3775

FIGURE 19 Simplified method for approximating flow from a horizontal pipe (1 in = 25.4 mm; 1 gpm = 0.227 m3/h).

FIGURE 19 Simplified method for approximating flow from a horizontal pipe (1 in = 25.4 mm; 1 gpm = 0.227 m3/h).

The edges of the orifice should be provided with a suitable radius tangential to the wall of the water passage and should be free from burrs or irregularities. Two pressure tap arrangements shown in Figure 27 indicate taps in conformity with the above. Where more than one tap is required at a given measuring section, separate properly valved connections should be made. As an alternative, separate instruments should be provided.

Multiple orifices should not be connected to one instrument except on those metering devices, such as venturi meters, where proper calibrations have been made.

All leads from the orifice should be tight and as short and direct as possible. For dry-tube leads, suitable drain pots should be provided and a loop of sufficient height to keep the pumped liquid from entering the leads should be formed. For wet-tube leads, vent cocks for flushing should be provided at any high point or loop crest to assure that tubes do not become airbound. All instrument hose, piping, and fittings should be checked under pressure prior to test to assure that there are no leaks. Suitable damping devices may be used in the leads.

If these conditions cannot be satisfied at the point of measurement, it is recommended that four separate pressure taps be installed, equally spaced about the pipe, and that the pressure at that section be taken as the average of the four separate values. If the separate readings show a difference of static pressure that might affect the head beyond the contract tolerances, the installation should be corrected or an acceptable tolerance determined.

Figures 21 to 27 show suitable arrangements for various types of instruments and formulas for translating instrument readings into feet (meters) of liquid pumped, for expressing instrument head as elevation over a common datum, and for correcting these formulas for the velocity head existing in the suction and discharge pipes.

Capacity, Gpm = 5.68 KD2 HI/2 Capacity, m3/h = 7.872 X 10~5KD2 HI/2 D = I.D. of Pipe, in. (mm) H = Vertical Height of water jets, in. (mm) K = a constant, varying from .87 to .97 for pipes 2 to 6 in. (51 to 152 mm) H = 6 to 24 in. (152 to 610 mm)

APPROXIMATE CAPACITY, GPM, FOR FLOW FROM VERTICAL PIPES

NOMINAL VERTICAL HEIGHT, H , OF WATER JET, IN,

I.D. PIPE,IN.

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Survival Treasure

This is a collection of 3 guides all about survival. Within this collection you find the following titles: Outdoor Survival Skills, Survival Basics and The Wilderness Survival Guide.

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