neqsim: Skill for Claude Code

NeqSim Controllability & Operability Skill

The "can this plant be operated?" half of process design — operating envelopes, turndown, startup/shutdown sequencing, control valve sizing, and steady-state operability checks. Pairs with neqsim-dynamic-simulation which solves the transient response.

When to Use

• Mapping operating envelope (P, T, flow, composition window where the plant runs)
• Turndown analysis (10–100% capacity)
• Control valve sizing per ISA-75 / IEC 60534
• Startup / shutdown sequence definition
• Recycle stability / loop interaction screening
• Identifying hidden constraints (compressor surge, tray weeping, HX pinch)
• Evaluating P&ID-derived valve changes such as closing an isolation valve, partly closing a control valve, opening a bypass, or changing controller mode

For P&ID-driven operational changes, load neqsim-pid-process-operations first to classify symbols, define the topology, bind plant tags, and turn each action into a NeqSim model delta.

For MCP or Java workflows that already have a ProcessSystem, use neqsim.process.operations.envelope.OperationalEnvelopeEvaluator or MCP runOperationalStudy with action="evaluateOperatingEnvelope". The evaluator does not duplicate equipment physics; it ranks margins from EquipmentCapacityStrategyRegistry, uses optional tagreader field data through OperationalTagMap, and can turn margin history into simple time-to-limit screening.

Standards: ISA-75.01 / IEC 60534-2-1, API 685 (control valves), NORSOK P-002 (operability).

Pattern 1 — Operating Envelope Map

Sweep two key handles (e.g. flow and composition) and check that every constraint is satisfied in the operating window:

double[] flows = linspace(0.1, 1.0, 10);   // 10–100% turndown
double[] gors  = linspace(50.0, 800.0, 8); // GOR variation

for (double f : flows) {
    for (double g : gors) {
        SystemInterface fluid = makeFluid(g);
        feed.setFlowRate(f * design_kgh, "kg/hr");
        process.run();
        envelope.recordPoint(f, g, checkConstraints(process));
    }
}