Two metrics are used when selecting the steam line diameter: pressure loss and steam velocity. In long distribution lines, it is usually the pressure loss that is decisive; because sufficient pressure must reach the user at the end of the line. This tool calculates the pressure loss for each pipe diameter at the flow rate and pressure you input and selects the smallest diameter that does not exceed the allowable value . You can also compare the next smaller and next larger diameters in the results table.
Formula
f: Darcy coefficient of friction (Swamee-Jain), L: pipe length, d: inner diameter, ΣK: local loss coefficients of elbows and valves, ρ: steam density, v: steam velocity.
Example
If a maximum pressure loss of 0.2 bar (20 kPa) is allowed in a line carrying 3,000 kg/h of saturated steam 100 m at a pressure of 7 bar(g), the choice is DN100 in a DIN 2448 pipe: pressure loss 16.6 kPa, steam velocity 22.2 m/s. At the next smaller size, DN80, the loss exceeds the limit.
Practical values
- A common design range is a loss of 0.1–0.5 bar per 100 m on the main distribution lines; the loss should not exceed 10% of the inlet pressure.
- You can add local losses by entering the number of elbows, globe valves, gate valves, and check valves from the advanced settings.
- Enter the steam temperature in the advanced settings for superheated steam lines.
Pipe inner diameters are taken from the tables of DIN 2448 / EN 10220 seamless steel pipe and ASME B36.10 Schedule 40/80. Steam properties are calculated with IAPWS-IF97, viscosity by IAPWS-2008; the coefficient of friction is found by the Swamee-Jain formula, an explicit approximation of the Colebrook equation.
You can use the steam pipe diameter calculation according to the speed limit for selection. To evaluate your steam system as a whole, you can take a look at our steam boiler guide and get a free quote for your project.