Absolute roughness

Absolute roughness

Pipe MaterialAbsolute roughness k (mm)
Aluminum new0,001-0,002
Brass0,015
Brass new0,001-0,002
Cast iron new0,25-0,8
Cast iron slightly rusted1,5
Cast iron very rusted3
Cast iron with bitumen layer0,2
Copper0,015
Copper new0,001-0,002
Epoxy, vinyl ester and isophthalic pipe0,005
Flexible rubber tubing smooth0,006-0,07
Glass0,015
Lead0,015
Lead new0,001-0,002
Ordinary concrete0,3-1
PVC and Plastic pipes0,0015-0,007
Rough concrete0,3-5
Sheet or asphalted cast iron0,01-0,015
Smoothed cement0,3
Stainless steel electropolished0,0001-0,0008
Stainless steel turned0,0004-0,006
Stainless steel, bead blasted0,001-0,006
Steel pipe after longer use0,2
Steel pipe galvanised0,15
Steel pipe new0,04
Steel pipe slightly rusted0,4
Steel pipe very rusted3,35
Stretched steel0,015
Weld steel0,045
Worn cast iron0,8-1,5

Absolute Roughness (k) is a measure of pipe wall irregularities. The absolute roughness has dimensions of length and is usually expressed in millimeter (mm) or feet (ft). Absolute Roughness is usually defined for a material and can be measured experimentally. Absolute roughness is important when calculating pressure drop particularly in the turbulent flow regime.

For each pipe material either a single pipe roughness value or a range of roughness values is normally provided by the manufacturer. The roughness value, usually denoted as e or k, is used in the calculating the relative roughness of a pipe against the size of its diameter.

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