HAZEN-WILLIAMS EQUATION

The Hazen-Williams formula can be used to calculate the pressure loss in a length of pipe due to friction dependent on the flow. This equation is commonly used for pressure drop calculations in American fire sprinkler systems, water distribution systems, and irrigation systems.
:
where:
P_d = pressure drop in pounds per square inch / foot
Q = flow in gallons per minute
C = factor (friction loss coefficient) - the higher the C factor, the smoother the pipe. Typical C factors used in design, which take into account some increase in roughness as pipe ages are as follows:
:Asbestos-cement - 140
:Cast iron - 100
:Cement-Mortar Lined Ductile Iron Pipe - 140
:Concrete - 100
:Copper - 150
:Steel - 120
:Galvanized steel - 120
:Polyethylene - 150
:Polyvinyl chloride (PVC) - 150
:Fibre-reinforced plastic (FRP) - 150
d = inside hydraulic diameter (inch)
An alternate form of the Hazen Williams Equation is:
:$V=1.318quad\; Cquad\; R\_h^\{0.63\}quad\; S^\{0.54\}$
where:
V = Velocity (in feet per second)
C = as above
R_h = Hydraulic Radius (in feet) (see Manning formula)
S = Energy Gradient or Friction Slope (h_f/L)
== In SI units==
$Q\; =\; 0,849\; ;\; C\; ,\; A\; ,\; R\_h^\{0,63\}\; ,\; S^\{0,54\}$
Q =
C = factor (friction loss coefficient)
A =
R_h =
S =

Contents

See also

References

External links

See also

★ Darcy-Weisbach equation

★ Fluid dynamics

★ Friction

★ Pressure

★ Volumetric flow rate

★ Water pipe

References

★ Turf Irrigation Manual, 5th Ed., by James A. Watkins, published by Telsco, 1987.

★ Fluid Mechanics, 10th Ed., by E. John Finnemore and Joseph B Franzini, published by McGraw Hill, 2002.

External links

★ Engineering Toolbox reference

★ Engineering Toolbox Hazen Williams Coefficients