Pipe pressure drop and sizing
Friction, fittings and elevation pressure drop for liquid lines — with velocity and pressure drop for every Schedule 40 size.
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The Pipe Sizing and Pressure Drop Excel tool does everything here and more: pressure drop or allowable flow for liquid, gas and steam lines, with fittings, elevation, choked-flow and flashing checks and a size table over every NPS of your schedule. Print-ready report, any units, visible formulas, no macros.
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How this calculator works
Pressure drop = friction + fittings + elevation. Friction by Darcy-Weisbach, ΔP = f·(L/D)·ρv²/2, with the Darcy friction factor solved exactly from the Colebrook equation (64/Re in laminar flow). Fittings and valves by the resistance-coefficient method, ΔP = ΣK·ρv²/2. Elevation, ρ·g·Δz. Water density and viscosity come from steam-table values for the temperature you enter.
The example is 200 m³/h of water at 25 °C in 100 m of 6" Schedule 40 steel pipe, ΣK = 5, rising 10 m: velocity 2.98 m/s, friction 0.47 bar, fittings 0.22 bar, elevation 0.98 bar — 1.66 bar in total. The sizing table shows every Schedule 40 size at the same flow, so you can pick the line in one look.
Limits: single-phase, incompressible liquid; for gases with more than about 10 % pressure drop, use a compressible-flow method. K values vary by maker and size — use the valve or fitting maker's value where you have it. References: Perry's Chemical Engineers' Handbook §6; Crane, Flow of Fluids (TP-410) for K values; Colebrook (1939); Ludwig Vol. 1 ch. 2; GPSA Sec. 17.