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:
| 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 |
Convert minor resistance in fittings to major frictional resistance:
| 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 |
