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Quantitative Risk Assessment

Flash fire, VCE, toxic release, thermal instability, energetic materials and Bow-Tie analysis — rigorous QRA for high-hazard facilities across Africa.

Quantitative Risk Assessment

Numbers That Drive Decisions

Quantitative Risk Assessment (QRA) provides the numerical basis for major hazard risk management decisions — determining whether risks from fire, explosion, toxic release or chemical reactivity are As Low As Reasonably Practicable (ALARP) and justified by the business activity.

Nexis Process Safety conducts QRA studies aligned to CCPS Guidelines for Chemical Process Quantitative Risk Analysis, COMAH requirements, and international consequence modelling best practice. Our studies support land-use planning decisions, insurance assessments, regulatory submissions and internal risk governance frameworks.

Commission a QRA Study

QRA Services

  • Flash Fire & Vapour Cloud Explosion (VCE) Modelling
  • Toxic Release & Dispersion Modelling
  • Thermal Instability Studies (DSC / heat flow calorimetry)
  • Energetic Material Evaluation
  • Reactive Chemical Hazard Studies
  • Bow-Tie Analysis
  • Risk Matrix Development & Calibration
  • COMAH / Major Hazard Assessment
  • Land-Use Planning Risk Assessment
  • Individual & Societal Risk Calculation
Consequence Modelling

Quantifying the Impact of Credible Worst-Case Scenarios

Understanding the potential consequences of a loss of containment event is fundamental to risk-based decision-making. Nexis PS uses industry-standard modelling tools to quantify fire, explosion and toxic hazard zones.

Fire Hazards

  • Flash fire extent modelling (flammable vapour clouds)
  • Pool fire heat flux calculation
  • Jet fire thermal radiation modelling
  • Fire ball / BLEVE analysis
  • Escalation analysis — domino effect assessment

Explosion Hazards

  • Vapour Cloud Explosion (VCE) overpressure modelling
  • TNT equivalency method
  • Baker-Strehlow-Tang (BST) and multi-energy methods
  • Blast wave peak overpressure and impulse
  • Structural vulnerability assessment

Toxic Release Hazards

  • Atmospheric dispersion modelling (Gaussian / dense gas)
  • ERPG / AEGL / IDLH toxic dose calculations
  • Shelter-in-place vs evacuation analysis
  • Emergency response zone determination
  • Toxic risk contour mapping
Thermal & Reactive Chemical Hazards

Understanding the Hazardous Properties of Your Materials

Chemical reactivity and thermal instability hazards are often poorly understood until a serious incident occurs. Nexis PS provides the technical expertise to characterise these hazards and design appropriate safeguards.

Thermal Instability Studies

For materials that may undergo exothermic decomposition or self-heating, we evaluate the onset temperature, decomposition energetics and gas evolution using calorimetric data and literature evaluation.

  • Self-Accelerating Decomposition Temperature (SADT) evaluation
  • DSC (Differential Scanning Calorimetry) data interpretation
  • Adiabatic Calorimetry (ARC) data interpretation
  • Storage temperature safe limits determination
  • Emergency cooling and venting requirement analysis

Reactive Chemical Hazards

We evaluate the hazards associated with mixing incompatible chemicals, unintended reactions and runaway scenarios, providing design and operating recommendations to prevent catastrophic events.

  • Chemical compatibility matrix development
  • Runaway reaction scenario analysis
  • Quench / inhibitor system effectiveness review
  • Emergency relief device sizing basis assessment
  • Material substitution and inherently safer design review
Bow-Tie Analysis & Risk Matrices

Visualising Risk for Effective Management

Bow-Tie Analysis

Bow-Tie diagrams provide a clear visual representation of the causes, consequences and barriers associated with a major accident hazard. They are powerful tools for communicating risk to operational teams and leadership.

  • Critical event (top event) identification
  • Threat and consequence mapping
  • Preventive and mitigative barrier identification
  • Barrier strength and degradation factor assessment
  • Safety critical task identification

Risk Matrix Development

A well-designed, calibrated risk matrix is fundamental to consistent risk decision-making. We design risk matrices that align with your risk appetite, industry benchmarks and regulatory expectations.

  • Consequence category definition (safety, environment, asset, reputation)
  • Likelihood scale calibration
  • Risk tolerance criteria
  • ALARP region definition
  • Integration with HAZOP, LOPA and MOC processes

Ready to Work With Nexis PS?

Talk to our process safety specialists today. We'll tailor a solution to your hazard profile, regulatory context, and operational goals.

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