BLEVE

BLEVE, pronounced ("blevvy"), is an acronym for "boiling liquid expanding vapour explosion". This is a type of explosion that can occur when a vessel containing a pressurized liquid is ruptured. Such explosions can be extremely hazardous.

A BLEVE can occur in a vessel that stores a substance that is usually a gas at atmospheric pressure but is a liquid when pressurized (for example, liquefied petroleum gas). The substance is stored partly in liquid form, with a gaseous vapour above the liquid filling the remainder of the container.

If the vessel is ruptured — for example, due to corrosion, or failure under pressure — the vapour portion may rapidly leak, lowering the pressure inside the container and releasing a wave of overpressure from the point of rupture. This sudden drop in pressure inside the container causes violent boiling of the liquid, which rapidly liberates large amounts of vapour in the process. The pressure of this vapour can be extremely high, causing a second, much more significant wave of overpressure (an explosion) which may completely destroy the storage vessel and project fragments over the surrounding area. BLEVEs can also be caused by an external fire near the storage vessel causing heating of the contents and pressure build-up.

A BLEVE can occur even with a non-flammable substance, sometimes one that's known for being extremely cold, like liquid nitrogen or liquid helium or other refrigerants or cryogens, and therefore is not usually considered a type of chemical explosion. However, if the substance involved is flammable, it is likely that the resulting cloud of the substance will ignite after the BLEVE has occurred, forming a fireball and possibly a fuel-air explosion, also termed a vapour cloud explosion (VCE). If the materials are toxic, a large area will be contaminated.

Significant industrial BLEVEs include accidents at Feyzin in France in 1966, Kingman, Arizona in 1973, Texas City, Texas in 1978, and San Juan Ixhuatepec in Mexico in 1984. In 1978, a BLEVE occurred after a road accident with an LPG truck in the Los Alfaques Disaster in Spain.

Some fire mitigation measures are listed under liquefied petroleum gas.