Friction Loss for Pipe Sizing
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A. Friction Losses in Pipe DARCY-WEISBACH formula L V 2 H f = f ( ----- ) ------ d 2g Where L = Length of pipe (ft) d = Inside diameter (ft) V = Velocity (ft /sec) g = Gravitational constant (ft/sec 2 ) f = DARCY-WEISBACH friction loss coefficient f = function (Re * ε/d) H f = Head loss due to friction (ft) ε = Absolute roughness (ft) Commercial pipe (new) ε (ft) Glass, drawn brass, copper, lead Wrough iron, steel Asphalted cast iron Galvanized iron Wood stave Concrete Riveted steel Smooth 0.00015 0.0004 0.00085 0.0006 - 0.003 0.001 - 0.01 0.003 - 0.03 Page 8 of 30
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Transcript of Friction Loss for Pipe Sizing
A. Friction Losses in Pipe DARCY-WEISBACH formula
L V2
Hf = f ( ----- ) ------ d 2g Where L = Length of pipe (ft) d = Inside diameter (ft) V = Velocity (ft /sec) g = Gravitational constant (ft/sec2) f = DARCY-WEISBACH friction loss coefficient f = function (Re * ε/d) Hf = Head loss due to friction (ft) ε = Absolute roughness (ft)
Commercial pipe (new)
ε (ft)
Glass, drawn brass, copper, lead Wrough iron, steel Asphalted cast iron Galvanized iron Wood stave Concrete Riveted steel
Smooth
0.00015
0.0004
0.00085
0.0006 - 0.003
0.001 - 0.01
0.003 - 0.03
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PIPE ROUGHNESS VALUES Jacques Chaurette p. eng.
www.lightmypump.com February 2003
Pipe absolute roughness values (RMS) Material Absolute roughness
(in x 10-3) Absolute roughness (micron or m x 10-6)
Riveted steel1 36-360 915-9150 Concrete1 12-120 305-3050
Ductile iron2 102 2591 Wood stave1 3.6-7.2 91-183
Galvanized iron1 6 152
Cast iron – asphalt dipped1 4.8 122 Cast iron uncoated1 10 254
Carbon steel or wrought iron1 1.8 45 Stainless steel1 1.8 45
Fiberglass3 0.2 5
Drawn tubing – glass, brass, plastic1
0.06 1.5
Copper2 0.06 1.5 Aluminium2 0.06 1.5
PVC2 0.06 1.5 Red brass2 0.06 1.5
Sources : 1. Cameron hydraulic data Book 2. Enginereed Software’s PIPE-FLO software www.engineered-
software.com 3. Fiberglass Pipe Handbook, SPI Composites Institute
B. Friction Losses in Piping Components
For purposes of calculating losses in a piping system, fittings and valves are made into equivalent lengths of pipe.
One 90O LR elbow has the same head loss as a piece of pipe 20D long. 90o Short radius elbow = 1 D 90o Long radius elbow = 1.5 D
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C. Equivalent lengths of pipe of various valves & fittings
Valve/Fitting
Equivalent
length L/D
Drawing
Elbows : # 90o Short radius # 90o Long radius # 45o Short radius # 45o Long radius
30 20 16 12
Tees* : Branch flow Run flow
60 20
Laterals* : Branch-Run flow Run-Branch flow Run-Run Run-Run Branch-Run reverse Run-Branch reverse
← →
30 40 20 25
130 130
Valves : # Globe-Conventional # Globe-60o Y Pattern # Globe-45o Y Pattern # Angle-Conventional # Cock -Straight through -Three way-Run -Three way-Branch Check -Conventional Swing -Clearway Swing -Globe Lift or Stop -Angle Lift or Stop -Inline Ball Gate-Disk
340 175 145 145
18 44
140
135 50
345 145 150 13
* For full size branches. Page 12 of 30
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Resistance coefficients for
various pipe entrance and exit conditions
L K = f ( ----- )
d Head loss due to friction at exit/entrance, HL = K (V2 /2g)
Entrances
K = 0.04
Well rounded entrance
K = 0.23
Slightly rounded entrance
K = 0.5
Sharp edged entrance
K = 0.78
Inward projected pipe entrance
Exits
K = 1.0
Rounded exit
K = 1.0
Sharp edged exit
K = 1.0
Projecting pipe exit
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