How to Align Your Shafts?
By: Thomas Yoon
In the last issue, we discuss about shaft seals and how liquid
is prevented from coming out from the pump housing even though
the shaft is rotating.
Some mechanical seals are made to very fine tolerances. Damage
to mechanical seals and bearings can sometimes be cause by the
misalignment of pump shaft with the motor shaft.
Whenever some of the motors or driven machinery is dismantled
or even when the machines are not running smoothly, alignment
has to be done.
The purpose of alignment is to ensure that the centerline of
the motor rotor shaft coincides exactly with the centerline of
the driven machinery. Alignment is essential to ensure that the
machine runs smoothly with minimum vibration.
Provided the two shafts are not bent crooked, the two alignments
to be checked and adjusted are: Offset alignment and Angular
Most alignments are rough alignment that can be done using
straight edge ruler and feeler gages. However for precision
alignment, the use of dial gauges with magnetic bases can be
The radial alignment is checked using a straight edge ruler. By
placing the ruler across the coupling halves at the top, bottom
and both sides any gaps between the 2 coupling halves will
indicate that the shaft is offset slightly. The misalignment can
be corrected by shifting the motor or by putting shims to raise
up the motor or driven machine.
By inserting a feeler gauge between the coupling faces and rotate
both coupling halves simultaneously we can check whether the
shafts have any angular displacement between them. The feeler
gauge readings at checked at four points on the shaft coupling.
Again the alignment is corrected by shimming or shifting the
The motor and the driven machine should be bolted solidly to the
base after finalizing the alignment positions of the equipment.
For more information on alignment and the
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