Flowserve Twin Screw Rotary - Manual (Page 24)

TWIN SCREW PUMPS. ORIGINAL USER INSTRUCTIONS. ENGLISH. 71569243 – 07/10
Page 21 of 53
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4.5 Initial alignment
4.5.1 Thermal expansion
The pump and motor will normally
have to be aligned at ambient temperature and should
be corrected to allow for thermal expansion at
operating temperature. In pump installations involving
high liquid temperatures, the unit should be run at the
actual operating temperature, shut down and the
alignment checked immediately.
4.5.2 Alignment methods
Ensure pump and driver are isolated
electrically and the half couplings are disconnected.
The alignment MUST be checked.
Although the pump will have been aligned at the
factory it is most likely that this alignment will have
been disturbed during transportation or handling. If
necessary, align the motor to the pump, not the pump
to the motor.
Direct Driven Units:
The importance of accurate alignment of pump and
driver shafts cannot be overemphasized.
IMPROPER ALIGNMENT IS THE PRIMARY CAUSE
OF VIBRATION PROBLEMS AND REDUCED
BEARING LIFE.
A flexible coupling is used to compensate for slight
changes in alignment which occur during normal
operation and is not used to correct for installation errors.
Install the pump and driver half couplings in accordance
with the coupling manufacturer's instructions. Note that
the coupling hub faces are not always mounted flush with
the ends of the shafts. Place the driver on the baseplate
such that the correct spacing is obtained between the
two half couplings. In the case of electric motors, such
as those with sleeve bearings, it may be necessary to
run the motor to establish the rotor magnetic center.
Consult the manufacturer's instruction manual for details.
The purpose of the alignment procedure is to ensure that
the pump and driver shafts are in parallel and angular
alignment under the normal operating conditions of load
and temperature. (See Fig. 2)
When the pump coupling and driver are assembled at
the factory, the units are aligned prior to shipment.
However, baseplates can be sprung or distorted during
shipment or installation and the alignment must be
checked before the unit is put in service. The coupling
spacer must be removed to make this check.
Figure 2
For pumps and drivers which operate at different
temperatures compensation must be made at the initial
alignment stage (when the units are at the same
temperature) to allow for thermal expansion during
operation. Consult the instruction manual supplied with
the driver for the manufacturer's recommendations.
Shaft alignment is greatly simplified by the use of a dial
indicator, or with extension rods and a magnetic base.
Before taking readings, ensure that the pump and driver
mounting bolts are secure, and that the thrust bearing
housing is properly aligned in the bearing frame or
cartridge. (See Section
6 MAINTENANCE ).