BLEVE and Heat Induced Tear Safety Notes

Flashcards covering definitions, hazards, parameters, and distinctions between Boiling Liquid Expanding Vapor Explosions (BLEVE) and Heat Induced Tears (HIT).

What does the acronym BLEVE stand for?

Boiling Liquid Expanding Vapor Explosion

Which UN number is assigned to Liquefied Petroleum Gases (LPG)?

UN1075

Which specific flammable gases are listed as LPGs (UN1075)?

UN1011 Butane, UN1012 Butylene, UN1055 Isobutylene, UN1077 Propylene, UN1969 Isobutane, and UN1978 Propane

What causes a BLEVE to occur?

A fire impinged or damaged tank car fails to contain its internal pressure and explodes with a sudden product release

Under what circumstance can a catastrophic BLEVE failure occur even in the absence of an active fire?

With damaged pressure tank cars

What are the four main hazards associated with an LPG BLEVE?

Fire, thermal radiation, blast, and projectiles

At what distance from an LPG BLEVE fireball can thermal radiation burn exposed skin in $2\,\text{seconds}$?

At a distance of about $4\,\text{times}$ the radius of a fireball

What effect can the blast of an open-air BLEVE produce at a distance of $4\,\text{times}$ the fireball radius?

It can break window glass and may cause minor damage to buildings

What is the furthest-reaching hazard resulting from an LPG BLEVE?

Projectiles (metal fragments thrown over large distances from tank failure)

What is a Heat Induced Tear (HIT)?

A rupture of a NON-PRESSURE tank car containing flammable liquids when exposed to the intense heat of a fire, where metal softens and internal pressure increases to cause containment failure

Where does a Heat Induced Tear (HIT) generally occur on a container, and what does it release?

At the vapor space (upper side) of the container, venting large quantities of flammable liquid and vapors at high speed

How do Heat Induced Tears (HITs) compare to BLEVEs regarding tank car fragments?

HITs rarely result in the projection of tank car fragments

Over what timeframe has heat induced tearing been observed to occur following an incident?

Within $20\,\text{minutes}$ of the derailment and as long as $10+\,\text{hours}$ following the initial fire