2. Centrifugal Pumps
From the Center
of a Circle
RADIAL DIRECTION
To the Outside of a Circle
A machine for moving fluid by accelerating the
fluid RADIALLY outward.
3. This machine consists of an IMPELLER
rotating within a case (diffuser)
Liquid directed into the
center of the rotating
impeller is picked up by
the impeller’s vanes and
accelerated to a higher velocity by the
rotation of the impeller and discharged by
centrifugal force into the case
(diffuser).
Centrifugal Pumps
4. Centrifugal Pumps
A collection chamber in the casing converts
much of the Kinetic Energy (energy due to
velocity) into Head or Pressure.
6. Head is a term for expressing feet of water column
Head can also be converted to pressure
"Head"
100
feet
43.3 PSI
Reservoir
of Fluid
Pressure
Gauge
7. Conversion Factors Between
Head and Pressure
Head (feet of liquid) =Pressure in PSI x 2.31 / Sp. Gr.
Pressure in PSI = Head (in feet) x Sp. Gr. / 2.31
PSI is Pounds per Square Inch
Sp. Gr. is Specific Gravity which for water is equal to
1
For a fluid more dense than water, Sp. Gr. is
greater than 1
For a fluid less dense than water, Sp. Gr. is less
than 1
8. Head
Head and pressure are interchangeable
terms provided that they are expressed in
their correct units.
The conversion of all pressure terms into
units of equivalent head simplifies most
pump calculations.
9. Diameter of
the Impeller
Thickness
of the impeller
Centrifugal Impellers
Thicker the Impeller- More Water
Larger the DIAMETER - More Pressure
Increase the Speed - More Water and Pressure
Impeller
Vanes
“Eye of the
Impeller”
Water
Entrance
10. Two Impellers in Series
Direction of Flow
Twice the pressure
Same amount of water
11. Multiple Impellers in Series
Placing impellers in series increases the amount of head
produced
The head produced = # of impellers x head of one impeller
Direction of Flow Direction of Flow
13. Pump Performance Curve
Step #1, Horizontal Axis
The pump's flow rate is plotted on the horizontal axis ( X
axis)
Usually expressed in Gallons per Minute
Pump Flow Rate
14. Pump Performance Curve
Step #2, Vertical Axis
Pump Flow Rate
The head the pump produces is plotted on
the vertical axis (Y axis)
Usually express in Feet of Water
Head
15. Pump Performance Curve
Step #3, Mapping the Flow and the Head
Pump Flow Rate
Most pump
performance curves
slope from left to
right
Performance Curve
Head
16. Pump Performance Curve
Important Points
Shut-off Head is the maximum pressure
or head the pump can produce
No flow is produced
Pump Flow Rate
Head
Shut-off Head
17. Pump Performance Curve
Important Points
Pump Flow Rate
Head
Maximum Flow
Maximum Flow is the
largest flow the pump can
produce
No Head is produced
18. System Performance Curves
System Performance Curve is a mapping
of the head required to produce flow in a
given system
A system includes all the pipe, fittings and
devices the fluid must flow through, and
represents the friction loss the fluid
experiences
19. System Performance Curve
Step #1, Horizontal Axis
System Flow Rate
The System's flow rate in plotted on the horizontal
axis ( X axis)
Usually expressed in Gallons per Minute
20. System Performance Curve
Step #2, Vertical Axis
Pump Flow Rate
The head the system requires is plotted on
the vertical axis (Y axis)
Usually express in Feet of Water
Head
21. System Performance Curve
Step #3, Curve Mapping
The friction loss is mapped onto the graph
The amount of friction loss varies with flow through
the system
Head
Pump Flow Rate
Friction Loss
22. Head
Pump Flow Rate
The point on the system curve that intersects
the pump curve is known as the operating
point.
27. Piping Design Equations
Heuristics for Pipe Diameter
0.494
0.408
0.343
3
:
2.607
:
1.065
,
,1000 /
, /
Liquids
w
D
Gases
w
D
D Diameter inches
w Mass Flowrate lb hr
Density lb ft
28. Energy Loss in Piping Networks
Incompressible Fluids
2 2
1 2 1 2 2 1
3
2
2
144 1
2
, /
, /
, /
, 32.174 /s
,
,
L
f
L
P P v v z z h
g
Density lb ft
P Pressure lb in
v Velocity ft sec
g Gravitational Acceleration ft
z Elevation ft
h Head loss ft
29. 2
4
2
2
1
2
2
0.00259
,
,
,
1 ,
L
K Q
h
d
Q Volumetric Flowrate gpm
d Pipe Diameter in
K Sum of all fittings
L
K f straight pipe
D
d
K Sudden enlargement
d
30. Friction Loss Factors for Fittings
Fitting K
Standard 90o
Elbow 30fT
Standard 45o
Elbow 16fT
Standard Tee
20fT Run
60 fT Branch
Pipe Entrance 0.78
Pipe Exit 1.0
31. Friction Loss Factors for Valves
Valve K
Gate valve 8fT
Globe Valve 340fT
Swing Check Valve 100fT
Lift Check Valve 600fT
Ball Valve 3fT
2
2
29.9
V
V
d
K
C
C Valve Coefficient
33. Energy Loss in Valves
Function of valve type and valve
position
The complex flow path through valves
can result in high head loss (of course,
one of the purposes of a valve is to
create head loss when it is not fully
open)
Ev are the loss in terms of velocity
heads
