18
PUMPS cont.
Pump Piping – General:
Caution:
The discharge valve only is to be used to throttle
pump flow, not the suction valve. Care must be
taken in the suction line layout and installation,
as it is usually the major source of concern in
centrifugal pump applications
OPERATION
Starting Pump:
• Ensure that the pump turns freely by hand, or
with some mechanical help such as a strap and
lever on larger pumps. Ensure that all protective
guarding is securely fixed in position.
• The pump must be fully primed on start up. Fill
the pump casing with liquid and rotate the shaft
by hand to remove any air trapped in the
impeller. On split coupled units, any air trapped
in the casing as the system is filled must be
removed by the manual air vent in the seal flush
line. Close-coupled units are fitted with seal
flush/vent lines piped to the pump suction area.
When these units operate residual air is drawn
out of the pump towards the suction piping.
• “Bump” or energize the motor momentarily and
check that the rotation corresponds with the
directional arrow on the pump casing.
• To reverse rotation of a three phase motor,
interchange any two power leads.
• Start the pump with the discharge valve closed
and the suction valve open, and then gradually
open the discharge valve when the motor is at
operating speed. The discharge valve may be
cracked” or open slightly at start up to help
eliminate trapped air.
• When stopping the pump: Close the discharge
valve and de-energize the motor.
• DO NOT run the pump against a closed
discharge valve for an extended period of time.
(A few minutes maximum)
• Should the pump be noisy or vibrate on start-up
a common reason is overstated system head.
Check this by calculating the pump operating
head by deducting the suction pressure gauge
value from the discharge gauge reading. Convert
the result into the units of the pump head as
stated on the pump nameplate and compare the
values. Should the actual pump operating head
be significantly less than the nameplate head
value it is typically permissible to throttle the
discharge isolation valve until the actual
operating head is equal to the nameplate value.
Any noise or vibration usually disappears. The
system designer or operator should be made
aware of this soon as some adjustment may be
required to the pump impeller diameter or drive
settings, if applicable, to make the pump suitable
for the system as installed.
Caution:
Check rotation arrow prior to operating the unit.
The rotation of all Vertical In-Line units is
“clockwise” when viewed from the drive end.
(Looking from on top of / behind the motor)
