Pumps, a prime mover, pumping system layout.ppt

WEL COME
PERSONALITY DEVELOPMENT AND
VOCATIONAL TRAINING
BY A.Antony Peter
TO

A Pump is a machine ,
when driven from
some external source
like a motor or a
diesel engine lifts
water or liquid from
lower level to higher
level.
A Pump is a machine
which converts
Mechanical energy into
Pressure energy.

PUMP
Pump is a mechanical device to increase the
pressure energy of a liquid. In most of the cases pump is
used for raising fluids from a lower level to a higher level.
This is achieved by creating a low pressure at the inlet or
suction end and high pressure at the outlet or delivery end
of the pump.Due to the low inlet pressure the fluid rises
from a depth where it is available and the high outlet
pressure forces it up to a height where it required

PUMPS
A Pumping system consists of
• Pump
• Prime Mover
• Suction Pipeline
• Delivery Pipeline

Strainer
& foot valve
Pump
Delivery
valve
Delivery pipe
Suction pipe
Layout of a pumping system
SH
Overhead
tank

CLASSIFICATION OF PUMPS
PUMPS
Positive displacement
pump
Rotodynamic pump
Reciprocating
pump
Rotary pump Centrifugal
pump
Axial
pump
Semi
Axial
pump

What is meant by positive displacement pump?
Positive displacement pump means that for changes
in efficiency the pump out let is Constant regardless
of pressure.The out let is positively sealed from the
inlet,So that what ever gets in is forced out through
out let port
Positive Displacement

CLASSIFICATION OF PUMPS
Reciprocating pump
Piston
pump
Plunger
pump
Bucket
pump

RECIPROCATING PUMP
A reciprocating pump consists of a piston
reciprocating inside a close fitting cylinder , thus
performing the suction and delivery strokes. The
reciprocating pump is a positive acting type which
means it is a displacement pump which creates lift and
pressure by displacing liquid with a moving piston. The
cylinder is alternately filled and emptied by forcing and
drawing the liquid by mechanical motion This type is
also called ‘Positive displacement’ pump

Centrifugal pump
Single
Stage
pump
Multi
Stage
pump

i) CENTRIFUGAL PUMP
The Pump which raises water or a liquid from lower level
to Higher level by the action of centrifugal force is known
as Centrifugal Pump.
This above idea of lifting water by centrifugal force was
first given by L.D.Vinci,an Italian Scientist and Engineer.

Centrifugal Pump
Foot valve
Suction Pipe
Pump casing
Delivery pipe
Impeller
+

Principle of operation of
centrifugal pumps
• The pump consists of an impeller which is
mounted in a housing. The impeller is driven at
1775 to 3400 rpm within the housing. The
water is drawn into the impeller and with the
rapid rotation of the impeller. Pressure and
velocity is created and water is thrown
outwards with force.The impeller is the only
moving part in the pump. The pump will not
work against high heads.
• Generally single stage pump is not used for
heads exceeding about 300 feet.

• The basic principle of operation on which a
centrifugal pumps functions :the first step in
operation of a pump is priming. Now the
revolution of the pump impeller inside a casing
full of water produces a forced vortex which is
responsible for imparting a centrifugal head to the
water. Rotation of impeller effects a reduction of
pressure at the center. This causes the water in the
suction pipe to rush into the eye. The speed of the
pump should be high enough to produce
centrifugal head sufficient to initiate discharge
against the delivery head.
Principle of operation of
centrifugal pumps

SUCTION PIPE.
Suction pipe of a centrifugal pump plays an important role.
A poorly designed suction pipe causes insufficient net
positive Suction head, vibration, noise and excess wear.
For this purpose bends in the suction pipe are avoided
and its Diameter is often kept larger.
DELIVERY PIPE.
A check valve is provided in the delivery pipe near the
pump, In order to protect the pump from hammer and also
to regulate The discharge from the pump .
The size and length of the Delivery pipe depends up on
the requirement.

Strainer and foot valve.
• This is fitted at the end of the suction pipe and is
submerged in water in such a way that it is only
a few cm above the bottom of water to be
pumped. The water from the sump or well first
enters the strainer which is meant to keep the
floating bodies away from the pump. In absence
of strainer, the foreign material will pass through
the pump and choke the pump. The cast foot
valve is a non return or one way valve opening
upward only. The water will pass through the
foot valve and will not allow the water to move
downwards.

Suction lift of a pump
• The theoretical suction lift or suction head
is equal to atmospheric pressure divided by
the density of the fluid being pumped. In
case of clean water ( cold ) it is 10.33
meters or 33.9 feet. Hence for other fluids
maximum suction lift is
10.33
specific gravity of fluid
meters

Priming of centrifugal pumps
• The pressure developed by the impeller of
centrifugal pump is proportional to the
density of the fluid in the impeller. If the
impeller is running in air , it will produce
only a negligible pressure, which may not
suck the water from its source. To avoid this ,
the pump is first primed . i.e. filled up with
water.

Single stage pump.
• It has one impeller keyed to the shaft.
This is generally horizontal but can be
vertical also.
• It is usually a low lift pump.

• It has two or more impellers keyed to a single shaft
and enclosed in the same casing. Pressure is built up
in steps.
• The impellers are surrounded by guide vanes and
water is led through a by - pass channel from the
outlet of one stage to the entrance of the next stage
until it is finally discharged into a wide chamber
from where it is pushed on to the delivery pipe.
• The pumps are used essentially for high working
heads and the no of stages depends on the head
required.
Multi stage pump

Volute casing
• In this, the impeller is surrounded by a spiral
casing. Such a casing provides a gradual
increase in the area of flow, thus decreasing
the velocity of water and correspondingly
increasing the pressure.
• But a considerable loss takes place due to
formation of eddies in this type of casing.

Vortex casing
• It is an improved type of volute casing, in
which the spiral casing is combined with a
circular chamber. In this casing , the eddies
are reduced to a considerable extent and an
increased efficiency is obtained.

Volute casing with guide blades
• In this type of casing , there are guide blades
surrounding the impeller. These guide blades
are arranged at such an angle, that the water
enters without shock and forms a passage of
increasing area, through which the water
passes and reaches the delivery pipe.
• The ring of the guide blades is called diffuser
and is very efficient.

Closed impeller pumps
• In this impeller , the vanes are covered with
shrouds on both sides. This impeller is meant to
handle non - viscous fluid such as ordinary water,
hot water and chemicals etc.
• For hot water cast steel impeller is recommended
• Non ferrous impellers are used for chemicals which
are liable to corrode a ferrous surface.
• For pumping acids, the impellers and all inside
surfaces in contact with the liquid should be coated
with stone.

Semi open impeller pump
• The impeller is provided with shroud on one
side only.
• This type of pump is used for viscous liquids
such as sewage water, paper pulp, sugar
molasses etc.

Open impeller pump
• The impeller is not provided with any shroud.
• Such pumps are used in dredgers and
elsewhere for handling mixture of water ,
sand pebbles and clay.
• The impellers has very rough duty to
perform and is generally made of forged
steel.

Check valve
• These are usually known as non
returning or foot valves.
• These are designed to permit fluid flow in
one direction only.
• These valves are used in suction pipes
mainly.

Globe check valves
• These valves are intended to prevent a
reverse flow in the line after a pump has
stopped. Or in the event of a leak.
• These valve prevent dangerous back flow
in a line when two or more fluids are
being supplied to a common point at
different pressures.

Butterfly valves
• These are low pressure valves of
extremely simple design which are used
to control or regulate flow.
• The movement is simple and straight
forward and is used only for 90 degree
rotation of the full movement.

Ball valves
• This valve is frequently used where it is
desired to provide a free opening for
thick liquids.
• The valves are guided in cages and rest in
a free open circular seat.
• The balls are carefully ground and
polished and properly balanced.

Effect of throttling the Valves
• Reducing the pump
capacity by throttling a
gate valve in a suction
line leads to cavitations,
excessive noise and
vibration
• Excessive throttling of a
discharge gate valve
leads to overheating of
the pump since only a
small percentage of the
rated flow is pumped
and the casing may be
unable to radiate enough
heat generated by the
excessive power so that
the temperature is
constant.

Satisfactory operation of a
stuffing box
• A fundamental rule for satisfactory operation of a
stuffing box is that there must be a controlled leakage,
This is necessary because in operation , a stuffing box
is a form of braking mechanism which generated heat.
This friction is held to a minimum by the use of
smooth polished surfaces and continuous supply of
lubricant from the packings to the shaft/ packing
interface. The function of stuffing box leakage is to
assist in lubrication and to carry of the generated heat
maintaining packing pressure at the lowest possible
level helps to keep the heat generation to a minimum.

Centrifugal pumps should not
be operated dry - why ?
• In centrifugal pumps since there is a relative motion
between the surfaces of the stationary and rotating
wear rings, there must be a clearance between
them.Some leakage must therefore occur during
operation.This leakage is necessary to act as a
lubricant and coolant to keep the surfaces separated
and to prevent and seizing of the surfaces.For this
reason , a pump should never be started unless it is
filled with liquid.

• If the discharge valve is closed, the flow
of liquid can be stopped without building
excessive pressure in the casing as the
impeller ids free to rotate in the liquid
resulting in generation of heat.
Centrifugal pumps should not be
operated keeping the discharge
valve- why ?

Radial flow pump.
• Ordinarily all centrifugal pumps are
manufactured with radial flow impellers

Mixed flow pump.
• The mixed flow impeller is just a
modification of radial flow type enabling it
to pump a large quantity of water. Flow
through the impeller is a combination of
radial and axial flows and the impeller
resembles the propeller of a ship.
• Some mixed flow impellers look like a screw
and are known as screw impellers.

Axial flow pumps
• It is a roto dynamic pump, it is hardly
justifiable to call it as a centrifugal pump
because centrifugal force is not called into
play for the generation of pressure.

Operation of reciprocating
pump
• During the suction stroke, the piston moves
towards the right, thus creating vacuum in
the cylinder. This vacuum causes the
suction valve to open and the water enters
the cylinder. During the delivery stroke, the
piston moves towards left, thus increasing
pressure in the cylinder . This increase in
pressure causes the suction valve to close
and delivery valve to open and the water is
forced into the delivery pipe.

o°
90°
180°
270°
Parts of a Reciprocating Pump
Rotating Crank
Suction Pipe
Delivery Pipe
Water Level
Hd
Hs
a
b

JET PUMP
• It is used for lifting water from the deep wells.A
jet pump in its simplest form consists of a pipe
having a convergent end at its bottom. The
upper end of the pipe leads to the required
height.Water under a high pressure is
introduced to nozzle. The pressure energy of the
water is converted in to kinetic energy,as it
passes through the nozzle.As a result of this,the
pressure in the convergent portion of the pipe is
considerably reduced and the water is sucked in
to the pipe.The sucked water after coming in
contact with the jet, is carried in to the delivery
pipe.

Throat
Nozzle
Discharge
Strainer

AIR LIFT PUMP
• Air lift pump utilises the compressed air for raising
water.Because the density of mixture of air in water is
much lower than the pure water.If such a mixture is
balanced against a water column, former will rise much
higher than the later.
• Air lift pump, in its simplest form consists of an open
vertical pipe with its lower end submerged into the liquid
to be raised.The upper end of the pipe leads to the
required height.The compressed air is introduced at the
bottom of the pipe through a nozzle.
• Advantages: It is quite simple in design.
• No moving parts.
• The initial as well as maintenance cost is very less
• Disadvantages: Efficiency of the pump is very low.

AIR WATER
WELL
Nozzle
AIR LIFT PUMP

CENTRIFUGAL PUMP
Low initial cost
Occupies less floor space
Construction is simple
Low maintenance cost
Less wear and tear
Can handle dirty water
Can run at higher speeds
Delivery is continuous
Operation is quite and simple
Needs priming
No air vessel is required
RECIPROCATING PUMP
Initial cost is much higher
Occupies more floor space
Complicated construction
High maintenance cost
More wear and tear
Can not handle dirty water
Can not run at higher speeds
Delivery is pulsating
Care is required in operation
Does not need priming
Air vessel is required
Difference between centrifugal &reciprocating pumps

Selection of pumps
• Nature of liquid to be pumped
Fresh or salt water , acid or alkaline
Cold or hot in condition
Specific gravity of the liquid
Viscous or non - viscous.
• Capacity
Required capacity as well as minimum and
maximum amount of liquid to be pumped
• Suction conditions
Suction head - how much ?
No of bends and elbows in the suction pipe.

Selection of pumps - contd
• Discharge conditions
Delivery head - how much ?
Friction head ?
Length and diameter of delivery pipe ?
• Total head
How much is total head ?

Selection of centrifugal pumps based on
specific speed
S.no Specific speed
in rpm
1 10 to 30 Slow speed pump, with radial flow at outlet
2 30 to 50 Medium speed pump , with radial flow at outlet
3 50 to 80 High speed pump , with radial flow at outlet
4 80 to 160 High speed pump , with mixed flow at outlet
5 160 to 500 High speed pump , with axial flow at outlet
6 Above 500 Very high speed pump.
Type of centrifugal pump

Specific speed of a centrifugal
pump
• The specific speed of a centrifugal pump
may be defined as the speed of an
imaginary pump, identical with the given
pump, which will discharge one liter of
water , while it is being raised through a
head of one meter.
• This helps in selecting the type of
centrifugal pump.

Specific speed of a centrifugal pump
SPECIFIC SPEED NS = N x √Q
(H)¾
N = Actual speed of the pump
Q = Quantity flowing in m³/sec
H = Delivery Head in m

CHECKING FOR PROPER
PUMP ALIGNMENT
• The coupling faces must be checked both
angular and axially.
• The angular alignment can be checked by
using a feeler or taper gauges between the
coupling faces.
• The axial alignment can be checked by
using straight edges and feeler gauges.

SEQUENCE OF OPERATION FOR
PROPER PUMPALIGNMENT
• Grout the bed plate by checking its level on all sides
by using wedges or steel blocks.
• After 3 to 4 days when the grout is set, remove the
wedges and mount the pump.
• Tighten the bolts and check the level again either
with the level or dial indicator.
• In case , some distortion is noticed correct it by
inserting shims and tighten the bolts firmly.
• Check the level again.

S.NO PARAMETERS COUPLEDPUMPS ELECTRICMONOBLOCK
1 Lossofpowerintransmission Upto5%dependinguponalignment Nil
2 Possibilitiesofmisalignment Toooften Nil
3 Matchingofpumpandmotorrating Maynotbecorrect Iscorrect
4 Dangerofoverloading/underloading Veryhigh Nil
5 Maintenance Cumbersome Negligible
COMPARISON OF MONOBLOCK AND
COUPLED PUMPS

0 N 2N 3N 4N 5N
Speed
Q
2Q
3Q
4Q
Discharge
Characteristic curve for Speed verses Discharge

0 N 2N 3N 4N 5N
Speed
H
2H
3H
4H
Head
Characteristic curve for Speed Vs Head

0 N 2N 3N 4N 5N
Speed
P
2P
3P
4P
Power Characteristic curve for Speed Vs Power

TIPS IN PUMPING SYSTEM
• To run the pump at the specified duty point
Deviation on the duty points result in part
load / over load conditions. This will affect the
efficiency of the pumps and motors thereby
power consumption.
• To check up for the mechanical freeness of the
pump and correct clearance I. E. at Bearings ,
Lubricants Gland packing Alignment etc.
Failure on the above will result in increased
friction which will force the pump to consume
more energy.

• To check up regularly for proper functioning of
valves, suction strainers pipelines and other
accessories.
Non compliance of the above will result in change
of pressures which will shift the duty point thereby
the power absorbed will vary.
• To change the wear out components / parts like
impellers, wear rings shaft protection sleeve and
gland packing etc with genuine spares periodically.
Failure of the above will increase the clearances,
excessive leakage will start which will all finally
reduce the efficiency of the pump.

• To run the pump at the specified duty point
Deviation on the duty points result in part load /
over load conditions. This will affect the
efficiency of the pumps and motors thereby power
consumption.
• To check up for the mechanical freeness of the
pump and correct clearance I. E. at Bearings ,
Lubricants Gland packing Alignment etc.
Failure on the above will result in increased
friction which will force the pump to consume
more energy.

ENERGYBALANCE OF A
CENTRIFUGAL PUMP
35
20
15
22
8
Delivered energy Piping Throttling of valves
Pump Motor

TROUBLE SHOOTING CHART
Pump fails Pump delivers Excess leak Heavy noise Bearings
to deliver low quantity in stuffing box or vibration heating up
Pump & suction line not
primed properly * * *
Excessive suction lift * * *
Air leak in suction line *
Foot valve not submerged * * *
Incorrect direction of *
rotation
Gland leak *
Foot valve too small *
Foot valve partly clogged *
Speed too low * *
Impeller is damaged * *
Impeller out of balance * * *
Insufficient or excessive *
lubrication
Bearings incorrectly fitted *
Stuffing box incorrectly *
packed
Pump shaft or sleeve worn *
Nature of trouble
Symptom

Pumps, a prime mover, pumping system layout.ppt

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