Enter flow, density and viscosity — get the recommended standard pipe size, the governing constraint, velocity and pressure drop.
Open the free calculator →Proper line sizing takes your process requirements as the input and returns the pipe diameter as the output — never the other way around. EnggiBasis scans standard pipe schedules and returns the smallest standard size that satisfies every limit you set:
It also tells you which constraint governs the result, so you know why the size came out the way it did.
The recommended maximum fluid velocity to limit erosion is:
Ve = C / √ρ
where Ve is the erosional velocity limit (ft/s), ρ is the fluid (or mixture) density (lb/ft³), and C is an empirical constant — commonly 100 for continuous service and 125 for intermittent service.
Frictional pressure drop along the pipe is:
ΔP = f · (L/D) · (ρ·v²/2)
with the Darcy friction factor f from the Colebrook-White equation (a function of Reynolds number and relative roughness), L the length, D the internal diameter and v the velocity.
EnggiBasis steps through standard pipe sizes (Sch 40, 80, etc.), computes velocity and ΔP for each, and returns the smallest one where velocity ≤ your limits and ΔP/100 m ≤ your allowable.
Sizing vs rating: a real sizing tool outputs the diameter. EnggiBasis also offers a "check a size" mode (diameter in → velocity & ΔP out) for when you're verifying an existing line.
Water-like liquid, continuous service:
| Input | Value |
|---|---|
| Flow rate | 50 m³/h |
| Density | 850 kg/m³ |
| Viscosity | 2 cP |
| Max velocity | 3 m/s |
| Max ΔP / 100 m | 25 kPa |
Result: recommended 4″ Sch 40 (ID 102.3 mm) — the size is set by the ΔP/100 m limit (the next size down exceeds it). Velocity ≈ 1.69 m/s, Reynolds ≈ 73,500 (turbulent), ΔP ≈ 25 kPa/100 m. Try it with your own numbers →
Choose the smallest standard diameter whose velocity stays under the erosional and design limits and whose pressure drop per 100 m stays under your allowable. EnggiBasis does this scan automatically and shows the governing constraint.
Ve = C / √ρ, with C ≈ 100 (continuous) or 125 (intermittent) and ρ the mixture density.
Liquid line sizing is free. Gas and two-phase line sizing are included in EnggiBasis Pro (₹99/month).
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