SIEMENS
FLENDER Standard Couplings
Coupling Preselection and Options
3/7
Siemens MD 10.1 · 2015
Selection of the coupling size
3
Coupling load under maximum and overload conditions
The maximum torque is the highest load acting on the coupling
in normal operation.
Maximum torques at a frequency of up to 25 times an hour are
permitted and must be lower than the maximum coupling torque.
Examples of maximum torque conditions are: Starting opera-
tions, stopping operations or usual operating conditions with
maximum load.
T
Kmax
≥
T
max
⋅
FT
Overload torques are maximum loads which occur only in com-
bination with special, infrequent operating conditions.
Examples of overload torque conditions are: Motor short circuit,
emergency stop or blocking because of component breakage.
Overload torques at a frequency of once a month are permitted
and must be lower than the overload torque of the coupling. The
overload condition may last only a short while, i.e. fractions of a
second.
T
KOL
≥
T
OL
⋅
FT
Coupling load due to dynamic torque load
Applying the frequency factor, the dynamic torque load must be
lower than the coupling fatigue torque.
Dynamic torque load
T
KW
≥
T
W
⋅
FF
⋅
Frequency of the dynamic torque load
f
err
≤
10 Hz frequency factor FF = 1.0
Frequency of the dynamic torque load
f
err
> 10 Hz frequency factor FF =
√
(
f
err
/10 Hz)
For the ZAPEX and ARPEX series, the frequency factor is always
FF = 1.0.
Checking the maximum speed
For all load situations
n
Kmax
≥
n
max
Checking permitted shaft misalignment
For all load situations, the actual shaft misalignment must be less
than the permitted shaft misalignment.
Checking bore diameter, mounting geometry and
coupling design
The check must be made on the basis of the dimension tables.
The maximum bore diameter applies to parallel keyways to
DIN 6885. For other keyway geometries, the maximum bore
diameter can be reduced. On request, couplings with adapted
geometry can be provided.
Coupling behavior under overload conditions
The ZAPEX, ARPEX, N-EUPEX, RUPEX and N-BIPEX coupling
series can withstand overloads until the breakage of metal parts.
These coupling series are designated as fail-safe.
The N-EUPEX DS, ELPEX-B, ELPEX-S and ELPEX coupling se-
ries throw overload. The elastomer element of these couplings is
irreparably damaged without damage to metal parts when sub-
jected to excessive overload. These coupling series are desig-
nated as non-fail-safe. These types that fail can be fitted with a
so-called fail-safe device. This additional component enables
emergency operation, even after the rubber element of the cou-
pling has been irreparably damaged.
Checking shaft-hub connection
The torques specified in the tables of power ratings data of the
coupling series do not necessarily apply to the shaft-hub con-
nection. Depending on the shaft-hub connection, proof of form
stability is required. Siemens recommends obtaining proof of
form strength by using calculation methods in accordance with
the current state of the art.
Fitting recommendations for the shaft-hub connection are given
in catalog section 15.
The coupling hub is frequently fitted flush with the shaft end face.
If the shaft projects, the risk of collision with other coupling parts
must be checked. If the shaft is set back, in addition to the load-
bearing capacity of the shaft-hub connection, the correct posi-
tioning of the hub must be ensured as well. If the bearing hub
length is insufficient, restorative forces may cause tilting move-
ments and so wear to and impairment of the axial retention. Also,
the position of the set screw to be positioned on sufficient shaft
or parallel key material must be noted.
Checking low temperature and chemically aggressive
environment
The minimum permitted coupling temperature is specified in the
Temperature factor FT table. In the case of chemically aggres-
sive environments, please consult the manufacturer.
FB – 1.0
1.5
Shaft-hub connection
Suggestion for calculation
method
Keyway connection to DIN 6885-1
DIN 6892
Shrink fit
DIN 7190
Spline to DIN 5480
Bolted flange connection
VDI 2230
Flange connection with close-fitting bolts
© Siemens AG 2015