6
PIPE
- can now be installed being sure to support the pipe
independent of the pump. Never use pipe smaller than
pump discharge and suction sizes, and preferably larger
especially on the suction (one or two sizes larger). The
suction line should be laid horizontally or with a gradual
slope upward toward the pump. There should not be any
high spots where air can collect and cause pump to lose
prime. Use eccentric reducers from larger suction pipe to
pump inlet to prevent formation of air pockets in the pipe
(Fig. 6). Run pipe as direct as possible with a minimum
OPERATION
Wire motor according to motor manufacturer’s specifica-
tions and according to state and local regulations. Discon-
nect motor/pump shaft coupling to prevent dry operation
of the pump when checking direction of rotation. Operat-
ing pump dry will cause damage to mechanical seal and
may cause rotating parts to seize. To check direction of
rotation jog motor starter, pump must rotate clockwise
when viewing from the driving end looking over the mo-
tor. Direction arrows are cast in impeller housings.
TO CHECK ROTATION UPON START-UP COU-
PLING SHOULD BE DISCONNECTED. JOG MOTOR
TO CHECK ROTATION. FAILURE TO FOLLOW THIS
PROCEDURE COULD RESULT IN DAMAGE TO THE
PUMP.
of elbows and fitting. Never place a pipe line elbow in
the horizontal plane directly at the pump suction (Fig. 7).
Between the elbow and the pump suction use a straight
pipe four to six pipe diameters long. Suction pipe reduc-
ers should be connected directly to the pump suction
whenever possible. Discharge pipe increasers should be
connected directly to the pump discharge whenever pos-
sible. Whenever possible avoid dynamic suction lifts of
more than 15’. Suction line must be tight for proper oper-
ation of the pump. Install a gate valve in discharge line as
close to the pump as possible, see Fig. 6. If a foot valve
is not used in the suction line, it is good practice to bell
out suction pipe to lower the entrance velocities at the
inlet (Fig. 8). Whenever possible the end of the suction
should be a minimum of 3’ below the low liquid level (Fig.
8). The liquid near the pump suction should be free from
agitation to prevent air entering the suction line. Liquid
coming back into the reservoir should not enter the reser-
voir near the pump suction pipe and the liquid should not
drop from a high level (Fig. 8). NEVER throttle the pump
on the suction side, always control flow by throttling on
the discharge side of the pump.
Fig. 6
Fig. 8
When using a strainer on the suction install it as close to
the pump as possible and select a strainer with a net area
of at least four times that of the suction pipe. It must be
inspected and cleaned regularly. NEVER force piping into
position by pulling it in place with the pump suction and
discharge flange bolts.
Fig. 7
PRIMING
No centrifugal pump will operate satisfactorily until it has
been properly primed. Do not attempt to prime pump
when operating and DO NOT under any circumstances
operate the pump without being completely primed.
Some of the most common methods of priming are
flooded suction, foot valve in suction line, ejector (steam,
water or air operated) and vacuum pump.
With flooded suction, remove the air vent in top of pump
casing to release entrained air.
With foot valve the pump and suction pipe must be filled
with the liquid being pumped. It is recommended to fill
the discharge pipe several feet above the pump dis-
charge, leave vent open while filling pipe and pump. The
pump will remain primed unless the foot valve leaks or if
the liquid is contaminated and does not allow foot valve
to close tight.
