2. The inspection and overhaul of a Francis is much more difficult job than that of the equivalent
Pelton turbine. The badly worn-out parts will have to be replaced by new ones and it will take a considerable time.
3. Cavitations is an ever-present danger in Francis as well as in all reaction turbines. The raising
of power house floor level to reduce the danger of flooding may be followed by endless cavitations
troubles.
4. Usually below 60% load, the Pelton is much better as it gives more efficiency than Francis of
low specific speed. If there is possibility of running the prime-mover below 50% load for a long period,
the Francis will not only lose its efficiency but the cavitation danger will become more serious.
5. The water hammer effect with the Francis is more troublesome than the Pelton turbine. Kaplan
versus Francis Turbine.
The advantages of Kaplan over Francis are listed below :
1. It is more compact in construction and smaller in size for the same power developed.
2. Its part-load efficiency is considerably high. The efficiency curve remains more or less flat
over the whole load range.
3. The frictional losses passing through the blades are considerably lower due to small number of
blades used.