Fluke db PRUFTECHNIK SHAFTALIGN touch, Manual

Page: 95 / 127

What is soft foot
Soft foot is the condition of machine frame distortion. Any cause that results in machine frame
distortion when the machine is anchored to its foundation is a soft foot. Some of the principal
causes are:
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Non-coplanar machine mounting surfaces
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Deformed machine frame or feet
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External forces e.g. from connecting pipe or bracketry
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Improper shimming or soiled machine feet
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Too many shims under a machine foot (a maximum of 5 shims should not be exceeded)
The consequences of forcibly tightening down the feet are deformed machine frames, bent
shafts and distorted bearings. This leads to high vibration and premature machinery failure.
Soft foot should be checked before aligning the shafts. This can be done quickly and con-
veniently with the aid of the soft foot function. With the sensor and reflector mounted on the
shaft in the usual way, the system is able to sense any machine movement when the machine
bolts are loosened individually. By entering the machine dimensions, the rugged device is able
to calculate, from shaft movement, by how much each foot has moved as it is loosened.
Once foot movements have been established, the results are interpreted and translated into
shim thicknesses to be placed under the feet. How straightforward this is, depends on the type
of soft foot present.
Parallel soft foot
In parallel soft foot, one or more feet are too short or too long. This usually results in the
machine rocking on the longer feet. This is corrected by shimming the shorter feet.
Angular soft foot
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