Page 375 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

Function of casing:

I To guide the water to and from impeller.
II To partially convert the kinetic energy into pressure energy.
Suction pipe with strainer and foot valve
• Suction pipe connects Centre of eye of impeller to sump from which liquid is to be lifted.

• Strainer (filter) is provided at the lower end of pipe to prevent the entry of any debris (mass of loose mud, soil,
rock and other) into the pump.
• A non-return valve is also providing at the lower end if pipe which allows the flow of water only in upward
direction.
Function of NRV (non-return valve)
i This valve does not allow the liquid to drain out from suction pipe when pump is not working.
ii This valve is help in priming.

Delivery pipe
• Delivery pipe is connected at its lower end to the outlet of pump and delivers the liquid to required height
(Overhead tank).

• A delivery valve is provided in the delivery pipe near the outlet of pump.
Function of delivery pipe
To regulate the supply of liquid from pump to delivery pipe.
Principal of centrifugal pump
When a certain mass of fluid is rotated by an external source, it is thrown away from the central axis of rotation
and centrifugal head is impressed, which enables the fluid to rise to a higher level
Working of centrifugal pump

a Initially, delivery valve is closed to reduce starting torque of motor and pump is primed, like suction valve,
casing and portion of delivery pipe up to the delivery valve are completely filled with liquid to be pumped. This
is done to ensure that, no air pocket is present in this portion.

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CITS : Automotive - Mechanic Diesel - Lesson 129 - 131