Determination of Coupling Size

The size of the coupling is selected according to the maximum torque requirement. According to the general formula we get

M_L= 9550 P/n [Nm]

In this formula P (kW) is the power required for driving the machine which is in mostcases lower than the nominal power of the motor.
n (1 /min) is the speed of the coupling. The torque requirement M_L calculated according to this formula is an average value, but in reality the torque transmitted through the coupling is irregular, according to the irregularity of the driving power and the machine.The maximum peck torque of the drive should be lower than the torque capacity of the selected coupling according to the table.

Where the precise irregularities of the torque are not known a service factor f should be applied.

 

M_max= f 9550 P/n [Nm]

This factor f is dependant on the type of drive and type of drive machine.

Service factor f

	Driven by
Type of the driven machine	Belt drives electric motors	Combustion engines 4 and 6 cylinders	Combustion engines 2 and 3 cylinders single cylinder steam engines	Single cylinder combustion engines
belt drives, small generators, small ventilators, rotary blowers	1,5	1,7	1,9	2,2
small hoists, larger ventilators, light machines, for metal, wood and textile, small conveyors	1,8	2,0	2,2	2,5
hoists for heavy loads, heavier conveyors, hanging conveyors, mixers, textile machines with high inertias	2,0	2,2	2,4	2,7
presses, shears, stamping machines, reciprocating pumps, calenders, pan grinders, hammer mills	2,5	2,7	2,9	3,2
welding generators, stone crushers, pinch roll drives, reciprocating compressors and reciprocating pumps without flywheels, rolling mills.	3,0	3,2	3,4	3,7

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