CENTAMAX couplings substantially improved
The principle of the CENTAMAX couplings was developed and introduced to the market 26 years ago by CENTA. In the meantime its design principle has become to be the state of the art and several further manufacturers adopted it.
The basic design idea consists of a rubber disc, vulcanised to a hub on its inner part and plugged-in by teeth to the driving flange. These couplings are torsionally very soft, show a linear characteristic, they are short, suitable for axial plug-in and therefore optimal for the connection to flywheels in flange housings of diesel engines.
Important areas of application: Generators, Marine propulsion, locomotives, splitter gearboxes, screw compressors and rotary pumps.
Modern Diesel engines clearly tend to higher power density and improved gas exhaustion values. Therefore the engines become „torsionally more active“, placing higher requirements on the couplings. In particular the demand for higher permissible power loss of the coupling is constantly rising in order to dissipate the intetrnal heat caused by damping of the coupling. In addition also higher ambient temperatures occur. The mixture of natural rubber normally used for such couplings, has already been optimized for higher temperature stability, so that no substantial improvement can be expected in this regard at the time being. A well-known alternative is silicone. This however is very expensive, results in a slightly progressive characteristic curve and clearly possesses lower strengths, in particular low tear resistance.
Therefore CENTA considered how the permissible power loss of the CENTAMAX couplings made of natural rubber can be increased.
In particular for large couplings for Diesel-driven generators the market required these amendments.
CENTA has now met these requirements by implementing the new CENTAMAX-HTC (high thermal capacity): the rubber discs of the coupling are devided to two slim halves. Thus the surface is increased by about 50% and the rubber wall thickness and resulting the heat route are halved. Together with the relevant processes for intensive inner and outer ventilation the allowable power loss has been increased by 100%.
This extraordinary improvement considerably reduces the internal temperature of the coupling, increases the lifetime and in many cases permits the use of a smaller coupling or avoids the necessity for an expensive, complex and space demanding double coupling.
The CENTAMAX HTC is vulcanized as one unit, therefore it is only moderately more expensive than the normal design, anyhow clearly cheaper than a two row coupling. Patent applications have been filed.
Such development and above all the proof of the obtained improvements are of course only possible with appropriate test benches. For some time CENTA now possesses a self-developed ultramodern dynamic test bench enabling such measurements.
The rotation of the couplings are superimposed by torsional vibrations on this testbench.
The speed, preload, amplitude and the frequency of oscillations can be adjusted and measured. The energy loss is calculated by the hysteresis loop and the frequency. The temperature is measured inside the coupling at „the Hotspot“ and in further places by telemetry transfer.
This method corresponds to the requirements of the classification societies and it provides reliable, exact results.
In addition the influence of different ventilation methods can be examined. Thus a systematic improvement, FMA analyses and trials result in the extraordinary improvement of the power loss, without exposing the rubber element to increased tension or local stress peaks by large vent holes. With this test bench and several further dynamic test benches for different tasks and various torques up to 750 kNm CENTA is completely self-sufficient and in the position to measure in its own test field all demanded characteristic values of the couplings, and also endurance tests for the determination of the life span and fatigue strength can be established, even for at present largest CENTAX coupling for 650 KNm.