Page 164 - Know and Understand Centrifugal Pumps

Pump and Motor Alignment

General observations on the alignment process between shafts
1. The alignment procedure should be repeated at various intervals to
identify installation errors and compensate for equipment operation.
This is the way to assure long equipment life. It is recommended to
go through the alignment procedure and make corrections in the
following stages:
w At Pump Installation: Be sure the motor shaft centerline is
below the pump shaft centerline so that it can be shimmed
upward. Make sure the motor mount boltholes have sufficient
play to allow for some lateral adjustment. Many pumps and
motor assemblies are shipped from the factory on a common
channel iron base plate. The manufacturer alleges that they are
already aligned at the factory. You need to verify and correct this
alignment in all cases.
w Mer connecting the piping and accessories: Before starting the
pump, repeat the procedure after all associated connections have
been made. If there is a marked difference, the problem may be
pipe strain distorting the pump casing through the suction and
discharge nozzles. This situation should be resolved with the
installation contractor or pipe fitters. Not correcting this
situation is sure to bring future maintenance problems from
misalignment.
Hot alignment: Allow the equipment to run for three or four
hours and come up to operating temperature, then shut-off the
pump and repeat the alignment procedure with the equipment
hot.

Running alignment: Mer the pump has been running for a
week or ten days, perform an alignment check to verify that the
equipment is not suffering pipe strain or binding from thermal
growth.
2. The base and cement foundation should be examined to verify a
correct installation. The pump and motor assembly should rest on a
common base.
w The base should be sufficiently strong to withstand the
machinery weight and minimize vibrations. Five times the mass
is the rule. If the pump, motor, and base plate weighs 1,000 lbs,
the foundation should weigh at least 5,000 lbs.
The base should be level and flat.
The base should be the proper size. This varies according to its
size and weight. It should have enough free adjacent space to
perform maintenance, alignment and proper cooling.

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