Reciprocating Compressor Screening

Use this skill for public, educational reciprocating-compressor screening. It estimates clearance volumetric efficiency, actual inlet capacity, the required number of stages, discharge temperature, and a rod-load utilisation ratio so an agent can scope a reciprocating-compression study before detailed selection.

When to Use

• When a user asks how many stages a reciprocating compressor needs or what its volumetric efficiency is.
• When an agent needs a quick actual-capacity and discharge-temperature estimate for a positive-displacement machine.
• When examples must run without confidential compressor data, vendor curves, or company specs.

Inputs

• suction_pressure: stage suction pressure P1 in bar absolute.
• discharge_pressure: final discharge pressure P2 in bar absolute.
• suction_temperature: suction temperature T1 in kelvin.
• swept_volume_rate_m3_h: geometric (swept) volume rate in m3/h.
• clearance_fraction: cylinder clearance fraction C, default 0.12.
• specific_heat_ratio: ratio of specific heats k, default 1.3.
• leakage_allowance: leakage/loss allowance L, default 0.03.
• rated_rod_load_kn: optional rated rod load in kN for the rod-load comparison.
• piston_area_m2: optional piston area in m2 for the rod-load comparison.

Outputs

• pressure_ratio: overall P2 / P1.
• stages: integer number of stages keeping each stage below max_stage_ratio.
• stage_pressure_ratio: per-stage pressure ratio.
• volumetric_efficiency: clearance volumetric efficiency.
• actual_inlet_capacity_m3_h: swept rate multiplied by volumetric efficiency.
• discharge_temperature_k: first-stage isentropic discharge temperature.
• rod_load_ratio: gas rod load divided by rated rod load, or null.
• capacity_warning: ok, watch, low-volumetric-efficiency, or discharge-temp-high.
• rod_load_warning: ok, watch, rod-load-exceeded, or no-rating.
• assumptions: public assumptions used by the placeholder model.

Engineering Method

The Python class ReciprocatingCompressorModel uses open positive-displacement relations only:

• staging splits the overall ratio so stage_ratio = (P2 / P1)^(1/stages) stays below max_stage_ratio (default 4.0).
• volumetric efficiency uses VE = 1 - C (r^(1/k) - 1) - L.
• actual inlet capacity uses Q_actual = swept_rate * VE.
• discharge temperature uses T2 = T1 r^((k-1)/k).
• gas rod load uses F = dP * piston_area, compared to the rated rod load.

This is educational and screening-only logic. It assumes constant k, ideal staging, no valve or pulsation losses, and gas-only rod load. It is not a replacement for validated reciprocating-compressor sizing or qualified rotating-equipment review.

Python Usage Pattern

from reciprocating_compressor_screening import ReciprocatingCompressorModel

model = ReciprocatingCompressorModel()
result = model.evaluate(
    suction_pressure=2.0,
    discharge_pressure=120.0,
    suction_temperature=313.15,
    swept_volume_rate_m3_h=800.0,
    rated_rod_load_kn=120.0,
    piston_area_m2=0.04,
)

print(result.stages)
print(result.volumetric_efficiency)
print(result.rod_load_warning)

Related NeqSim Functionality

For validated compression calculations, redirect to NeqSim classes:

• neqsim.process.equipment.compressor.Compressor — rigorous polytropic compression with real-gas properties.
• neqsim.process.equipment.compressor.ReciprocatingCompressor — proposed reciprocating-compressor model (volumetric efficiency, valve losses, rod load); candidate NeqSim gap.
• neqsim.process.mechanicaldesign.compressor.CompressorMechanicalDesign — compressor mechanical design and feasibility.

This skill is a public triage layer that decides when to invoke a validated reciprocating-compressor model.

Validation Checklist

• Suction and discharge pressures are positive and P2 > P1.
• Clearance fraction is in (0, 1) and leakage allowance in [0, 1).
• Tests cover staging, volumetric efficiency, a rod-load comparison, and invalid input.
• Results are described as educational screening indicators.
• Real selection is redirected to validated NeqSim compressor classes and qualified review.

Common Mistakes

Limitations

• No proprietary compressor data, vendor curves, or company specs are included.
• No valve losses, pulsation, or real-gas property variation are modelled.
• Rod load uses gas load only; inertia and load reversal are not included.

References

• API Standard 618, Reciprocating Compressors for Petroleum, Chemical, and Gas Industry Services.
• API Standard 619, Rotary-Type Positive-Displacement Compressors.
• NeqSim repository: https://github.com/equinor/neqsim