 10.13

High static system / 10.14

System with two subsystems / 10.15

High static system with variable supply pressure / 10.15

System with high supply pressure and no static pressure / 10.17

System with variable supply pressure and no static pressure / 10.18

•

Selecting variable-speed pumps / 11.4 Increased Pump Speed for Variable-Speed Pumps / 11.5 Decreased Pump Speed for Variable-Speed Pumps / 11.9 Selecting a Larger Impeller at Maximum Motor Horsepower / 11.11 Proper Use of Affinity Laws with Constant -Speed Pumps / 11.13 Number of Pumps Operating in Parallel / 11.15

xii CONTENTS

Jockey Pumps / 11.21

Efficiency of a Pumping System / 11.21

Wire-to-Water Efficiency / 11.23

Calculated wire-to-water efficiency of single constant-speed pumps / 11.25

Calculated wire-to-water efficiency of a single variable-speed pump / 11.27

Calculated wire-to-water efficiencies of multiple-pump systems / 11.27

Total kW Input for a Pumping System / 11.28

Conclusions / 11.31

Total kW input indication and pump programming / 11.32

Use of Adaptive Control / 11.34

Total kW input for variable-speed pumping systems with a small lead pump / 11.35

Pump Control / 11.35

Pump Start-Stop Procedures in Response to Physical Events / 11.36

System activation or shut-down / 11.36

System demands such as level, flow, or pressure / 11.36

Emergency backup on pump failure / 11.37

Sequencing of Pumps / 11.37

Alternation of Operating Pumps / 11.39

Pump Speed Control / 11.40

Sensors for pump speed control / 11.43

Communication from Remote Transmitters / 11.44

Effects of Water Systems on Pump Performance / 11.45

Using Centrifugal Pumps as Turbines / 11.47

Wet well volume / 12.1

Inlet Bell Design Diameter / 12.2

Intake Structures for Solids Bearing Liquids / 12.10

Trench-type wet wells for solids handling liquids / 12.10

Circular wet pits for solids handling pumps / 12.12

Testing Intake Structures / 12./2

Remedial Measures for Intake Structures / 12.12

Strainers, Screens, and Trashracks / /2.12

Strainers / 12.13

Screens and trashracks / 12.14

Summary / 12.15

PART 4 Clear Water Pumping

CHAPTER 13 Pumps for Central Water Treatment Plants 13.3

Introduction / 13.3 Types of Water Plants Utilizing Rainwater / 13.3 Surface-water treatment plants / 13.4 Underground water treatment plants / 13.6 Desalinization / 13.11

Water Reuse / 13.11 Recharge / 13.12 Summary / 13.12

CHAPTER 14 Water Pumps for Municipal Water Distribution 14.1

Introduction / 14.1 Primary Pumping Stations / 14.1 System head curves for primary pumping / 14.2 Variable- or constant-speed primary pumps / 14.3 Secondary Pumping Systems / 14.4

Multiple pumping stations / 14.7 Calculation of Friction Loss in Municipal Water Systems / 14.9 Hydraulic Shock from Long Discharge Lines / 14.9

Summary / 14.13

CHAPTER 15 Pumps for Plumbing Systems 15.1

Introduction / 15.1 Cold Water Systems / 15.1 Water flow / 15.1 Pressure losses in cold water systems / 15.3 Calculation of pump head for cold water plumbing systems / 15.6 Materials for cold water pumping systems / 15.6

Pumps for domestic water / 15.7 Cold water system configuration / 15.8 Sizing the hydro-pneumatic tank / 15.10

Cold water system head curves and areas / 15.14 Location of pressure switches and transmitters / 15.17 Hot Water Systems / 15.19

Sewage Ejectors / 15.20

Storm Water / 15.21 Graywater / 15.21 Additional Reading / 15.22

Introduction / 16.1 Types of Fire Pump Installations / 16.1 Location of fire pump installations / 16.4

Types of Fire Pumps I 16.4

Rate of Flow of Stationary Fire Pumps for Water I 16.7

Fire pump performance I 16.8

Fire Pump Accessories I 16.8

Fire Pump Fittings I 16.9

Fire Pump Drivers I 16.14

Electric motors I 16.14

Electrical power supply I 16.15

Diesel engines I 16.16

Testing Fire Pumps and Their Installation I 16.16

Shop tests of fire pumps I 16.16

Field testing for approval of the entire installation I 16.17

Well design criteria I 17.11

Drilling the well I 17.11

Well development I 17.12

Selection of the production pump I 17.13

Finalized design flow rate I 17.15

Well Pumps for Farm Domestic Water I 17.15

Pumps for Animal Waste Disposal Systems I 17.15

Agricultural Use of Sewage Plant Sludge and Effluent I 17.16

PART 5 Solids Handling Pumping

CHAPTER 18 Performance of Positive Displacement Pumps 18.3

Introduction I 18.3

Basic Performance of Positive Displacement Pumps I 18.3

Performance of Rotary Pumps I 18.4

Rotary screw pumps I 18.4

Large screw pumps (Archimedes principle) I 18.5

Progressive cavity pumps I 18.8

Flexible element pumps I 18.11

Basic Configurations of Sewage Lift Stations I 19.1

Constant-Speed Sewage Lift Station I 19.1

Variable-Speed Sewage Lift Station I 19.6

Control for a variable-speed sewage pumping station I 19.6

Energy savings from constant wet-well control I 19.7

Pump addition and subtraction points I 19.11

Adaptive control for pump transition points I 19.14

Programming with flow meters I 19.16

Multiple Sewage Lift Stations I 19.17

Friction Loss in Sewage Lift Stations I 19.20

Types of Pumps for Lift Stations I 19.22

Grinder Pump Systems I 19.23

Hydraulic Shock from Long Force Mains I 19.24

Special Control Procedures for Sewage Wet Wells I 19.26

Resume I 19.28

CHAPTER 20 Pumps for Sewage Treatment Plants 20.1

Introduction I 20.1

Types of Sewage Treatment Plants I 20.1

Main Flow Pumps I 20.3

Sludge and Grit Pumps I 20.4

Use of Variable-Speed Drives in Sewage Plants I 20.5

Soil Conservation Service method I 21.2

Computerized runoff models I 21.2

Source of Water I 21.2

Storm Water Pumps I 21.3

"Contractor" pumps I 21.4

Pump Head I 21.4

Above Ground Flood Plain Stations I 21.4

Below Ground Stations I 21.5

Summary I 21.10

PART 6 Installing, Testing, and Operating Pumps

CHAPTER 22 Installation of Water Pumps and Pumping Systems 22.3

Introduction I 22.3

Preinstallation Procedures I 22.3

Pump and Pumping System Bases I 22.4

CONTENTS

Connecting Piping to Pumps I 22.8

Pump fitting sizing I 22.8

Pump fitting ap-angement I 22.10

Expansion Provisions at Pumps I 22.10

Electrical Provisions for Pumps I 22.11

Electrical connections for pump motors I 22.11

Safety controls for pumps I 22.11

Alignment of Pumps, Motors, and Engines I 22.12

Initial Operation of Pumps I 22.12

Direction of Rotation of Pumps I 22.12

Pressure and differential pressure transmitters I 23.9

Temperature indicators and transmitters I 23.9

Centrifugal pumps: Volute and axial flow types (includes vertical pumps) I 24.2

Positive displacement pumps I 24.2

Performance Tests I 24.3

Centrifugal pumps-Volute type I 24.3

Vertical pump tests I 24.4

Submersible pump tests I 24.4

Positive displacement pump tests I 24.4

Net Positive Suction Head Required (NPSHR) Test I 24.5

Priming Time for Self-Priming Centrifugal Pumps I 24.5

Installation of instrumentation I 24.7

Test Reports and Records I 24.7

Accuracy of Pump Head-Capacity Curves I 24.8

Understanding Factory Tests of Pumps I 24.8

Summary I 24.8

CHAPTER 25 Operating and Maintaining Water Pumps 25.1

Introduction I 25.1

Checking for Efficient Selection of Water Pumps I 25.1

Constant- or Variable-Speed Pumps I 25.2

Proper Selection and Operation of Variable-Speed Pumps I 25.3

Selection of variable-speed pumps I 25.3

Operation of variable-speed pumps I 25.3

Checking Pump Performance I 25.4

Checking a pump at design flow I 25.4

Pump operation at the shutoff or no-flow condition I 25.6

Graphical observation of pump performance I 25.6

Vibration I 25.6

Control Signals for Speed Control I 25.8

Sequencing and Alternation I 25.9

Applications of Factory-Assembled Pumping Systems I 26.1

Typical Factory-Assembled Pumping Stations I 26.2

Factory-Assembled Control Centers for Existing Pumps I 26.2

Complete Pump Houses I 26.6

Advantages of Factory-Assembled Pumping Systems I 26.8

Graphical Description of Flow in an Existing System I 27.2

Evaluation of Existing Procedures I 27.4

Trimming the Pump Impeller I 27.4

Changing to a Variable-Speed Pump I 27.6

Evaluation of Existing Pumps and Motors I 27.7

Evaluation of the Number of Pumps I 27.7

Control of Existing Pumps I 27.8

Variable-Speed Control and Drives for Modified Systems I 27.8

Actual Generation of a System Head Area for an Existing System I 27.9

Synopsis I 27.10

CHAPTER 28 Summary of Water System Energy Evaluations 28.1

Introduction I 28.1

Pumping System Efficiencies I 28.1

Water System Efficiencies I 28.2

Purpose of Efficiency Equations I 28.2

Sustained System and Equipment Efficiencies I 28.3

Summary I 28.3

APPENDIX A Abbreviations and Symbols A.3

APPENDIX B Terms and Nomenclature B.1

APPENDIX C Glossary of Equations C.1

APPENDIX D Conversion of English Units to SI Units D.1

Index 1.1

PREFACE

The purpose of this book is to provide information on water pumps and their tion to water systems This book is organized to be a sourcebook on pumps for watersystem designers, owners, and operators It is not intended to be a reference book fordesigners of pumps Excellent books are available already on the detailed design ofpumps

applica-This book will include a number of descriptions of pumping installations formunicipal water and sewage, storm water, plumbing, fire protection, and agriculturalapplications General information about design, construction, and operation of cen-trifugal and positive displacement pumps will be provided

Disclaimer: This book offers no final answers on how to design a specific water system or to apply pumps to it It has brought together technical data and, it is hoped has provided answers to particular pumping applications in these industries.

There are so many excellent books on every aspect of pumps and their application.This book is, in many ways, a synopsis of these books References are includedthroughout this book that provide extensive, continued reading Many of them should

be in the library of any serious designer or user of pumps

The format for this book has been developed to provide a working handbook Theremay appear to be an excessive amount of cross referencing and many variations of thesame formula The reason for these inclusions is to provide rapid access to the desiredsubject The water system designer, owner, or operator who uses this book should beable to reach a pumping subject quickly without having to hunt through several chap-ters A section called "Location of Figures" has been included following the Contents

to make it easier to find a specific figure Many of the figures, although located in onechapter, apply to the pumps and water systems in other chapters

Much of the technical data required for applying pumps to these systems isincluded in this book It is hoped that it can become a source of pump informationfor the water system designer With the advent of electronic, on-line data services forthese industries, much additional information will continue to be made available to thedesigner or user of water pumps

This book is being written at a time of great changes in our methods of cating technical information This technological revolution is probably the greatestsince the invention of the printing press Also, digital electronics is just now bringingits tremendous potential to the way we design these water syr;tems, select equipment forthem, and control the flow of water in them Recognizing the electronic revolution that

communi-we are in the midst of, an effort has been made to point the reader toward new methods

of information transmission that will become commonplace in the near future.Another significant event in the water pumping field is the realization of the greatcapability of the variable-speed pump in saving energy and improving the perfor-mance of water systems So far, most variable-speed pumps in these industries have

been applied to larger water systems Now they are being installed on smaller systems.

The ongoing increase in cost and unavailability of electrical energy, along with the

continued reduction in cost of variable-speed drives, will result in a great many water

pumps being variable speed during the twenty-first century

Two great facts thrust themselves forward as this book was prepared They are:

1 There is so much inexactness in the data used to design water systems and their

pumps For example:

a What do we mean when we use the word "water"? Do we mean distilled or

pure water? Or do we mean water furnished by the local water company? All of the

data furnished in this book makes no reference as to what the water is when

prop-erties such as its specific gravity or viscosity are defined It is presumed that the

sci-entific data included pertains to pure water, but that is not what is coursing through

most of these water systems

b Pipe and fitting friction is at best an inexact science The Hydraulic Institute

+10 percent for steel pipe, and the listed losses for steel and cast iron fittings can

vary from -10 to +35 percent We, at this writing, have very little information on

the friction loss for water flowing through reducing tees or other reducers such as

12" X 10" fittings Work is now being done to advance our knowledge of such

pipe fitting losses

c Pump manufacturing must have acceptable tolerances to achieve any

rea-sonable production These tolerances are basically -0 to +8 percent variation in

pump head at rated flow and efficiency Recognizing also that pumps are tested at

specific suction pressures and temperatures and operated at other pressures and

temperatures, it is obvious that tested pump performance is quite different from that

achieved with the pump in operation on one of these water systems

2 Realizing the above inexactness, in the past, the water system designer resorted

design overpressure and to make the systems function properly The variable-speed

pump now can eliminate many overflow and overpressure factors included in the

design condition Also, variable-speed drives can eliminate many of the mechanical

devices that were used in the past

With the development of digital electronics and the variable-speed pump, we now

have the tools to allow for the above inexactness during design and eliminate it in

operation We can remove much of the old mechanical complexity that was used to

destroy excess pump pressure

One of the most significant control procedures in this book, "Total kW Input for a

Pumping System" in Chapter 11, uses total kW input as a control procedure for

pumps operating in parallel or series This is a relatively new concept for

program-ming pumps on and off Not only is it applicable to pumps of all kinds, it is a useful

method of staging any set of devices that are operating together This can include

fans, blowers, filters, presses, mixers, or any energy-consuming equipment where

more than one device is operating on a fluid stream

The kW input to variable-speed drives and motors is so easy to attain and evaluate

with various numbers of equipment in operation If the equipment is maintaining the

process variable, adding a device should reveal a reduction in total kW input; if it does

not, the device should not have been started Similarly, if stopping a device does not

reveal a reduction in total kW input, it should not have been stopped This procedure

of "kW input" should provide an energy-saving program on the operation of manypumping systems

When writing a technical book, the symbols, abbreviations, and names used are soimportant The symbols and nomenclature used herein are basically those used in thewater industries Included is a table that describes these symbols and abbreviations A

number of distinctions have been made, namely that pump head is always define as h while water system head is labeled H This distinction between pump head and water

system head must be maintained, as they are not always the same Likewise, pump

done on it is the water horsepower, Pw.

Throughout the book, every effort was made to distinguish pump characteristicsfrom those of the water system This may seem trite, but in all water system analysis,

we must always remember whether we are evaluating a water system or a pump forthat system

In view of the great amount of detailed information that had to be gathered to duce this handbook, a number of people who are recognized as authorities in their field

pro-of endeavor have been called on and have responded to pro-offer advice in its developmentand writing Most of the information acquired for this book came through long asso-ciations with manufacturers, consulting engineers, contractors, salesmen, and servicetechnicians Their practical experience is the foundation of this book

Following is a list of some of these knowledgeable people: Russell Fediuk of GeneralElectric Supply Division, Cincinnati, OH; Ronald E Kastner, President of CorporateEquipment Company, Cincinnati, OH; George Ries, Vice-President (retired), PeerlessPumps, Yorba Linda, CA; Richard H Osman, Vice President of Robicon, Pittsburgh,PA; Keith H Sueker, P.E., Pittsburgh, PA; Lawrence Tillack, tekWorx, L.L.c.,Cincinnati, OH; William F Reeves, P.E., of Cincinnati, OH; and David Castelleni, P.E.,

of Cincinnati, OH Grateful acknowledgment is made to these engineers and authorities.This handbook would have been impossible without their assistance

In particular, recognition must be given to the careful review made of the script by John H Doolin of the Hydraulic Institute This effort revealed many neededchanges to eliminate typographical errors, incorrect calculations, and wrong symbols.The author wishes to acknowledge also his appreciation of the great profession ofengineering It has provided a field of work so rewarding in knowledge and personalrelationships

manu-TABLE OF SYMBOLS

AND TERMINOLOGY

Following are the symbols and tenninology nonnally used in the pumping industry When using these tenns, distinction should always be made as to whether they are being applied to a water system or the pump itself.

13(Beta) Meter or orifice ratio Dimensionless

E (epsilon) Absolute roughness Dimensionless

g Gravitational acceleration feetlsecond 2 ftlsec 2

Hep A control pressure in a water system feet ft

•

of a system

-xxiv TABLE OF SYMBOLS AND TERMINOLOGY

NPSHA Net positive suction head available feet ft

NPSHR Net positive suction head required feet ft

-IL (mu) Absolute viscosity lb-sec/square foot Ib-sec/ft2

v (nu) Kinematic viscosity square feet per second ft2/sec

psia Absolute pressure pounds/square inch psia

psig Gauge pressure pounds/square inch psig

P A Atmospheric pressure pounds/square inch psi

P. Atmospheric pressure feet of water ft

P p Plastic pipe pressure rating pounds/square inch psi

Pv Vapor pressure of water feet of water ft

Pc System energy consumed kilowatts kW

Ps System useful energy kilowatts kW

P kW Electric power kilowatt-hour kWH

q Rate of flow cubic feet/second cfs

Q Rate of flow gallons per minute gpm

RE Reynolds number Dimensionless

-SDR Standard dimension ration Dimensionless

-S Hydraulic design stress-pipe pounds/square inch psi*

s Specific gravity Dimensionless

-t Temperature degrees Fahrenheit of

v Velocity feet per second ft/sec or fps

V Volume cubic feet or gallons fe or gal**

1.1 Energy and hydraulic gradients

CHAPTER 2. PHYSICAL DATA FOR WATER PUMPING SYSTEMS

2.1 Solubility of air in water2.2 Velocity of sound in water

CHAPTER 3. SYSTEM FRICTION

3.1 Economic pipe sizing3.2 Description of the Bernoulli theorem3.3 Moody diagram for steel or wrought iron pipe3.4 Moody diagram for asphalt-dipped cast iron pipe3.5 Chart for kinematic viscosity and Reynolds number3.6 Loss coefficients for ells

3.7 Loss coefficients for reducing ells

xxvi LOCATION OF FIGURES

3.12 System configuration for calculating maximum system pressure

3.13 Maximum system pressures

3.14 System arrangement for networking

3.15 Node pressures in psig for simulation No.1

3.16 Supply from tanks, pumps stopped, simulation No.2

CHAPTER 4 BASIC DESIGN OF CENTRIFUGAL

PUMPS

4.1 Basic centrifugal pump configurations

4.2 Radial and mixed flow impellers

4.3 Typical pump head-flow curve

4.4A Power balance at constant speed

4.4B Power losses in double-suction pumps

4.5 Family of head-flow curves

4.6 Centrifugal pump impeller vector diagram

4.7 Inlet and discharge vector diagrams

4.8A Quality pump suction design

4.8B Average pump suction design

4.9 Impeller shapes with variations in specific speed

4.10 Relation of impeller types to specific speed

4.11 Variation of pump curves with specific speed

4.12 Open and semitype impellers

4.13 Open mixed-flow impeller

4.14 Diagrams of most centrifugal pump impellers

4.15 Extended line shafting for centrifugal pumps

4.16 Typical natural frequency band of a propeller type pump

4.17 Types of NPSHR curves

4.18 Pressure gradient along liquid path in pump

4.19 Net positive suction head available

4.20 Inducer for reducing NPSH required

CHAPTER 5 THE PHYSICAL DESIGN OF

5.1 Forces and leakages in a volute-type pump

5.2 Forces and leakages in an axial flow (turbine) pump

LOCATION OF FIGURES

5.3 Axial thrust in volute-type pumps5.4 Axial thrust versus rate of flow curves for axial flow pumps5.5 Actual thrust curve for a vertical turbine pump with enclosed impeller5.6 Comparison of the effect of casing designs on radial forces

5.7 Double volute pump5.8 Common packing arrangement5.9A Cyclone separator

5.9B Pump discharge water for seal flushing5.10 Basic parts of a mechanical seal5.11 Single flat-casing-ring construction5.12 Double flat-casing-ring construction5.13 Hook or L type casing ring

5.14 Efficiency decrease due to casing ring clearance5.15 Relative position of head shaft adjustment on axial flow pumps5.16 Basic configuration of volute impellers

5.17 Horizontal, close-coupled volute pump for clear service5.18 Submersible, close-coupled volute pumps for solids handling5.19 Horizontal, flexible-coupled volute pump for clear service5.20 Horizontal, flexible-coupled volute pump for solids handling5.21 Vertical, in-line, close-coupled volute pump for clear service5.22 Vertical-mounted, flexible-coupled volute pump for clear service5.23 Vertical-mounted volute pump with suction elbow for clear service5.24 Vertical-mounted volute pump, close coupled for solids handling5.25 Vertical-mounted volute pump, flexible coupled, for solids handling5.26 Horizontal, multistage volute pump, flexible coupled for clear service5.27 Horizontal, self-priming volute pump, flexible coupled for clear service5.28 Horizontal, self-priming volute pump, flexible coupled for solids handling5.29 Horizontal vortex pump, flexible coupled

5.30 Horizontal, single-stage, double-suction volute pump5.31 Vertical, single-stage, double-suction volute pump5.32 Horizontal, two-stage, double-suction volute pump5.33 Vertical, single-stage, double-suction volute pump with column and dischargehead

5.35 Four subassemblies for an axial flow pump5.36 Horizontal, axial flow pump with propeller type impeller and integral dis-charge head

5.37 Horizontal, axial flow pump with mixed flow impeller and integral discharge head

xxvIII LOCATION OF FIGURES

5.38A Horizontal, multistage axial flow pump, flexible coupled

5.38B Vertical, multistage axial flow pump flexible coupled

5.39A Cast iron head for axial flow pump, nonpressurized base

5.39B Cast iron head for axial flow pump, pressurized base

5.40A Steel fabricated head for axial flow pump, nonpressurized base

5.40B Steel fabricated head for axial flow pump, pressurized base

5.41 Below-base discharge for axial flow pumps

5.42 Two-piece top shaft for axial flow pumps

5.43 Flange-type top-shaft couplings for axial flow pumps

5.44 Open line shaft assemblies for axial flow pumps

5.45 Enclosed line shaft assemblies for axial flow pumps

5.46 Standard type oiler for enclosed line shaft assemblies

5.47 Enclosed impellers for vertical turbine pumps

5.48 Deep well turbine pump with open line shaft and enclosed impellers

5.49 Vertical, multistage turbine pump with submersible motor

5.50 Vertical, multistage turbine pumps in barrels or cans

5.51 Vertical, multistage, close-coupled turbine pump

5.52 Vertical, mixed-flow pump with open line shafting for clear service

5.53 Vertical, mixed-flow pump with enclosed line shafting for solids handling

service

5.54 Vertical propeller pump with enclosed line shafting for clear service

5.55 Horizontal, regenerative turbine, flexible coupled

CHAPTER 6 CENTRIFUGAL PUMP

PERFORMANCE

6.1 Typical head-flow curve for centrifugal pumps

6.2 Efficiency as a function of specific speed and capacity

6.3 Efficiency increase due to improved surface finish of mixed flow impeller

6.4 Turbine performance with three levels of impeller finish

6.5 Classical affinity law curves

6.6 Affinity laws for a pump operating with static head

6.7 Aberration in affinity laws pertaining to pump impeller diameter

6.8 Head-flow and horsepower curves compared to specific speed and impeller

profiles

6.9 Drooping head-flow curve

6.1OA Head-flow curve for a high specific speed pump

6.10B Operating range for a high specific speed pump6.11 Certified efficiency curve

6.12 Properly developed head-flow curves6.13 Separate brake horsepower curves6.14 Flat-curved and steep-curved pumps6.15A Series-parallel pumping

6.16B Two-stage pumps operating in parallel6.16 Parallel operation of pumps with unequal head-flow curves6.17 Variable-speed curves for one pump diameter

6.18 Best efficiency curves for small single-suction volute pumps6.19 Head-flow curves for three equal pumps operating in parallel6.20 Single pump performance under variable speed

6.21 Two-pump performance under variable speed6.22 Three-pump performance under variable speed6.23 Centrifugal pumps and entrained-air problems6.24 Effect of air in pump suctions

6.25 Vortexing in open tanks6.26 Surface vortex suppression6.27 Special vortex suppressors

CHAPTER 7. POSITIVE DISPLACEMENT PUMPS

7.1 Types of rotary pumps7.2 Sliding vane pump7.3 Flexible member pumps7.4 Exploded view of a flexible hose pump7.5 Lobe-type pumps

7.6 Gear pumps7.7 Screw pumps7.8 Open screw pump (Archimedes principle)7.9 Enclosed screw pump (Archimedes principle)7.10 Terms and definitions for an open type screw pump' (Archimedes principle)7.11 Flights for an open type screw pump

7.12 Progressive cavity pump7.13 Piston pumps

7.14 Diaphragm pump with ball type valves

xxx LOCAnON OF FIGURES

CHAPTER 8. PUMP DRIVERS AND

VARIABLE-SPEED DRIVES

8.1 Electric motor performance curves

8.2 Typical wire-to-shaft efficiencies for variable-speed drives for centrifugal

pumps

8.3 Six-pulse variable-frequency drives

8.4 Pulse width modulated (PWM) variable-frequency drives

8.5 Multipulse rectifiers

8.6 Load-commutated inverter

8.7 MV filter-commutated thyristor drive

8.8 MV current-fed GTO inverter

8.9 Neutral-point-clamped inverter

8.10 Multilevel series-cell inverter

8.11 Conversion cell of multilevel VFD

8.12 Cycloconverter induction motor drive

8.13 Form for computing harmonic distortion

8.14 Running limit for variable-frequency drives

8.15 Variation of wire-to-shaft efficiency with system static head

8.16 Enclosures for variable-frequency drives

8.17 Gasoline engine performance curves

CHAPTER 9. THE MOVEMENT OFWATER

9.1 Pump suction and discharge fittings

9.2 Pump check valves

CHAPTER 10 CONFIGURING A PUMPED

WATER SYSTEM

10.1 Components of system head

10.2 System head curve for a water system with one pump and 20 ft of static head

10.3 Friction losses for a pumping system with five pumps

10.4 Head-flow curve for each of five pumps

10.5 System head curve adjusted for pump fitting losses

10.6 Typical water system with 10 loads of 60 gpm each

10.7 Typical water system with 10 loads at 40-percent capacity10.8 Typical water system with four loads near pumps at full capacity10.9 Typical water system with four loads far from pumps at full capacity10.10 System head area for a theoretical water system and actual system head area10.11 All-friction system and system head curve

10.12 High static system and system head curve10.13 Combination water system and system head area

10.14 High static system with variable supply pressure with system head area10.15 System with high supply pressure and system head curve

10.16 System with variable supply pressure and no static head10.17 Hydraulic gradients for multiload system

10.18 Hydraulic gradient for high static water system with variable supply pressure

CHAPTER 11. BASICS OFCENTRIFUGAL PUMP APPLICATION TO WATER SYSTEMS

11.1 Correct and incorrect points of pump selection11.2 Pump operating point

11.3 Typical operation of two 50-percent pumps11.4 Point pump selection for variable-speed pumps11.5 Increased pump speed selection

11.6 Increasing impeller diameter11.7 Efficiency curves for pump of Fig 11.611.8 Uniform system head curve and calculation of pump operating point11.9 Uniform system head curve and percent horsepower curve

11.10 Percent head-flow and system head curves11.11 Low-head, high-flow system with six pumps11.12 Comparison of one constant- and one variable-speed pump with two variable-speed pumps

11.13 Selection of jockey pumps11.14 Typical wire-to-water efficiencies of constant-speed pumps11.15 Instrumentation for wire-to-water efficiency indication11.16 Instrumentation for measuring total kW input

11.17A kW Input for Tables 11.4, 11.5, and 11.6

LOCATION OF FIGURES

11.21 Three-pump operation area

11.22 Basic speed control for variable-speed pump

11.23 Piping and wiring for multiple-pressure transmitters

11.24 Pump relief valve connections

11.25 Turbine/generator installation for energy recovery

11.26 System head and turbine curves

11.27 Typical turbine/generator assembly

11.28 Turbine/generator performance

11.29 Turbine generator on irrigation system or water supply

11.30 Turbine/pump for potable water

11.31 Vacuum pump and tank for priming

11.32 Vacuum-controlled central automatic priming

11.33 Float valve and switch for priming control

11.34 Schematic diagram of priming system using makeup water

11.35 Location of control valves on pumps

CHAPTER 12. PUMP INTAKE DESIGN

12.1 Vortex classification

12.2 Open-bottom installations for axial flow pumps

12.3 Suction can classifications

12.4 Rectangular sump arrangement

12.5 Rectangular sump dimensions

12.6 Formed intake structures

12.7 Trench-type intakes for clear service installations

12.8 Trench-type intakes for solids handling liquids

12.9 Pumps sensitive to loss of prime

12.10 Circular wet well for solids handling with constant wet well control

12.11 Mechanically cleaned bar screen

12.12 Travelling screen with trashrack and fish escape

CHAPTER 13. PUMPS FOR CENTRAL WATER

TREATMENT PLANTS

13.1 Treatment process for 120-million-gallon river plant

13.2 Post filtration treatment process

13.3 Subsurface conditions for development of a groundwater aquifer13.4 Underground well field and treatment plant

13.5 Production well section13.6 Pitless adapter for a well pump in a flood plain13.7 Well water treatment process

CHAPTER 14. WATER PUMPS FOR MUNICIPAL WATER DISTRIBUTION

14.1 Vertical turbine pump in a clear well14.2 Elevated tank near water plant clear well14.3 System head curve for Fig 14.2 system14.4 Water system with intermediate draw-off14.5 Variation in system head curve due to intermediate draw-off14.6 Use of radio telemetry with variable-speed pump

14.7 Cincinnati Water Works distribution of water14.8 Simulation of pressure waves with and without anticipatory relief valves14.9 Location of relief valve

14.10 Relief valve with surge anticipation

CHAPTER 15. PUMPS FOR PLUMBING SYSTEMS

15.1 Conversion offixture units to gpm demand15.2 Typical plumbing system for cold water15.3 Small pumping system for cold water15.4 High-head plumbing system using vertical can pumps15.5 High-rise plumbing system with bladder tank at top of building and jockeypump

15.6 Plumbing system with suction and roof tanks15.7 Plumbing system with roof tank

15.8 Closed plumbing system with little storage

15.10 High-rise system with suction tank15.11 Low-rise development with elevated storage tank15.12 Low-rise development with little storage

xxxiv LOCATION OF FIGURES

15.13 Low-rise development with supply tank

15.14 Low-rise development with supply tank and elevated tank

15.15 System head curve for a small system with constant supply pressure

15.16 System head area for small system with variable supply pressure

15.17 System head area for multiple load, plumbing system

15.18 Effect of pipe aging on system head

15.19 System head area with no constant (static) head

15.20 System head area where supply pressure can maintain system pressure at light

and medium loads

15.21 Sewage ejector installation

15.22 Packaged sewage ejector

CHAPTER 16 FIRE PUMPS

16.1 Typical foam pump piping and fittings

16.2 Typical water mist pump piping and fittings

16.3 Double-suction, volute type fore pump

16.4 Vertical turbine fire pump

16.5 Single-suction volute pump for fire service

16.6 Vertical, multistage jockey pump

16.7 Fittings for single- or double-volute fire pumps, motor driven

16.8 Fittings for single- or double-volute fire pumps, engine driven

16.9 Fittings for vertical turbine fire pump, motor driven

16.10 Fittings for vertical turbine fire pump, engine driven

16.11 Fuel system for diesel engine-driven fire pump

CHAPTER 17 PUMPS FOR AGRICULTURE

17.1 Large portable pump

17.2 Portable pumping system for dust control on roads

17.3 Photograph of center pivot irrigation assembly

17.4 Center pivot irrigation system

17.5 Typical application rates at a radius of 1000 ft from the pivot

17.6 Horizontal pumping systems for golf course irrigation

17.7 Vertical turbine installation for golf course irrigation

17.8 Vertical turbine assemblies for golf course irrigation

17.9 Jet pumps for domestic water

18.4 Flow and brake horsepower curves for a lobe pump18.5 Operating range of a screw pump

18.7 Typical performance curves for an open screw pump18.8 Progressive cavity pump

18.9 Actual capacity of progressive cavity pump at various viscosities18.10 Performance of a hose pump

18.11 Typical power pump performance18.12 Discharge rate for power pumps18.13 Head-flow curves for a ball type diaphragm pump

CHAPTER 19 PUMPS FOR SEWAGE COLLECTION SYSTEMS

19.1 Basic types of sewage lift stations19.2 Sewage lift station

19.3 "Pump-down" control19.4 Sewage lift station with high friction head19.5 Performance curves for two-pump sewage lift station with constant speed19.6 Relation of pump flow, system flow, and sump volume

19.7 Vs• pumping volume for sewage wet-well

19.8 Constant wet well-level control19.9 Pump kW curves for three variable-speed sewage pumps

19.11 Multiple pump and system curves for sewage lift station with four speed pumps

variable-19.12 Pump kW versus system flow for sewage pumps of Fig 19.11

19.13 NPSHR control for pumps of Fig 19.11

19.14 Multiple sewage lift stations with common force main

19.15 System head area for three sewage lift stations of Fig 19.14

19.16 Head-flow curves and area for a sewage lift station with two 100-percent flow,

constant-speed pumps

19.17 Pump head-flow curves for 50 and 67 percent pumps for the stations of Fig 19.14

19.18 Multiple sewage lift stations at different elevations and connections

19.19 Comparison of mixed-flow pump with underground station

19.20 Centrifugal type grinder pump

19.21 Progressive cavity type grinder pump

19.22 Grinder pump performance, centrifugal type

19.23 Grinder pump performance, progressive cavity type

19.24 Typical grinder pump installation

19.25 Typical grinder pump installation at a residence

19.26 Rate of rise control for sewage lift station

CHAPTER 20 PUMPS FOR SEWAGE

TREATMENT PLANTS

20.1 Ideal hydraulic gradient for a sewage treatment plant

20.2 Hydraulic gradient for a sewage treatment plant with effluent pumping

20.3 Hydraulic gradient for a sewage treatment plant with influent pumping

20.4 Hydraulic gradient for a sewage treatment plant with influent pumping and

efflu-ent pumping during flooding of receiving stream

20.5 Typical system head curves for sludge

20.6 Sludge diagram for the Mill Creek Sewage Plant, Cincinnati, OH

20.7 Control of the flow of activated sludge

20.8 Schematic for recharge

CHAPTER 21. STORM WATER PUMPS

21.1 Contractor pump for dewatering

21.2 Storm water station elevation drawing

21.3 Storm water station discharge piping

21.4 Strom water pump installation

21.5 Storm water intake structure

21.6 Float switch assembly

21.7 Storm water station for underground water

LOCATION OF FIGURES xxxvII

21.8 System head area for system of Fig 21.621.9 kW input for three-pump storm water station

CHAPTER 22. INSTALLATION OF WATER PUMPS AND PUMPING SYSTEMS

22.1 Pump bases22.2 Installation of pumping system base22.3 Typical base installation for pumps with flat base plate22.4 Typical base installation for pumps with formed metal bases22.5 Seismic installation of floor bolts

22.6 Seismic installation of pump bases

CHAPTER 23. INSTRUMENTATION FOR WATER PUMPING SYSTEMS

23.1 Full-throated magnetic flow meter with bonding and grounding procedures23.2 Insertion type magnetic flow meter

23.3 Speed variation in pump head-flow curves23.4 Submersible diaphragm level transmitter23.5 Bubbler type, level transmitter

CHAPTER 25. OPERATION AND MAINTENANCE

OF WATER PUMPS

25.1 Single pressure gauge for checking pump performance25.2 Graphical representation of pump operating point for one pump25.3 Graphical representation of pump operating point for two pumps

CHAPTER 26. FACTORY-ASSEMBLED PUMPING SYSTEMS

xxxvIII LOCA nON OF FIGURES

26.5 Fire pump system with vertical, in-line fire pump

26.6 Engine-driven fire pump package for a large warehouse

26.7 Sewage pumping system with two self-priming pumps and standby

engine-driven generator

26.8 Variable-speed pumping control center for existing pumps

26.9 Engine-driven fire pump with the house and all utilities

26.10 Fire pump house with engine-driven and electric motor-driven fire pumps

26.11 Municipal booster station with house, engine-driven generator, and

calibra-tion room

26.12 Underground municipal water booster station

26.13 Municipal water pump house

CHAPTER 27 RETROFITTING EXISTING WATER

PUMPING SYSTEMS

27.1 Evaluation of an existing pump installation

27.2 Calculation of trimmed impeller diameter

27.3 Instrumentation for generating an actual system head area

27.4 Comparison of design and actual system head areas

THE BASIC TOOLS

OF DESIGN

CHAPTER 1

DIGITAL ELECTRONICS

AND WATER PUMPS AND SYSTEMS

INTRODUCTION

The emergence of digital electronics has had a tremendous impact on industrial eties throughout the world In the water system industry, the development of digitalelectronics has brought an end to the use of many mechanical devices; typical of this

soci-is the diminsoci-ished use of mechanical devices for the control of pressure in water tems Today's digital control systems, with built-in intelligence, more accuratelyevaluate water and system conditions and adjust pump operation to meet the desiredwater flow and pressure conditions

sys-Drafting boards and drafting machines have disappeared from the design rooms

sys-tems Computer programs developed for specific design applications are rapidly andaccurately doing the tedious calculations that were once done manually All of thishas left more time for creative engineering on the part of designers to the benefit oftheir clients

COMPUTER-AIDED CALCULATIONS OFWATER

LOADS AND PIPE FRICTION

The entire design process for today' s water systems, from initial design to final missioning, has been simplified and improved as a result of the new, sophisticatedcomputer programs Today's technology allows the informed engineer to graphi-cally design the piping system while, at the same time, entering friction data aboutspecific components When completed, the software gives a.clear representation ofthe entire system, which the engineer can use to find specific data about anyonepoint in the system

com-1.3

1.4 THE BASIC TOOLS OF DESIGN

HYDRAULIC GRADIENT DIAGRAMS

The hydraulic gradient diagram provides a visual description of the changes in total

pressure in a water system In the past, most of these diagrams were drawn manually.

The actual drawing of the pressure gradient diagram is now being evaluated for

con-version to software; when this is completed, engineers will be able to produce

com-plex designs rapidly and with unparalleled accuracy The programs will further enable

engineers by automatically performing complex piping friction calculations, along

with displaying the results

The hydraulic gradient diagram has proved to be an invaluable tool in the

develop-ment of water systems The diagram will appear throughout this book for various types

of water systems Its generation will be explained in Chap 10 The difference between

a pressure gradient and the energy or hydraulic gradient of a water system should be

while the hydraulic gradient includes only the static and pressure heads This is shown

in Fig 1.1 Velocity head is usually a number less than 5 feet and is not used to move

water through pipe as are static or pressure heads Using the energy gradient with the

velocity head included increases the calculations for developing these diagrams;

there-fore, the hydraulic gradient is used instead Velocity head cannot be ignored, however,

as it represents the kinetic energy of the water in the pipe Velocity head will be

DIGITAL ELECTRONICS AND WATER PUMPS AND SYSTEMS 1.5

emphasized in this book when it becomes a factor in pipe design, particularly in ing around equipment and in the calculation of pipe fitting and valve losses

pip-SPEED AND ACCURACY OF ELECTRONIC DESIGN OF WATER SYSTEMS

The tremendous amount of time saved by electronic design enables the engineer toevaluate a water system under a number of different design constraints The designercan load one set of design requirements into a computer, and while the computer isdoing all of the detailed calculations for that program, the engineer can be looking intovariations that might affect the design After all of the variations have been run, thedesigner can select the one that provides the optimum system conditions that meetthe specifications of the client As a result, the designer now has time to play "what if"

to achieve the best possible design for a water system In the past, the engineer was

often time driven and forced to utilize much of a past design to reach a deadline for

a current project Now the engineer can model pumping system performance under anumber of different load conditions and secure a much more complete document onthe energy consumption of proposed pumping systems

The designer can compute the diversity of a water system with much greater

accu-racy Diversity is merely the actual maximum flow for a water system divided by thetotal connected load For example, assume that the total load on a water system is 800gpm, but all of the calculated loads on that system require 1000 gpm, the diversity in

EOUATION SOLUTIONS BY COMPUTER

A number of equations are provided herein for the accurate solution of pressures,flows, and energy consumptions of water systems These equations have been kept tothe algebraic level of mathematics to aid the water system designer in applying them

to computer programs Computer software is now commercially available to assist inthe manipulation of these equations

1.8 THE BASIC TOOLS OF DESIGN

ELECTRONIC COMMUNICATION

With the technical advances that are occurring in communications, rapid communication

is available between various engineering offices and their clients Databasing can be

linked between main and branch offices of a multi-office firm so job and data sharing can

be established between the various offices as desired by the engineering management

Interoffice communication has also been accelerated with the use of electronic

mail such as e-mail Such mail can reduce the time required for asking crucial

ques-tions and receiving responses It reduces error with regard to documentation and

maintains a file on the correspondence

ELECTRONIC DESIGN OFTHE PIPING AND

ACCESSORIES

Similar to load calculations and general system layout, digital electronics has invaded

the actual configuration of the water system itself, including the methods of generating

hot or cold water, the storage of water, and the distribution of water in the system The

distribution of water in a system no longer depends on mechanical devices such as

pressure-regulating valves, balancing valves, and other energy-consuming, mechanical

devices that force the water through certain parts of the system How this is done will

be described in detail in chapters on the specific design of each of the water systems

under consideration in this book

ELECTRONIC SELECTION OFWATER PUMPING

EQUIPMENT

A major part of the water system designer's work is the selection of pumps for a water

system In the past, designers depended on manufacturers' catalogs to furnish the

tech-nical information that provided the selection of the correct pumps for a water system

This had to be done with the hope that the catalogs were current Now comes the

CD-ROM disc and on-line data services that provide current information and rapid

converting their technical catalogs to software such as CD-ROM discs, providing both

performance and dimensional data The day of the technical catalog is almost gone

ELECTRONIC CONTROL OFWATER PUMPING

SYSTEMS

Along with these changes in mechanical design, electronic control of water systems,

in the form of direct, digital control or programmable logic controllers, has all but

eliminated older mechanical control systems The advent of universal protocols has

enabled most control and equipment manufacturers to interface together on a single

DIGITAL ELECTRONICS AND WATER PUMPS AND SYSTEMS 1.7

installation This allows companies to focus on a particular aspect of the system whilestill providing the necessary information to a Supervisory Controller

ELECTRONICS AND WATER PUMPING SYSTEMS

How do all of these electronic procedures relate to water pumping systems? Efficientpump selection and operation depend on the accurate calculation of a water system'sflow and pump head requirements Digital electronics has created greater design accu-racy that guarantees better pump selection Incorrect system design will result in (I)pumps too small and incapable of operating the water system or (2) pumps too large,with excess flow and head resulting in inefficient operation The use of electronicdesign aids has improved the chances of selecting an efficient pumping system foreach application Accurate calculation of flow and head requirements of constant-speed pumping systems has reduced the energy destroyed in pressure-regulatingvalves that are used to eliminate excessive pressure

ELECTRONICS AND VARIABLE-SPEED PUMPING SYSTEMS

One of the greatest effects on water systems by electronics is the development of variablefrequency drives for pumps The day of the constant-speed pump with its fixed head-capacity curve is coming to an end, giving way to the variable-speed pump which canadjust more easily to system conditions, using much less energy and exerting smallerforces on the pump itself Along with the constant-speed pump go the mechanical devicesdescribed above which overcame the excess pressures and flows of that constant-speedpump The variable-frequency drive with electronic speed control and pump programmingmatch the flow and head developed by pumps to the flow and head required by the watersystem without mechanical devices such as pressure valves All of the contingenciesincluded by the water system designer for pipe aging, future load additions, etc., are elim-inated from the actual pumping system operation by the variable-speed drive that providesonly the flow and head required for the current conditions of the piping and water uses

ELECTRONIC COMMISSIONING

Another great asset of electronics applied to water systems is its use during the sioning process There are always changes in drawings and equipment during the finalstage of starting and operating a water system for the first time Many of these changes inequipment and software can be recorded easily through the \lse of portable computers

commis-or other hand-held electronics The agony of insuring that "as-built" drawings are ccommis-orrecthas been reduced greatly

Electronic instrumentation and recording devices have accelerated the sioning of water systems These instruments enhance verification of compliance of theequipment of a water system

commis-1.8 THE BASIC TOOLS OF DESIGN

One of the basic purposes of this book is to describe the above uses of electronics in

the design and application of pumps to water systems This must be done with

recog-nition that the rapid development of new software and equipment is liable to relegate

any description of digital electronics to obsolescence at the time of writing The

devel-opment of on-line data services is going to change even further the way we design

these water systems

Water system design engineers must understand how current their offices are in the

use of available electronic equipment and services; this insures that they are providing

current system design at a minimum cost to their company The engineers who do not

use electronic equipment, network their office, or subscribe to on-line data services as

they become available will not be able to keep up with their contemporaries in design

accuracy and speed

One of the reasons for the writing of this book was to produce a handbook for water

pumps and systems that would provide basic design and application data and embrace

the many and rapid changes that have occurred in water system design and operation

This handbook has been written to guide the student and inexperienced water system

designer and, at the same time, provide the knowledgeable designer with some of the

latest procedures for improving water system design and operation It is hoped that it

will be a sourcebook for other texts that concentrate on specific aspects of water pump

design and application

The advent of electronic control and the variable speed pump has made obsolete

many of the older designs of these water systems We have the opportunity now to

pro-duce highly efficient systems and to track their performance electronically, insuring

that the projected design is achieved in actual operation

This chapter includes standard operating conditions for water pumping equipment.Also, this chapter brings together much of the technical data on air, water, and electric-ity necessary for designing and operating these water systems The only information onwater not included in this chapter is pipe friction which will be described in Chap 3.Some subjects, such as fire pump configuration (Chap 16) or design of intakestructures (Chap 12), cannot be discussed in detail The actual referenced documentsmust be sought for such information The information herein merely highlights thebasic requirements of these standards and is not meant to replace them

It is hoped that most of the technical information needed by the water systemdesigner for pump application is included in this book The cross-sectional area, insquare feet, and the volume, in gallons, of commercial pipe and circular tanks havebeen included on a lineal foot basis This is valuable information for the designer inthe calculation of the liquid volume of water systems and storage tanks

STANDARD OPERATING CONDITIONS

All equipment and piping of a water system is based on particular operating conditionssuch as maximum temperature or pressure Usually, the designer specifies these condi-tions, and the equipment or piping manufacturers should verify that their products con-form to these water system specifications It is the responsibility of the design engineer

to check these conditions and insure that they are compatible with the system conditions

It is very important that variations in electrical service as well as maximum ambient airtemperature be verified for all operating equipment

2.1

2.2 THEBASICTOOLSOFDESIGN

Standard Air Conditions

Standard air conditions must be defined for ambient and ventilation air Ambient air

is the surrounding air in which all water equipment must operate Standard ambient

air is usually listed as 70°F while maximum ambient air temperature is normally

specified as 40°C (lQ4°F) This temperature is the industry standard for electrical and

electronic equipment For some boiler-room installations in public buildings where

water pumping equipment may be installed, the ambient air standard may be listed as

high as 60°C (l40°F) It is incumbent on the designer to insure that the equipment is

compatible with such ambient air conditions

Along with ambient air temperature, the designer must be concerned with the

quality of ventilation air This is the air that is used to cool the operating equipment

as well as providing ventilation for the building The designer must insure that the

equipment rooms are not affected by surrounding processes that contain harmful

sub-stances This includes chemicals in the form of gases or particulate matter Hydrogen

sulfide is particularly dangerous to copper-bearing equipment such as electronics

Sewage treatment operations generate this gas, so it is very important that any

equip-ment installed in sewage treatequip-ment facilities be protected from ambient air that

can include this chemical Dusty industrial processes must be separated from

equip-ment rooms to keep equipequip-ment clean Dust that coats electric motors or electronics

will have a substantial effect on the performance and useful life of that equipment

The designer must be aware of the presence of any such substances that will harm

the equipment

Ventilation air does not bother the operation of the pump itself, but it does affect

variable-speed drives This is the air that is used to cool this electrical equipment

Evaluating the ventilation air for the equipment installation is an important part of the

design process and for the equipment selection Outdoor air data, including maximum

wet bulb and dry bulb temperatures, are listed in weather data for most principal cities

Indoor air quality must be verified as well, both from a chemical content basis and

from a temperature basis Ventilation or mechanical cooling may be needed to remove

heat generation in the equipment rooms to insure that the design standards of the

equipment are not exceeded

One situation that has occurred recently involves the application of variable-speed

drives to pumps for sewage plants and pumping stations In the past, switchgear was

installed in these facilities without concern for small amounts of hydrogen sulfide in

the air Variable-frequency drives were installed with the assumption that they could

operate in the same atmosphere, and the fact that such drives required ventilation air

was ignored The result was failure of these drives due to corrosion caused by the

hydrogen sulfide This demonstrates that care should be taken to insure that the

ambi-ent conditions are satisfactory for new equipmambi-ent being contemplated for a specific

installation

Operating Pressures

Gauge pressure is that water pressure that is measured by a gauge on pumping

equip-ment or piping It is the total dynamic pressure of a water stream less the velocity head,

v 2 /2g For a water system at rest, it is the total dynamic pressure In this book, it is the

hydraulic gradient at any point in a water system Following is the basic equation forgauge, absolute, and atmospheric pressures

For example, if a water system is operating at 75 psig pressure at an altitude of 1000feet, from Table 2.1, the atmospheric pressure is 14.2 psi, so the absolute pressure is89.2 psia

The atmospheric pressure of outdoor air varies with the altitude of the installation

of pumping equipment and must be recognized in the calculation of net positive tion head available (NPSHA) for pumps (see Chap 4) Table 2.1 describes the varia-tion of atmospheric pressure with altitude This table lists atmospheric pressure in feet

suc-of water, PA' as well as pounds per square inch For water temperature in ranges suc-of 32

to 85°F, the feet of head can be used directly in the net positive suction head (NPSH)and cavitation equations found in Chap 4 on basic pump design For precise calcula-tions and higher temperature waters, the atmospheric pressure in psia must be cor-rected for the specific volume of the water at the operating temperature See Eq 4.5that corrects the atmospheric pressure in feet of water to the actual operating temper-ature of the water and at the elevation for the pumping system

TABLE 2.1 Variationof AtmosphericPressurewith Altitude

THEBASICTOOLSOF DESIGN

THERMAL EQUIVALENTS

There are some basic thermal and power equivalents that should be summarized for

water system design This book is based on one BTU (British Thermal Unit) being

equal to 778.26 foot pounds This conforms to Keenan and Keyes' Thermodynamic

Properties of Steam that defines the BTU similarly as 778.26 foot pounds Other

sources equate different values that vary the thermal equivalent of a brake horsepower

or a kilowatt The following thermal and power equivalents will be found in this book

1 BTU (British Thermal Unit) = 778.26 ft-Ib

1 brake horsepower (BHP) = 33,000 ft-Ib/min

1 brake horsepower hour (BHPHR) = 2544 BTU/hr

=0.746 kilowatt hour (kWH)

1 kWH = 1.341 BHP

=3411 BTU/hr

WATER DATA

Water is not as susceptible to varying atmospheric conditions as is air, but its

tem-perature and quality must be measured Standard water temperature can be stated as

TABLE 2.2 Viscosities of Water

Temp of water(OF) fL,absolute viscosity (centipoise) v, kinematic viscosity (fe/see)

Seconds Saybold Kinematic viscosityUniversal (SSU) Centistokes fe/see

SOURCE: Cameron Hydraulic Data,FlowserveCorporation

32°F, 39.2°F (point of maximum density), or 60°F It is not very important which ofthese temperatures is used for most water pump calculations, as water is near a den-sity of 1.0 for all ofthem The kinematic viscosity does vary frpm 1.93 to 1.21 X 10-5fe/see for these temperatures, but this should not affect most calculations for thesewater systems

Operations with water at temperatures above 85°F must take into considerationboth the specific gravity and viscosity Tables 2.2 and 2.3 provide this data

2.8 THEBASICTOOLSOFDESIGN

Viscosity of Water

There are two basic types of viscosity: (1) dynamic or absolute and (2) kinematic

Dynamic viscosity is expressed in force-time per square length terms; in the metric

system, it is stated in centipoise The kinematic viscosity is the absolute viscosity

divided by the mass density of the liquid In the water pumping world, the most used

viscosity is the kinematic type which will be stated in centis tokes in the metric system

and in square feet per second or in SSU (Saybold Seconds Universal) in the English

system In the water systems addressed in this book, the practice is to use the kinematic

losses; this enables the Reynolds number to become dimensionless Most sludge

oper-ations utilize SSU for determining the effect of viscous liquids on efficiency and brake

horsepower of pumps for these liquids

If the viscosity of a liquid is expressed as an absolute viscosity in centipoise, the

conversion formula to kinematic viscosity in square feet per second is:

'Y

where J.L= absolute viscosity in centipoise

'Y= specific weight in Ib/ft3

If the viscosity is expressed as the kinematic viscosity in the metric system as

stokes, the conversion formula for kinematic viscosity in the English system is:

v (ft2/sec) = 0.10764 Xv(centistokes) (2.3)

other English units of length, flow, and head are used in water pumping As stated

above, this is the term required for computing the Reynolds number with English units

Contemporary computer programs for pipe friction automatically include this data for

the water under consideration Table 2.2 provides the absolute viscosity in centipoise

and the kinematic viscosity in square feet per second

Table 2.3 provides some useful viscosity conversions between the three most

mon terms for viscosity used in these water industries This table should aid in

com-puting friction loss of piping for liquids such as sewage sludge

For viscosity values of 70 centistokes and higher, use the following equation:

Vapor Pressure and Specific Weight for Water, 32 to 212°F

The vapor pressure of water for various temperatures must be included, as this

informa-tion is necessary in evaluating the possible occurrence of cavitainforma-tion It is also used in the

calculation of NPSHA for pumping installations that is included in Chap 4 on basic

pump design Vapor pressure is the absolute pressure, psia, at which water will change

from liquid to steam at a specific temperature For each temperature of water, there

is an absolute pressure at which water will change from a liquid to a gas Table 2.4

TABLE 2.4 Vapor Pressuresand SpecificWeightsfor Water (32 to 212°F)

square inch at these temperatures for NPSH calculations Specific weight is the density

in pounds per cubic foot of water at a particular temperature

•

Solubility of Air in Water

It is important to know the amount and source of air in these water systems Air isundesirable in pumps due to its great effect on the pump's performance and useful life

2.8 THEBASICTOOLSOFDESIGN

TABLE 2.5 MaximumSolubilityof Air in Water

Ratio of absorbed air volume to water volume (expressed as a decimal)

SOURCE: Technical Bulletin 8-80,WestWarrick,RI,AmtrolInc.,p.14, 1985,usedwithpermission

Air enters a water system entrained or dissolved in the water Air should not enter

the system from any other source Air occurs naturally in water; Table 2.5 provides the

basic data on the solubility of air in water

The actual volumes of air absorbed in the water are not as important as the

changes that occur in this solubility as pressures and temperatures of the water in

the system are increased or decreased What is important is, as indicated in this table, the

increases with system pressure This chart demonstrates Henry's Law, which states

that the amount of air dissolved in water is proportional to the pressure of the water

system This chart should be used in place of similar charts for open tanks where the

only pressure listed is atmospheric pressure at 0 psig In such charts, the amount of

air dissolved in the water approaches 0 at 212°F It is evident from this chart that the

water in these systems can contain a greater amount of air at all gauge pressures

above 0 psig Figure 2.1 is a graphical representation of this data, demonstrating the

increased solubility of air in water as the pressure increases Likewise, the

solubil-ity decreases with the temperature of the water As water at 50 psig and 50°F

tem-perature is heated to 140°F, the solubility drops from a ratio of air to water of 0.10

down to 0.055

An interesting and easy experiment to observe the release of air when water is

heated is as follows:

1 Take a frying pan and fill it with potable water from the kitchen cold water faucet

2 Place it on the stove and heat the water to boiling

3 Note that bubbles form as soon as the temperature begins to rise This is air ing out of solution with the water, as the water cannot hold as much air with thehigher temperature

com-4 As the water approaches near 212°F, the water begins to boil

5 Allow the water to cool and then reheat the water to boiling

6 Note that this time bubbles do not appear until steam begins to form Thisdemonstrates that the water has been de aerated during the first boiling It alsoprovides a visual example of what happens to cold water when it is heated in awater system

Although hot water does not exist in any of the systems un(Jer consideration herein,with the exception of the plumbing field with domestic water in buildings, the samerelease of air occurs in pump suctions where a reduction in water pressure occurs.Because of this change in the solubility of air in water, air can be a problem on pumpstaking a suction lift from open tanks

Velocity of Sound in Water

Water hammer, caused by pressure waves, is an important subject for water pumps and

systems, as it can be very destructive of pumps and piping It will be discussed in detail

in Chap 9 on the movement of water It is informative to understand the speed of such

pressure waves by realizing that sound moves faster in water than it does in air Figure 2.2

compares the velocity of sound in water with pipe diameters from 6 in to 78 in, all with

1/4-in pipe wall thickness For 6-in pipe, the velocity is around 4200 ft/sec, or over

twice that of sound in air at sea level This demonstrates the necessity for managing

possible pressure waves caused by valves opening and closing rapidly or by pumps

being started or stopped abruptly

AND TANKS

Table 2.6 provides the cross-sectional area, in equivalent square feet, and the volume,

in gallons, of commercial steel pipe and circular tanks per linear foot of such pipe and

tanks The volume of the pipe or tank can be determined by multiplying the

cross-sec-tional area by the length or height in feet The length in gallons has been provided to

simplify the calculations for HVAC water system volume and tank storage

ELECTRICAL DATA

Following is a brief review of electrical power supply and its use with water pumps

Chapter 8 provides a detailed evaluation of electric motors The standard frequency for

electric power in the United States is 60 hertz (Hz) or cycles Many foreign countrieshave standardized on 50 Hz; there may be some rural areas of the United States stilloperating on 50 Hz power Tables 2.7 and 2.8 provide nominal power distribution volt-ages and standard nameplate voltages for motors operating on both 60 and 50 Hz.Electric power utilities are allowed a variation of ± 5 percent from the distribution sys-tem voltages listed in these tables

The most popular power for water pump applications is 480 volt, three phase.Single-phase power is seldom used above 7'/2 hp The 208-volt service is derived from

a Y-connected transformer in the building being served; three-phase motors as high as

60 hp are available for this voltage The higher voltages of 2400 and 4160 are usedgenerally on motors of 750 hp and larger

Electrical machinery, such as motors and variable-speed drives, has specified age tolerances that are greater than those of the electrical utility The electrical design

volt-2.12 THEBASICTOOLSOF DESIGN

TABLE 2.7 Standard60-HzVoltages

Nominal distribution system voltageMotor nameplate voltage Below 125hp 125hp and up

-SOURCE: AC Motor Selection and Application Guide, Bulletin GET-6812B,Ft

Wayne,IN, GeneralElectricCompany,p 2 used with permission

TABLE 2.8 Standard 50-HzVoltages

Nominal distribution system voltageMotor nameplate voltage Below 125hp 125hp and up

-NOTE: Distributionsystemvoltagesvaryfromcountryto country;therefore,motor

nameplatevoltageshouldbe selectedfor the countryin whichit willbe operated

SOURCE: AC Motor Selection and Application Guide,Bulletin GET-68l2B, Ft

Wayne,IN, GeneralElectricCompany,p 2, used with permission

PHYSICALDATAFORWATERPUMPINGSYSTEMS 2.13

engineer must develop the building power distribution to insure that its voltage dropdoes not exceed the voltage tolerances of the electrical equipment Typically, the volt-age tolerance of most electric motors is ± 10 percent, and those for most variable-speed drives appears to be +10 and -5 percent The water system designer shouldverify the actual tolerances for this equipment For example, the utility voltage at abuilding transformer may be 480 volts ±5 percent or 456 to 504 volts A 460-volt,variable-speed drive has an allowable voltage variation of 437 to 506 volts Therefore,the building power distribution system must be designed so that the power supply

to the variable-speed drive does not drop below 437 volts under any load condition

Power factor correction equipment can be required by public utilities or state lawabove a certain size of motor The designer should check this at the beginning ofthedevelopment of a certain project Generally, public utilities do not require power fac-tor correction at most places in their electrical distribution until the load approaches

500 kV A

The popularity of the variable frequency drive has created a problem for public ities This is the harmonic distortion caused by the alteration of the sine wave by thevariable-frequency drive The public utility furnishing power on a project may have aspecification on the maximum allowable harmonic distortion Also, the owner of thefacility may have tolerances on harmonic distortion The possibility of these limita-tions existing on a specific project should be checked at the beginning of the design ofthe electrical power distribution system

util-More information on power factor correction and harmonic distortion is included

in Chap 8

EFFICIENCY EVALUATION OFWATER SYSTEMS

Several expressions of efficiency will be provided in the following chapters that relate

to the effectiveness of pump selection and application These will include:

1 System efficiency, which determines the quality of use of pump head in a watersystem This will be expressed as kW/MGD

2. Wire-to-water efficiency of a pumping system or kW/MGD which demonstratesthe use of energy in a pumping system

These efficiencies are possible now that digital computers are available to performthe calculations rapidly and accurately The equations for water systems and equip-ment included herein enable the plant or system operator to observe these efficienciesand insure that the water systems are functioning at optimum efficiency

It is important that the water system designer be well versed in the physical conditionsavailable at the point of installation of each project Local codes and services must bechecked for compatibility to the final design The manuals of the technical societies

are excellent sources for additional reading, particularly those of American Water

Works Association, Water Environment Federation, and the Institute of Electrical and

Electronic Engineers

BOOKS FOR A PERSONAL LIBRARY

The following books form a nucleus for a good personal library

Cameron Hydraulic Data,Ingersoll-DresserPumps,FlowserveCorporation

Ganic,E.N., and Hicks,T.G (eds.),Handbook of Essential Engineering Information and Data,

McGraw-Hill,New York, 1991

Karassik,1.1.,et al (eds.),Pump Handbook, 3rd ed., McGraw-Hill,New York, 2001

MA,1998

CHAPTER 3 SYSTEM FRICTION

The designer of water systems should not be without copies of the Hydraulic

Institute's Engineering Data Book, 2nd ed., and the latest issue of Cameron Hydraulic

Data published by Ingersoll-Dresser Pumps, Flowserve Corporation These two

doc-uments have contributed greatly to the complex subject of pipe friction

As pointed out in the introduction to this book, pipe friction analysis is, at best, aninexact science Much needs to be done to obtain better information on pipe and fit-ting friction The increasing cost of energy that may confront owners and operators ofthese water systems will provide the driving force to achieve better piping friction dataand better piping design Technical societies are now studying current data on pipe fit-ting losses to insure that this data is reasonable

This chapter is based on water and sewage which are considered to be Newtonianliquids Such liquids do not have a change of viscosity caused by any motion of the liq-uid when the temperature of the liquid is constant Non-Newtonian liquids are sludgesthat will be discussed in Chap 20

TOTAL OWNING COST

Good piping design always balances first cost against operating cost, taking into

con-sideration all factors that exist on each installation These are the two basic parametersthat influence pipe sizing in these water industries

Obviously, piping costs increase and power costs decrease with increases in pipediameter for the same design flow First cost is the primary mason for increased costswith pipe size; maintenance mayor may not increase with pipe size The economicpipe size is at the minimum point of the overall costs of owning the pipe Figure 3.1and Table 3.1 describe this

3.1

TABLE 3.1 Total OwningCost of Piping

owningcosts

12 $12,000 $16,000 $28,000

Obviously, the total owning costs of the piping system should be generated for

each installation The derivation of this data is beyond the scope of this book, but

there are programs available for computing these costs in detail The Handbook of

Civil Engineering Calculations, McGraw-Hill, 2000, offers information on

veloc-Information exists that indicates that velocities in the range of 10 to 17ft/sec in water

systems do not create erosion or noise in steel pipe Therefore, there should be no limit

on flow in steel pipe based on velocity Likewise, in plastic pipe there should not be alimit of 5 ftlsec on short runs of pipe around equipment Instead, the overall, control-

ling factor in piping design should be friction which increases exponentially with

veloc-ity Friction in piping is the principal source of operating costs for these water systems.These conflicting views on the maximum allowable water velocity in steel, castiron, copper, and plastic piping do recognize the hydraulic radius of commercial pipe.The hydraulic radius of a pipe is the area of a pipe divided by the circumference of itsinner surface It is calculated as follows:

Obviously, the hydraulic radius increases with pipe diameter, and, therefore, theallowable velocity should increase with the pipe diameter Hydraulic radii for com-mercial pipe are shown in Table 3.2 It is quite clear that 36" ID pipe with a hydraulicradius of 9.0 must be rated velocity-wise differently than 3" Schedule 40 pipe with ahydraulic radius of 0.8

Hydraulic radius is an alternative guideline for the reevaluation of the friction forflow of water in piping and pipe fittings The current information on pipe friction andrecommended velocities in pipe are too dependent on testing done on small pipe and par-ticularly small pipe fittings The data is then extrapolated for larger pipe It is very diffi-cult to test large pipe fittings such as those with diameters greater than 24 in

There are several recommendations for allowable velocity in steel and plastic pipe;some are based upon a particular maximum friction loss per 100 ft Actually, as indi-cated elsewhere, final pipe velocity is within the province of the designer who isresponsible for first cost as well as operating costs Here is, an excellent opportunityfor the designer to use computer capability in sizing the piping He or she can makeseveral computer runs at different pipe sizes to achieve the economically desirablepipe size This should be done for the major piping such as loops and headers The size

of smaller branches will fall more into the realm of the designer's experience

TABLE 3.2 MaximumCapacitiesin gpm and HydraulicRadiusfor Steel Pipe

Table 3.2 is a general recommendation to designers as to maximum steel pipe

velocity Velocities in piping of other materials such as copper and thermoplastic will

be discussed with the other performance criteria for them

It is obvious that Table 3.2 is but a preliminary road map for the knowledgeable

piping designer With the information currently available, the pipe designer must rely

to some extent on his or her own actual experience

PIPE VELOCITY IS DESIGNER'S

RESPONSIBILITY

It is also very clear from Table 3.2 that sizing all pipe and, particularly large pipe in

the range from 20" and larger diameters, requires a detailed analysis of the entire

pip-ing system to achieve the economical size for a particular installation It cannot be

based on any rules pertaining to velocity or friction loss per hundred feet Reiterating,

it is the designer's responsibility to determine pipe size and maximum velocity There

are so many judgment calls in the final selection of pipe diameter; it is not a simple

process For a hypothetical example, if you have 12,000 gallons per minute of water

flowing in a pump header, you could use 20" diameter steel pipe if the header is only

30 ft long This would reduce the cost of the piping and tees where the pumps are

con-nected On the other hand, if the water supply main runs for 10,000 ft to a group of

buildings, you may require the use of 24" or 30" pipe to reduce the overall friction loss

3.6

The cost of piping accessories and the length of pipe involved affect the decision on

the final pipe size These are the evaluations that a good pipe designer must make

PIPE AND FITTING SPECIFICATIONS

Elements of these water systems are connected together by means of piping In mostcases, this piping is cast iron, steel, copper, or plastic Most steel piping used in theseindustries for low-temperature applications conforms to ASTM Specifications A-53 orA120 Higher-temperature applications, such as hot water in public buildings, may becopper Local and ASME codes should be checked for detailed pipe, flange, bolting, andfitting specifications for particular applications Steel fittings follow ANSI Specification

B 16.5, while cast iron fittings comply with ASTM Specification B 16.4 Plastic pipe andfittings conform to various ASTM standards that will be reviewed with plastic pipe

GENERAL PIPE FRICTION ANALYSIS

As water flows through pipe, friction is generated that resists the flow Energy isrequired to overcome this friction, and this energy must be derived from (1) pumps,(2) reduction in system pressure, or (3) changes in static head How this is done in

Theorem The total energy at any point in a piping system can be computed by this

the-orem Figure 3.2 describes this; this diagram has been simplified by maintaining stant flow and elevation The friction head is achieved by a reduction in systempressure Similar diagrams could be drawn for variable flow and static head As indi-

con-cated in the Introduction, the capital H is for system head; this is not necessarily the pump head, h.

For example, assume:

1 Steel pipe is 5 ft below the ground, and ground level is assumed to be the datumfor all energy measurements Often, this is the elevation above sea level, U.S

2 The pressure in the pipe is 40 psig

3 200 gpm of water at 50°F water is flowing in a 4" diameter pipe At this flow,

FIGURE 3.2 Description of the Bernoulli Theorem (From Rishel, HVAC Pump Handbook,

McGraw-Hill, used with permission.)

4 The total head, Hs, in the 4" pipe above is 40 X 2.31 - 5 + 0.4=87.8 ft This is

the energy gradient at this particular point in the piping If sea level is the datum and

+ 0.4, or 487.8 ft

Equation 3.2 is for the energy gradient at any point in a water system The Bernoulli

Theorem is used to calculate the variation in total head as water flows through a

sys-tem Since this book does not evaluate water systems where there is a change of state,

the other terms often found in Bernoulli's Theorem do not apply Changes in water flow

and elevation, as well as loss of head due to friction in the system, result in a different

value for the hydraulic gradient at every point in a water system

Bernoulli's Theorem must be studied carefully to insure that it is fully understood

This theorem states simply that the total energy must be accounted for at every point

in any system analysis All of the water systems that are considered in this book are of

the delivery or open-ended type Water is seldom returned to its source There may be

3.7

some loops in sewage or water treatment plants, but they are a small part of the totalsystems reviewed here

that it is seldom used in water distribution calculations Therefore, it is not included inthe hydraulic gradients described in this handbook The total energy gradient for awater system does include the velocity head It should not be ignored totally, as it doescome into importance when determining the flow in pipe around pumps Also, it is thecorrect basis for computing friction loss in pipe fittings

Pipe Friction Formulas

The amount of friction that is created by flow of water in piping has been determined

by a number of people Today, there are two principle formulas for determining pipefriction These are the Darcy-Weisbach and the Hazen-Williams formulas:

Darcy- Weisbach Formula

For practical purposes, the friction factor,f, can be calculated from the Moody gram described below

dia-Table 3.4 provides the friction loss in steel and cast iron pipe as developed in Cameron

Hydraulic Data, published by Ingersoll-Dresser Pumps, Flowserve Corporation This

table is based on the Darcy-Weisbach and Colebrook equations They are assumed tohave a roughness parameter,E,in feet of 0.000 15 for steel and 0.0004 for cast iron There

is no consideration for aging in this table, as it is recognized that the increase in roughnessvaries from one location to another The Hydraulic Institute recommends that 15 percentshould be added to the values in the table for commercial installations It is strongly rec-

ommended that anyone involved in piping design use both the Cameron Hydraulic Data and the Hydraulic Institute Engineering Data Book as referenc~s.

3.8 THE BASIC TOOLS OF DESIGN

d==inside diameter of pipe (in)

There are a number of sources for securing the data for theseequations in either

tab-ular or software form Before any data on pipe friction is used, either in tabtab-ular or

computer software form, be sure that the pipe under consideration is the same inside diameter as that in the tables or computer software! The following tables demonstrate

some of these sources for pipe friction data in tabular form

Reynolds Number and the Moody Diagrams

friction undei'varying velocities and viscosities

- From the Moody diagram (Fig 3.3), the friction factor,f, is 0.0195

-The Moody diagram, named after its originator, is describedin Fig 3.3 for steel pipe

and Fig 3.4 for cast iron (Note: The scale of these drawingsis so small that it is

TABLE 3.3 Hazen-Williams C Factors