Centrifugal pump pptx

1. Dr. subhash technical campus

2. Centrifugal pumps
In this part of the lesson we will take a closer look at Centrifugal pumps

3. Centrifugal pumps - theory and
characteristics
A centrifugal pump can be further defined as a machine
which uses several energy transformations in order to
increase the pressure of a liquid. The energy input into the
pump is typically the fuel source energy used to power the
driver.

4. Centrifugal pumps - theory and
characteristics
 Energy input
 Most commonly, this is electricity used to power an electric
motor.
 Alternative forms of energy used to power the driver include
high-pressure steam used to drive a steam turbine.
 Fuel oil used to power a diesel engine.
 High-pressure hydraulic fluid used to power a hydraulic
motor.
 Compressed air used to drive an air motor.
 Regardless of the driver type for a centrifugal pump, the
input energy is converted in the driver to a rotating
mechanical energy, consisting of the driver output shaft,
operating at a certain speed, and transmitting a certain
torque, or horsepower.

5. Centrifugal pumps - theory and
characteristics
Velocity and pressure
levels Fluid flow
A particular feature of
centrifugal pumps is that the
power absorbed is a minimum
at zero flow, and therefore can
be started up against a closed
valve.
By increasing the size of the
impeller, and/or the speed of
pump rotation, we can achieve
larger pumping rates.
The diagram illustrates that velocity and pressure levels vary as the fluid
moves along the flow path in a centrifugal pump.

6. Centrifugal pumps - theory and
characteristics
 Consequently, no pumping action can occur unless this non-
condensable gas is first eliminated, a process known as
priming the pump.
 Hence we need a fluid flow through the impeller in order to
achieve a vacuum. Thus when these pumps are not primed,
or loose suction during operation they will not self-prime
themselves. In order to prime or re-prime these pumps we
can use a priming system
 If vapours of the liquid being pumped are present on the
suction side of the pump, this results in Cavitation, which
can cause loss of prime or even serious damage to the pump.

7. Centrifugal Pumps - Cavitation
When the pressure falls below the vapour pressure of the liquid at a
given temperature, boiling occurs and small bubbles of vapour are formed.
These bubbles will grow in the low-pressure area and implode when they
are transported to an area of pressure above vapour pressure. The term
given to this local vaporisation of the fluid is Cavitation.

8. Centrifugal Pumps - Cavitation
 The collapsing of the bubbles is the area of Cavitation we
are concerned with, as extremely high pressures are
produced, which causes noise and erosion of the metal
surface.
 The area of pipeline ...
 This cavitation effect...
 To reduce cavitation ...
 Click on an item to jump to it.

9. Centrifugal Pumps - Cavitation
When the pressure falls below the vapour pressure of the liquid at a
given temperature, boiling occurs and small bubbles of vapour are
formed. These bubbles will grow in the low-pressure area and implode
when they are transported to an area of pressure above vapour pressure.
The term given to this local vaporisation of the fluid is Cavitation.

10. Centrifugal Pumps - Cavitation
 The collapsing of the bubbles is the area of Cavitation we
are concerned with, as extremely high pressures are
produced, which causes noise and erosion of the metal
surface.
 The area of pipeline where Cavitation mainly occurs is the
pump suction, where the liquid is subjected to a rapid rise in
velocity, and hence a fall in static pressure.

11. Centrifugal Pumps - Cavitation
When the pressure falls below the vapour pressure of
the liquid at a given temperature, boiling occurs and
small bubbles of vapour are formed. These bubbles will
grow in the low-pressure area and implode when they are
transported to an area of pressure above vapour pressure.
The term given to this local vaporisation of the fluid is
Cavitation.
 The collapsing of the bubbles is the area of Cavitation we are
concerned with, as extremely high pressures are produced, which
causes noise and erosion of the metal surface.

12. Centrifugal Pumps - Cavitation
 This Cavitation effect on the pump can cause damage on
the casing and impeller.
 During Cavitation, a liquid/vapour mixture of varying
density is produced.
 This results in fluctuations in pressure (caused by the liquid
column being drawn in), and causes fluctuations in the
discharge pressure, pump power absorbed (shown on the
ammeter), and hence pump revolutions.

13. Centrifugal Pumps - Cavitation
When the pressure falls below the vapour
pressure of the liquid at a given temperature,
boiling occurs and small bubbles of vapour are
formed. These bubbles will grow in the low-
pressure area and implode when they are
transported to an area of pressure above vapour
pressure. The term given to this local vaporisation
of the fluid is Cavitation.

14. Centrifugal pumps - Priming
Centrifugal pumps although suitable for most general marine duties,
suffer in one very important respect; they are not self priming and require
some means of removing air from the suction pipeline and filling it with
the liquid.

15. Centrifugal pumps - Priming
 Where the liquid to be pumped is at a higher level than the
pump, opening an air release cock near the pump suction
will enable the air to be forced out as the pipeline fills up
under the action of gravity. This is often referred to as
"flooding the pump".
 Alternatively, an air-pumping unit can be provided to
individual pumps or as a central priming system connected
to several pumps.
 The water ring or liquid ring primer can be arranged as an
individual unit mounted on the pump and driven by it, or as
a motor driven unit mounted separately and serving several
pumps, known as a central priming system.

16. Centrifugal Pumps - Central
Priming System

17. Centrifugal pumps-component
parts

18. Centrifugal pumps-component
parts
 This is a vertical , single stage ,single entry , centrifugal
pump for general marine use .
 The mainframe and casing, together with a motor support
bracket, house the pumping element assembly.
 The volute casing is split in two halves along a vertical plane.
 Since the suction and discharge nozzles are provided in the
rear half of the casing, the rotating element can be taken out
by removing only the front half casing without disturbing
the rest of the pump.

19. Centrifugal pumps - component
parts
 The pumping element is made up of a top cover, a pump
shaft, an impeller, a bearing bush and a sealing arrangement
around the shaft.
 The sealing arrangement may be a packed gland or a
mechanical seal and the bearing lubrication system will vary
according to the type of seal.
 Replaceable wear rings are fitted in the casing around the
top and bottom faces of the impeller.
 The motor support bracket has two large apertures to
provide access to the pumping element, and a coupling
spacer is fitted between the motor and pump shaft to enable
the removal of the pumping element without disturbing the
motor or vice versa

20. Packing

21. Centrifugal Pumps - Double Entry
Pumps