4. Pump is a machine which transfers mechanical energy to
liquid in order to move it from source to destination.
Purpose
- To increase flow rate (velocity)
- Pressure (low to high)
- Elevation (same or higher)
Introduction
6. A positive displacement traps a
fixed amount of liquid and
then forces this trapped
volume into the discharge pipe
No internal recycling
They are either reciprocating
or rotary
Positive Displacement Pumps
7. In Recips, there is a stationary chamber that contains a piston,
plunger or diaphragm.
Reciprocating Pumps
13. A propeller whips & add energy
to liquid.
Liquid leaves the propeller in the
same direction as it enters.
Designed for large capacities.
Less pressure.
Axial or Propeller Pump
14. Works on the principle of
centrifugal force
Centrifugal Pump
15. MAIN PARTS OF CENTRIFUGAL
PUMPS
A. Stuffing Box
B. Packing
C. Shaft
D. Shaft Sleeve
E. Vane
F. Casing
G. Eye of Impeller
H. Impeller
I. Casing Wear Ring
J. Impeller
K. Discharge Nozzle
18. Used to minimize friction between
moving parts and constrains relative
motion.
Main Types
Radial or Journal Bearings
Axial or Thrust Bearings
Centrifugal Pump - Bearings
19. Static Seals
Sealing takes place between the
surfaces which do not move relative to
one another.
Examples: Gaskets, Packing's etc.
Dynamic Seals
Sealing takes place between the
surfaces which move relative to one
another.
Examples: Mechanical Seals, Labyrinth
seals etc.
Centrifugal Pump - Seals
20. Having two or more
impellers on a shaft in series.
Used for higher discharge
head.
Impellers are located at the
center of shaft.
Rotor is supported at shaft
ends.
Multistage Centrifugal Pump
21. Mixture of impeller & propeller
pumps.
Can be single or multistage.
Designed for intermediate
capacity & head.
Usually used for high suction lifts
as deep well pumps
Mixed or Turbine Pump
22. Comparison
Positive Displacement Pumps Centrifugal Pumps
o Complicated in construction
o More number of parts
o More wear and tear
o Can not run at high speed
o Pulsating delivery
o Check valve may be required
o They are self primed
o Suitable for low flow rates and
higher pressure
o Simple in construction
o Lesser number of parts
o Less wear and tear
o Can run at high speed
o Continuous delivery
o No check valve
o Needs priming
o Suitable for high flow rates and
less pressure
23. Pressure:
tells us how much of the hydraulic
resistance needs to be overcome by
the pumping element
Static Head:
Height of liquid
H = Pressure
Density x g
Friction Head:
Loss of energy due to Piping
resistance. Should be as less as
possible.
Important Terms
25. NPSH:
Suction head minus the vapor pressure of Liquid at a given
temperature.
NPSH Available:
Absolute Head (Pressure) available at the pump suction minus
the vapor pressure of liquid at given temperature.
NPSH Required:
Minimum head (Pressure) required at pump suction to avoid
vaporization at impeller eye.
Important Terms
26. CAVITATION:
NPSHr > NPSHa
Formation of bubbles
inside pump body
Implosion of these
bubble
High Vibration
Pitting of impeller &
body.
Seal Leakage
Important Terms
27. Removal of gas or vapor from pump body by using liquid to
be pumped
Centrifugal pumps are not self primed and need priming
before startup
To keep pump primed all the time locate suction source
higher than pump level
Priming
30. Check that the lube oil levels are adequate.
Check the gland lubrication supply is turned on.
Prime the pump.
Open the suction valve.
Close the discharge valve.
Start the pump.
Open the discharge valve.
Centrifugal Pump - Startup
31. Close the discharge valve
Stop the pump
Close the suction valve
Centrifugal Pump - Shutdown
