Page 376 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

b Now, electric motor is started to rotate the impeller. The rotation of impeller in a casing (full of liquid), produces
a forced vertex. This force vertex is responsible for imparting the centrifugal head to the liquid. It creates
vacuum at the eye of impeller and causes the liquid to rise into the suction pipe from the water sump.
c The speed of impeller is gradually increased, so that, it can produce sufficient centrifugal head, which can
initiate discharge from delivery pipe.
d When the liquid is being continuously sucked and passes through eye of casing enters at the Centre of impeller
or at inlet tips of vanes of impeller, the delivery valve is opened. This liquid is impelled out by the rotating vanes
and liquid pumps out into the casing.

e Due to impeller action, the pressure head and velocity head of liquid both are increased and liquid passes
through delivery pipe from casing and is lifted to required height and discharge into the overhead tank.
f The liquid is continuously sucked from sump to impeller eye and delivered through the delivery pipe as long
as motion is given to impeller.
g Before stopping the pump delivery pipe should be closed otherwise there may be some backflow of pressurized
liquid from reservoir.

Classification of reciprocating pump, construction and

operation. Installation technique of reciprocating pump.

Tools and equipment required & procedure

Objectives: At the end of this lesson you shall be able to
• explain classification of reciprocating pump, construction and operation
• eemonstrate installation techniques of reciprocating pump
• select tools and equipment required for installation of pump.

Classification of reciprocating pump, construction and operation
Reciprocating - Reciprocating pumps are used where a precise amount of fluid is required to be delivered, also
where the delivery pressure required is higher than can be achieved with other types.
The fluid is moved by the means of a piston that travels in a cylinder. After being drawn into the cylinder through
an inlet valve, the piston continues moving down the cylinder. As the piston moves back up the cylinder, the liquid
is discharged at a preset pressure, controlled by a delivery valve.
The liquid is ejected from the cylinder into the piping system in pulses, which are transmitted to the suction and
discharge piping; therefore, hold-down supports could be required on the piping system on the suction and the
discharge side of the pump. The three classes of reciprocating pumps are piston, plunger, and diaphragm.
Working
To help visualize how a reciprocating pump works, let’s look at a single piston and split the process into four parts.

Action 1: The plunger or piston is pulled back. The action increases the volume of the cavity. As the cavity volume
expands, fluid is drawn in through the inlet to fill the expanding cavity.

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CITS : Automotive - Mechanic Diesel - Lesson 129 - 131