Runout

With the coupling disconnected, mount the
magnetic base of the dial indicator to the motor
half coupling, position the indicator on the pump
half coupling and center the indicator plunger.

Rotate the pump shaft until the dial indicator
reaches a maximum travel, then zero the dial indicator.
Rotate the pump shaft again until the dial
indicator reaches a maximum value. This shows the
amount of runout.

If the runout on the pump side is in excess of
the acceptable limit of 0.002”, the pump shaft runout
should be checked as above, except with the dial
indicator applied to the shaft. If the shaft runout is
0.001” or less, the shaft can be considered acceptable,
but the coupling is eccentric. If, however, the
shaft runout is greater than 0.001”, the shaft should
be straightened. By switching the position of the
dial indicator, the driver shaft can be checked in the
same manner with the same limitations.

Soft Foot

To check for soft foot prior to alignment, when
there are no shims under the motor feet, start by
trying to fit a 0.005” shim under each foot. If the
shim fits under a foot, make up the gap by gradually
increasing the shim thickness until a tight fit is
achieved. If shims are already in place, ensure that
there are no more than four of them in any one
location. If there are, consolidate them by using
thicker shims. Check at each foot for loose shims
and make up the gap by gradually increasing shim
thickness until a tight fit is achieved at all feet.

A final soft-foot check should be performed
only after any vertical angular misalignment has
been corrected. When that has been achieved,
mount the dial indicator to contact the foot to be
checked and set the indicator to zero. Loosen the
hold-down bolt on that foot and record the dial
indicator reading, then retighten the hold-down
bolt. Repeat this process with all four feet.

Soft-foot conditions in excess of 0.002” should
be corrected by adding shims to the foot with the
largest soft-foot value. Note that excess shims will
result in increased soft foot at the other feet. Check
other feet and make any necessary corrections.

But, Let’s Be Practical. While dial indicators are
still a viable method of establishing shaft alignment,
laser alignment systems are now providing increased
accuracy that reduce maintenance costs
while improving reliability. In today’s workplace,
where fewer people are expected to do more, these
systems reduce the time it takes to achieve a high
level of accuracy—and do so without the need for
mathematical graphing and calculating expertise.