Specifications

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(d) Pump stops delivering after running for sometime: Leaks in the suction side especially
joints. Check if sufficient water is in the well. Check motor control circuits and protection circuits.
(e) Pump vibrates badly : Check alignment, bed bolts not tightened properly, impellers not
properly balanced. Check for worn out bearings or bent shaft. Bearings may have excessive
clearances; shaft couplings are not properly assembled. Impeller may have been choked.
(f) Pump is noisy in operation : Check all points under item (e) above. The impeller may be
touching the casing. Air-bubbles may be passing through the pump. Cavitation effect due to bad
design.
(g) Pump motor getting overloaded and becoming hot : Voltage at the motor terminals may
be too low. Pump delivering water at reduced delivery head. Single phasing in case of 3-phase
motor. Check voltages on all three phases. In case of 3-phase motor, used after overhauling,
coil connections may not have been proper. Incorrect size of impeller. Excessively tight stuffing
box, seized spindle or insufficient seepage.
(h) Excessive corrosion : This may be due to presence of certain chemicals in the water.
Stainless steel may be used for certain parts of the pump.
(i) Excessive scoring of impeller parts. : Due to passage of sand or gritty matter. Due to
cavitation efforts, especially if at the tips.
(j) Cracked pipe flanges: Due to excessive strain on the flanges caused by improper method
of supporting the pipes, improper alignment of joint surfaces, and use of excessive force to
bring the flange holes to align when bolting. Due to water – hammer action. Due to excessive
vibration.
QUESTIONS
Part - A
Choose the Correct Answer (1 Mark)
1. The part due to which water gets the centrifugal force is called
A) Casing or volute B) stuffing box C) spindle D) impeller
2. The purpose of the gland packing rope is to
A) Prevent impeller from coming out B) Prevent leakage of water from
the casing near the spindle
C) Provide lubrication to the spindle D) Prevent air leakage from the casing.
3. Impeller is generally made of
A) Galvanised steel B) Bronze C) Cast iron or gun metal D) Copper alloy