Here a clear idea has been given about Centrifugal Pump and Reciprocal Pump.

1. Introduction:
Pump: A pump is a contrivance which provides energy to a fluid in a fluid system; it assists to increase
the pressure energy or kinetic energy, or both of the fluid by converting the mechanical energy.
Two types of pump are found:
i. Centrifugal Pump,
ii. Reciprocating Pump.
Objectives:
1. To know the characteristics and uses of pump.
2. To know the basic differences between Centrifugal and Reciprocating Pump.
3. To know the basic mechanism of both pumps.
Centrifugal Pump: A centrifugal pump is a pump which raises the water from a lower level to a higher
level by the action of centrifugal force.
Figure:Centrifugal Pump
Figure: Impeller

2. Mechanism of Centrifugal Pump:
Principle Parts of Centrifugal Pump:
 Impeller with its shaft
 Volute Case.
The mechanism of a centrifugal pump is explained step-wise below:
1. The delivery valve is closed and the pump is primed that is, suction pipe, casing and portion of the
delivery pipe up to the delivery valve are completely filled with the liquid (to be pumped) so that no air
pocket is left.
2. Keeping the delivery valve still closed the electric motor is started to rotate the impeller. The rotation
of the impeller causes strong suction or vacuum just at the eye of the casing.
3. The speed of the impeller is gradually increased till the impeller rotates at its normal speed and
develops normal energy required for pumping the liquid.
4. After the impeller attains the normal speed the delivery valve is opened when the liquid is
continuously sucked (from sump well) up the suction pipe, it passes through the eye of casing and enters
the impeller at its center or it enters the impeller vanes at their inlet tips. This liquid is impelled out by
the rotating vanes and it comes out at the outlet tips of the vanes into the casing. Due to impeller action
the pressure head as well as velocity heads of the liquid are increased (some of this velocity heads is
converted into pressure head in the casing and in the diffuser blades/vanes if they are also provided).
5. From casing, the liquid passes into pipe and is lifted to the required height (and discharged from the
outlet or upper end of the delivery pipe).
Figure:Parts of Centrifugal Pump

3. 6. So long as motion is given to the impeller and there is supply of liquid to be lifted the process of
lifting the liquid to the required height remains continuous.
7. When pump is to be stopped the delivery valve should be first closed, otherwise there may be some
backflow from the reservoir.
Reciprocating Pump:
The reciprocating pump is a positive displacement pump as it sucks and raises the liquid by actually
displacing it with a piston/plunger that executes a reciprocating motion in a closely fitting cylinder.
Mechanism of Reciprocating Pump:
Figure:ReciprocatingPump
Figure: Reciprocating Pump

4. This pump consists of a mechanical device that moves a plunger back and forth in a closely fitted
cylinder. The plunger is driven by the power source, and the power motion is converted from a rotating
action to a reciprocating motion by the combined work of a speed reducer, crank, and a connecting rod.
The cylinder, composed of a cylinder wall, plunger, and check valve, should be located near or below
the static water level to eliminate the need for priming. The pumping action begins when the water
enters the cylinder through a check valve.
When the piston moves, the check valve closes, and in so doing forces the water through a check valve
in the plunger. With each subsequent stroke, the water is forced toward the surface through the discharge
pipe.
Conclusion:
i. From this lab experiment I’ve learnt about two types of pump. These are centrifugal pump and
reciprocating pump. Though we were not able to do this experiment practically, by the help of
internet as well as theoretical study, we got a clear idea about these pumps. We came to know
about the mechanism of these pumps as well as about the parts.
ii. Basic difference between Centrifugal pump and Reciprocating pump are given below:
Centrifugal Pump Reciprocating Pump
a. It is one of the rotary pumps which
used kinetic energy of impeller.
a. It is a positive displacement type pump
which is forced by piston.
b. It continuously discharges the fluid. b. It does not discharge the fluid
continuously.
c. Centrifugal pump have problem of
priming.
c. It does not have any problem of
priming.
d. It uses impellers to transfer energy to
fluid.
d. It uses piston cylinder device to transfer
energy to fluid.
e. These pumps required less
maintenance.
e. These required higher maintenance.
f. Centrifugal pumps are easy to install.
These required less floor space.
f. These pumps are difficult to install.
These required more floor area.
iii)
Uses of Centrifugal Pump:
1. Oil refineries and power plants.
2. Municipal water applications.
3. They are used to move the general water supply from the pressure main in cases where a little or
no suction lift is required.
4. They can also be used for boiler feed applications, wastewater management, flood protection,
drainage and irrigation.

5. 5. Centrifugal pumps also have numerous building applications. They are used to provide booster
service into homes. They are also used in fire protection sprinkler systems or to circulate hot
water. They can also be used for drainage and air conditioning systems.
Uses of Reciprocating Pump:
In various purpose reciprocating pump are used. These are respectively agriculture. Chemical,
desalination, horizontal drilling, general industries, mining, oil and gas refineries, pulp and paper, sewer
cleaning. To use water in these various purpose reciprocating pump are used. The total efficiency of a
reciprocating pump is about 10 to 20% higher than a comparable centrifugal pump.
Prepared by
Md. Asiqul Alam
B.Sc in Textile Engineering
Port City International University, Chittagong