Check
Explanation/comment
Checked
Do not connect the piping to the
pump until:
•
The grout for the baseplate or
sub-base becomes hard.
•
The grout for the pit cover be-
comes hard.
•
The hold-down bolts for the
pump are tightened.
—
This helps to prevent misalignment due to thermal expansion
of the piping.
Make sure that all piping compo-
nents, valves and fittings, and pump
branches are clean prior to assembly.
—
4.5.2 Suction piping checklist
The sizing and installation of the suction piping is extremely important. It must be selected and installed
so that pressure losses are minimized and sufficient liquid flows into the pump when it is started and op-
erated. Many NPSH problems can be directly attributed to improper suction piping systems.
CAUTION:
•
Flange loads from the piping system, including those from the thermal expansion of the
piping, must not exceed the limits of the pump. Deformation can result in contact with ro-
tating parts, which can result in excess heat generation, sparks, and premature failure.
•
Air pockets can form in the top of the reducer and the pipe when operating on suction lift.
Never use a concentric reducer in a horizontal line.
Piping checklist
Check
Explanation/comment
Checked
Check that the elbows in the suction piping
for horizontal double-suction pumps are in-
stalled per the Hydraulics Institute Stand-
ards since there is always an uneven turbu-
lent flow around an elbow.
When there is an elbow in a position other than the
vertical when in relation to the pump suction nozzle,
this causes more liquid to enter one side of the impel-
ler than the other. The result is highly unequalized
thrust loads that overheat the bearings and cause
rapid wear, which adversely affects the hydraulic per-
formance. See the Example of unbalanced loading
figure.
Check that pipe reducers on the inlet side
have no more than one pipe diameter re-
duction in a single reducer.
This avoids excessive turbulence and noise.
When operating on a suction lift, check that
the suction pipe slopes upward to the pump
nozzle.
A horizontal suction line must have a gradual rise to
the pump. Any high point in the pipe can become fil-
led with air and prevent proper operation of the pump.
(Optional) You can install a short section of
pipe adjacent to the suction flange such as
Dutchman or a spool piece that is designed
so that it can be readily dropped out of the
line.
This facilitates the cleansing of the liquid passage of
the pump without dismantling the pump. With this ar-
rangement, anything that clogs the impeller is acces-
sible with the removal of the spool piece or pipe sec-
tion.
4.5 Piping checklists
34
Model 3410 Installation, Operation, and Maintenance Manual
