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Fittings and Minor Pressure Loss

Minor pressure loss with 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:

Fittings - Minor Pressure Loss Coefficients
FittingMinor 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
Fittings - Minor Pressure Loss Coefficients vs. Dimensions
Minor Loss Coefficient - ξ
FittingNominal bore (mm)
152025324050
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

Convert minor resistance in fittings to major frictional resistance:

Frictional resistance in fittings
for various velocities and values of Minor Loss Coefficient
Velocity
(m/s)
Minor Loss Coefficient - ξ
123451015
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
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