BLEVE (boiling liquid expanding vapor explosion)
Rupture of a vessel holding a liquid heated above its normal boiling point, followed by a fireball if the product is flammable; dangerous for LPG, propane and butane.
In a propane tank the gas is a liquid under pressure. If a nearby fire heats the wall, pressure rises, the steel weakens above the liquid level, and the tank tears open at once. The liquid flashes instantly to vapor, hence the name, boiling liquid expanding vapor explosion, and ignites into a fireball several hundred meters across. On November 19, 1984, at San Juanico near Mexico City, an LPG terminal chained a series of these explosions: some five hundred dead according to the UK HSE, six hundred and fifty according to Mexico's civil protection agency, a neighborhood destroyed. Two consequences for insurance. The BLEVE is the loss against which safety distances and spray systems for storage spheres are sized, and inspectors dwell on it. And it creates a domino effect: fragments and heat from one vessel that bursts rupture its neighbors, so a terminal with several spheres has a probable maximum loss close to the value of the whole tank farm. Industrial policies often attach a condition on water spray and thermal protection, and an insured that let it lapse to save money no longer has full cover. The risk also leaves the site by road: a road accident involving an LPG truck is a BLEVE waiting to happen. Not to be confused with the UVCE, which starts from a leak and a cloud, not from a vessel that bursts.
Textbook case: a truck fire spreads to a 1,500 cubic meter butane sphere at a depot. The sphere bursts in a BLEVE and two neighboring spheres follow. The depot is worth 140 million dollars and loses 120 million. The industrial policy required cooling spray; it had been out of service for three months, which the insurer cites to cut the claim payment.
BLEVE, boiling liquid expanding vapor explosion, tank explosion, LPG tank explosion, San Juanico
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