COEFFICIENTS OF FRICTION

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Absolute surface roughness

0.0005 mm – 0.0007 mm
(0.0127 inch – 0.01778 inch)

The values of Hazen-Williams coefficient

The values of the head losses in the charts were calculated using the Hazen-Williams formula with Hazen-Williams coefficient C= 155

Manning coefficient:

n= 0,005 - 0,007

Reduction factors for higher temperatures

The values of the head losses J in the charts are correct for 20°C. At higher temperature the head losses are lower.

For different temperatures, multiply the value of J by the following reduction factors:

10°C – 1.03
20°C – 1.00
30°C – 0.98
40°C – 0.93
50°C – 0.91
60°C – 0.88
70°C – 0.85
80°C – 0.83
90°C – 0.81

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