Siemens Flender H2NV Series, Assembly And Operating Instructions Manual, Page: 36 / 62

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BA 5060 EN 04/2011
6.9 Screw­connection classes, tightening torques and initial­tensioning forces
6.9.1 Screw­connection classes
The specified screw connections are to be fastened applying the tightening torques specified in the table
below.
Table 7: Screw­connection classes
Screw-
connection
class
Distribution of
emitted torque on
the tool
Tightening procedure
(Usually the tightening processes lie within
the stated tool distributions)
C ± 5 % up to ± 10 %
‐ Hydraulic tightening with mechanical screwdriver
‐ Torque-controlled tightening with torque wrench
or signal-emitting torque wrench
‐ Tightening with precision mechanical screwdriver
with dynamic torque measuring
D ± 10 % up to ± 20 %
‐ Torque-controlled tightening with mechanical screwdriver
E ± 20 % up to ± 50 %
‐ Tightening with pulse screwdriver or impact wrench
without adjustment checking device
‐ Tightening by hand, using a spanner without torque
measuring device
Foundation bolts, hub bolts and bearing­cover bolts must always be tightened in
accordance with screw­connection class "C"!
6.9.2 Tightening torques and initial­tensioning forces
The tightening torques apply to friction coefficients of μ
total
= 0.14.
The friction coefficient μ
total
= 0.14 applies here to lightly oiled steel bolts, black­annealed or
phosphatised and dry, cut mating threads in steel or cast iron. Lubricants which alter the friction
coefficient must not be used and may overload the screw connection.
Table 8: Initial­tensioning forces and tightening torques for screw connections of strength classes
8.8; 10.9; 12.9 with a common friction coefficient of μ
total
= 0.14
Nominal
thread
diameter
Strength
class
of the bolt
Initial-tensioning force
for screw-connection classes
from table 7
Tightening torque
for screw-connection classes
from table 7
C D E C D E
d
mm
F
M min.
N
M
A
Nm
M10
8.8 18000 11500 7200 44.6 38.4 34.3
10.9 26400 16900 10600 65.4 56.4 50.4
12.9 30900 19800 12400 76.5 66.0 58.9
M12
8.8 26300 16800 10500 76.7 66.1 59.0
10.9 38600 24700 15400 113 97.1 86.6
12.9 45100 28900 18100 132 114 101
M16
8.8 49300 31600 19800 186 160 143
10.9 72500 46400 29000 273 235 210
12.9 85000 54400 34000 320 276 246
M20
8.8 77000 49200 30800 364 313 280
10.9 110000 70400 44000 520 450 400
12.9 129000 82400 51500 609 525 468
M24
8.8 109000 69600 43500 614 530 470
10.9 155000 99200 62000 875 755 675
12.9 181000 116000 72500 1020 880 790