Torque calculation and match of marine propulsion system

Power transmission of the propulsion device depends on max input of the device. Propulsion application type, prime mover type and vessel type affect actual input torque. Please kindly contact our technical engineer for propulsion type selection.

Rated input torque MP of prime mover (diesel, electric motor or hydraulic motor) is important technical date for propulsion type selection. Calculation formula is as below:

Mp ≤ Sf * MR

Mp = N * 9549/n

Sf = fz * fl * fs

Mp: Output torque of prime mover(Nm)

Sf: Rudder propeller service factors

Mr: Max input torque of rudder propeller(Nm)

N: Output power of prime mover (KW)

N: Input speed of rudder propeller (r/min)

The design torque can not be taken as the basis for propulsion type selection according to our experience. Different operation conditions must be taken into consideration. Common safety coefficient Sf of torque design can be based on the following:

Sf=0.75: Full power continuous rating 24 hours service (Container ships, push tugs)

Sf=0.9: Intermettent service with eventual full load (harbor tugs, floating crane)

Sf=1.0: Auxiliary installations (Tunnel thruster, DP-installations)