Soft foot
133
5.5 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 principal causes are:
› Non-coplanar machine mounting surfaces,
› Deformed machine frame or feet,
› External forces e.g. from connecting pipe or bracket,
› Improper shimming or dirty machine feet.
› Too many shims under a machine foot (a maximum of 3 should be used)
The consequences of forcibly tightening down the feet are deformed machine
frames, bent shafts and distorted bearings. This leads to high vibration and premature
failure.
Soft foot should be checked before aligning the shafts, and this can be done quickly
and conveniently with the aid of the ROTALIGN Ultra iS Shaft soft foot function. With
the sensALIGN laser and sensor mounted on the shaft in the usual way, the system is
able to sense any machine movement when the machine bolts are loosened individu-
ally. By entering the machine dimensions, the computer 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
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
The base of the foot is at
an angle to its foundation
and they are only partly in
contact. In this case, suspect
foot is checked with a feeler
gauge and corrected by
building a custom ‘shim
wedge’ or machining the
underside of the foot
Summary of Contents for ROTALIGN Ultra iS
Page 1: ...ROTALIGN Ultra iS Operating handbook Shaft alignment...
Page 11: ...ROTALIGN Ultra iS Shaft handbook 10 This page intentionally left blank...
Page 56: ...55 Horizontal shaft alignment 1 2 4 5 6...
Page 123: ...ROTALIGN Ultra iS Shaft handbook 122 Page intentionally left blank...
Page 141: ...ROTALIGN Ultra iS Shaft handbook 140 This page intentionally left blank...
Page 177: ...ROTALIGN Ultra iS Shaft handbook 176 Page intentionally left blank...
Page 207: ...ROTALIGN Ultra iS Shaft handbook 206 Page intentionally left blank...
Page 213: ...ROTALIGN Ultra iS Shaft handbook 212 Declaration of conformity...