Pressure Drop Screening

Use this skill for public, educational line pressure-drop screening. It estimates a single-phase Darcy-Weisbach pressure gradient and compares it to a recommended pressure-gradient guideline so an agent can flag lines that may exceed standard hydraulic limits before moving to validated line sizing.

When to Use

• When a user asks whether a line pressure drop sits within recommended limits.
• When an agent needs a quick pressure-gradient triage to scope a hydraulic or debottlenecking study.
• When examples must run without confidential piping classes, project line lists, or company piping specs.

Inputs

• fluid_velocity: actual flowing velocity in the line in m/s.
• mixture_density: flowing mixture density in kg/m3.
• viscosity: flowing dynamic viscosity in Pa.s.
• pipe_inner_diameter: pipe inner diameter in m.
• length: line length used for the total pressure drop in m, default 100.0.
• roughness: absolute pipe roughness in m, default 4.6e-5 (commercial steel).
• guideline_bar_per_100m: recommended maximum pressure gradient in bar per 100 m, default 0.5.

Outputs

• reynolds_number: flow Reynolds number.
• friction_factor: Darcy friction factor from laminar or Haaland turbulent form.
• dp_per_100m_bar: screening pressure gradient in bar per 100 m.
• dp_total_bar: screening total pressure drop over the line length in bar.
• guideline_ratio: ratio of the pressure gradient to the recommended guideline.
• pressure_drop_warning: ok, watch, or high.
• assumptions: public assumptions used by the placeholder model.

Engineering Method

The Python class PressureDropModel uses open, published correlations only:

• the Reynolds number uses the standard Re = rho v D / mu form.
• the friction factor uses f = 64 / Re in laminar flow and the public Haaland explicit approximation of the Colebrook equation in turbulent flow.
• the pressure gradient uses the Darcy-Weisbach form dP/L = f (1/D) (rho v^2 / 2).
• the guideline ratio compares the pressure gradient to a configurable recommended gradient aligned with NORSOK P-002 and GPSA style line pressure-gradient guidelines.

This is educational and screening-only logic. It is not a piping standard, a line sizing method, a vendor method, a two-phase or transient hydraulic method, or a replacement for validated hydraulic design and a qualified process engineering review.

Python Usage Pattern

from pressure_drop_screening import PressureDropModel

model = PressureDropModel()
result = model.evaluate(
    fluid_velocity=12.0,
    mixture_density=50.0,
    viscosity=1.2e-5,
    pipe_inner_diameter=0.2,
    length=100.0,
)

print(result.pressure_drop_warning)
print(result.dp_per_100m_bar)
print(result.guideline_ratio)

If the optional neqsim Python package is available, the result records that fact so an agent can recommend moving to validated NeqSim hydraulic models (for example PipeBeggsAndBrills) for real pressure-drop calculations. If it is not installed, the example still runs with public placeholder logic.

Related NeqSim Functionality

For validated pressure-drop calculations, redirect to existing NeqSim classes instead of this screening placeholder:

• neqsim.process.equipment.pipeline.PipeBeggsAndBrills — Beggs and Brills multiphase pipe flow with elevation, holdup, and friction.
• neqsim.process.equipment.pipeline.AdiabaticTwoPhasePipe and neqsim.fluidmechanics flow solvers — rigorous single and two-phase hydraulics.
• neqsim.process.mechanicaldesign.heatexchanger.ThermalDesignCalculator — tube-side f L/D (rho v^2 / 2) pressure drop inside exchangers.

This skill is a public triage layer that decides when to invoke those validated models.

Validation Checklist

• Inputs are positive and densities, velocities, and viscosities are in SI units.
• Example inputs are public and synthetic.
• Tests cover laminar, turbulent, warning, and invalid-input cases.
• Results are described as educational screening indicators.
• Real hydraulic design is redirected to validated methods, NORSOK P-002, GPSA, and qualified review.

Common Mistakes

Limitations

• No proprietary piping classes, project line lists, or company piping specs are included.
• No two-phase, slug, flashing, or transient pressure-drop modelling is performed.
• No fittings, valves, elevation, or acceleration pressure losses are included.

References

• NeqSim repository: https://github.com/equinor/neqsim
• NeqSim Skills Guide: https://github.com/equinor/neqsim/blob/master/docs/integration/skills_guide.md