neqsim-pump-hydraulics-screening

name	neqsim-pump-hydraulics-screening
calculation_basis	screening
version	0.1.0
description	Educational centrifugal-pump hydraulics screening for hydraulic/shaft power, NPSH-available, and best-efficiency-point window using public pump relations and affinity laws. USE WHEN: a task needs a public, screening-level pump power, NPSH-available estimate, and BEP-window check before detailed pump selection.
last_verified	2026-06-18
requires	{"python_packages":[],"java_packages":[],"env":[],"network":[]}

Pump Hydraulics Screening

Use this skill for public, educational centrifugal-pump hydraulics screening. It estimates hydraulic and shaft power, the available net positive suction head (NPSHa), and the best-efficiency-point (BEP) flow ratio so an agent can scope a pumping duty and decide whether to invoke validated NeqSim pump calculations.

When to Use

• When a user asks roughly how much power a pump duty needs.
• When an agent needs a quick NPSH-available margin and cavitation triage.
• When an agent must check that an operating flow sits inside a sensible BEP window.
• When examples must run without confidential pump curves, vendor data, or company specs.

Inputs

• flow_rate: operating volumetric flow in m3/h.
• head: pump differential head in m.
• density: pumped-fluid density in kg/m3.
• efficiency: pump hydraulic efficiency, default 0.70.
• suction_pressure: optional suction pressure in bar absolute (for NPSHa).
• vapor_pressure: optional fluid vapor pressure in bar absolute (for NPSHa).
• static_suction_head: optional static suction head in m, default 0.
• friction_loss: optional suction friction loss in m, default 0.
• npsh_required: optional NPSH required in m (for the margin).
• bep_flow_rate: optional best-efficiency-point flow in m3/h (for the ratio).

Outputs

• hydraulic_power_kw: hydraulic (fluid) power.
• shaft_power_kw: estimated shaft power.
• npsh_available_m: available NPSH, or null if suction data is not supplied.
• npsh_margin_m: NPSHa - NPSHr, or null if not enough data.
• bep_ratio: flow_rate / bep_flow_rate, or null if BEP flow not supplied.
• pump_warning: ok, watch, off-bep, npsh-deficit, or no-rating.
• assumptions: public assumptions used by the placeholder model.

Engineering Method

The Python class PumpHydraulicsModel uses public pump relations only:

• hydraulic power uses P = rho * g * Q * H, with Q converted from m3/h to m3/s.
• shaft power uses P_shaft = P_hydraulic / efficiency.
• available NPSH uses NPSHa = (P_suction - P_vapor) / (rho * g) + static_suction_head - friction_loss.
• the BEP check uses the flow ratio Q / Q_bep against a public preferred window (default 0.70 to 1.20).

This is educational and screening-only logic. It assumes constant density, a single operating point, and does not model affinity-law scaling beyond the inputs, suction recirculation, viscosity correction, minimum-flow recycle, or vendor curves. It is not a replacement for validated pump selection and a qualified rotating-equipment review.

Python Usage Pattern

from pump_hydraulics_screening import PumpHydraulicsModel

model = PumpHydraulicsModel()
result = model.evaluate(
    flow_rate=120.0,
    head=95.0,
    density=820.0,
    efficiency=0.74,
    suction_pressure=4.0,
    vapor_pressure=1.5,
    static_suction_head=3.0,
    friction_loss=0.8,
    npsh_required=3.5,
    bep_flow_rate=130.0,
)

print(result.pump_warning)
print(result.shaft_power_kw)
print(result.npsh_margin_m)

Related NeqSim Functionality

For validated pump calculations, redirect to existing NeqSim classes:

• neqsim.process.equipment.pump.Pump — rigorous pump power and head with real-fluid properties.
• neqsim.process.equipment.pump.PumpCurve / PumpChart — vendor head, efficiency, and power curves.
• neqsim.process.equipment.pump.ESPPump / JetPump — specialized pump types.

This skill is a public hydraulics triage layer that decides when to invoke those validated pump classes.

Validation Checklist

• Flow, head, and density are positive.
• Efficiency is in the interval (0, 1].
• NPSHa is only reported when suction and vapor pressures are supplied.
• Tests cover power, NPSH margin, BEP ratio, and invalid input.
• Real selection is redirected to validated NeqSim pump classes and qualified review.

Common Mistakes

Symptom	Cause	Fix
Power off by a factor	Flow left in m3/h not converted to m3/s	The model converts internally; pass m3/h
NPSHa missing	Suction or vapor pressure not supplied	Provide both suction_pressure and vapor_pressure
BEP ratio missing	bep_flow_rate not supplied	Provide the pump BEP flow
Cavitation not caught	Constant-density assumption near bubble point	Use the validated NeqSim Pump with real properties

Limitations

• No proprietary pump curves, vendor data, or company specs are included.
• No viscosity correction, suction recirculation, or minimum-flow recycle is modeled.
• No real-fluid property variation across the pump is included.

References

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