Kaplan Turbines 3
The 
Kaplan
turbine is aimed at very low head sites (down to 2 metres) - in particular existing
mill sites which would require very little modification to the existing civil
works.
also
manufactures a special type of Kaplan turbine which is housed within a spiral
case.
This spiral cased Kaplan turbine is especially effective in the 20 to 35 metre head range, as site conditions in this range normally have penstocks supplying water to the turbines.
The runner and guide vane configuration are basically the same as the usual Open flume Kaplan turbine with the guide vanes being supplied by a fabricated Steel spiral case.
The high head supplying the turbine means that a high rotational speed of the runner is obtainable and therefore the runner can normally be directly mounted onto an extended generator shaft, giving a higher overall efficiency.
The runner blade push rod then passes through a hole bored in the centre of the generatorshaft. A smaller turbine house is called for with the vertical Kaplan, thus reducing costs of civil works.