Agent skill

Neqsim Controllability Operability

by equinor in equinor/neqsim

Process controllability and operability — operating envelope mapping, turndown analysis, startup/shutdown sequencing, control valve sizing per ISA-75 (Fl, Fp, choked flow), rangeability…

Apache-2.0Auto-check passed

Install Neqsim Controllability Operability

skills CLI
$ npx skills add equinor/neqsim --skill neqsim-controllability-operability -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install equinor/neqsim neqsim-controllability-operability --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/equinor/neqsim.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.github/skills/neqsim-controllability-operability .claude/skills/neqsim-controllability-operability && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
neqsim-controllability-operability
GitHub stars
156
Token cost
~2.9k tokens
SKILL.md length
864 words
Files
1
Skills in repo
12
Repo updated
First seen
Licence
Apache-2.0

At a glance

Process controllability and operability — operating envelope mapping, turndown analysis, startup/shutdown sequencing, control valve sizing per ISA-75 (Fl, Fp, choked flow), rangeability…

  • : a task involves operability assessment
  • SKILL.md covers When to Use, Pattern 1 — Operating Envelope…, Pattern 2 — Control Valve… and Pattern 3 — Recycle Stability, plus 6 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
  • Turndown studies

What it does

Neqsim Controllability Operability is an agent skill from equinor/neqsim. Process controllability and operability — operating envelope mapping, turndown analysis, startup/shutdown sequencing, control valve sizing per ISA-75 (Fl, Fp, choked flow), rangeability, hunting/loop tuning, recycle stability. USE WHEN: a task involves operability assessment, turndown studies, control valve sizing, startup/shutdown procedures, or 'will this design operate?' questions. Complements neqsim-dynamic-simulation (transient solver) with steady-state operability framing.

Its SKILL.md is about 2.9k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

The repository describes itself as: NeqSim is a library for calculation of fluid behavior, phase equilibrium and process simulation. The licence is Apache-2.0.

When your agent uses it

  • : a task involves operability assessment
  • Turndown studies
  • Control valve sizing
  • Startup/shutdown procedures

Example prompts

  • “will this design operate?”
  • “/neqsim-controllability-operability”

What it can do on your machine

Read from SKILL.md and the folder at commit 068e6ed. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are java).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Neqsim Controllability Operability loads about 2.9k tokens when it runs. Until then it costs about 130 tokens; SKILL.md has 864 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~130
When it runs · the whole SKILL.md, loaded when a task matches
~2.9k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from equinor/neqsim at commit 068e6ed, republished under its Apache-2.0 licence (© equinor). 864 words, ~2,854 tokens.

Download SKILL.mdSave it as .claude/skills/neqsim-controllability-operability/SKILL.md (or your agent's skills folder).
name
neqsim-controllability-operability
description
Process controllability and operability — operating envelope mapping, turndown analysis, startup/shutdown sequencing, control valve sizing per ISA-75 (Fl, Fp, choked flow), rangeability, hunting/loop tuning, recycle stability. USE WHEN: a task involves operability assessment, turndown studies, control valve sizing, startup/shutdown procedures, or 'will this design operate?' questions. Complements neqsim-dynamic-simulation (transient solver) with steady-state operability framing.
version
1.0.0
last_verified
2026-04-26
requires.java_packages
neqsim.process.equipment.valve, neqsim.process.controllerdevice

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:

java
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));
    }
}

Constraints to check on every point:

ConstraintCheckSource
Compressor surgeQ_actual > Q_surge × 1.10Vendor curve
Compressor stonewallQ_actual < Q_choke × 0.95Vendor curve
Separator vapor velocityv < K × √((ρL−ρV)/ρV)NORSOK P-100 (K=0.107)
Separator residence timet_res ≥ 3 min liquid, ≥ 30 s gasAPI 12J
HX ΔTminΔT > 5 °C everywherePinch design
Column floodingC_factor < 0.85 × C_floodSouders–Brown
Column weepingC_factor > 0.55 × C_floodTray vendor
Pump NPSHaNPSHa > NPSHr + 1 m marginAPI 610
Control valve opening20% < travel < 80%ISA-75

Pattern 2 — Control Valve Sizing (ISA-75)

java
import neqsim.process.equipment.valve.ThrottlingValve;

ThrottlingValve cv = new ThrottlingValve("LV-1101", inletStream);
cv.setOutletPressure(P_downstream_bara);
cv.run();

double Cv_required = cv.getCv();          // ISA-75 sizing
double opening     = cv.getPercentValveOpening();
double dpRatio     = cv.getDeltaPressure() / cv.getInletPressure();
boolean choked     = dpRatio > cv.getFL() * cv.getFL() * (1 - cv.getFf() * cv.getXt());

Sizing rules:

  • Pick valve such that normal flow is at 60–70% open
  • Minimum flow must be at > 20% open (rangeability check)
  • Maximum flow must be at < 90% open (margin)
  • For choked flow: use Fl × ΔP_choke instead of actual ΔP

Rangeability:

Trim typeRangeability
Linear30:1
Equal percentage50:1
Quick opening10:1

If turndown ratio > rangeability, you need a split-range or two valves in parallel.

Seat Leakage Tightness (screening)

To rank candidate valve tightness requirements (isolation/ESDV block valves vs throttling control valves), use the ValveSeatLeakageClass enum (neqsim.process.equipment.valve). It covers EN 12266-1 Rates A–G (isolation valves) and ANSI/FCI 70-2 Classes II–VI (control valves); Class IV (0.01% of rated capacity) is the typical control-valve default, Class VI is the soft-seat essentially-zero-leakage class:

java
import neqsim.process.equipment.valve.ValveSeatLeakageClass;

ValveSeatLeakageClass ctrl = ValveSeatLeakageClass.FCI_70_2_CLASS_IV;
boolean tight = ctrl.isEssentiallyZeroLeakage();   // false for Class IV, true for Class VI

// ANSI/FCI 70-2 Class V closed-form liquid leak-rate screening estimate (test medium water)
double leakRateMlPerMin =
    ValveSeatLeakageClass.estimateFciClassVLeakRate(50.0e5 /* Pa */, 0.10 /* m port */);

This is screening-level only and not a substitute for a manufacturer seat-leakage test certificate. See docs/process/ValveMechanicalDesign.md for the full reference.

Pattern 3 — Recycle Stability

A process with strong recycles can have multiple steady states or be unstable:

java
ProcessSystem.RecycleConvergenceMonitor mon = process.getRecycleMonitor();
process.run();
double[] residual = mon.getMassResidualHistory();
// Plot residual vs iteration — should be monotone decreasing.
// If oscillating: recycle interactions; if diverging: bad initial guess or fundamental instability

Stabilization tactics:

  • Increase damping factor on recycle stream (0.3–0.7)
  • Set initial guess from previous-load solution (warm start)
  • Decompose with ProcessModel so each area converges first
  • Add an explicit pressure setpoint instead of free-floating P
Show full SKILL.md (382 more words)Show less

Pattern 4 — Startup / Shutdown Sequence

Document each major mode as a state machine:

StateP / T / flowActive controllersActive SIFs
Cold shutdownatmospheric, ambientnoneall in OOS
Pressurizationramp to design × 0.3 in 30 minPIC slow rampHIPPS armed
Cold circulationfull rate, ambient (recycle to flare)LIC, FICall armed
Heat-upramp 50 °C/h to design TTIC, LIC, FICall armed
Normaldesign pointall loops in AUTOall armed
Emergency BDdepressurize per API 521 in 15 mincontrollers trippedBDV open

Use neqsim-dynamic-simulation to validate the transient.

Pattern 5 — Loop Tuning Sanity

For each PID:

  • Gain (Kp): 0.5 × Ziegler–Nichols ultimate; tighten only if oscillation
  • Integral (Ti): 1–3 × dead time
  • Derivative (Td): usually off; only for slow exotherms / temperature

Common bad loops:

  • Level on a vessel with rapid throughput change → use averaging level (P-only, low gain)
  • Composition (e.g. column reflux) → cascade onto temperature
  • Surge control on compressor → fast PI + proportional kicker

Pattern 6 — Operability Scorecard for the Report

Operability Scorecard
=====================
Turndown        : 25–110% of design     PASS (target ≥ 25%)
Compressor      : surge margin 18% @ low end   PASS (≥ 10%)
Column          : flooding margin 22% @ high end  PASS (≥ 15%)
Recycle stab.   : converges in 8 iters @ all loads  PASS
Control valves  : 4 valves outside 20–80% range — RESIZE
Startup time    : 6.5 hr (cold→full)    PASS (target ≤ 8 hr)
SD time         : 12 min API 521 BD     PASS (target ≤ 15 min)

Common Mistakes

MistakeFix
Sizing CV with normal ΔP and forgetting choked flowAlways check σ = ΔP / Fl² × ΔP_max; if exceeded use choked formula
One CV across full 10–110% rangeRangeability > 30:1 needs split-range or two valves
Designing only at 100% flowMin/max constraints often govern (surge, weeping, NPSH)
Ignoring recycle interactions until commissioningDecompose with ProcessModel, verify convergence at each load
Aggressive Kp on level controlCauses throughput oscillation downstream; use P-only averaging
No startup BD pathCold flare/atmospheric vent path required for trip-from-pressurized
Using "design rate" pump curvePumps often run at 60–80% Qbep at normal — pick BEP at normal

Validation Checklist

  • Operating envelope plotted with turndown range and at least 2 disturbance axes
  • All control valves: 20% < normal opening < 80%
  • Compressor surge margin ≥ 10% at lowest expected flow
  • All recycles: convergence in ≤ 20 iterations across the envelope
  • Startup sequence documented as state machine with controller modes
  • Emergency BD validated dynamically per API 521 (≤ 15 min to 50% MAWP)
  • Operability scorecard included in the report (results.json → operability section)

© equinor, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .github/skills/neqsim-controllability-operability of equinor/neqsim.

Open the folder on GitHubat commit 068e6ed

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Neqsim Controllability Operability next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

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Questions about Neqsim Controllability Operability

What does Neqsim Controllability Operability do?

Process controllability and operability — operating envelope mapping, turndown analysis, startup/shutdown sequencing, control valve sizing per ISA-75 (Fl, Fp, choked flow), rangeability…. Neqsim Controllability Operability is an agent skill from equinor/neqsim. Process controllability and operability — operating envelope mapping, turndown analysis, startup/shutdown sequencing, control valve sizing per ISA-75 (Fl, Fp, choked flow), rangeability, hunting/loop tuning, recycle stability.

When should I use Neqsim Controllability Operability?

Neqsim Controllability Operability fits situations like: : a task involves operability assessment; turndown studies; control valve sizing; startup/shutdown procedures.

How do I install Neqsim Controllability Operability in Claude Code?

Run `npx skills add equinor/neqsim --skill neqsim-controllability-operability -a claude-code`. Or copy the skill folder (.github/skills/neqsim-controllability-operability in equinor/neqsim) into .claude/skills/neqsim-controllability-operability in your project. Claude Code loads it when a task matches its description.

How do I install Neqsim Controllability Operability in Codex?

Run `npx skills add equinor/neqsim --skill neqsim-controllability-operability -a codex`. Or copy the skill folder (.github/skills/neqsim-controllability-operability in equinor/neqsim) into .agents/skills/neqsim-controllability-operability in your project. Codex loads it when a task matches its description.

Can I use Neqsim Controllability Operability in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add equinor/neqsim --skill neqsim-controllability-operability -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/neqsim-controllability-operability, .gemini/skills/neqsim-controllability-operability, .github/skills/neqsim-controllability-operability and .opencode/skills/neqsim-controllability-operability in your project.

What does Neqsim Controllability Operability need to run?

SKILL.md names no scripts, command-line tools or credentials: Neqsim Controllability Operability is instructions for the agent only.

Does Neqsim Controllability Operability access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Neqsim Controllability Operability safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Neqsim Controllability Operability use?

Neqsim Controllability Operability is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Neqsim Controllability Operability use?

About 2.9k tokens (SKILL.md is roughly 11k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Neqsim Controllability Operability?

Skills that share tags, products or a category with Neqsim Controllability Operability: Control UI (openclaw/openclaw, 392k stars), Token Map (nexu-io/open-design, 100k stars), Mapping Mitre Attack Techniques (mukul975/Anthropic-Cybersecurity-Skills, 34k stars) and Maps Geography (asgeirtj/system_prompts_leaks, 69k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Neqsim Controllability Operability?

equinor (a GitHub organization) maintains it in equinor/neqsim, which has 156 GitHub stars. The repository holds 12 skills in this directory. The repository was last updated on October 8, 2026.

Source: equinor/neqsim on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.