Page 285 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

– Cooling is effectively done by water only.

– Can be used for lifting water from any depth of sump or borewell as suction pipe is not used.
Disadvantages
– Erection cost and initial cost of purchasing will be high.
– In case of any defects, it is necessary to remove entire unit along with the pipe line.

– Requires skilled worker for both erection and maintenance work.
Jet pumps : Another variety of centrifugal pump commonly used in the domestic wells an d borewells is the jet
pump. In jet pumps, the motor and pump are assembled together in one block (Fig 4).

Fig 4

The bottom portion of the pump has two connecting pipes. One is called suction pipe and the other is called
ejection pipe. A portion of the water is sent through the ejection pipe to the jet assembly and it aids the water in
the suction pipe to be lifted upwards by Venturi principle.
Suction, ejection and delivery pipes and motor capacity could be selected with the help of the performance

Table 1.
Almost all types of pumps may be independent units to be coupled with an electric motor through belts or couplings
or may be single(mono) blocks comprising both motor and pumps.

Location of pump set : The pump should be installed as near as possible to the water source in order to reduce
the suction lift and to achieve better performance.
Ample space should be provided around the pump for easy inspection and maintenance whenever required.

Before starting the pump ensure that.
– Shaft rotates freely by hand.
– The gland box is properly tightened.
– The valve, if there is any on the delivery branch, is opened.
Check the following during running condition.
– The direction of rotation is correct.

– Pump is running smoothly.
– Leakage of stuffing box is normal ie., 50 to 60 drops per minute in gland packed pump.
– The ball bearings do not get excessively hot.

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CITS : Power - Electrician & Wireman - Lesson 101-103