Definitions Symbols And Units

For a detailed discussion of letter symbols, definitions, description of terms, and table of letter symbols in general use, the user is referred to ASME Power Test Code1 and to "SI Units—A Commentary" in front matter of this handbook.

Standard Units Used in Pump Testing The following definitions and quantities from the Hydraulic Institute standards2 are used throughout the industry in pump testing.

volume The standard units of volume are the U.S. gallon and the cubic foot (cubic meter). The standard U.S. gallon contains 231.0 in3 (0.00379 m3), and 1 ft3 = 7.4805 gal (0.028 m3). Rate of flow is expressed in gallons per minute (cubic meters per hour), cubic feet per second, or million gallons per 24-h day. The specific weight (mass) w of pure water at 68°F (20°C), at sea level and 40° latitude, is 62.315 lb/ft3 (0.998 kg/liter). For other temperatures or locations, proper specific weight corrections should be made. See Table 1 and the appropriate ASME power test codes.

head The unit for measuring head is the foot (meter). The relation between a pressure expressed in pounds per square inch (kilopascals) and one expressed in feet (meters) of head is in USCS units head, ft = lb/in2 X 144

w where w = specific weight of liquid being pumped under pumping conditions, lb/ft3 (kg/l)

All pressure readings must be converted to feet (meters) of the liquid being pumped, referenced to a datum elevation, which is defined as follows. For a horizontal shaft unit, the datum elevation is the centerline of the pump shaft (Figure 1). For vertical-shaft single-suction pumps, it is the entrance eye to the first-stage impeller (Figure 2). For vertical-shaft double-suction pumps, it is the impeller-discharge horizontal centerline (Figure 3).

velocity head The velocity head hv is computed from the average velocity V, obtained by dividing the flow by the pipe cross-sectional area. velocity head is determined at the point of gage connection and is expressed by the formula h V2

g = acceleration due to gravity = 32.17 ft/s2 (9.81 m/s2) (Table 2)

flooded suction Flooded suction implies that the liquid must flow from an atmospherically vented source to the pump without the average or minimum pressure at the pump datum dropping below atmospheric pressure with the pump operating at specified capacity.

total suction lift Suction lift exists where the total suction head is below atmospheric pressure. Total suction lift hs is the reading of a liquid manometer or pressure gage at the suction nozzle of the pump, converted to feet (meters) of liquid, and referred to datum minus the velocity head at the point of gage attachment.

total suction head Suction head exists when the total suction head hs is above atmospheric pressure. Total suction head is the reading of a gage at the suction of the pump converted to feet (meters) of liquid and referred to datum plus the velocity head at the point of gage attachment.

total discharge head Total discharge head hd is the reading of a pressure gage at the discharge of the pump, converted to feet (meters) of liquid and referred to datum plus the velocity head at the point of gage attachment.

total head Total head H is the measure of the work increase per pound kilogram of liquid, imparted to the liquid by the pump, and is therefore the algebraic difference between the total discharge head and the total suction head. Total head, as determined on test where suction lift exists, is the sum of the total discharge head and total suction lift. Where positive suction head exists, the total head is the total discharge head minus the total suction head.

TABLE 1 Specific weight of water in air

Latitude 32 (0) 40 (4.4) 50 (10) 60 (16) 70 (21) 80 (27) 90 (32) 100 (38)

At sea level

0° 62.1741 62.1823 62.1654 62.1227 62.0578 61.9729 61.8701 61.7514

10 62.1840 62.1921 62.1753 62.1325 62.0677 61.9828 61.8800 61.7612

20 62.2125 62.2206 62.2038 62.1610 62.0961 62.0112 61.9083 61.7895

30 62.2562 62.2643 62.2475 62.2046 62.1397 62.0547 61.9518 61.8328

40 62.3098 62.3179 62.3011 62.2582 62.1932 62.1082 62.0051 61.8861

50 62.3670 62.3751 62.3582 62.3153 62.2503 62.1652 62.0620 61.9429

60 62.4208 62.4289 62.4120 62.3691 62.3040 62.2188 62.1156 61.9963

70 62.4647 62.4728 62.4559 62.4130 62.3478 62.2626 62.1593 62.0399

At 2000 ft

0° 62.1665 62.1747 62.1578 62.1151 62.0502 61.9654 61.8626 61.7438

10 62.1764 62.1845 62.1677 62.1250 62.0601 61.9752 61.8724 61.7537

20 62.2049 62.2130 62.1962 62.1534 62.0885 62.0036 61.9008 61.7819

30 62.2486 62.2567 62.2399 62.1970 62.1321 62.0471 61.9442 61.8253

40 62.3022 62.3103 62.2935 62.2506 62.1856 62.1006 61.9976 61.8786

50 62.3594 62.3675 62.3506 62.3078 62.2427 62.1576 62.0545 61.9354

60 62.4132 62.4213 62.4044 62.3615 62.2964 62.2112 62.1080 61.9888

70 62.4571 62.4652 62.4484 62.4054 62.3402 62.2550 62.1517 62.0324

At 4000 ft

0° 62.1588 62.1669 62.1501 62.1073 62.0424 61.9576 61.8549 61.7361

10 62.1686 62.1767 62.1599 62.1172 62.0523 61.9675 61.8647 61.7459

20 62.1971 62.2052 62.1884 62.1456 62.0807 61.9959 61.8930 61.7742

30 62.2408 62.2489 62.2321 62.1893 62.1243 62.0394 61.9365 61.8176

40 62.2944 62.3025 62.2857 62.2428 62.1779 62.0929 61.9899 61.8709

50 62.3516 62.3597 62.3429 62.3000 62.2349 62.1498 62.0467 61.9277

60 62.4054 62.4135 62.3967 62.3537 62.2886 62.2035 62.1003 61.9811

70 62.4493 62.4574 62.4406 62.3976 62.3325 62.2472 62.1440 62.0247

At 6000 ft

0° 62.1508 62.1589 62.1421 62.0993 62.0345 61.9497 61.8469 61.7282

10 62.1607 62.1688 62.1520 62.1092 62.0444 61.9595 61.8568 61.7380

20 62.1891 62.1972 62.1804 62.1377 62.0728 61.9879 61.8851 61.7663

30 62.2328 62.2409 62.2241 62.1813 62.1164 62.0315 61.9286 61.8097

40 62.2864 62.2946 62.2777 62.2349 62.1699 62.0849 61.9819 61.8630

50 62.3436 62.3517 62.3349 62.2920 62.2270 62.1419 62.0388 61.9198

60 62.3974 62.4055 62.3887 62.3458 62.2807 62.1955 62.0924 61.9732

70 62.4413 62.4495 62.4326 62.3896 62.3245 62.2393 62.1361 61.0168

Temperature, °F (°C)

Latitude

32 (0)

40 (4.4)

50 (10)

60 (16)

70 (21)

80 (27)

90 (32)

100 (38)

At 8000 ft

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