| name | neqsim-dry-gas-seal-screening |
| calculation_basis | screening |
| version | 0.1.0 |
| description | Educational dry gas seal supply and condensation screening for centrifugal compressors. USE WHEN: a task needs a public, screening-level estimate of seal-gas and separation-gas supply demand and a seal-gas condensation-margin check (cavity temperature versus hydrocarbon dew point) before detailed dry gas seal system design per API 692. |
| last_verified | 2026-06-19 |
| requires | {"python_packages":[],"java_packages":[],"env":[],"network":[]} |
Dry Gas Seal Screening
Use this skill for public, educational dry gas seal screening on centrifugal compressors. It estimates the seal-gas and separation-gas supply demand from the primary seal leakage rate and flags retrograde-condensation risk by comparing the seal cavity temperature against a hydrocarbon dew point at the seal/vent reference condition.
When to Use
- When a user asks whether a compressor dry gas seal has adequate seal-gas supply margin.
- When an agent needs a quick condensation-risk triage for the primary vent / standpipe dead-leg before a detailed seal study.
- When examples must run without confidential seal vendor data, machine line lists, or project seal-gas conditioning specifications.
Inputs
seal_leakage_rate_nl_per_min: primary seal leakage rate at standard conditions in NL/min per seal.seal_cavity_temperature_c: seal cavity (process-side) temperature in degrees C.hydrocarbon_dew_point_c: hydrocarbon dew point at the seal/vent reference condition in degrees C.seal_count: number of seals supplied (default 2: drive end and non-drive end).supply_margin: seal-gas supply margin over leakage, dimensionless, default 1.25.separation_gas_rate_nl_per_min: separation (secondary) gas rate per seal in NL/min, default 0.0.
Outputs
total_seal_gas_supply_nl_per_min: screening seal-gas supply demand.separation_gas_supply_nl_per_min: screening separation-gas supply demand.seal_gas_supply_margin_ratio: the applied supply margin over leakage.condensation_margin_c: seal cavity temperature minus the hydrocarbon dew point.condensation_warning: ok, watch, or high (a small or negative margin means higher condensation risk).assumptions: public assumptions used by the placeholder model.
Engineering Method
The Python class DryGasSealModel uses open, public concepts only:
- seal-gas supply demand is the primary seal leakage multiplied by the seal count and a supply margin, reflecting the API 692 intent that supply must exceed leakage to keep the seal faces clean.
- separation-gas supply demand scales with the seal count.
- the condensation margin compares the seal cavity temperature against a hydrocarbon dew point at the seal/vent reference condition. A small or negative margin flags retrograde condensation risk in the primary vent piping and standpipe dead-legs, which is the failure mode that seal-gas conditioning units exist to prevent.
This is educational and screening-only logic. It is not a seal vendor method, not a seal-gas conditioning design, and not a replacement for validated dry gas seal analysis and a qualified rotating-equipment review.
Python Usage Pattern
from dry_gas_seal_screening import DryGasSealModel
model = DryGasSealModel()
result = model.evaluate(
seal_leakage_rate_nl_per_min=280.0,
seal_cavity_temperature_c=44.0,
hydrocarbon_dew_point_c=40.0,
seal_count=2,
supply_margin=1.25,
separation_gas_rate_nl_per_min=120.0,
)
print(result.condensation_warning)
print(result.total_seal_gas_supply_nl_per_min)
print(result.condensation_margin_c)
If the optional neqsim Python package is available, the result records that fact so an agent can recommend moving to validated NeqSim seal-gas dew-point and condensation analysis. If it is not installed, the example still runs with public placeholder logic.
Validation Checklist
Common Mistakes
| Symptom | Cause | Fix |
|---|
| Condensation never flagged | Dew point taken at cavity pressure instead of the vent/expanded condition | Use the hydrocarbon dew point at the seal/vent reference condition |
| Supply demand looks low | Supply margin set to 1.0 | Use a supply margin above 1.0 consistent with the seal-gas control philosophy |
| Wrong total supply | Seal count not matching the machine arrangement | Set seal_count to the actual number of seals supplied |
Limitations
- No seal vendor leakage curves, clearance models, or qualification data are included.
- No isenthalpic (Joule-Thomson) expansion or transient standpipe cooldown is modelled.
- No seal-gas conditioning unit (heater/separator) sizing is performed.
- Not suitable for safety-critical, design, guarantee, or standards-compliance work.
Related NeqSim Functionality
This educational screening corresponds to validated, rigorous functionality in the NeqSim Java library that a qualified engineer should use for design-grade work:
neqsim.process.equipment.compressor.DryGasSealAnalyzer — isenthalpic seal-gap expansion, retrograde condensation mapping, dead-leg cooldown, condensate accumulation, and seal-gas conditioning unit sizing per API 692.neqsim.process.measurementdevice.HydrocarbonDewPointAnalyser — hydrocarbon dew-point evaluation for the seal-gas stream.neqsim.process.equipment.valve.ThrottlingValve — Joule-Thomson expansion modelling across the seal gap.
In Python the same classes are reachable through the neqsim package (for example from neqsim import jneqsim).
References
