What is a BLEVE and how does a fireball form?

A BLEVE (Boiling Liquid Expanding Vapor Explosion) occurs when a vessel containing pressurized liquefied gas fails catastrophically, usually due to fire impingement weakening the vessel wall. The sudden depressurization causes the superheated liquid to flash to vapor, and if the contents are flammable, the expanding vapor cloud ignites forming a fireball. The fireball rises buoyantly and can produce intense thermal radiation at significant distances.

How is BLEVE fireball diameter calculated?

Fireball diameter is calculated using the CCPS correlation: D = 5.8 * M^0.333, where D is the maximum fireball diameter in meters and M is the mass of flammable material in kilograms. This correlation is based on experimental data from large-scale BLEVE tests and is widely used in consequence analysis per API 2510 and the TNO Yellow Book.

What thermal radiation thresholds cause burn injuries?

Thermal radiation injury thresholds depend on both intensity and duration. For BLEVE fireballs: 37.5 kW/m2 causes significant structural damage; 12.5 kW/m2 is the threshold for first-degree burns with brief exposure; 25 kW/m2 causes second-degree burns; and 37.5 kW/m2 causes third-degree burns. Safe separation distances are typically set at 4.7 kW/m2 (pain threshold at 60 seconds) or 1.6 kW/m2 for public exposure.

BLEVE Fireball Calculator | Boiling Liquid Expanding Vapor Explosion

Vessel & Fluid

Fluid Type

Vessel Volume

US gallons

Liquid Fill Level

Fluid Mass (override)

If entered, overrides vessel volume × fill level calculation

Heat of Combustion

BTU/lb

Liquid Density

lb/ft³

Environment & Receptor

Ambient Temperature

°F

Relative Humidity

Distance to Receptor

Receptor Height

Height of person or equipment above grade (typically 6 ft for personnel)

Understanding BLEVE Fireball Analysis

What is a BLEVE?
A Boiling Liquid Expanding Vapor Explosion (BLEVE) occurs when a vessel containing pressurized liquefied gas ruptures catastrophically. Fire impingement weakens the vessel wall above the liquid level, leading to failure, flash vaporization, and a massive fireball if the contents are flammable.

Key Parameters:
Fireball Diameter: D = 5.8 × M^0.333
Fireball Duration: t = 0.45 × M^0.333
Surface Emissive Power: 200-350 kW/m²
Radiation: q = SEP × F × τ

Key Standards:
API 2510 (LPG installations), CCPS Guidelines (consequence analysis), TNO Yellow Book (fire & explosion models), NFPA 58 (LP-Gas Code), 49 CFR 195 (hazardous liquid pipelines).

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Results

Fireball Diameter

feet

Fireball Duration -

Fireball Center Height -

Fuel Mass -

Surface Emissive Power -

View Factor at Distance -

Atmospheric Transmissivity -

Thermal Radiation at Distance -

Thermal Dose -

Safe Distance (4.7 kW/m²) -

1st Degree Burn Distance -

2nd Degree Burn Distance -

3rd Degree Burn Distance -

Formulas

D_max = 5.8 × M^0.333 (meters)

Duration: t = 0.45 × M^0.333 (seconds)

Height: H = 0.75 × D_max

Radiation: q = SEP × F_view × τ_a

View Factor: F = (D/2)² / (4 × L²)

Standards & References

API 2510
Design & Construction of LPG Installations
CCPS Guidelines
Consequence Analysis of Chemical Releases
TNO Yellow Book
Methods for Calculation of Physical Effects
NFPA 58
Liquefied Petroleum Gas Code
API RP 752
Permanent Occupied Buildings in Petrochemical Plants

Engineering Notes

BLEVE mechanism: Fire impingement heats vessel wall above liquid level, weakening metal until rupture at 60-80% of design pressure
Fireball rise: Fireball initially forms at grade then rises buoyantly; maximum diameter reached in first 1-3 seconds
Radiation fraction: Typically 25-40% of total combustion energy radiates outward; remainder is convected upward
Water spray: Vessel water deluge systems can prevent BLEVE by keeping wall cool; 0.25 gpm/ft² minimum per NFPA 15
Fragments: BLEVE also produces vessel fragments that can be projected hundreds of meters; not modeled here

Thermal Radiation Thresholds

1.6 kW/m² — No harm, safe for public exposure
4.7 kW/m² — Pain threshold at 60 sec exposure
12.5 kW/m² — 1st degree burns, piloted ignition of wood
25.0 kW/m² — 2nd degree burns, spontaneous ignition
37.5 kW/m² — 3rd degree burns, significant damage

BLEVE Fireball Calculator

Vessel & Fluid

Environment & Receptor

Understanding BLEVE Fireball Analysis

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Results

Formulas

Standards & References

Engineering Notes

Thermal Radiation Thresholds

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