Root Cause Analysis Framework

The neqsim.process.diagnostics package provides a structured root cause analysis (RCA) framework for diagnosing equipment operational anomalies. It integrates four evidence sources via Bayesian-inspired confidence scoring:

Reliability Data — Prior probabilities from public reliability databases (IOGP/SINTEF, CCPS 1989, IEEE 493-2007, Lees 2012, SINTEF PDS) with optional OREDA overlay
Historian — Likelihood scoring from time-series trend, threshold, and correlation analysis
STID — Cross-reference against design conditions
Simulation — Verification scoring from NeqSim process model perturbation

Architecture

Symptom (enum)
    │
    ├── HypothesisGenerator  →  Generate candidate hypotheses
    │       │
    │       └── Reliability priors (ReliabilityDataSource)
    │           Sources: IOGP/SINTEF, CCPS, IEEE 493, Lees, OREDA
    │
    ├── EvidenceCollector     →  Analyze historian + STID data against expected signals
    │       │
    │       ├── Trend analysis (linear regression R²)
    │       ├── Threshold exceedance
    │       ├── Rate-of-change step detection (3σ)
    │       └── Pearson correlation (|r| > 0.7)
    │
    ├── SimulationVerifier    →  Clone ProcessSystem, perturb, compare
    │
    └── RootCauseReport       →  Ranked hypotheses with confidence scores

Each built-in hypothesis carries expected signal fingerprints. For example, compressor bearing degradation expects increasing vibration and bearing temperature, while liquid ingestion expects a step change in vibration and high upstream separator or scrubber level. Evidence that matches the fingerprint is marked as supporting; opposite behavior is marked as contradictory; unrelated trends are ignored.

Confidence Scoring

Each hypothesis receives a confidence score calculated as:

\[\text{confidence} = P_{\text{prior}} \times L_{\text{historian}} \times V_{\text{simulation}}\]

Where:

$P_{\text{prior}}$ — Prior probability from reliability data (IOGP/SINTEF, CCPS, IEEE 493, etc.)
$L_{\text{historian}}$ — Likelihood score from time-series evidence
$V_{\text{simulation}}$ — Verification score from simulation direction-of-change matching

Data Sources

ReliabilityDataSource loads failure rates and repair times from multiple public databases, requiring no commercial license:

Source	Coverage	Access
IOGP Report 434 / SINTEF	Offshore O&G equipment, safety systems	Free
CCPS Process Equipment Reliability Data (1989)	Vessels, piping, instruments, valves	Published handbook
IEEE 493-2007 (Gold Book)	Industrial power and electrical equipment	Purchasable standard
Lees’ Loss Prevention (2012)	Generic process industry failure rates	Textbook
SINTEF PDS Data Handbook	Safety-instrumented system failure rates	Purchasable
API 689	Rotating and process equipment reliability	Purchasable standard
OREDA (optional)	Offshore equipment (consortium license)	Commercial

Supplementary CSVs are loaded automatically. Primary data takes precedence over supplementary entries, so users can override any value by editing equipment_reliability.csv.

Supported Equipment Types

Equipment Type	Symptoms	Hypothesis Categories
Compressor	HIGH_VIBRATION, HIGH_TEMPERATURE, LOW_EFFICIENCY, SURGE_EVENT, TRIP	Bearing wear, seal leak, fouling, surge, valve fault
Pump	HIGH_VIBRATION, LOW_EFFICIENCY, TRIP	Cavitation, impeller wear, seal failure, motor fault
Separator	LIQUID_CARRYOVER, PRESSURE_DEVIATION, FOULING	Demister damage, control malfunction, wax/hydrate, inlet device
Heat Exchanger	HIGH_TEMPERATURE, LOW_EFFICIENCY, PRESSURE_DEVIATION	Fouling, tube leak, baffle damage, bypass
Valve	FLOW_DEVIATION, ABNORMAL_NOISE	Trim erosion, actuator fault, positioner drift, cavitation

Java Usage

import neqsim.process.diagnostics.*;

// Build process
ProcessSystem process = ...; // existing process model
process.run();

// Create analyzer
RootCauseAnalyzer rca = new RootCauseAnalyzer(process, "Export Compressor");
rca.setSymptom(Symptom.HIGH_VIBRATION);

// Optional: add historian data
Map<String, double[]> data = new HashMap<>();
data.put("vibration_mm_s", new double[]{2.1, 2.3, 2.8, 3.5, 4.2});
data.put("bearing_temp_C", new double[]{65, 67, 72, 78, 85});
double[] timestamps = {0, 1, 2, 3, 4};
rca.setHistorianData(data, timestamps);

// Optional: design limits
rca.setDesignLimit("vibration_mm_s", 0.0, 4.5);

// Run analysis
RootCauseReport report = rca.analyze();

// Output
System.out.println(report.toTextReport());
String json = report.toJson();

Python (Jupyter) Usage

RootCauseAnalyzer = ns.JClass("neqsim.process.diagnostics.RootCauseAnalyzer")
Symptom = ns.JClass("neqsim.process.diagnostics.Symptom")

rca = RootCauseAnalyzer(process, "Export Compressor")
rca.setSymptom(Symptom.HIGH_VIBRATION)
report = rca.analyze()

# Get JSON report
import json
result = json.loads(str(report.toJson()))
for h in result["hypotheses"]:
    print(f"{h['rank']}. {h['name']} — confidence: {h['confidenceScore']:.3f}")

MCP Tool

The runRootCauseAnalysis MCP tool exposes this framework to LLM agents:

{
    "processJson": "{\"fluid\": {...}, \"process\": [...]}",
    "equipmentName": "Export Compressor",
    "symptom": "HIGH_VIBRATION",
    "historianCsv": "timestamp,vibration,bearing_temp\n0,2.1,65\n1,2.3,67\n2,2.8,72",
    "designLimits": { "vibration": [0, 4.5] },
    "simulationEnabled": true
}

processJson is passed as a JSON string to the MCP runner. The schema catalog entry run_root_cause_analysis shows the exact input fields and output shape.

Custom Hypotheses

HypothesisGenerator generator = new HypothesisGenerator();
generator.register("compressor", Symptom.HIGH_VIBRATION,
    new Hypothesis.Builder()
        .name("Coupling misalignment")
        .description("Flexible coupling misalignment causing 1x/2x vibration")
        .category(Hypothesis.Category.MECHANICAL)
        .priorProbability(0.15)
        .addExpectedSignal("vibration|2x|axialVibration", Hypothesis.ExpectedBehavior.INCREASE,
            2.5, "Misalignment normally increases axial and 2x vibration")
        .addAction("Laser alignment check")
        .build());

RootCauseAnalyzer rca = new RootCauseAnalyzer(process, "Compressor");
rca.setHypothesisGenerator(generator);

Classes

Class	Description
`Symptom`	Enum of 12 observable symptoms (TRIP, HIGH_VIBRATION, etc.)
`Hypothesis`	Ranked failure hypothesis with evidence, confidence, and actions
`HypothesisGenerator`	Registry-based generator with built-in equipment libraries
`EvidenceCollector`	Time-series analysis (trend, threshold, correlation)
`SimulationVerifier`	Process model perturbation and direction-of-change scoring
`RootCauseReport`	Ranked report with JSON, text, and results map output
`RootCauseAnalyzer`	Main orchestrator integrating all components