| Introduction | Contents |



by J. Chaurette, prof. eng


The purpose of this book is to describe how pressure can be determined anywhere within a pump system. The inlet and outlet of a pump are two locations where pressure is of special interest. The difference in pressure head (the term pressure head refers to the energy associated with pressure) between these two points is known as the Total Head. A system equation will be developed based on fundamental principles from which the Total Head of the pump can be calculated, as well as the pressure head anywhere within the system. These principles can be applied to very complex systems.

Friction loss due to fluid flow in pipes is the most difficult component of Total head to calculate. The methods used to calculate friction loss for different types of fluids such as water and viscous fluids of the Newtonian type and wood fiber suspensions (or stock) will be explained.

The fluids considered in this book belong to the categories of viscous and non-viscous Newtonian fluids. Wood fiber suspensions are a special type of slurry. There is an excellent treatment on this subject by G.G. Duffy in reference 2. For the reader?s benefit a condensed version is given here. Slurries, which are an important class of fluids, are not considered. I recommend reference 7, which provides a complete treatment of the subject. However, all the principles for Total Head determination described in this book apply to slurry fluid systems. The only exception is the methods used to calculate pipe friction head.

Centrifugal pumps are by far the most common type of pump used in industrial processes. This type of pump is the focus of the book. The challenge in pump sizing lies in determining the Total Head of the system, not the particular pump model, or the materials required for the application. The pump manufacturers are generally more than willing to help with specific recommendations. Information on models, materials, seals, etc., is available from pump manufacturer catalogs.

Often when approaching a new subject, our lack of familiarity makes it difficult to formulate meaningful questions. Chapter 1 is a brief introduction to the components of Total Head. I hope it proves as useful to you as it did to me.



Chapter 1 - An Introduction to pump systems

1.0 Hydrostatic pressure and fluid column height
1.1 The three forms of energy
1.2 The relationship between elevation, pressure and velocity in a fluid
1.3 The difference between pressure and head
1.4 Fluid systems
1.5 The driving force of the fluid system
1.6 The components of Total Head
1.7 Negative (relative) pressure
1.8 The siphon effect
1.9 Specific gravity

Chapter 2 - The application of thermodynamics to pump systems

2.0 Energy and thermodynamic properties
2.1 Closed systems and internal energy
2.2 Closed systems, internal energy and work
2.3 Open systems and enthalpy
2.4 Open systems, enthalpy, kinetic and potential energy
2.5 Work done by the pump
2.6 Fluid and equipment friction loss
2.7 The control volume
2.8 The determination of Total Head from the energy balance
2.9 System or Total Head equation for a single inlet-single outlet system
Example 2.1-Calculate the Total Head for a typical pumping system
2.10 Method for determining the pressure head at any location
Example 2.2 Calculate the pressure head at a specific point in the system
2.11 System or Total Head equation for a single inlet-double outlet system
2.12 General method for determining Total Head in a system with
multiple inlets and outlets
2.13 General method for determining Total Head in a system with
multiple pumps, inlets and outlets
2.14 General method for determining the pressure head anywhere in a system
with multiple pumps, inlets and outlets

Chapter 3 - The Components of Total Head

3.0 The Components of Total Head
3.l Total Static Head
3.2 Suction Static Head
3.3 Net Positive Suction Head (N.P.S.H.)
Example 3.1-Calculate the Net Positive Suction Head Available (N.P.S.H.A.)
3.4 Pump intake suction submergence
3.5 Discharge Static Head
Example 3.2 – Calculate the Suction & Discharge Static Head
3.6 Velocity Head Difference
3.7 Equipment Pressure Head Difference
3.8 Pipe Friction Head Difference for newtonian fluids
3.9 Fitting Friction Head Difference for newtonian fluids, K method and 2K
3.10 Pipe Friction Head Difference for wood fiber suspensions

Chapter 4 - Pump Selection, Sizing, Interpretation of Performance Curves

4.0 Pump classes
4.1 Coverage chart for centrifugal pumps
4.2 Performance curve chart
4.3 Impeller diameter selection
4.4 System curve

4.5 Operating point
4.6 Safety factor on Total head or capacity
4.7 Pump operation to the right or left of B.E.P.
4.8 Pump shut-off head
4.9 Pump power

Chapter 5 - Field Measurements

5.0 Real live measurements
5.1 Total Head
5.2 Net Positive Suction Head Available (N.P.S.H.A.)
5.3 Shut-off head
5.4 Equipment head difference
5.5 Flow measurement
5.6 Calculating flow based on power consumed by the motor



Appendix A

Useful equations (FPS and SI unit systems)
The definition of viscosity
Rheological (viscous behavior) properties of fluids

Appendix B

The Newton-Raphson iteration technique applied to the Colebrook equation

Appendix C

The determination of slurry density based on the volume and weight concentration of the solid particles

Appendix D

The use of imperial (FPS) units

Appendix E

Power factors and efficiency values for ABB electric motors