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selected. The usual method for increasing
NPSH is to raise the static head on the
pump inlet, (H
s
).
By definition, NPSH means: “net positive
suction head” above the vapor pressure
of the pumped liquid available at the cen-
terline of the pump. It should always be
given in feet of pumped liquid. The NPSH
is actually a measurement of the amount
of energy available in the pumped liquid
to produce the required absolute entrance
velocity in the pump. If a pump requires
more energy (or NPSH) than is available
at a given capacity, the pressure at the in-
let will fall below the vapor pressure of the
pumped liquid and loss of performance
will result.
P
s
= Pressure in the suction vessel in
PSIA.
P
vp
= Vapor pressure of the pumped fluid
in PSIA.
H
s
= Static height of the pumped fluid
above (+) or below (-) the centerline of the
pump.
H
f
= All friction losses from the vessel to
the pump.
NPSH = 2.31( )+ H
s
- H
f
For boiling liquids, P
s
and P
vp
are equal.
This item then becomes zero and can be
omitted from the equation.
1D6 Noise
Regenerative turbine pumps typically pro-
duce a high pitched whine that increases
in intensity as the differential pressure pro-
duced in the pump increases. While high
frequency sound is attenuated more easily
than lower frequencies, piping structures
and the fluids in them readily transmit
noise. Motors, bearings, and other rotating
components add to noise and sometimes
create objectionable harmonics.
Careful pump installation can contribute to
noise reduction. Proper alignment of the
pump and driver is essential.
Adequate supports for the inlet and
discharge piping is equally important.
A degree of noise reduction may be
obtained when the pumping unit is sup-
ported free of building structures by the
use of vibration isolators, flexible piping
and conduit connections. Elastomer type
couplings are the best choice to separate
motor noises from the fluid and piping
structure.
1D7 Freezing
When ambient temperatures drop below
the freezing point of the fluid in a pump,
consideration should be given to heating,
insulating, or draining the pump. If you
choose draining the pump, and it will only
be for a short period, first remove the
drain plugs and drain the lines to and from
the pump. Carefully blow out the pump
with compressed air to clear all internal
cavities of fluid.
1E Recommended Spare Parts
FOR CRITICAL SERVICES - a duplex in-
stallation, with two identical pumping units
P
s
- P
vp
sp. gr.
in parallel, is the safest and many times
the most cost effective choice.
FOR IMPORTANT SERVICES - a stand-
by pump, ready for installation is advised.
Special pricing and new pump warranty is
offered for factory rebuilding. Turn around
time can be as short as one or two days
for standard models.
FOR ROUTINE MAINTENANCE - only
the mechanical seals and a complete set
of “O” ring gaskets are recommended.
Should additional components show
wear, they are available from stock at the
factory.
FOR SERVICING A PUMP THAT DOES
NOT PRODUCE RATED HEAD - me-
chanical seals, “O” ring gaskets, impeller,
motor bracket, and cover.
FOR REBUILDING A PUMP - all the
components required for servicing plus
bearings, shaft, and drive keys for flexible
coupled pumps, should be obtained.
(A factory rebuild should be considered
whenever your disassembly indicates
rebuilding is necessary as this is usually
more economical.)
The factory recommendation for spare
parts are all of those needed for rebuilding
a pump and are shown on the exploded
view drawings for each individual type of
pump.
T31 SERIES
Installation
CLOSE COUPLED PUMPS
FLEXIBLE COUPLED PUMPS
A.
Location
B.
Foundation
C.
Leveling
D.
Alignment
E.
Piping
In order to insure that pumping equip-
ment is installed properly and to obtain
reliable pump operation, it is recom-
mended that only experienced, qualified
erecting engineers undertake this task.
Read the instructions thoroughly before
beginning.
2A Location
The first consideration for locating a
pump is elevation. The lowest possible
elevation using the shortest possible
suction piping is usually the best. Ques-
tions regarding possible locations should
be resolved by making inlet head calcu-
lations including all friction losses. The
one producing the highest inlet pressure
should be selected. One reason for this
precaution is that, the greater the inlet
pressure, the less likelihood of NPSH
problems. Also a flooded suction is
particularly helpful on start-up when the
seals or the entire pump can be ruined
because it is not properly primed and
purged of air.
A dry, easily accessible location is
also important. Allow ample clearance
around the unit for free air circulation. If
a dry location is not available, the pump
can be mounted on a foundation, above
the floor. Specify motor enclosure, pump
materials, or coatings to suit the worst
conditions expected. Place the pump
so that it can be easily inspected and
serviced during operation. Sufficient
head room should be provided, particu-
larly when lifting devices will be used for
heavier assemblies.
2B Foundation
Baseplates alone are not rigid enough
to maintain alignment of the unit. The
pump foundation is used as a support
for the baseplate to maintain align-
ment of the unit. If the baseplate is to
be grouted to the foundation, it is only
necessary to embed the edges. It is
unnecessary to completely fill under the
baseplate. DO NOT grout the unit to
the foundation until it has been properly
aligned.
The foundation must be a permanent
rigid installation of concrete or other
material of sufficient mass to absorb all
normal vibrations. Locate the founda-
tion bolts using a layout or template in
relation to the suction and discharge
piping. If concrete is being used,
foundation bolts of the specified size
can be enclosed in a pipe sleeve two
to three diameters larger than the bolts
to compensate for minor variations in
alignment.
Close coupled pumps can be mount-
ed on a steel base prior to installation
or mounted directly to the foundation.
Place shims under one or more of the
motor feet so that strain and distortion
will not result when the mounting bolts
are tightened.
2C Leveling (Flexible Coupled Pumps
Only)
If the unit is received with the pump and
motor mounted on the baseplate:
1. Place the unit in position.
2. Disconnect the coupling halves. Do
not reconnect until all alignment
procedures have been completed.
2.
