19. Factor Governing Selection of Turbines
1.SPECIFIC SPEED AND HEAD
TURBINES SPECIFIC SPEED
(mhp-m)
HEAD RANGE
(Meters)
PELTON 15-60 ABOVE 200
FRANCIS 80-400 30-600
KAPLAN 300-800 10-80
BULB/TUBULAR 600-1200 3-25
27. Comparison Between Francis Type & Pelton Type Hydro Turbines
Francis Turbine
1. Better Peak Efficiency
2. Safe operation zone is 100% to 60%
Load.
3. At Load below 60% Noise vibration
and pressure pulsations have been
observed resulting in fall in efficiency
4. Higher speed rise ,pressure rise.
5. Susceptible to presence of silt in
water ,the components under water
get eroded resulting in fall in
efficiency ,increased vibrations Noise
and cavitations.
6. Elaborate maintenance requirement.
7. For maintenance of parts underwater
complete dismantling of turbine and
generator is required.
8. Overall cost less.
9. P.H Shall be smaller.
Pelton Turbine
1. Better Efficiency at part loads.
2. Safe operation zone is 100% to 25%
Load.
3. Safe operation at lower loads without
appreciable fall in efficiency. It can be
further improved by operating with
less the numbers of nozzles.
4. Low speed rise ,pressure rise.
5. Even after Erosion the efficiency
remains more or less same.
6. Maintenance requirements are less.
7. The parts can be refitted without
dismantling other components of
Turbine and generator.
8. Overall cost more.
9. P.H Shall be Bigger.
