WHAT IS A BLEVE?
A BLEVE is a boiling liquid expanding vapor explosion, which occurs when pressurized liquid inside of a vessel, such as a propane tank, reaches temperatures higher than that liquid’s boiling point. If the vessel can no longer contain the pressure inside of the sealed tank due to the high temperatures, it will mechanically fail, causing the explosion.
Whether or not a fire occurs is contingent on if the liquid inside of the tank is flammable. If it is, a fire will often occur. If the vessel contains non-flammable liquid (such as a steam boiler), a BLEVE will occur, but the vapors will not ignite.
Heat does not have to be present for a BLEVE to occur. Mechanical damage or overfilling can also cause the vessel to explode.
A second-stage BLEVE can occur if a vessel releases combustible vapor into an area where it then mixes with air in the presence of a source of an ignition. Then, the explosion can stress the heated vessel and cause it to rupture, resulting in an explosion of the vapor.
HOW CAN A BLEVE BE PREVENTED?
The complete rupturing of a vessel can be prevented by incorporating a sort of vent mechanism to let vapors eject directly up into the atmosphere.
If the vapor is not able to be ejected straight up, the pressurized vessel should be kept in an enclosure that will contain any explosion pressure and control the blast.
SPRINKLER HEAD WORKS ON THESE PRINCIPLE.
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