COEFFICIENTS OF FRICTION
Absolute surface roughness
0.0005 mm–0.0007 mm
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
Calculating Pexgol pipes for boreholes
Pexgol pipes can be used as riser pipes for boreholes. For energy-saving reasons, we recommend choosing a Pexgol pipe with head losses that do not exceed J=5%, and preferably lower. However, please note that designing these pipes is complicated, due to the complex three dimensional stress regime in these applications.
Pexgol’s Technical Department will calculate the pipe design for you after receiving the completed borehole questionnaire.
