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5.2 Fluid Transport 169
Table 5.1 Values of the Hazen-Williams Coefficient, C, for Different Conduit Materials and Age
of Conduit
Age
Conduit Material New Uncertain
Cast-iron pipe, coated (inside and outside) 130 100
Cast-iron pipe, lined with cement or bituminous enamel 130 a 130 a
Steel, riveted joints coated 110 90
Steel, welded joints, coated 140 100
Steel, welded joints, lined with cement or bituminous enamel 140 a 130 a
Concrete 140 130
Wood stave 130 130
Cement-asbestos and plastic pipe 140 130
a
For use with the nominal diameter, that is, the diameter of unlined pipe.

EXAMPLE 5.4 MATHEMATICAL AND GRAPHICAL BASIS OF THE PIPE FLOW DIAGRAM
The pipe flow diagram (Fig 5.3) establishes the numerical relationships between Q, v, d, and s for
a value of C 100. Conversion to other magnitudes of C is simple because both v and Q vary di-
rectly as C. Show the mathematical and graphical basis of this diagram.

Solution:
s
1. Written in logarithmic form, Eq. 5.36, Q gpd 405 Cd 2.63 0.54 , is:
(a) log Q gpd 4.61 2.63 log d 0.54 log s, or
(b) log s 8.54 4.87 log d 1.85 log Q gpd
A family of straight lines of equal slope is obtained, therefore, when s is plotted against Q
on log-log paper for specified diameters d. Two points define each line. Pairs of coordi-
nates for a 12-in. pipe, for example, are as follows:
(a) Q 100,000 gpd, s 0.028 %
(b) Q 1,000,000 gpd, s 2.05%.
s
2. Written in logarithmic form, Eq. 5.34, v 0.115 Cd 0.63 0.54 , is as follows:
log v 1.0607 0.63 log d 0.54 log s

If the diameter d is eliminated from the logarithmic transforms of Eqs. 5.36 and 5.34,
then
(a) log Q 0.180 4.17 log v 1.71 log s
(b) log s 0.105 2.43 log v 0.585 log Q.
A family of straight lines of equal slope is obtained when s is plotted against Q on log-log
paper for specified velocities v. Two points define each line. Pairs of coordinates for a
velocity of 1 ft/s, for example, are as follows:
(a) Q 100,000 gpd, s 1.5%
(b) Q 10,000,000 gpd, s 0.10%.