Power Plant Engineering

374 POWER PLANT ENGINEERING

where Ha = Atmospheric pressure head in meter of water
Hv = Vapour pressure in metre of water corresponding to the water temperature
H = Working head of turbine (difference between headrace and tailrace level in meters)
h = Height of turbine outlet above tailrace level in meters.
The values of Ha with respect to the altitudes above sea level and the values of H,, with respect to
the water temperatures are tabulated in the tables (11.5) and (11.6). The values of critical factor depend
upon the specific speed of the turbine. The critical values of cavitation factors with respect to specific
speed are tabulated in tables.

Table 11.5. Altitude Vs Atmospheric Pressure

Altitude above sea level in metres 0 1000 2000 3000 4000

Baromatric mm of Hg 760 676 595 528 463

Pressure Metres of water 10.35 9.2 8.1 7.2 6.3

Table 11.6. Saturation Pressure as Function of Temperature

Temp °C Pressure in kg/cm^2 Pressure in mm of Hg Pressure in metres of

water

0 0.0012 4.60 0.062

2 0.00716 5.30 0.072

4 0.00829 6.30 0.083

6 0.00953 7.04 0.095

8 0.01093 8.05 0.1095

10 0.01251 9.23 0.1251

12 0.01429 10.50 0.1430

14 0.01629 12.05 0.1630

16 0.01853 13.70 0.1855

18 0.02103 15.50 0.2105

20 0.12383 17.60 0.2385

22 0.02700 19.95 0.2700

24 0.00040 22.40 0.3040

26 0.03430 25.30 0.3430

28 0.03850 28.40 0.3850

30 0.04330 32.00 0.4330

32 0.04850 35.80 0.4850

34 0.05420 40.00 0.5420

36 0.06050 44.70 0.6060

38 0.06760 50.70 0.6760

40 0.07520 55.50 0.7520

42 0.08360 61.70 0.8360

44 0.09280 68.50 0.9280

46 0.10280 76.00 1.0280

48 0.11380 84.00 1.1310

50 0.12580 93.00 1.2580