Automatic Scenario Generation

This document describes the automatic safety scenario generation infrastructure added to NeqSim.

Overview

Process safety analysis requires systematic evaluation of failure modes. The AutomaticScenarioGenerator class automatically identifies potential failures from process topology and generates scenarios for what-if analysis.

Key Features

Usage

Basic Usage

ProcessSystem process = new ProcessSystem();
// ... configure process with valves, compressors, coolers, etc. ...

AutomaticScenarioGenerator generator = new AutomaticScenarioGenerator(process);

// Enable specific failure modes
generator.addFailureModes(
    FailureMode.COOLING_LOSS,
    FailureMode.VALVE_STUCK_CLOSED,
    FailureMode.COMPRESSOR_TRIP
);

// Generate single-failure scenarios
List<ProcessSafetyScenario> singleFailures = generator.generateSingleFailures();

// Generate combination scenarios (up to 2 simultaneous failures)
List<ProcessSafetyScenario> combinations = generator.generateCombinations(2);

Convenience Methods on ProcessSystem

// Quick scenario generation
List<ProcessSafetyScenario> scenarios = process.generateSafetyScenarios();

// With combination depth
List<ProcessSafetyScenario> combinations = process.generateCombinationScenarios(2);

Failure Modes

Mode Description HAZOP Deviation Applicable To
COOLING_LOSS Complete loss of cooling No flow Coolers
HEATING_LOSS Complete loss of heating No flow Heaters
VALVE_STUCK_CLOSED Valve stuck closed No flow Valves
VALVE_STUCK_OPEN Valve stuck open More flow Valves
VALVE_CONTROL_FAILURE Control valve failure Other Control valves
COMPRESSOR_TRIP Compressor emergency stop No flow Compressors
PUMP_TRIP Pump emergency stop No flow Pumps
BLOCKED_OUTLET Downstream blockage No flow Separators
POWER_FAILURE Loss of electrical power Other All electrical
INSTRUMENT_FAILURE Instrument/control failure Other All
EXTERNAL_FIRE Fire exposure High temperature All
LOSS_OF_CONTAINMENT Leak or rupture Less pressure All

HAZOP Deviations

Deviation Description
NO_FLOW Complete loss of flow
LESS_FLOW Reduced flow rate
MORE_FLOW Increased flow rate
REVERSE_FLOW Flow in wrong direction
HIGH_PRESSURE Pressure above normal
LOW_PRESSURE / LESS_PRESSURE Pressure below normal
HIGH_TEMPERATURE Temperature above normal
LOW_TEMPERATURE Temperature below normal
HIGH_LEVEL Liquid level too high
LOW_LEVEL Liquid level too low
CONTAMINATION Unwanted substance present
CORROSION Material degradation

Running Scenarios

Manual Execution

// Generate scenarios
List<ProcessSafetyScenario> scenarios = generator.generateSingleFailures();

for (ProcessSafetyScenario scenario : scenarios) {
    // Create a copy of the process for each scenario
    ProcessSystem copy = process.copy();
    
    // Apply the scenario
    scenario.applyTo(copy);
    
    // Run simulation
    try {
        copy.run();
        
        // Analyze results
        analyzeScenarioResults(scenario, copy);
        
    } catch (Exception e) {
        // Scenario caused simulation failure - important finding!
        recordFailedScenario(scenario, e);
    }
}

Automated Execution with ScenarioRunResult

The generator provides built-in scenario execution capabilities:

// Run all single-failure scenarios automatically
List<ScenarioRunResult> results = generator.runAllSingleFailures();

// Or run specific scenarios
List<ProcessSafetyScenario> scenarios = generator.generateSingleFailures();
List<ScenarioRunResult> results = generator.runScenarios(scenarios);

// Get execution summary
String summary = generator.summarizeResults(results);
System.out.println(summary);

ScenarioRunResult

Each result contains:

Field Type Description
scenario ProcessSafetyScenario The scenario that was run
successful boolean Whether simulation completed without error
errorMessage String Error message if failed (null otherwise)
resultValues Map<String, Double> Key results: pressures, temperatures, levels
executionTimeMs long Execution time in milliseconds

Example Summary Output

=== Scenario Execution Summary ===
Total scenarios: 12
Successful: 10 (83.3%)
Failed: 2 (16.7%)

Failed scenarios:
  - COOLING_LOSS on Cooler-1: Simulation did not converge
  - COMPRESSOR_TRIP on MainCompressor: Exceeded iteration limit

Failure Mode Summary

String summary = generator.getFailureModeSummary();
System.out.println(summary);

// Output:
// Failure Mode Analysis Summary
// =============================
// Total potential failures: 42
//
// By Equipment Type:
//   ThrottlingValve: 12 failure modes
//   Compressor: 8 failure modes
//   Cooler: 6 failure modes
//   Separator: 8 failure modes
//   Pump: 8 failure modes

Integration with Existing Safety Framework

The AutomaticScenarioGenerator complements the existing safety framework:

Best Practices

  1. Systematic Coverage: Enable all relevant failure modes for comprehensive analysis
  2. Prioritization: Focus detailed analysis on high-consequence scenarios
  3. Combination Limits: Limit combination depth to 2-3 for practical analysis
  4. Documentation: Record all scenario results for safety case
  5. Regular Updates: Regenerate scenarios after process modifications