Multiphase Pipe Sizing Calculator
Professional pipe sizing with detailed pressure drop analysis, velocity criteria, equivalent length for fittings, and flow regime prediction. Based on Darcy-Weisbach, Crane TP-410M, and API RP 14E standards.
Liquid Phase Methodology
Darcy-Weisbach: \[ \Delta P = f \cdot \frac{L_{eq}}{D} \cdot \frac{\rho V^2}{2} \]
\(L_{eq} = L_{straight} + \sum L_{equivalent}\) (fittings). Friction factor \(f\) via Swamee-Jain:
\[ f = \frac{0.25}{\left[\log_{10}\left(\frac{\varepsilon}{3.7D} + \frac{5.74}{Re^{0.9}}\right)\right]^2} \]
Reynolds number \(Re = \frac{\rho V D}{\mu}\).
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📊 Design Criteria (Velocity & ΔP/L Limits) - Click to toggle
| Service Type | Avg ΔP/L | Max ΔP/L | Max Total ΔP | Velocity Range |
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Source: GPSA Engineering Data Book, Section 17; API RP 14E; Perry's Chemical Engineers' Handbook
Liquid Pipe Sizing — Darcy-Weisbach Method
Liquid pipe sizing is the process of selecting the optimal pipe diameter for single-phase liquid flow. It is fundamental in water supply, chemical processing, pump discharge, and cooling water systems. The Darcy-Weisbach equation is the industry standard for calculating frictional pressure drop in liquid pipelines.
Key Parameters for Liquid Flow
- Flow rate — volumetric flow (m³/hr or gpm) determines velocity and pipe diameter.
- Density and viscosity — affect Reynolds number and friction factor.
- Pipe roughness — carbon steel (0.045 mm) vs. stainless steel (0.002 mm) changes friction.
- Fittings — elbows, tees, and valves add equivalent length.
Design Criteria for Liquid Lines
Typical velocities: 0.6–2.4 m/s for water, 1.5–4.5 m/s for pump discharge. Pressure drop limits range from 0.06 kPa/m (pump suction) to 1.5 kPa/m (short lines).
Liquid Example: Water flow 50 m³/hr, density 1000 kg/m³, viscosity 1 cP, pipe length 100 m, 2 elbows.
Result: Recommended 3" pipe, velocity 2.1 m/s, pressure drop 0.34 bar/100m.
Liquid Phase FAQs
Gas Pipe Sizing — Crane TP-410M Isothermal Method
Gas pipe sizing is more complex than liquid due to compressibility. As gas flows, pressure drops and density changes, affecting velocity. The Crane TP-410M isothermal method accounts for these effects, solving iteratively for outlet pressure.
Key Parameters for Gas Flow
- Mass flow rate — kg/hr or lb/hr (gas density changes with pressure).
- Inlet pressure and temperature — determine density and compressibility.
- Pipe roughness — gas lines typically use smoother pipe (0.028 mm).
- Fittings — equivalent length method applies to gas as well.
Design Criteria for Gas Lines
Velocities: 10–30 m/s for gas inside battery, 15–40 m/s for compressor discharge. Pressure drop: 0.05–0.11 kPa/m typical.
Gas Example: Methane flow 5,242 kg/hr, inlet 22 barg, 25°C, density 19.02 kg/m³, 100 m pipe.
Result: Recommended 3" pipe, outlet velocity 18.5 m/s, pressure drop 0.087 bar/100m.
Gas Phase FAQs
Two-Phase Pipe Sizing — Lockhart-Martinelli & API RP 14E
Two-phase flow occurs when gas and liquid flow together in a pipeline. This is common in oil & gas production, refinery overheads, and chemical reactors. The interaction between phases creates complex flow regimes (slug, annular, stratified) that affect pressure drop and erosion.
Key Parameters for Two-Phase Flow
- Liquid and gas mass flow rates — determine phase fractions.
- Densities and viscosities — for both phases.
- API RP 14E C-factor — 100 for continuous service, 125 for non-continuous.
- Flow regime — predicted using Mandhane map.
Design Criteria for Two-Phase Lines
Erosional velocity limit: \(V_{max} = \frac{C}{\sqrt{\rho_m}}\). Pressure drop is calculated using the Lockhart-Martinelli multiplier.
Two-Phase Example: Liquid 10,000 kg/hr, gas 500 kg/hr, densities 800 and 5 kg/m³, viscosities 0.5 and 0.015 cP.
Result: Recommended 4" pipe, mixture velocity 3.2 m/s, regime: Slug Flow, erosional check PASS.