Capital Equipment News June 2015

THE ADVANTAGES of turbo coupling By Pierre Sanson

C onstant flow turbo coupling has been designed for vehicles in order to help eliminate the shock effects that the drivetrain may experience throughout day- to-day operation. This, in turn, reduces wear and tear dramatically, thus decreas- ing maintenance costs. Turbo couplings are of the utmost importance in the commercial vehicle market, partially due to the sheer size and weight of the vehicles, and par- tially due (at least in South Africa) to the dubious nature of the drivers. But how exactly can a component eliminate shock effects so easily? Simply put, the torque transfer system is designed so that there is no solid and mechanical contact. Usually through the use of a mineral oil, turbo couplings make use of a liquid torque-transfer system in order to give the vehicle its drive. Voith Turbo is the worldwide leader when it comes to these hy- drodynamic couplings, and an analysis of their system reveals exactly how it works. While the system as a whole is easier to un- derstand with a diagram, the system can be explained as two wheels that are not connect- ed or touching in any way, but are encased to- gether and form part of a closed system. On the sides of the wheels that face each other there

are hollowed out slats, and in these slats rests the coupling’s liquid. The first wheel, known as the pump wheel, is driven by the motor. This starts spinning and the torque transmitted by the engine is converted into the kinetic ener- gy of the liquid. This liquid, essentially thrown into the slats of the second wheel, known as the turbine wheel, starts it spinning and in so doing, converts the kinetic energy of the liquid back into mechanical energy and provides the vehicle with drive. Of course, at a standstill the liquid is at rest, and at start-up the pump wheel and the tur- bine wheel are turning at different speeds until what is called nominal operation is achieved. This means that the two wheels are turning at almost the same speed (the minor difference in speed being called the nominal slip), but what is important to note here is that the liquid transfer between the two wheels ceases. The flow becomes stationary and the liquid, for all intensive purposes, becomes a solid component in the drivetrain, this means that only the torque required by the driven machine is transmitted. Voith have paid special attention to the min- ing industry in recent years and have now developed a water-operated turbo coupling.

The water-operated coupling could be used in any application; however, it was designed with a specific view to end-users in the mining in- dustry. The industry’s vast demands on output, safety and environmental protection have re- stricted much of the old technology used; how- ever, Voith have turned this into an opportunity for innovation. Water as an operating medium for the turbo coupling holds significant improvement over the use mineral oil. Most notably, it is far more readily available, and it is environmentally friendly. On top of this, also take into account that it is often the case that vehicles at min- ing sites will be operating underground. It is undoubtedly safer to use water in such cir- cumstances. “The water coupling transmits power smoothly and virtually wear-free, without any mechan- ical contact between the torque-transmitting components,” Voith advertise. This innovative coupling is not only important to the vehicles that are involved in mining operations though. These couplings can run any numbers of belt conveyers, fans and pumps that may be on site as well. It is evident that, among others, the mining industry is set to receive huge benefit thanks to this innovation from Voith Turbo. b

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