API 2000 tank vent-demand and capacity screening

Api2000TankVentingScreeningKernel provides a narrow deterministic screen for API-2000 7th Ed. It aggregates caller-controlled normal in-/out-breathing demand, compares the resulting normal and emergency demands with externally rated capacities, and checks the corresponding rated pressure/vacuum conditions against tank limits. Every calculated result remains SCREENING and requires engineering review; it is not an API conformity decision or a vent-sizing method.

API’s 2025 refining catalog identifies API Standard 2000, 7th Edition, March 2014. The public API edition preview describes normal and emergency vapor venting for aboveground petroleum/product storage tanks and refrigerated tanks, and excludes external floating-roof tanks. This first kernel intentionally narrows applicability further to caller-verified, non-refrigerated fixed-roof service. Use the purchased standard and project procedure to derive demands, combinations, settings, ratings, and acceptance criteria.

Calculation boundary

All gas demands and capacities must use the same stated reference temperature and absolute pressure. For maximum liquid filling rate $Q_f$, caller-controlled outbreathing displacement ratio $R_o$, maximum withdrawal rate $Q_w$, caller-controlled inbreathing displacement ratio $R_i$, and externally established thermal/other demands, the kernel reports:

\[Q_{normal,out}=Q_fR_o+Q_{thermal,out}+Q_{other,out}\] \[Q_{normal,in}=Q_wR_i+Q_{thermal,in}+Q_{other,in}.\]

The total emergency outbreathing demand is supplied directly. NeqSim deliberately does not derive it from tank size, wetted area, fire exposure, product properties, or API tables. Each utilization is demand divided by externally rated available capacity. Pressure margins are the controlled tank positive-pressure or vacuum limit minus the pressure/vacuum magnitude at the corresponding rated capacity.

Runnable Java example

StandardEdition edition = StandardEdition.defaultEdition(StandardType.API_2000);
Api2000TankVentingScreeningKernel.Input input = Api2000TankVentingScreeningKernel.Input
    .builder(edition, "Tank")
    .liquidFillingRateM3PerS(0.1)
    .fillingOutbreathingVolumeRatio(1.05)
    .liquidWithdrawalRateM3PerS(0.08)
    .withdrawalInbreathingVolumeRatio(1.0)
    .thermalOutbreathingRateM3PerS(0.02)
    .thermalInbreathingRateM3PerS(0.03)
    .otherNormalOutbreathingRateM3PerS(0.005)
    .otherNormalInbreathingRateM3PerS(0.005)
    .totalEmergencyOutbreathingRateM3PerS(0.5)
    .normalOutbreathingRatedCapacityM3PerS(0.2)
    .normalInbreathingRatedCapacityM3PerS(0.15)
    .emergencyOutbreathingRatedCapacityM3PerS(0.6)
    .tankMaximumPositiveGaugePressurePa(5000.0)
    .tankMaximumVacuumPressurePa(2000.0)
    .normalOutbreathingRatedGaugePressurePa(3000.0)
    .normalInbreathingRatedVacuumPressurePa(1500.0)
    .emergencyOutbreathingRatedGaugePressurePa(4500.0)
    .flowReferenceTemperatureK(288.15)
    .flowReferencePressurePaAbsolute(101325.0)
    .fixedRoofNonRefrigeratedApplicabilityVerified(true)
    .ventDemandBasisVerified(true)
    .ratedCapacityBasisVerified(true)
    .pressureVacuumBasisVerified(true)
    .normalCombinationBasisVerified(true)
    .emergencyCombinationBasisVerified(true)
    .build();

EngineeringCalculationResult<Api2000TankVentingAssessment> result =
    new Api2000TankVentingScreeningKernel().calculate(input, null);
Map<String, Object> report = result.getValue().toMap();

For these demonstration inputs, normal outbreathing demand is 0.13 reference m3/s, normal inbreathing demand is 0.115 reference m3/s, and emergency utilization is approximately 0.83333. These are deterministic regression values, not API table values or an independent standard benchmark.

The executed notebook uses the same API, plots liquid-movement sensitivity, and demonstrates fail-closed behavior when rated-capacity evidence is not verified.

Fail-closed evidence boundary

Calculation is blocked unless all of the following are explicit and internally valid:

exact unamended 7th edition and Tank/SimpleTankFiller applicability;
non-negative movement rates, displacement ratios, thermal demands, and other normal demands, with positive aggregated demand in both normal directions;
positive externally established total emergency demand and all three rated capacities;
positive tank positive-pressure and vacuum limits and non-negative rated pressure/vacuum magnitudes;
positive common gas-flow reference temperature and absolute pressure; and
external verification of fixed-roof/non-refrigerated scope, demand basis, rated-capacity basis, pressure/vacuum basis, normal combinations, and emergency combinations.

Capacity or pressure-limit exceedance is a visible calculated finding, not a readiness blocker. Verification flags are attestations: licensed calculations, device curves, tank data, scenarios, and accountable approvals remain external evidence.

Not implemented

The kernel does not calculate or approve:

API thermal, movement, fire, or other vent-demand table values and equations;
vent area, discharge coefficient, device type, set pressure, blowdown, or manufacturing details;
scenario completeness, fire exposure/wetted area, product vapor generation, or reactive cases;
line losses, backpressure, manifolds, discharge location, dispersion, or emissions;
flame arresters, detonation arresters, inert-gas blanketing, or control-system interaction;
external floating roofs, refrigerated storage, buried tanks, pressure vessels, or unsupported liquids without a separately controlled applicability basis; or
installation, inspection, testing, marking, vendor certification, or conformity assessment.

API 650/620/625 tank mechanical design and construction remain separate. Likewise, transient tank pressure/vacuum response and collapse analyses are not replaced by this steady rated-capacity screen.