Installation
Model 3410 Installation, Operation, and Maintenance Manual
30
Piping checklist
Check
Explanation/comment
Checked
Check that the elbows in the suction
piping for horizontal double-suction
pumps are installed per the Hydraulics
Institute Standards since there is al-
ways an uneven turbulent 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 impeller than the other. The result is highly
unequalized thrust loads that overheat the bear-
ings and cause rapid wear, which adversely
affects the hydraulic performance. See the Ex-
ample of unbalanced loading figure.
Check that pipe reducers on the inlet
side have no more than one pipe
diameter reduction 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 filled with air and prevent proper opera-
tion of the pump.
(Optional) You can install a short sec-
tion 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 pas-
sage of the pump without dismantling the pump.
With this arrangement, anything that clogs the
impeller is accessible with the removal of the
spool piece or pipe section.
Example of unbalanced loading
CAUTION:
Risk of excessive axial load or cavitation. Do not install an elbow directly before the suction of
a double suction pump if the plane of the suction is parallel to the pump shaft. Alternatively,
install an elbow with straightening vanes to help evenly distribute the flow.
This figure shows the unbalanced loading of a double-suction impeller due to the uneven flow
around an elbow that is adjacent to the pump:
1. Pump casing
2. Impeller
3. Pump suction flange
4. Suction elbow
5. Water velocity increases here and causes a greater flow to one side of the impeller.
Figure 16: Unbalanced loading of double-suction impeller