Fittings and Minor Pressure Loss

Minor pressure loss for fittings in piping heating systems

Minor pressure loss in a piping system is caused by valves, elbows and other components. The tables below can be used as an indication of the minor loss coefficients of some common components in piping systems:

Fitting Minor Loss Coefficient - ξ
Radiators 3.0
Boilers 2.5
Abrupt velocity change 1.0
Cross-over 0.5
Tee, straight way 1.5
Tee, branch 1.5
Tee, counter current 3.0

Minor Loss Coefficient - ξ
Fitting Nominal bore (mm)
15 20 25 32 40 50
Radiator valve, angle
Radiator valve, straight
7
4
4
2
4
2
4
2
Gate valve, screwed
Gate valve, flanged
1.5
0
0.5
0
0.5
0
0.5
0
0.5
0
0.5
0
Elbow 2 2 1.5 1.5 1.0 1.0
Bend 1.5 1.5 1 1 0.5 0.5

The table below can used to convert minor resistance in fittings to major frictional resistance:

Frictional resistance of fittings
for various velocities and values of Minor Loss Coefficient - ξ
Velocity
m/s
Minor Loss Coefficient - ξ
1 2 3 4 5 10 15
0.24 0.029 0.057 0.086 0.115 0.144 0.285 0.43
0.50 0.125 0.25 0.375 0.50 0.62 1.25 1.87
0.75 0.28 0.56 0.84 1.12 1.40 2.80 4.20
1.0 0.50 1.00 1.50 2.00 2.50 5.00 7.50
1.2 0.72 1.44 2.15 2.85 3.60 7.20 10.80
1.5 1.12 2.25 3.35 4.50 5.60 11.20 16.8
1.7 1.44 2.90 4.30 5.80 7.20 14.4 21.6
2.0 2.00 4.00 6.00 8.00 1.00 19.9 29.9
2.4 2.85 5.70 8.60 11.50 1.44 28.7 43.1
2.8 3.90 7.80 11.70 15.60 1.95 39.1 58.6
3.0 4.50 9.00 13.50 17.90 2.24 44.9 67.3

Related Topics

  • Heating - Heating systems - capacity and design of boilers, pipelines, heat exchangers, expansion systems and more

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