Neqsim Acoustic Induced Vibration Screening

Acoustic-Induced Vibration Screening

Use this skill for public, educational acoustic-induced-vibration (AIV) screening of gas pressure-reducing devices. It estimates the generated sound power level, the pipe diameter-to-thickness ratio, an allowable sound power level, and a likelihood-of-failure (LOF) index so an agent can scope an AIV study before a detailed piping-vibration assessment. It complements the flow-induced-vibration-screening skill, which covers gas flow-induced vibration through a kinetic-energy index.

When to Use

• When a user asks whether a control valve, relief valve, or restriction orifice creates an AIV risk.
• When an agent needs a quick sound-power-level and LOF estimate downstream of a high pressure drop.
• When examples must run without confidential valve data, vendor noise curves, or company specs.

Inputs

• mass_flow_kg_s: gas mass flow through the device in kg/s.
• upstream_pressure_bar: upstream pressure P1 in bar absolute.
• downstream_pressure_bar: downstream pressure P2 in bar absolute.
• pipe_outside_diameter_mm: downstream pipe outside diameter in mm.
• wall_thickness_mm: downstream pipe wall thickness in mm.
• molecular_weight: gas molecular weight, default 19.
• temperature_k: gas temperature in kelvin, default 313.15.
• downstream_pipe_length_m: downstream pipe length in m, default 10.
• sound_power_level_db: optional measured/known sound power level; if omitted it is computed.

Outputs

• pressure_drop_ratio: (P1 - P2) / P1.
• sound_power_level_db: supplied or computed sound power level in dB.
• diameter_thickness_ratio: pipe D / t.
• allowable_sound_power_level_db: allowable sound power level from the D / t correlation.
• likelihood_of_failure: dimensionless AIV LOF index.
• downstream_pipe_length_m: echoed downstream pipe length.
• risk_warning: low-risk, medium-risk, or high-risk.
• assumptions: public assumptions used by the placeholder model.

Engineering Method

The Python class AcousticInducedVibrationModel uses the open Energy Institute / Carucci-Mueller AIV screening form only:

• sound power level uses PWL = 10 log10[(dP/P1)^3.6 * mdot^2 * (T/MW)^1.2] + constant.
• diameter-to-thickness ratio uses D / t.
• allowable sound power level uses PWL_allow = reference - slope * (D / t), so higher D / t lowers the limit.
• likelihood of failure uses LOF = 1 + (PWL - PWL_allow) / spread, clamped at zero, so higher PWL and higher D / t both raise the LOF.

This is educational and screening-only logic. The correlation constants are documented screening approximations, not certified AIV limits. It assumes a single gas pressure-reducing device, ignores branch-connection geometry, weld type, and downstream fitting layout, and is not a replacement for a validated AIV assessment or qualified piping-vibration review.

Python Usage Pattern

from acoustic_induced_vibration_screening import AcousticInducedVibrationModel

model = AcousticInducedVibrationModel()
result = model.evaluate(
    mass_flow_kg_s=12.0,
    upstream_pressure_bar=90.0,
    downstream_pressure_bar=20.0,
    pipe_outside_diameter_mm=323.9,
    wall_thickness_mm=9.5,
)

print(result.sound_power_level_db)
print(result.likelihood_of_failure)
print(result.risk_warning)

Related NeqSim Functionality

For validated vibration screening, redirect to NeqSim classes:

• neqsim.process.safety.vibration.AcousticInducedVibrationLOF — proposed AIV likelihood-of-failure model (PWL, D/t, allowable-PWL correlation); candidate NeqSim gap.
• neqsim.process.safety.vibration.FlowInducedVibrationLOF — proposed flow-induced-vibration model; candidate NeqSim gap.
• The flow-induced-vibration-screening community skill — gas flow-induced vibration through a kinetic-energy index.

This skill is a public triage layer that decides when to invoke a validated AIV assessment.

Validation Checklist

• Upstream and downstream pressures are positive and P1 > P2.
• Pipe outside diameter exceeds twice the wall thickness.
• Tests cover sound-power-level computation, a supplied sound-power-level path, a high-risk case, and invalid input.
• Results are described as educational screening indicators.
• Real assessment is redirected to validated NeqSim vibration classes and qualified review.

Common Mistakes

Limitations

• No proprietary valve data, vendor noise curves, or company specs are included.
• Branch-connection geometry, weld type, and downstream fitting layout are not modelled.
• The correlation constants are documented screening approximations only.

References

• Energy Institute, Guidelines for the Avoidance of Vibration Induced Fatigue Failure in Process Pipework, 2nd Edition.
• Carucci, V. A., and Mueller, R. T., Acoustically Induced Piping Vibration in High Capacity Pressure Reducing Systems, ASME 82-WA/PVP-8.
• NeqSim repository: https://github.com/equinor/neqsim