1.1 Torque Capaity --- Diesel Engine Drives
The HTB 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 Maximum Torque Tkmax. ( Tkmax = 3 XTkn )
There is additional torque capacity built within the coupling for short circuit torques.
The published " Vibratory Torque Tew, relates to the amplitude of the permissible continuous torque fluctuation.
The Vibratory Torque values shown in the technical data are the frequency of 10 Hz. The measure of acceptability of the coupling for vibrating drives is published as " Allowable Dissipated Heat at Ambient Temperature 30 C.
1.2 TRANSIENT TORQUES
Prediction of transient torques in marine drives 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 ususally 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 applications of propulsion devises such as thrusters or water jets, need to be considered when designing the coupling connection.
2 STIFFNESS PROPERTIES :-
Poona couplings remains fully flexible under all torque conditions. The HTB 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,variation is as shown in the technical data on page no.-29.
2.2 RADIAL STIFFNESS :-
the radial stiffness of the coupling is torque dependent, and is shown in the technical data on page no. 29
2.3:-- TORSIONAL STIFFNESS :-
The torsional stiffness of the coupling is dependent upon applied torque and temperature as shown in the technical data on page no. 29.
2.4 PREDICTION OF THE SYSTEM TORSIONAL VIBRATION CHARACTERISTICS---
An adequate prediction of the systems torsional vibration characteristics, can be made by the following method:
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 as 2.4.1, but using the maximum temperature connector factor St 200. and dynamic magifier connector factor M 200 for the selected rubber,.Use tables on page 28 to adjust values for both torsional stiffness and dynamic magnifier. i.e. Ct 200 = CtdynX St200
2.4.3 __ Review calculations 2.4.1 and 2.4.2 and if the speed range is clear of criticals which do not exceed the allowable heat dissipation values 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.