619920

Note: All values are in pounds per cubic foot, 1 lb/ft3 = 16 kg/m3; 1 ft = 0.048 m.

Density of water from Source 1, p. 296

Gravity formula from Source 4, p. 488

Go = 980.616 (1 - 0.0026373 cos 20 + 0.0000059 cos2 20)

Altitude correction = 0.0003086 X altitude in meters.

Standard gravity = 980.665 cm/s2

Density of air from Source 2:

where H is in meters

Sources:

1. Smithsonian Physical Tables, 9th rev. ed.

2. National Advisory Committee for Aeronautics, TN 3182.

3. American Society of Mechanical Engineers, PTC 2-1971.

4. Smithsonian Meteorological Tables, 6th rev. ed.

Note: All values are in pounds per cubic foot, 1 lb/ft3 = 16 kg/m3; 1 ft = 0.048 m.

Density of water from Source 1, p. 296

Gravity formula from Source 4, p. 488

Go = 980.616 (1 - 0.0026373 cos 20 + 0.0000059 cos2 20)

Altitude correction = 0.0003086 X altitude in meters.

Standard gravity = 980.665 cm/s2

Density of air from Source 2:

where H is in meters

Sources:

1. Smithsonian Physical Tables, 9th rev. ed.

2. National Advisory Committee for Aeronautics, TN 3182.

3. American Society of Mechanical Engineers, PTC 2-1971.

4. Smithsonian Meteorological Tables, 6th rev. ed.

NET positive suction head The net positive suction head (NPSH) hsv is the total suction head in feet (meters) of liquid absolute determined at the suction nozzle and referred to datum less the vapor pressure of the liquid in feet (meters) absolute.

driver input The driver input ehp is the input to the driver expressed in horsepower (kilowatts). Usually this is electric input horsepower (kilowatts).

FIGURE 1 Horizontal pump

Dolu-n eievclor FIGURE 2 Vertical single-suction pump

Dolu-n eievclor FIGURE 2 Vertical single-suction pump

FIGURE 3 Vertical double-suction pump

pump input Pump input bhp is the power delivered to the pump shaft and is designated as brake horsepower (brake kilowatts).

liquid OR water power Water power whp (wkW) is the useful work delivered by the pump and is usually expressed by the formula

in USCS units whp =-3960-

where sp. gr. = specific gravity of liquid, referred to water at 68°F (20°C) Q = flow rate, gpm(m3/h) H = total head, ft (m)

TABLE 2 Variation of acceleration of gravity with latitude and altitude

Altitude above mean sea level, ft Latitude 0 2000 4000 6000 8000 10,000 12,000

10 32.0929

20 32.1076

30 32.1301

40 32.1577

50 32.1872

60 32.2149

70 32.2375

32.0816 32.0754

32.0867 32.0805

32.1014 32.0952

32.1239 32.1177

32.1515 32.1454

32.1810 32.1748

32.2087 32.2026

32.2314 32.2252

32.0693 32.0631

32.0744 32.0682

32.0890 32.0829

32.1115 32.1054

32.1392 32.1330

32.1687 32.1625

32.1964 32.1902

32.2190 32.2129

32.0569 32.0508

32.0620 32.0558

32.0767 32.0705

32.0992 32.0930

32.1269 32.1207

32.1563 32.1501

32.1841 32.1779

32.2067 32.2005

Note: All values are in feet per second per second; 1 ft/s2 = 0.3048 m/s2; 1 ft = 0.3048 m Gravity = 980.616 (1 - 0.0026373 cos 20 + 0.0000059 cos2 20)(1.0/30.48) Correction for altitude = -0.003086 ft/s2/1,000 ft

The international standard value of gravity adopted by the International Commission on Weights and Measures is 980.665 cm/s2 (32.17405 ft/s2) at sea level and approximately latitude 45°. Sample Computation Given:

Water temperature = 40°F (4.4°C) Altitude correction for gravity:

0.0003086 X 3657.60 = 1.128785 cm/s2 Gravity corrected for latitude and altitude:

Gravity = 980.616 (1 - 0.0026373 cos 140° - 0.0000059 cos2140°) - 1.128735 = 981.471784 cm/s2 Density corrected for gravity:

Density = (0.9999988 X 981.471784/980.6650 X 1.000028) = 1.0007930 g/cm3 Correcting for buoyancy of air:

Density = 1.0007930 - 0.0008491 = 0.9999438 g/cm3 Density in USCS units: Density = 0.9999438 X 62.4279606 = 62.4244543 lb/ft3

Sources:

1. "Smithsonian Physical Tables," 9th Rev. Ed.

2. American Society of Mechanical Engineers, PTC 2—1971

This formula is derived on p. 13.36.

efficiency Pump efficiency Ep is the ratio of the power delivered by the pump to the power supplied to the pump shaft; that is, the ratio of the liquid power (also known as water power) to the brake power expressed in percent:

In USCS units Ep = X 100

p bhp

p kW

Overall efficiency Eo is the ratio of the power delivered by the pump to the power supplied to the input side of the pump driver; that is, the ratio of the output power to the input power to the driver.

In USCS units

whp ehp

In SI units prime mover Ratings The prime movers for driving pumps are rated according to established standards. For example, for electric motor drivers, see the standards of the latest edition of the National Electrical Manufacturers Association.

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