1.1 Torque Capacity-- Diesel Engine Drives
The DCB Coupling is selected on the " Nominal Torque, Tkn " without service factors.
The full torque capacity of the coupling for transient vibration whilst passing through major criticals on run up is published as the Maxium Torque, Tkmax
( Tkmax = 3 X Tkn )
There is additional torque capacity built within the coupling for short circuit torques.
The published " Vibratory torque, TKw ", relates to the amplitude of the permissible continuous torque fluctuation.The vibratory torque values shown in the "Technical Data are at a frequency of 10 Hz. The measure of acceptability of the coupling for vibrating drives is published as " Allowable dissipated Heat at Ambient Temperature 30o C. "
1.2 TRANSIET TORQUE--
Prediction of transient torques in marine driven can be complex. Normal installations are well provided for by selecting couplings based on the " Nominal torque Tkn " Transients, such as start up and clutch manoeuvre, are usually within the " Maximum Torque, Tkmax " for the coupling.
Care needs to be taken in the design of couplings with shaft brakes, to ensure coupling torques are not increased by severe deceleration.
Sudden torque application of propulsion, such as thrusters or waterjets, need to be considered when designing the coupling connection.
2.0 STIFFNESS PROPERTIES
The Poona Couplings remains fully flexible under all torque conditions. The DCB series is a non-bonded type operating with the Rubber-in-Compression principle.
2.1 AXIAL STIFFNESS
When subject to axial misalignment, the coupling will have an axial resistance which gradually reduces due to the effect of vibratory torque.
The axial stiffness of the coupling is torque dependent. The variation is as shown in the Technical Data on pages 16 to 22
2.2 RADIAL STIFFNESS
The radial stiffness of the coupling is torque dependent, and is as shown in Technical Data on pages 16 to 22.
2.3 TORSIONAL STIFFNESS
The torsional stiffness of the coupling is dependent upon applied torque and temperature as shown in the Technical Data on pages 16 to 22.
2.4 PREDITION OF THE SYSTEM TORSIONAL VIBRATION CHARACTERISTICS
2.4.1 Use the torsional stiffness, as published in the catalogue, which is based upon data measured at 30 C ambient temperature.
2.4.2 Repeat the calculation made in 2.4.1 but using the maximum temperature connction factor St100 and dynamic magnifier connection factor M100 for the selected rubber. Use tableson page 15 to adjust values for both torsional stiffness and dynamic magnifier i.e. Ct100 = Ctdyn x St100
2.4.3-- Review calculations
2.4.1 and 2.4.2 and if the speed range is clear of critical which do not exceed the allowable heat dissipation value as published in the catalogue then the coupling is considered suitable for the application, with respect to the torsional vibration characteristics. If there is a critical in the speed range , then the actual temperature of the coupling should be calculated at this speed. |
