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Engineering Toolbox/Straight-Pipe Pressure Drop

Pressure, Level & Process

Straight-Pipe Pressure Drop

Estimate major friction loss through a straight circular pipe using Darcy-Weisbach. Inputs are kept explicit so the result can be reviewed as an engineering screening calculation.

Straight-run inputs

Use actual line-condition volumetric flow and fluid properties at the relevant operating condition.

Leave blank for automatic laminar/Colebrook calculation. Use only a validated Darcy factor; this field is also required if you intentionally estimate transitional flow.

The prefilled roughness is an example only. Replace it with the engineering basis appropriate to the actual pipe material and condition.

Field use

Screen straight-run friction before adding the rest of the system.

Useful for checking whether line friction is materially significant before valves, fittings, elevation, control elements or other losses are added in a fuller hydraulic assessment.

Calculation basis

ΔP = f (L/D) (ρv²/2)

The automatic factor uses f = 64/Re for laminar flow or the iterative Colebrook-White relation for turbulent flow. The factor is the Darcy/Moody factor.

Scope: steady, fully developed, single-phase, incompressible-flow screening in straight circular pipe. Excludes valves/fittings and other minor losses, static/elevation head, compressibility, flashing, acceleration, two-phase/multiphase effects and non-Newtonian fluids. Standard-condition gas flow must first be converted to actual line-condition volumetric flow.

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