These couplings operate via the hydrodynamic principle: two bladed wheels (pump and turbine) surrounded by a shell form a working chamber where circulating fluid transmits the mechanical output of the motor to the driven machine.

The transmitting power of the coupling can be easily and steplessly adjusted via the filling level inside the working chamber. The load created by counter torque and masses to be accelerated, which affects the motor during start-up, is solely determined by the turbo coupling while the driven machine is de-coupled.

San Juan’s armoured face conveyor (AFC), supplied by Joy Mining UK, is 300m long and features two main drives and one tail drive, each with a nominal rating of 850kW. A water-operated, fill-controlled Voith turbo-coupling type 562 DTPK (Joy TTT) is installed between each motor and each gearbox.

Advantages include virtually load-free start-up of the asynchronous motor, individual drives can be switched on one after another as a result of variable filling levels of the coupling, automatic torque limitation during start-up, and smooth and fast build-up of torque at the chain

In Australia drives such as these are installed at the Ulan and Moranbah North mines in New South Wales and Queensland respectively.

San Juan’s 5km-long conveyor system (Conveyor Continental) includes two conveyors driven by three drives each. All of the 10 drives are fitted with a fill-controlled Voith turbo coupling type 650 TPKL rated at 550kW.

Voith said the new coupling has been developed especially for materials handling. It incorporates an independent unit with integrated operating fluid supply, no moving parts on the outside, virtually load-free start-up of the drive motor; and automatic load sharing with multi-motor drives.

Voith said the hydrodynamic couplings were cost-effective and efficiently designed to be suitable in mining environments.