Goulds Pumps 3410 - IOM - Manual (Page 24)

DOWELING
Pump units may, if desired, (or required in specification) be
doweled on diagonally opposite feet. This should not be done until the unit has been run for a sufficient length of
time and alignment is within the above alignment tolerance.
SUCTION AND DISCHARGE PIPING
!
Flange loads from the piping system, including
those from thermal expansion of the piping, must
not exceed the limits of the pump. Casing
deformation can result in contact with rotating parts
which can result in excess heat generation, sparks
and premature failure.
The introduction of pumpage into a piping system which is not
well designed or adjusted may cause strain on the pump, leading
to misalignment or even impeller rubbing. Since slight strain may
go unnoticed, final alignment should be done with the system full
and up to final temperature.
Pipe flanges should not impose any strain on the pump. This can
be checked by a dial indicator. Any strain must be corrected by
adjustments in the piping system.
When installing the pump piping, be sure to observe the following
precautions:
Piping should always be run to the pump.
Do not move the pump to pipe. This could make final alignment
impossible.
Both the suction and discharge piping should be independently
anchored near the pump and properly aligned so that no strain is
transmitted to the pump when the flange bolts are tightened. Use
pipe hangers or other supports at necessary intervals to provide
support. When expansion joints are used in the piping system they
must be installed beyond the piping supports closest to the pump.
Tie bolts and spacer sleeves should be used with expansion joints
to prevent pipe strain. Do not install expansion joints next to the
pump or in any way that would cause a strain on the pump
resulting from system pressure changes. When using rubber
expansion joints, follow the recommendations of the Technical
Handbook on Rubber Expansion Joints and Flexible Pipe
Connectors. It is usually advisable to increase the size of both
suction and discharge pipes at the pump connections to decrease
the loss of head from friction.
Install piping as straight as possible, avoiding unnecessary bends.
Where necessary, use 45° or long radius 90° fittings to decrease
friction losses.
Make sure that all piping joints are air-tight.
Where flanged joints are used, assure that inside diameters match
properly.
Remove burrs and sharp edges when making up joints.
Do not “spring” piping when making any connections.
Provide for pipe expansion when hot fluids are to be pumped.
SUCTION PIPING
When installing the suction piping, observe the following
precautions. (See Fig. 14)
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 will flow into the
pump when started and operated.
Many NPSH (Net Positive Suction Head) problems can be
directly attributed to improper suction piping systems.
Suction piping should be short in length, as direct as
possible, and never smaller in diameter than the pump
suction opening. A minimum of five (5) pipe diameters
between any elbow or tee and the pump should be allowed.
If a long suction pipe is required, it should be one or two
sizes larger than the suction opening, depending on its
length.
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CAUTION
An elbow should not be used directly before the suction of
a double suction pump if its plane is parallel to the pump
shaft. This can cause an excessive axial load or NPSH
problems in the pump due to an uneven flow distribution
(See Fig. 13). If there is no other choice, the elbow should
have straightening vanes to help evenly distribute the flow.
Eccentric reducers should be limited to one pipe size
reduction each to avoid excessive turbulence and noise.
They should be of the conical type. Contour reducers are
not recommended.
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3410 IOM 1/2010
Fig. 13