Joe Evans, Ph.D   (About the Author)                 About the Tutorials

Click on the categories below to view the available tutorials

                    Basic Hydraulics - Centrifugal Pumps                Pump Evaluation, Selection & Testing Tools

                    Basic Hydraulics - Displacement Pumps              Electricity, Motors, & Controls

                    Other Pump Topics                                    The Puzzler

                    Sewage & Wastewater                                Pumps & Systems Magazine Columns

                    Variable Speed Pumping                               Other Educational Sites

VAST  (Various And Sundry Things)

Some of my older papers have an invalid email address. Contact me at

Basic Hydraul
ics - Centrifugal Pumps

Click on a topic below for a brief description of its contents.

A Brief Introduction to Centrifugal Pumps

Centrifugal Farce & Affinity

Centrifugal Pump Dynamics

Liquid Friction - The Tarantino Effect

Specific Gravity & Viscosity - Parts 1 & 2

Net Positive Suction Head - NPSHa & NPSHr

Centrifugal Pump Efficiency

Preservation of Efficiency - Affinity Revisited

Cavitation - A Largely Misunderstood Phenomenon

When Bubbles Don't Burst - Why Cavitation is Damaging

Waterhammer - Its All About Conserving Energy

Waterhammer - Parts 1 & 2

Radial Thrust Calculator

Suction Specific Speed & Suction Energy Calculators

Wire to Water Energy Calculator

Centrifugal Pump Operation at Off Design Conditions - Karassik

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When Bubbles Don't Burst - Why Cavitation is Damaging

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System Energy Calculator

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Off BEP Energy Calculator

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Basic Hydraulics - Displacement Pumps

Click on a topic below for a brief description of its contents.

Positive Displacement Pumps - Part 1 Reciprocating Pumps

Positive Displacement Pumps - Part 2 Rotary Pumps

Viking Pump Company - PD Pump White Papers

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Other Pump Topics

Click on a topic below for a brief description of its contents.

Constant Pressure Booster Systems

The Self Priming Pump

How Curve Shape Can Influence Pump Selection

Siphons & the Siphon Effect - That Sucking Sound

Pascal's Principle - Paradox Lost

Parallel Pumping - Parts 1 & 2

Two Steps to Longer Pump Life - Parts 1 & 2

Centrifugal Pump Operation at Off Design Conditions - Igor Karassik

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Centrifugal Pump Operation at Off Design Conditions - Parts 1 - 3

In the mid eighties, Igor Karassik wrote a three part series that described the problems associated with off BEP operation.  Part 1 explores radial thrust and temperature rise while Part 2 looks at internal recirculation and air binding.  Part 3 discusses discharge recirculation and discharge bypasses.  All are written in a very understandable manner which is the goal of Pump Ed 101.  These are scanned files and the resolution is not very good.  In your Acrobat tool bar, increase the page size to 130% for an easier read.

Download Part 1

Download Part 2

Download Part 3

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Two Steps to Longer Pump Life - Parts 1 & 2

This tutorial explores the two most important preventive maintenance steps that influence pump and motor life.  Part 1 looks at off BEP operation and outlines how to determine the "as built" operating point.  Part 2 investigates current unbalance and the corrective measures that should be taken.

Download Part 1

Download Part 2

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Parallel Pumping - Parts 1 & 2

Sometimes the flow and head of two pumps operating in paralle is not what we expect it to be.  This tutorial takes a look at the performance of identical and dissimilar pumps and the effect of the system curve.  Part 1 compares the pumps and Part 2 factors in the system curve.

Download Part 1

Download Part 2

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Pascal's Principle - Paradox Lost

The pressure exerted by a colum of water depends upon its density and hight - - it has absolutely nothing to do with the its volume.  In this tutorial we take a close look at this paradox and provide various examples that support Pascal's Principle.


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Siphons & The Siphon Effect - That Sucking Sound

In this turorial we explain how a pipeline siphon works and provide several examples of how they can affect pump performance.


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How Curve Shape Can Influence Pump Selection

Some pump curves are very steep while others are pretty flat.  And, ofcourse there many inbetween.  This turorial looks at how the shape of a performance curve can influence a pump's performance in a particular application.


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Sewage & Wastewater

Click on a topic below for a brief description of its contents.

Air vs Oil Filled Sewage Pump Motors

Sewage Pump Impeller Selection

Vortex Action - How Lower Efficiency Can Reduce Cost

Lower Flow Nonclogs - Solids Handling Options

Pressure Sewer Systems

Lift Station Maintenance

Pump Cycle Time Calculator

Wastewater Pump Draw Down Calculator

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Pump Start and Cycle Time Calculator

See my April 2010 Pumps & Systems article for a description of this calculator.

Download   excel  xlsx

Download    excel xls

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Lower Flow Nonclogs - Solids Handling Options

There are times when pumps installed in lower flow applications need the ability to pass a full 3" spherical solid.  Should you install a 4" pump and run to the left of the performance curve?  Probably not.  This tutoral provides several options that will enhance pump life.


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Vortex Action - How Lower Efficiency Can Reduce Cost

Vortex pumps have a bad reputation in the engineering community because of their low hydraulic efficiency.  It turns out that their lower maintenance will often substantially reduce overall operating costs even though electrical costs may be slightly higher.  This tutorial explains vortex action and provides several examples that show why this type of pump may be a better choice.


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Variable Speed Pumping Systems

Click on a topic below for a brief description of its contents.
Variable Frequency 101

Resonant Frequency & Critical Speed

Resonant Frequency Demonstration

PID Control - What, Why, How ?

Balancing Voltage & Frequency - Fluxuating Flux

Variable Frequency Control - Other Advantages

Comparing Energy Consumption - To VFD or Not to VFD

VFD Pump Selection - Frequency vs RPM ?
Lift Station Level Control - Almost Utopia

Variable Fixed Speed Control - Float Switch Activation

VFD Pump Selection - Constant Pressure

VFD Pump Selection - Circulation

VFD Pump Selection - Level Control

Variable Speed Pump Selection - Parts 1 - 3

Pump Evaluation, Selection & Testing Tools

Click on a topic below for a brief description of its contents.
VFD Evaluation & Selection Tools

Variable Speed Pump Analysis Comprehensive - Excel

Parallel Pump Control Analysis - Excel

Parallel Pump Performance Analyzer 12/13 - Excel

VSPA50 - 50hz Variable Speed Pump Analyzer - Excel

VSPA60 - 60hz Variable Speed Pump Analyzer - Excel

Hertz: My Original Variable Frequency Sizing Tool - Excel

CPSA: An Older Centrifugal Pump Selection Assistant - Exel

WWPSA: A Variable Frequency Sizing Tool for Level Control - Excel

Pump Evaluation & Testing Tools

Series / Parallel Pumping Analyzer - Excel

SDSCA: Simplex / Duplex System Curve Analyzer - Excel

Radial Thrust Calculator - Excel

Suction Specific Speed & Suction Energy Calculators - Exce

Pump Field Test Calculator - Excel

Pump Cycle Time Calculator - Excel

Simple Wastewater Pump Draw Down Calculator - Excel

Wire To Water Energy Calculator - Excel

System Energy Calculator - Excel

Off BEP Energy Calculator - Excel

Other Calculators

Pump RPM, Hertz, Impeller Trim & Pulley Calculators - Excel

Submersible Motor Flow Velocity Calculator - Excel

TDH Calculator - Domestic Submersible Well Pumps - Excel

Pump & Motor HP At Lower Frequencies - Excel

Pipe & Fitting Friction Calculator - Excel

Lots of Pump & Motor Stuff Calculator - Excel

Pump Field Test Calculator

The 2013 version of my field test calculator allows detailed testing of pumps in the field.  There are four different tabs that directly address testing of above ground centrifugals (suction & discharge gauge method), submersible wastewater (discharge gauge method) and lineshaft turbines (discharge gauge method).  After entering the required data the calculator will calculate velocity, velocity head, TDH, average voltage, average current, unbalanced voltage and current, water HP, test point HP, pump efficiency and the cost per 1000 gallons pumped.  If multiple points are tested an H/Q test curve is generated automatically on page 3.  All equations used for calculations are shown on the spreadsheet.  Complete instructions are included.  See my Jan 2011 and May 2014 Pumps & Systems articles for more information.

Download    excel xlsx

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Submersible Motor Flow Velocity Calculator

This simple calculator allows you to enter the motor OD and casing ID for a submersible well pump application.  It then calculates the flow velocity past the motor, the effective flow ID and the friction per motor foot.

Download    excel xlsx

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Wastewater Pump Draw Down Calculator

Draw Down is a common technique for evaluating wastewater pump performance.  This simple, Excel program standardizes the measurement process and also calculates TDH.  Both flow and TDH are required to evaluate pump performance and locate the operating point on the pump H/Q curve.  Discharge velocity head is also calculated and included in the TDH calculation.  See my December 2011 Pumps & Systems article for more information.  The Drawdown combo calculator is designed for older wells that use a partition to accommodate both wet and dry pits in the same well.  A drawing on the sheet explains their use.

Drawdown    excel xlsx  updated 12/13

Drawdown combo    excel xlsx   updated 12/13

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  Pump RPM, Hertz, Impeller Trim & Pulley Calculators

These four calculators use the affinity laws to calculate changes in pump flow, head & BHP based upon changes in pump speed or impeller diameter.  Follow the directions for data entry and then click on the tabs to view the H/Q curves.  (These calculators were updated on 11/17/12.  The origional versions were test versions that were uploaded accidentally.  If you downloaded the calculators prior to 11/17/12, you should replace them with the current ones.)

RPM Calculator    excel xlsx

Hertz Calculator    excel xlsx

Trim Calculator    excel xlsx

Pulley Calculator    excel xlsx

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Pump Start and Cycle Time Calculator

See my April 2010 Pumps & Systems article for a description of this calculator

Download    excel xlsx

Download    excel xls

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Pump & Motor HP At Lower Frequencies

When pump speed is reduced, the required HP reduces as the cube of the change in speed.  When a VFD reduces motor speed the available HP is also reduced.  In cases where lower HP motors are used to run a pump at some maximum frequency, it is important to make sure that the HP available at that frequency is sufficienct.  This calculator will show you the required vs available HP.  See my January 2013 Pumps & Systems article for more information.

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Pipe & Fitting Friction Calculator

There are many online friction calculators available but, there are times when you cannot go online to use them.  Although not as comprehensive as some of the online versions, this calculator allows you to compute the friction for up to three piping segments.  It also allows you to select the valves and fittings for each segment.

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Lots of Pump & Motor Stuff Calculator

This calculator allows you to compute lots of pump and motor stuff from catalog and field test data.  On the pump side it computes specific speed, suction specific speed, min & max acceptable flow, actual pump efficiency and cost per 1000 gallons pumped just name a few.  On the motor side it computes HP, torque, kVA, power cost per hour, voltage unbalance and current unbalance just to name a few.  It also includes a simple pipe friction calculator.  You will have to check it out to see the rest.

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AC Power

The AC Induction Motor

The Single Phase Induction Motor

The Cowern Papers
Power Factor - Parts 1 & 2

Process Control - Parts 1 & 2

Confusing Units of Measure - Work, Power,  & Torque

Inertia - Confusing Units Revisited

Confusing Units of Measure - Work, Power, & Torque

This tutorial could be located under other categories because it applies to all rotating machinery.  It compares the units of measure, used in a rotational environment, with their linear cousins.  Hopefully it makes them a little more understandable.


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Inertia - Confusing Units Revisited

Rotational inertia is quite different than its linear cousin but there are times when we need to understand its relationship with torque.  This tutorial investigates rotational inertia, compares it with linear inertia, and uses some simple examples to show the effects of its contributors.


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Process Control - Parts 1 & 2

This two part tutorial attempts to make process control understandable.  Part 1 takes a look at very simple control algorithms while Part 2 investigates the more complex PID control used in VFD applications.  Also see "PID Control" under the Variable Speed section for another approach.

Download Part 1

Download Part 2

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Power Factor - Parts 1 & 2

This tutorial takes a detailed look at the cause and effects of PF.  Part 1 (Electricity Behaving Badly) explains PF and it causes.  Part 2 (Electricity Behaving Better) investigates potential fixes and shows their effect.

Download Part 1

Download Part 2

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(Various And Sundry Things)

Click on a topic below for a brief description of its contents.
Publications From a Previous Life

Other Educational Sites

Pump Calcs

Operators Guide to Centrifugal Pumps

SALINITY - The Very Best Finishing Salts
Speed dating 50 plus hamburg
Hawaiian Vacation

Pump Ed 101 Background Image
Convert - Desktop Conversion Utility

Why Newton Invented Calculus

Sizing Pumps After Sunset

PumpTech Pipeline Newsletters & Product Info

Web Site Development & Hosting

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The Tutorials

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Joe Evans

The Up And Down Puzzler (Initial & Final Velocity)
The Restricted Pipe Puzzler (Bernoulli Principle)

The Water Column Puzzler (Hydrostatic Paradox)
The Sinking Float Puzzler (Buoyancy)

The Barrel Burst Puzzler (Pascals Experiment)
The False Force Puzzler (Centrifugal Force)

The My Shafts Bigger Than Yours Puzzler (Torque)
The WK2 Puzzler (Inertia)
The Belt Tightening Puzzler (Mechanical Friction)
The Warranty Puzzler (Time Dilatation)

The Water Supply Puzzler (Exponential Function)

The Worn Pump Puzzler ( Axial & Radial Thrust)
The Differing Pressure Puzzler (Eductors)

The Corrupted Curve Puzzler (Positive Displacement Pumps I & II)
The Leaking Pump Puzzler (Hydraulic Ram)
The Air Lock Puzzler (Siphon)

The Drawdown Puzzler (Hydropneumatic Tanks)
The Priming Puzzler (Centrifugal Pump Priming)
The Suction Air Puzzler (Pipeline & System Air)

Electrical Puzzlers
The Mumbo-Jumbo Puzzler (Motor Insulation)

The Right Motor Puzzler (Service Factor)
The Kill A Watt Puzzler (Reactance)

The Starting Puzzler (Motor Starting Techniques)
The Changing Voltage Puzzler (Three Phase Connections)

The Distorted Wave Puzzler (Harmonics)
The Syntax Puzzler (Boolean Logic)

The Grounded Pump Puzzler (Corrosion Protection)
The Country Boy Puzzler (Phase Generator)

The 4 Motor Puzzler (Tesla Meets Newton)

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This short course is intended for the new comer to the centrifugal pump environment. It is also a good review for those who are a bit rusty. Topics covered include the performance curve, centrifugal force & peripheral velocity, series operation, parallel operation, the affinity laws, friction, specific gravity & viscosity, suction lift, and NPSH. It also references several "Puzzlers" for further study of specific topics.

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VSPAnalysis is a comprehensive excel program that will allow you to view the operational characteristics of a centrifugal pump operating under VFD control and allows you to select the best pump for a particular application.   It produces variable speed curves showing head, efficiency, horsepower, KW and cost per 1000 gallons pumped.  It has complete instructions and a discription of the included example.  For more information see my Jan 2011 Pumps & Systems magazine article.  The standard version plots the variable frequency curves from 30-60hz in 5hz increments.  "VSPAnalysys 2hz" plots the variable frequency curves from 40-60hz in 2hz increments.

VFPPA is excel programs that allows you to view the operational characteristics of two or more centrifugal pumps operating under VFD control.  It will help you determine the most efficient operating method (synchronous or individual speed control).  It has complete instructions and a discription of the included example.  For more information see my Oct 2010 Pumps & Systems magazine article.

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Two useful pieces of information that can be used to identify pumps that are prone to cavitation due to suction recirculation are Suction Specific Speed (S) and Suction Energy (SE).  This calculator will allow you to calculate both.  For more information on S see Terry Henshaw's Oct - Dec 2009 Pumps & Systems
articles on NPSH and Suction Specific Speed.  You can read them at
See my Feb 2010 Pumps & Systems magazine article for additional information.  The calculators were updated on 3/31/11.

Download  (2.4M Excel Document .xlsx)

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Convert is a Windows based, desktop, conversion utility that is one of the most comprehensive I have run across.  It allows you to convert just about any unit of measure to dozens of others.  It also allows you to set up your own custom conversions.

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VFD Pump Selection - Constant Pressure - Joe Evans, Ph.D

VFD Pump Selection - Variable Flow / Variable Pressure - Circulation - Joe Evans, Ph.D

With this tutorial, we begin our discussion of applications that require varying flows but do not require constant pressure. Circulation is one of the more popular variable speed applications for many reasons.  We begin with a discussion of closed loop applications, show a typical system curve, and then illustrate the pump curves used for single and variable speed operation.  We then move on to open loop systems and provide  similar information.  Another discussion of this topic can be found in the "Pumps & Systems" section of this site.

Download  (183K Acrobat Document)

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VFD Pump Selection - Level Control - Joe Evans, Ph.D

In this tutorial, we take a close look at waste water pump down applications and show how they can often benefit from conversion to level control.  We begin with a discussion of wet and dry pit installations and show an example of the pumps used in pump down applications.  We then show the same pump operating in a level control environment.  We end with some guidelines on pump selection.  Another discussion of this topic can be found in the "Pumps & Systems" section of this site.

Download  (232K Acrobat Document)

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TDH Calculator - Domestic Submersible Well Pumps - Joe Evans, Ph.D

The TDH Calculator is a very simple visual that allows easy calculation of the TDH required for domestic submersible well pump applications.  It breaks down TDH into six, individual components and illustrates their relationship both above and below ground.  They are available as a PDF document or Excel spreadsheet.  The Excel version performs interactive calculations.

Download  (54K Acrobat Document)

Download  (Excel Spreadsheet)

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Lift Station Maintenance for the Complete Idiot - Steve Cottrell, Enco Southwest Inc.

Don't let the title offend you (Dummies was already taken).  Steve's guide is written for that building maintenance guy who wakes up one morning and finds that he now has responsibility for a submersible lift station!  It is simple, straight forward and will keep that station up and running. 

Download  (1120K Acrobat Document)

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Centrifugal Pump Intro for PP (Part 1 Elementary Mechanics & Hydraulics) - Joe Evans, Ph.D

This Power Point presentation is designed for audiences with a "limited" knowledge of centrifugal pumps.  It can be presented in as little as an hour or as a morning or afternoon class if you go into more detail.  Use the script to guide you through the slide show.  Don't have Power Point on your PC?  No problem - - download the pdf version and show it as slides on  a PP projector or TV monitor.

As the title implies, this tutorial presents the basic mechanics and hydraulics of centrifugal pump operation.  It begins by dispelling the myth of "centrifugal force" and shows that acceleration of a fluid is its sole purpose.  It then moves on to a discussion of the pump "curve" and shows examples of series and parallel operation.  It touches on specific gravity and why we typically rate pump performance in feet of head.  We review the laws of affinity and illustrate them with a pump operating under VFD control.  We finish with a discussion of suction conditions and liquid friction.

Download  (707K Power Point)         DownLoad  (177K pdf Version)       Download  (92K pdf Script)

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WWPSA  A Variable Frequency Sizing Tool - Level Control - Joe Evans, Ph.D

The Wastewater Pump Selection Assistant is an excel program that allows you to evaluate a submersible or dry pit pump that will be used in a level control application.  You can enter up to eight flow and head points from a 60 hz performance curve and then view its operating curves from 30 to 60 hz.  If you enter a system curve and the "pump down" elevation you can also view the same pump operating in a pump down environment.  Finally, if you enter the hydraulic efficiencies for each point, brake horsepower will be calculated automatically and displayed as "data labels" on each of the curves.  Scroll down to the bottom of the spreadsheet for complete directions and notes on the example that is included.

Download  (128K Excel Document)

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Cavitation - A Largely Misunderstood Phenomenon - Joe Evans, Ph.D

About the Author

Joe Evans lives in beautiful Rhododendron Oregon and retired from PumpTech Inc on 12/31/15.  Since entering graduate school, a continuing interest has been one of computer control of mechanical and electronic systems.  It began with the introduction of the minicomputer, in the late sixties, and continued with the advent of the PC and PLC in the eighties and nineties.  He accidentally entered the pump industry in 1986, and has been trapped there since.  He is passionate about the sharing of knowledge and its ability to replace memorization with understanding.  Click below if you would like to view a resume of his academic and professional experience.  For a little history, click on the "Publications From a Previous Life" link which can be found in the VAST section of my home page.

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The Cowern Papers

Ed Cowern received his BS in Electrical Engineering from MIT and is a district manager for Baldor.  His clear and understandable technical papers on electricity and electric motors make them a very useful reference.

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Web Site Development & Hosting

Pueo Advanced Media offers web site development & hosting and is the brain child of my son Jamie.  Whether you need a "plain Jane" site like mine (well maybe not quite as plain as mine) or something much more sophisticated, he can provide it at a reasonable cost.  Hosting is also inexpensive and starts at under $ 7.00 per month.  Click below and take a look at some of his work.  And, I am sure that he would want to make it perfectly clear that he did not do mine (but he does host it).  I have to take full responsibility for its "no frills" look.

Pueo Advanced Media

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Why Newton Invented Calclus - Joe Evans, Ph.D

Math -- one of those four letter words that can bring on anxiety attacks.  It is sad that such a useful science has gotten such a bad rap.  But, quite frankly, you can blame it on the teachers for it is they who have missed this great opportunity.  This short tutorial provides a brief history of calculus and gives some every day examples of why is still needed today -- even in the pump industry.  It also takes a few jabs at our educational system for not doing a better job of presenting math in high school and college.  But, most importantly, it promotes less complex math (algebra) as a component that can help us better understand basic hydraulics and mechanics.

Download  (122K Acrobat Document)

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Three Phase Motor Starting Techniques - Joe Evans, Ph.D

New comers to the pump industry are often unfamiliar with many of the three phase motor starting techniques that employed pre-semiconductor technology.  Surprise - - most of them are still in use and will probably be here for some time to come.  The primary purpose of alternative starting techniques is to reduce the system loading during starting.  The typical AC induction motor has an inrush current, during starting, that is about five to seven times that of run current.  Today, the VFD can provide a soft start and stop automatically just by ramping the input frequency.  In the past it was not always that easy.  This tutorial will review the most common methods of motor starting.

Download  (282K Acrobat Document)

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Positive Displacement Pumps - Parts 1 & 2 - Joe Evans, Ph.D

There are many pump designs that fall into the positive displacement category but, for the most part, they can be nicely divided into two basic groups.  The reciprocating group operates via pistons, plungers, or diaphragms while rotary pumps use gears, lobes, screws, vanes, and peristaltic action.  Their common design thread is that energy is added to the pumped fluid only periodically where, in dynamic pumps, it is added continuously.  See my September & October 2009 Pumps & Systems magazine articles for additional reading.

Part 1 of this tutorial covers reciprocating designs while Part 2 deals with rotary units.

Download  (Part 1 - 187k Acrobat Document)     
Download  (Part 2 - 138k Acrobat Document)

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Viking Pump PD Pump White Papers

In the mid 80's Viking Pump Company published a couple of very useful white papers for positive displacement pump users.  AD-19 was all about NPSH while AD-6 covered pressure and vacuum.  Both are available below in pdf format.

Download  AD-19 2 mb pdf

Download  AD-6  2 mb pdf

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Sizing Pumps After Sunset - Joe Evans, Ph.D

Background Image - Impellers

The background on my home page is one I developed for my first web site in the mid 90's.  It provides a bit of pump based art work without detracting from the content.  Below are a couple of images of the area where I live.  Mt. Hood is a dormant volcano that last erupted in 1907 and is the second most climbed mountain in the world.  It is surrounded by the 1.2 million acre Mt. Hood National Forest which has over 1200 miles of hiking trails.  Most importantly, it is in my back yard!  The image on the left is the North side as seen from Lost Lake.  The one on the right is the Sandy river which originates in
the glaciers and runs through our community.

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Series / Parallel Pumping Analyzer with Autoplot - Joe Evans, Ph.D

Centrifugal Pump Efficiency - What, How, Why, When ? - Joe Evans, Ph.D

The recipie for Pump Ed 101's educational seminars and training is a simple one.  Combine the subject matter with many years of hands on experience, a dash of simple physics, a bit of history, and a generous portion of practical examples.  Stir well and sprinkle with interaction.  The result is a learning experience for everyone involved, regardless of their prior knowledge of the subject.

The seminars shown below have been presented to a wide range of audiences over the past twenty years.  They are updated continuously and the current Power Point versions include lots of Java based animations that can often clarify many of those, otherwise, subtle points.  My audiences include engineering firms, refineries, utilities, AWWA, WEF, MEA, NGWA, RWA, and other pump oriented organizations.  Drop me an email if you are interested in an on site seminar or have questions.

Click below to download the pdf that describes the seminars that are approved for CEU credits in Oregon, Washington & Idaho.  Depending upon the acrediting agency, presentations must be a minimum of one or three hours.   Half day seminars can be a mix of various one hour presentations.  Seminars are sponsored by PumpTech and can be presented in Washington, Oregon, Idaho and parts of Montana.

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As you search the web for more information on variable frequency applications you might get the feeling that we have reentered the era of pre WWII.  Some of the sites out there profess that VFD's have no rightful place in our society and that there is no pump application worthy of their use.  Most of these opinions come from those who offer competing products and they will show a pump curve or power analysis that proves that their product can always do a better job.  I have even read some tax payer sponsored research that goes way over the line.  One concluded that magnetic coupling systems offer power savings similar to that of VFD's.  This certainly may be true in some instances but, the data used in this particular study was so skewed even Enron would have been concerned !

The same thing can happen on the other side of the aisle - - but it is usually due to a lack of knowledge rather than deceit.  Many of the VFD articles in the trade press tend to be written by VFD manufacturers.  And, although they have some pretty smart people, most have a limited knowledge of pump applications. Therefore the examples given tend to be more theoretical than practical.

Here is a good rule of thumb:  no single application control technique will always be the best choice for a given application.  If someone tells you that theirs is always best - - take them off your "favorites" list.  In my variable frequency tutorials, I try to use pump curves that are more typical rather than one that is "perfect".  This allows you to compare application results in a more realistic light.  

The P (proportional) in PID is not too frightening but, what about those other two letters?  Are not the integral and derivative parts of that mathematics known as calculus?  And, isn't calculus frightening?  Well fear no more because this "layman's" discussion of PID control will help you understand what it is, why we use it, and how it works.  We start with a discussion of open and closed loop control and give examples of each.  We then move on to proportional control and the applications it supports.  We end with a discussion of the integral and derivative functions and how they can temper the, sometimes, unruly nature of the proportional controller.  Another discussion of this topic can be found in the "Pumps & Systems" section of this site.

So, your waste water application will not lend itself to level control operation.  Or, maybe you just prefer float switches over transducers and ultrasonic devices.  Whatever the reason, VFS or variable fixed speed control might be a viable alternative to that pump down application.  Today you can combine an inexpensive VFD with standard float switch technology and get a multispeed pumping system that can increase application flexibility and efficiency.  This short tutorial takes a look at VFS control and how it compares to standard pump down applications.

There can be times when we over estimate the flow expected during parallel operation of two non-clogs.  SDSCA is an excel spread sheet that allows you to analyze the operation of the same non-clog running under simplex and duplex (parallel) operation.  It will generate a system curve based upon the information entered and give you the head required at design flow.  You can then enter the curve data for a selected pump and the simplex and duplex operational curves will be plotted against the system curve.  Scroll down for detailed instructions.  The data used in the example can be found under the "Notes" tab.

Sept 2006 - Centrifugal Farce & Affinity                                            

Nov 2006 - Preservation of Efficiency - Affinity Revisited                   Dec 2006 - Liquid Friction - The Tarantino Effect

Jan 2007 - When Bubbles Don't Burst - Why Cavitation is Damaging      Feb 2007 - Pascal's Principle - Paradox Lost

Mar 2007 - Balancing Voltage & Frequency - Fluxuating Flux                 Apr 2007 - Comparing Energy Consumption - To VFD or Not to VFD

May 2007 - How Curve Shape Can Influence Pump Selection                  Jun 2007 - Power Factor Part 1 - Electricity Behaving Badly

July 2007 - Power Factor Part 2 - Electricity Behaving Better                Aug 2007 - Vortex Action - How Lower Efficiency Can Reduce Cost

Sept 2007 - Lift Station Level Control - Almost Utopia                            Oct 2007 - Confusing Units of Measure - Work, Power, & Torque

Nov 2007 - Siphons and the Siphon Effect - That Sucking Sound            Dec 2007 - Variable Frequency Control - Other Advantages

Jan 2008 - Process Control Part 1 - Smart and Not So Smart Control       Feb 2008 - Process Control Part 2 - Even Smarter Control

Mar 2008 - Parallel Pumping Part 1 - Parallel and  Not So Parallel           April 2008 - Parallel Pumping Part 2 - Other Considerations

May 2008 - Net Positive Suction Head - NPSHa & NPSHr                       June 2008 - Two Steps to Longer Pump Life - Part 1

July 2008 - Two Steps to Longer Pump Life - Part 2                               Aug 2008 - Waterhammer - Part 1  What & Why

Sept 2008 - Waterhammer - Part 2  Causes & Variables                           Oct 2008 - Lower Flow Nonclogs - Solids Handling Options

Nov 2008 - Variable Speed Pump Selection - Part 1 Cp-Vf                       Dec 2008 - Variable Speed Pump Selection - Part 2 Vp-Vf

Jan 2009 - Variable Speed Pump Selection - Part 3 Vp-Vf (+Cp)              Feb 2009 - Resonant Frequency & Critical Speed

Mar 2009 - Specific Gravity & Viscosity - Part 1                                     April 2009 - Specific Gravity & Viscosity - Part 2

May 2009 - Variable Speed Performance Analyzer - 50hz                       June 2009 - Inertia - Confusing Units Revisited

July 2009 - Why The Left Can Be Dangerous                                          Aug 2009 - Planning for System Growth

Sept 2009 - PD Pump Hydraulics - Part 1 Reciprocating                           Oct 2009 - PD Pump Hydraulics - Part 2 Rotary

Nov 2009 - Corrosion - A Natural Process                                               Dec 2009 - Magnetic Couplings - Extra Benefits

Jan 2010 - Radial Thrust Calculator                                                        Feb 2010 - Suction Calculators

Mar 2010 - Energy Calculator                                                                 April 2010 - Cycle Time

May 2010 - BEBOP                                                                                  June 2010 - AC Power - Part 1

July 2010 - AC Power - Part 2                                                                 Aug 2010 - AC Power - Part 3

Sept 2010 - AC Power - Part 4                                                                 Oct 2010 - VFD Parallel Pump Analyzer

Nov  2010 - Coating & Restoration - Part 1                                                Dec  2010 - Coating & Restoration - Part 2

Jan 2011 - Variable Speed  Pump Analysis                                                Feb 2011 - Testing Pumps in the Field

Mar 2011 - AC Motors Part 1                                                                     April 2011 - AC Motors Part 2

May 2011 - AC Motors Part 3                                                                    June 2011 - AC Motors Part 4

July 2011 - AC Motors Part 5                                                                    Aug 2011 - AC Motor Torque

Sept 2011 - Switched Reluctance Motors                                                   Oct 2011 - Modeling & Design Software

Nov 2011 - Suction Specific Speed Revisited                                             Dec 2011 - Wastewater Drawdown Calculator

Jan 2012 - Off BEP Energy Calculator                                                       Feb 2012 - Centrifugal Pump Efficiency Part 1

Mar 2012 - Centrifugal Pump Efficiency Part 2                                          April 2012 - Centrifugal Pump Efficiency Part 3

May 2012 - Centrifugal Pump Efficiency Part 4                                          June 2012 - Centrifugal Pump Efficiency Part 5

July 2012 - Centrifugal Pump Efficiency Part 6                                          Aug 2012 - Bernoulli - Part 1

Sept 2012 - Bernoulli - Part 2                                                                     Oct 2012 - Velocity Head

Nov 2012 - Affinity Calculators                                                                  Dec 2012 - Learning

Jan 2013 - Volts per Hertz & VFD HP                                                         Feb 2013 - Branch Line Pumping Options Part 1

Mar 2013 - Branch Line Pumping Options Part 2                                          April 2013 - Three False Forces & One Real Force

May 2013 - Motor HP & Torque Versus VFD Frequency                               June 2013 - Wye / Delta Part 1

July 2013 - Wye / Delta Part 2                                                                  Aug 2013 - Wye / Delta Part 3

Sept 2013 - Breadth of Efficiency                                                             Oct 2013 - Dezincification

Nov 2013 - Wastewater Pump S Values                                                       Dec 2013 - Parallel Analyzer

Jan 2014 - Hydraulic Rams                                                                        Feb 2014 - The Cost of Pumping

Mar 2014 - AC Motor Efficiency                                                                April 2014 - Igor Karassik

May 2014 - Submersible WW Pump Testing Part 1                                       June 2014 - Submersible WW Pump Testing Part 2

July 2014 - Voltage Variation & Unbalance Part 1                                       Aug 2014 - Voltage Variation & Unbalance Part 2

Sept 2014 - Power Factor A Tale of Two Currents Part 1                            Oct 2014 - Power Factor A Tale of Two Currents Part 2

Nov 2014 - Power Factor A Tale of Two Currents Part 3                             Dec 2014 - Goodbye!!

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Other Publications - Joe Evans, Ph.D

The work I did prior to 1986 was quite different than what I do today.  I attended grad school (69 - 73) during an interesting era.  The advent of the minicomputer in the late 60's and early 70's allowed us to accomplish things that were impossible for those before us.  All of a sudden, data generated by scientific instruments (especially the gas chromatograph - mass spectrometer (GC-MS)) that used to take months to analyze provided results within days.  Back then the typical minicomputer was the size of a filing cabinet and had 2 - 4 K of memory.  Data storage was on paper tape or maybe mag tape if you were lucky.  It was still the time of the slide rule and analog recorders and just comparing the area under two plotted curves could take hours.  Much of our work on instrument automation was sponsored by NASA and the Robert A Welch Foundation. We were also chosen as one of the few labs to analyze the soil samples gathered by the first NASA Lunar Lander project.

In 1973 I entered the army as captain and chief of the Air Chemistry Branch of the Army Environmental Hygiene Agency.  This agency was the army's version of the EPA/NIH and its research was designed to protect our troops and reduce our impact on the environment.  One of our major projects at the time was monitoring the detoxification and disposal of our WWII nerve gas stock pile at Rocky Mountain Arsenal (which, by the way, was stored for decades right at the end of the main runway of the old Denver airport).  During my stay I continued my work on instrument automation and also the miniaturization of those instruments for use in the field.

After leaving the army in 1975 I joined Finnigan Corporation, a major GC-MS developer and manufacturer of the era.   I was in charge of the East Coast applications lab in Washington DC and later moved into the position of product manager.  By the mid 70's the minicomputer had advanced substantially and this technology gave us the ability analyze the data provided by a GC-MS in real time - - not days.

In 1977 I made the decision to move to Hawaii and, except for the University of Hawaii, there were no job opportunities that could make use of my past experience.  Hawaii is a major union state and unfortunately this spilled over to the university and I doubted that I would fit in well in that environment.  So, on a lark, I changed directions and took a position with IBM.  Oddly enough, my minicomputer experience paid off and over the next five years I worked in industrial automation as well as distributed processing in the business community.  One of our major accomplishments was the implementation of a on line directory assistance system at Hawaiian Telephone.  It was a distributed processing system that consisted of three layers of minicomputers and fixed head disk drives that could perform searches as deep as nine levels of indent in seconds.   The result was a directory assistance operator reduction of about two thirds which the union, of course, did not see this as a useful technological advance.  Although it was nowhere near the speed of Google, it was lightning fast for its day.

In 1983, the Queen's Medical Center (Hawaii's largest healthcare organization) offered me the position of VP of Information Services.  I learned early on that accepting this job was a mistake as I was unaware of the politics and in fighting that went on in these "non-profit" organizations.  Still, in less than three years we were able to take them to the forefront of the information age.  We were the first company in Hawaii to employ personal computers instead of dumb terminals and we had our own "intranet" email system in early '84.  Unfortunately continuing confrontations with the CEO (a psychiatrist who was having an affair with the head of nursing who had a striking resembalance to "Miss Piggy") led to my demise in late '85.

In 1986 I accidentally fell into the pump industry.  And, as most of you know, once you are in this industry it is hard to escape!  Below are several papers that I published or took part in prior to that fall.

Isolation and Partial Characterization of Supernatant and Mitochondrial Shrimp Muscle Malate Dehydrogenases

This paper, published in Comparative Biochemistry & Physiology (Pergamon Press), was a result of the research performed for my masters thesis.  It is co-authored by my advisor and two of my associates.  The work was sponsored by the National Institutes of Health and the Robert A Welch Foundation.

Program ELAL:  An Interactive Minicomputer Based Elemental Analysis of Low & Medium Resolution Mass Spectra

This paper, published in Analytical Chemistry (American Chemical Society), was a result of some of my doctorial research and follow on work done at the U.S. Army Environmental Hygene Agency.  The program was the first to computerize the manual elemental analysis methods developed by Dr. Fred McLafferty at Cornell University.

Monitoring Organic Vapors

This paper, published in  Environmental Science & Technology (American Chemical Society), was a result of my continuing work at the U.S. Army Environmental Hygene Agency.  It discusses the ongoing micro-computerization and miniaturization of environmental monitoring instruments.  It was co-authored by Jim Arnold of Varian Associates, a physicist and major contributor to technology advances in mass spectrometry and nuclear magnetic resonance (NMR) spectrometry (now known as magnetic resonance imaging (MRI) due to our ignorance and fear of that other "n" word).  The mass spectrometer described in this paper was the predecessor of the one that was aboard the Mars Lander.

User Written Software Extends the Use of GC-MS Data Systems

Published in Finnigan Spectra (Finnigan Corporation), this article revisits the use of Program ELAL and introduces a new program known as FINL (fragment ion and neutral loss analysis).  FINL automated another manual elemental analysis methodology that was developed by McLafferty at Cornell University.

Good dating manga

In 1983 I left IBM and assumed the position of VP of Information Services at The Queen's Medical Center in Honolulu.  One of the first things that we did was to initiate a news letter to keep the employees of our almost 150 departments up to date on what we were doing.  This is the first issue.

The Queen's Medical Center - - A Royal Link to the Past and the Future

In late '83 we entered into an agreement with Management Science America (MSA) to install their GL, AP, and Payroll/Personnel systems and their "Peachpak" interactive PC products.  This article highlights our accomplishments over a period of just one year.

OA Reigns Supreme at Queen's Medical Center

In 1985, "Today's Office" (Hearst Business Publications) selected Queen's as one of the nation's leader's in office automation and asked me to write an article outlining what we had done to get there.  This was my last non-pump article!

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Education Links
If you have suggestions for additional educational links, please e-mail me at

Intro To Pumps - Basic Pump Training & Weekly Pump Industry News
FreeCalc.Com - Lots of Good Online Calculators
All About Circuits - AC, DC, and Much More


Light & Matter - Free Physics Text Books

Pump School -
A Rotary Pump Course

  Applied Flow Technology - Free Pump System Modeling Software

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Pump Calcs is a web site that offers a number of very useful calculators and conversion utilities.  It is sponsored by Pumps & Systems magazine.

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My nephew Hugh and his wife Elvira own and operate a very different vacation rental outside Pahoa, on the Big Island of Hawaii, just 25 miles north of the Volcanos National Park.  It offers ocean views in a truly rual environment.  In this area of the island, lava pools and black sand beaches rim the coast but just a few yards inland it becomes a beautiful forest.  They have several different units that can accomodate from two to fifteen people and will even provide three meals a day if you wish.  The rates - - outrageously inexpensive!  The picture below is of the Ohana House.  For more information and a tour of the grounds, click on their web site link below.

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Robert Perez has worked in the petrochemical Industry
for 30 years.  He has written many papers on rotating
equipment and also taught the Rotating Equipment course
at Texas A & M University.  His new book was written
specifically for those who are responsible for the
operation and maintenance of centrifugal pumps. Click on
the link below to review the topics covered.

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PumpTech, Inc. Newsletter - - PumpTech Pipeline

In 2010, I began a quarterly newsletter for my employer PumpTech.  Pdf versions are available below.  In addition to featuring our products and packaged systems, it also has lots of pump related info.  If you use full screen mode in Acrobat you can use the page links to move through the document.  If you would like to subscribe to the email version, click on the email link below and send us your name, company and preferred email address.

Check out PumpTech at:  or sign up for the email newsletter at:  60 year old woman dating site

Spring 2010            Summer 2010           
Fall 2010            Winter 2011        Spring 2011        Summer 2011         Fall 2011        Winter 2012

Spring 2012               Summer 2012               Fall 2012           Winter 2013        Summer 2013      Winter (Feb) 2014

Winter (Dec) 2014

Spring (May) 2016

Chick on the links below to download the brochures & data sheets for several PumpTech packaged systems.

iRover   Wet Well Retrofit   Vacuum Assist   Hydronix Brochure   MeterMan Brochure   PolyMan

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SALINITY LLC - Gourmet herb and spice infused finishing salts handcrafted in Southern Oregon

My stepdaughter, Laine, and her friend Jody own a very unique business down in Grants Pass Oregon.  They handcraft the most delicious finishing salts that I have ever tasted.  They combine the finest grey sea salt with organically grown herbs and spices to create a unique end to any of your favorite dishes.  The herbs and spices are all grown locally with one exception.  The ginger comes from my nephew Hugh's organic ginger farm on the Big Island of Hawaii !  Click on the link below to learn more and order online.

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