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Thermal expansion should be taken into account when aligning the machine. The
temperature of the machine is lower during installation than it will be during
operating conditions. For this reason the shaft centre is going to lie higher when
the machine is in operation. Depending on the type of coupling, the distance
between the machine and the driven equipment may have to be compensated
because of thermal expansion. The upward thermal expansion of the electrical
machine can be estimated using the following formula:
H=a
T
H [mm]
Where:
a = 10
10
-6
K
-1
T
= 40 K
H =
shaft height [mm]
Due to the thermal expansion of the electrical machine, the vertical movement of
the shaft is approximately 0.04-0.05 mm for each 10 °C difference in temperatures
as illustrated in
Figure 3-6. The correlation between thermal expansion and
machine temperature rise.
0,00
0,05
0,10
0,15
0,20
0,25
0,30
0,35
0
5
10
15
20
25
30
35
40
45
50
55
Temperature increase/[K]
Th
er
m
al
e
xp
an
si
on
/[m
m
]
AMG 0180
AMG 0200
AMG 0250
AMG 0280
AMG 0315
AMG 0355
AMG 0400
AMG 0450
AMG 0500
Figure 3-6. The Correlation between thermal expansion and machine temperature
rise.
Permissible misalignment
Definite alignment tolerances are impossible to state as too many factors have an
influence. Too large tolerances will cause vibration and may possibly lead to
bearing or other damages.
Therefore, it is recommended to aim at as narrow tolerances as possible.
Maximum permissible misalignments are shown in
Table 3-1. Recommended
permissible misalignments.
For definitions of misalignment, see
Figures 3-3.
Checking of misalignment of coupling discs
and
3-4. Definition of misalignment.
NOTE: Tolerances given by the coupling manufacturers indicate tolerances for
the coupling, not for the driving-driven machine alignment. The
tolerances given by the coupling manufacturer should be used as a
guideline for the alignment only if they are narrower than the maximum
