The selection of flexible
couplings based on
transmitted torque:
If you know the torque capacity required for a particular
application the kW rating can be calculated by using
formula A and then the kW/100 rpm and service factor
(SF) can be calculated by using the coupling selection
process previously explained.
A.If the torque (Nm) and shaft speed (rpm) are known:
kW = Nm x RPM
9550
A nominal or rated torque for a particular coupling is
usually derived from the kW/100rpm power rating
(based on a steady load, service factor of 1) which is
the common industry standard for a coupling selection.
A coupling which is rated at 3.09kW/100rpm would
have a rated torque of 295Nm, this can be calculated
through by using formula B. Couplings are a constant
torque device and by using formula A and altering the
rpm you can calculate the couplings rated kW capacity
throughout its designed speed range. If a rated torque
(Nm) or power (kW) is given for a coupling by using
formula’s A or B you can determine the couplings
rated capacity range in either. When calculating for
either ratings, service factors are necessary as per the
selection process on page three, so that the correctly
rated coupling is selected to do the job.
B. If the kW and shaft speeds (rpm) are known:
Nm = kW x 9550
RPM
The maximum torque rating refers to the maximum
torque force capacity a coupling is capable of
transmitting. This is usually used to determine a
coupling’s suitability for speeds of less than 100rpm
where torque (twist) capacity (Nm) is more relevant
than the power rating (kW) based on speed. The same
calculations and information are used as above to
determine the coupling size.
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