How the size is chosen
The calculator tries every standard size from 15 NB upward and picks the smallest one that keeps both the velocity and the pressure drop per 100 m within the usual limits for that fluid. Pipe inside diameters are from ASME B36.10M and B36.19M.
v = Q / A ΔP = f × (L / D) × ρv² / 2
f from the Churchill equation (laminar, transition and turbulent flow)
f from the Churchill equation (laminar, transition and turbulent flow)
| Fluid | Velocity (m/s) | Max ΔP (bar/100 m) |
|---|---|---|
| Cooling, process and chilled water | 1.0 – 2.5 | 0.4 |
| Solvents and process liquids | 1.0 – 2.5 | 0.4 |
| Pumped condensate | 0.5 – 1.5 | 0.3 |
| Saturated steam | 10 – 30 | 0.3 |
| Compressed air | 3 – 10 | 0.1 |
| Nitrogen | 3 – 15 | 0.15 |
Good to know
- Pump suction lines are usually one size larger than the discharge, at about 1 m/s, to protect the pump from cavitation.
- Steam and gases: enter the line pressure; the gas is lighter at low pressure, so the same flow needs a bigger pipe.
- Viscous liquids: choose Solvent or process liquid and set the density and viscosity under More options.
Results are estimates for planning and checking. Final line sizes should follow your design basis.