2. Goals
• Describe how centrifugal and positive-displacement
pumps operate and common applications.
• Calculate system head requirements.
• Determine head, pump efficiency, and pump.
horsepower from a typical centrifugal pump curve.
• Define net positive suction head (NPSH) and
understand how it relates to cavitation.
• Compute NPSH required by a pump.
• Determine an appropriate pump (impeller diameter,
efficiency, etc.) for a given required head.
• Describe how to modify system to operate on the
appropriate pump curve.
3. Background
Fluid Moving Equipment
Fluids are moved through flow systems using pumps, fans,
blowers, and compressors. Such devices increase the
mechanical energy of the fluid. The additional energy can
be used to increase
• Velocity (flow rate)
• Pressure
• Elevation
4. Background
Pump, fan, blower, and compressor are terms
that do not have precise meaning. Generally
pumps move liquids while fans, blowers and
compressors add energy to gasses.
Pumps and fans do not appreciably affect the
density of the fluids that they move and thus
incompressible flow theory is applicable.
5. Centrifugal Pumps
Most common type of pumping machinery. There are many
types, sizes, and designs from various manufacturers who
also publish operating characteristics of each pump in the
form of performance (pump) curves. The device pictured on
the cover page is a centrifugal pump.
Pump curves describe head delivered, pump efficiency, and
net positive suction head (NPSH) for a properly operating
specific model pump.
Centrifugal pumps are generally used where high flow rates
and moderate head increases are required.
8. Positive Displacement Pumps
To move fluids positive displacement pumps admit a
fixed volume of liquid from the inlet into a chamber
and eject it into the discharge.
Positive displacement pumps are used when higher
head increases are required. Generally they do not
increase velocity.
10. Pump Head
What happens if the MEB is multiplied through by g (gc/g)?
2
4
2
1
ˆ 2
2
V
K
D
L
f
p
z
g
V
g
g
W
i
What are the units (SI)?
2
2
m
s
kg
m
N
2
2
2
3
m
s
s
kg
m
kg
m
W/g has units of length and is known as the pump head
^
13. Example
What pump horsepower is required to pump 150 GPM
of water at a total head of 225 ft using a Goulds Model
3196 operating at 3540 RPM ?
What is the required NPSH ?
What is the pump efficiency ?
14. System Response
What happens when flow control valve is closed?
• Resistance (f) increases
• Flow rate decreases
• Need more head to recover flow rate
Tank A
2
Tank B
1
3
