| name | neqsim-vacuum-collapse-screening |
| calculation_basis | screening |
| version | 0.1.0 |
| description | Educational vacuum-collapse (implosion) screening for a blocked-in vessel that cools down, with vacuum-depth and external-rating flags. USE WHEN: a task needs a public, screening-level check of whether a closed vessel cooldown or steam/vapour condensation can pull a vacuum below the external pressure rating, without proprietary vacuum-collapse design methods. |
| last_verified | 2026-05-31 |
| requires | {"python_packages":[],"java_packages":[],"env":[],"network":[]} |
Vacuum Collapse Screening
Use this skill for public, educational vacuum-collapse (external-pressure implosion) screening examples. When a vessel is blocked in and cools down, the trapped vapour contracts and any condensable vapour (for example steam) condenses, so the internal pressure can fall below atmospheric and pull a vacuum. This skill provides a simple final-pressure estimate, a vacuum-depth indicator, and an external-rating flag that help agents structure early reverse-pressure questions before moving to a validated NeqSim constant-volume cooldown model and a vessel external-pressure (buckling) review.
When to Use
- When a user asks for a quick, public vacuum-collapse triage for a blocked-in vessel.
- When an agent needs a placeholder estimate of how deep a cooldown or condensation vacuum could be.
- When examples must run without confidential vessel geometry, external-pressure ratings, or company vacuum design bases.
Inputs
initial_pressure: starting pressure in bara.initial_temperature: starting temperature in C.cold_end_temperature: final cooled temperature in C (must be below the initial temperature).condensable_fraction: fraction of the initial vapour that condenses on cooldown, 0.0 to 1.0, default 0.0.external_pressure_rating: vessel external-pressure (vacuum) rating in bara, default 0.0 for full vacuum.atmospheric_pressure: atmospheric pressure in bara, default 1.01325.
Outputs
estimated_final_pressure_bara: ideal-gas constant-volume final pressure after cooldown and condensation.vacuum_depth_bar: amount the final pressure sits below atmospheric, in bar (0.0 when no vacuum).margin_to_rating_bar: final pressure minus the external-pressure rating; negative means the rating is exceeded.vacuum_present: True when the final pressure is below atmospheric.exceeds_rating: True when the final pressure falls below the external-pressure rating.verdict: no_vacuum, vacuum_within_rating, or vacuum_exceeds_rating.collapse_warning: ok, watch, or high.assumptions: public assumptions used by the placeholder model.
Engineering Method
The Python class VacuumCollapseModel uses open placeholder calculations only:
- the non-condensing pressure drop uses the ideal-gas constant-volume relation
P2 = P1 * (T2 / T1) for a rigid, blocked-in vessel.
- any
condensable_fraction is removed from the vapour, scaling the final pressure by (1 - condensable_fraction) as a screening proxy for steam or vapour condensation.
- the vacuum depth is the atmospheric pressure minus the final pressure, floored at zero.
- the rating margin is the final pressure minus the external-pressure rating, and a negative margin sets the exceeds-rating flag.
- warnings combine a vacuum-present indicator with the exceeds-rating flag.
This is educational and screening-only logic. It is not an external-pressure (buckling) standard, a vessel design method, a vendor method, or a replacement for a validated NeqSim constant-volume cooldown model and a code external-pressure review (for example ASME BPVC Section VIII external pressure).
Python Usage Pattern
from vacuum_collapse_screening import VacuumCollapseModel
model = VacuumCollapseModel()
result = model.evaluate(
initial_pressure=1.8,
initial_temperature=120.0,
cold_end_temperature=20.0,
condensable_fraction=0.85,
external_pressure_rating=0.5,
)
print(result.verdict)
print(result.estimated_final_pressure_bara)
print(result.vacuum_depth_bar)
print(result.margin_to_rating_bar)
print(result.collapse_warning)
If the optional neqsim Python package is available, the result records that fact so an agent can recommend moving to the validated NeqSim VacuumCollapseAnalyzer, which performs a real constant-volume (TVflash) cooldown of the actual fluid, tracks condensation, and reports a cooling curve and make-up gas requirement. If it is not installed, the example still runs with public placeholder logic.
Validation Checklist
Common Mistakes
| Symptom | Cause | Fix |
|---|
Treating estimated_final_pressure_bara as a design vacuum | Ideal-gas placeholder ignores real-fluid condensation and make-up | Use the NeqSim VacuumCollapseAnalyzer constant-volume cooldown model |
| Missing deep vacuum on steam systems | condensable_fraction left at 0.0 for a condensing vapour | Set a realistic condensable fraction or use the rigorous model |
| Ignoring external-pressure rating | external_pressure_rating not provided | Confirm the vessel external-pressure (vacuum) rating before screening |
| Assuming a vacuum breaker removes the risk | Make-up or vacuum-relief device not credited in screening | Verify vacuum relief sizing in the validated workflow |
Limitations
- No proprietary vessel geometry, external-pressure rating, or project vacuum design bases are included.
- No real-fluid condensation, multi-phase behaviour, or make-up gas flow is modelled.
- No shell buckling, stiffener, or out-of-roundness external-pressure calculation 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.safety.vacuum.VacuumCollapseAnalyzer — constant-volume (TVflash) cooldown of a blocked-in vessel, vacuum-depth versus external rating, cooling curve, and make-up gas requirement.neqsim.process.safety.vacuum.VacuumCollapseResult — structured result with the cooling curve, verdict, and JSON export.
In Python the same classes are reachable through the neqsim package (for example from neqsim import jneqsim).
References
