Within the Kvaerner Hydro Group we have a wide experience and knowledge   of all sizes of Francis turbines. We have delivered one of the world's most powerful water turbines - 469 MW - to Harsprånget power station.

The pump turbine can be regarded as a modified double-acting centrifugal pump. If  the direction of rotationis is reversed it will operate as a Francis turbine. When the energy price is high, the unit is operating as a turbine. When the price is low,the direction of rotation is reversed and the water is pumped up to it soriginal   level againl. The pumping is a method to store energy when there is a  surplus of electric energy. The pumped  water can  be used later on  for turbine operation when the need of electrical energy is larger and the electricity prices higher. We are far ahead within this field and have delivered one of the biggest pump turbines in the world for 334 MW to Juktan in Sweden.

An ordinary Francis runner functions for different reasons unsatisfactorily as pump runner. A centrifugal pump runner is on the other hand possible to use as a turbine runner. Therefore the reversible pump turbine runner is mainly designed on basis of the pump function.

To avoid cavitation problems at pump operation, the pump turbine has to be placed at a very low level in relation to the tail water level (TWL). The runner is often placed 10-15 metres below TWL. This can be compared with the conditions of an ordinary Francis turbine, which in general has the runner level 1-4 m below TWL. A consequence of this is that the reversible pump turbine has a very large margin to cavitation at turbine operation.

Pump turbine Photo >