%P 1685-1691
%V 29
%J Transaction of the ASAE
%R 0596
%N 6
%X EROSION caused by water discharged from gated
pipe openings can be reduced by dissipating excess
energy with orifices placed in the gated pipe couplings.
Laboratory tests were conducted to determine graphical
relationships and coefficients for estimating the head loss
for orifices made from galvanized sheet metal. The loss
coefficient, Ko, is a function of the orifice-to-pipe
diameter ratio, ?o, and can be expressed by an equation
of the form Ko = a?bo where a and b are empirical
constants determined from the tests. Comparisons made
between machined, square edge orifices commonly used
for flow measurement, and those made in sheet metal
shops for irrigation showed that the irrigation orifices
have a higher discharge coefficient and a lower head loss
coefficient than do the square edge orifices. Square edge
orifices placed in irrigation pipe couplings behaved
similarly to those for flow measurement, particularly in
the mid and lower ranges of the diameter ratio, ?o.

The head loss ratio, R, as defined by the ASME (1959)
is the same for, (a) square edge orifices used for flow
measurement, (b) square edge orifices installed in
aluminum irrigation pipeline joint couplings, and (c)
sheet metal orifices made for irrigation installed in pipe
couplings. The ratio can be represented by the equation
R=1-0.9 ?o 1.7.
%A Allan S. Humpherys
%T Energy Dissipation in Low Pressure Irrigation Pipelines. I. Butterfly Valves and Discs
%L nwisrl473
%D 1986