Hazard Studies & Risk Assessment

Consequence & Dispersion Modelling

Quantified thermal, explosion, and toxic consequence zones for risk assessment and emergency planning

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What this study delivers

Consequence &
Dispersion Modelling

Consequence and dispersion modelling quantifies the physical effects of loss-of-containment events — fire, explosion, and toxic gas dispersion — to determine hazard ranges for risk assessment, facility siting, emergency planning, and land use planning purposes.

Consequence & Dispersion Modelling — Overview
Study execution

How the study is executed

A structured, facilitated process — from scope definition through close-out — producing defensible, actionable outputs.

Scenario Register & Source-Term Definition

Extract loss-of-containment scenarios from HAZOP / QRA; define representative orifice sizes (small / medium / large), release heights, orientations, fluid phases (vapour, liquid, two-phase, cryogenic), and ambient conditions; build scenario register with inventory mass.

Thermal Radiation Modelling

Model pool fires (Thomas correlation, SFPE), jet fires (Chamberlain / Cook-Cullis), and flash-fire LFL envelopes; calculate radiation iso-contours at 4 / 12.5 / 37.5 kW/m² thresholds; apply view-factor correction for receptor angle.

Explosion Overpressure Assessment

Apply TNT / Multi-Energy / Baker-Strehlow-Tang for screening scenarios; deploy FLACS or KFX CFD for high-consequence VCE cases with congestion parameterisation; produce overpressure and impulse iso-contour maps for occupied-building and facility-siting input.

Toxic Gas Dispersion Analysis

Model toxic release source terms (flash, two-phase, aerosol, evaporating pool) and atmospheric dispersion using PHAST / ALOHA / SAFETI; calculate hazard distances to AEGL-1 / AEGL-2 / ERPG-2 / IDLH / SLOT / SLOD with stability-class and wind-speed sensitivity.

BLEVE & Multi-Effect Scenario Modelling

Model BLEVE fireball (Roberts / Hasegawa correlation) for pressurised liquefied gas scenarios; assess Boilover and tank-farm scenarios; combine fire, explosion, and toxic effects for multi-effect scenarios including domino escalation thresholds.

Risk Integration & Emergency Planning Output

Integrate consequence contours into QRA risk aggregation (LSIR / F-N); produce GIS-compatible hazard-distance tables and contour maps; derive Emergency Response Planning Zone (ERPZ), shelter-in-place criteria, and F&G detector placement inputs per API RP 14C.

Consequence & Dispersion Modelling — Scope
Study scope

What the study covers in full

Pool fire and jet fire thermal radiation modelling (ALOHA, PHAST, SAFETI)
Vapour cloud explosion (VCE) overpressure: TNT equivalence, BST, CCPS multi-energy
BLEVE fireball thermal radiation and fragment trajectory
Toxic gas and vapour dispersion: ERPG, IDLH, AEGL hazard distances
Flash fire flammable envelope and consequence zones
Sensitivity analysis: wind speed, stability class, release height
EPA RMP worst-case and alternative release scenario analysis
Results integration into QRA risk contours and F-N curves
Why it matters

Outcomes of Consequence & Dispersion Modelling

Hazard Distance Quantification
  • Quantifies hazard distances for safe layout and escape route design
  • Identifies worst-case scenarios for emergency planning zone definition
  • Supports F&G detector placement and alarm setpoint determination
  • Provides input to occupied building risk assessment (OBRA)
EPA RMP / COMAH Consequence Defence
  • EPA RMP Off-Site Consequence Analysis (OCA) compliance
  • COMAH/SEVESO consequence analysis for Safety Report
  • OSHA PSM PHA consequence evaluation support
  • Satisfies planning authority development control requirements
Operational Zone & Layout Clarity
  • Informs safe working distances during hot work and maintenance
  • Identifies equipment items with highest consequence potential
  • Supports SIMOPS (simultaneous operations) risk evaluation
  • Provides basis for emergency response planning zones
Layout Optimisation Value
  • Avoids over-conservative exclusion zones that limit operational flexibility
  • Identifies whether high-consequence items warrant inherent safer design
  • Reduces cost of consequence modelling errors in facility siting
  • Supports risk-informed layout optimisation
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