07
SUCTION PIPING:
1. Properly installed suction piping is necessary for
trouble-free pump operation. Flush suction piping before
connection to the pump.
2. Never place a pipe line elbow in the horizontal plane
directly at the pump suction. Use a straight pipe 4 to 6
pipe diameters long between the elbow & the pump
suction.
3. Use suction pipe one or two sizes larger than the pump
suction, with an eccentric reducer, sloping side down, at
the suction flange (Fig. 7). Suction piping should never be
smaller than the pump suction.
4. Never throttle pump on the suction side, always control
flow by throttling on the discharge side of the pump.
When using a strainer on the suction, install it as close to
the pump as possible & select a strainer with a net area of
at least four times that of the suction pipe.
5. Whenever possible the end of the suction should be a
minimum of 3’ below the liquid level (Fig 5). The liquid
near the pump suction should be free from agitation to
prevent air entering the suction line.
6. Liquid coming back into the reservoir should not enter
near the pump suction pipe, & the liquid should not drop
from a high level (Fig. 6).
7. If a foot valve is not used in the suction line, it is good
practice to bell out the suction pipe to lower the entrance
velocities at the inlet (Fig. 5).
Fig. 5
SUCTION LIFT CONDITIONS
1. Pipe must be free from air pockets.
2. Pipe must slope upwards to pump.
3. All connections must be air tight.
4. Whenever possible avoid dynamic suction lifts of more
than 12’.
5. A means of priming the pump must be provided.
SUCTION HEAD/SUCTION CONDITIONS
1. An isolation valve should be installed in the suction
pipe at least four diameters from the suction to allow
closing of the line for pump inspection and maintenance.
2. Pipe must be free from air pockets.
3. Piping should be level or slope gradually downward
from the source.
4. No part of the piping should extend below pump
suction flange.
5. The size of the entrance from the supply should be one
or two sizes larger than the pipe.
6. To prevent vortices and air entrainment at the supply,
the entrance from the supply must be adequately
submerged below the liquid surface.
DISCHARGE PIPING
1. A gate valve & check valve should be installed in the
discharge line. The check valve should be installed
between the gate valve and the pump (Fig. 6) this will
allow for inspection of the check valve. The gate valve is
required for priming, flow regulation, & for maintenance
of the pump. The check valve is required to prevent pump
or seal damage from reverse flow through the pump
when the motor is turned off.
2. Discharge pipe increasers should be connected
between the pump & the check valve (Fig.7).
3. If quick closing valves are installed in the system, cush-
ioning devices should also be installed to protect the
pump from surges & water hammer.
Fig. 6
FINAL PIPING CHECK
After all piping connections have been made to the
pump:
1. Rotate the shaft by hand to ensure that there is no
binding and all parts are free.
2. Recheck pump alignment to detect any pipe strain, if
pipe strain exists correct piping.
NPSHA must always exceed NPSHR as shown on
performance curves. Reference Hydraulic Institute for
NPSH and pipe friction values needed to evaluate
suction piping.
! WARNING !
Return
Return
Wrong
Correct
D/2
3” Min
Low Liquid
Level
D
