LB-e
Absolute roughness K in mm for various materials
|
Drawn glass, lead, copper and brass tubes |
|
0 – 0.0015 |
|
Drawn steel tubes |
New |
0.04 (0.02 – 0.1) |
|
Cleaned after long service |
0.15 – 0.20 |
|
|
Moderately rusted or slightly fouled |
≤ 0.40 |
|
|
Heavily fouled |
≤ 3.0 |
|
|
Galvanized sheet steel Galvanized steel tubes |
Smooth (air ducts) |
0.07 |
|
Normally galvanized |
0.15 |
|
|
Welded steel pipes |
New |
0.05 (up to 0.1) |
|
New bituminized |
0.05 |
|
|
Used, cleaned |
0.15 – 0.20 |
|
|
Uniformly rusted |
≤ 0.40 |
|
|
Slightly fouled |
1 – 1.5 |
|
|
Heavily fouled |
2 – 4 |
|
|
Riveted steel pipe |
|
0.9 (0.5 – 10) |
|
Cast iron pipes |
New |
0.26 (up to 1) |
|
New bituminized |
0.10 – 0.15 |
|
|
Slightly rusted |
1.0 – 1.5 |
|
|
Fouled |
1.4 – 4.0 |
|
|
Concrete conduits |
Smooth finish |
0.3 (up to 0.8) |
|
Rough |
1.2 (up to 3) |
|
|
Fibrous concrete pipes |
(Eternit; Toschi) |
0.05 –0.1 |
|
Wooden boards |
Unplaned |
0.7 |
|
Planed |
0.2 |
|
|
Brickwork |
Normal bonds |
1.3 |
|
Plastic tubes |
|
≤ 0.0015 |
Values submitted as a guide in estimating the velocity w of various media in tubes
|
Medium |
|
w in m/s |
|
Oil |
In oil lines |
1 - 2 |
|
Water |
In lines of some length |
0.5 - 1 |
|
In heat exchanger tubes |
1 - 3 |
|
|
Downstream from reciprocating pumps |
1 - 2 |
|
|
Downstream from centrifugal pumps |
1.5 - 3 |
|
|
Upstream from turbines |
2 - 7 |
|
|
Gases |
At low pressures |
5 - 30 |
|
At moderate pressures |
5 - 20 |
|
|
At high pressures |
3 - 6 |
|
|
Compressed air |
In ducts |
2 - 4 |
|
Steam |
1 - 10 bar |
15 - 20 |
|
10 - 40 bar |
20 - 40 |
|
|
40 - 125 bar |
30 - 60 |
Coil geometry