KAPLAN TURBINES 1
Unique in the fact that this type of turbine can only be installed in the vertical orientation, Kaplan turbines have a high specific speed which means that direct coupling to the generator is possible but only at higher heads and lower flows.
This means that a speed increaser will be necessary on most applications.
A gearbox is recommended on turbines whose output would exceed 75 kW, but below this a belt drive would be acceptable.
The Kaplan runner comprises a cast hub on which blades are mounted.
The hub is normally cast in S.G. Iron but higher output turbine hubs are cast in Steel.
The blades are normally cast in Aluminium Bronze or Stainless Steel, depending on the operating conditions and quality of the water passing through the turbine.
The runner blade operating mechanism is located within the hub.
Angular movement of the blades occurs via a mechanical linkage system operated by a push rod through the centre of the main turbine shaft. The push rod is operated by a hydraulic actuator.
The water is directed radially i.e. at right angles to the orientation of the turbine shaft, onto the runner blades by vertically orientated guide vanes.
The guide vanes are operated by a linkage system which, via PLC control, is linked with the runner blade actuation system. This ensures the highest possible efficiency output from the turbine over a wide range of flows.
As the entire turbine is immersed in a structure which is almost continually full of water, the treatment of corrosion-prone metal parts is of utmost importance.
therefore
applies specialised coatings to these parts to reduce corrosion, and thereby
increase the life of the turbine and associated metalwork.