During a BLEVE explosion investigation, in a boiler such as a water tank, the temperature of the water creates a certain stream or vapor pressure in the air space(vapor space) above the liquid. The steam pressure in the vapor space is controlled by the heater temperature which in turn is controlled by the gas feeding the tank burner. If the gas valve sticks or fails in an open position, the boiler will continue to heat. If this over heating occurs the vapor space pressure will continue to rise and the liquid temperature can exceed the boiling temperature of 212° F.
In rare instances where the pressure relief valve also fails or fails to activate, the temperature of the water can exceed 212° F and the pressure can far exceed one atmosphere. If the steel tank then ruptures and exposes the high temperature/high pressure contents to one atmosphere pressure, the water which is far above the 212° F boiling temperature, will immediately flash to a vapor, many times at the volume of the liquid water. The expanding vapor cannot be contained in the boiler or hot water tank resulting in a Boiling Liquid Evaporating Vapor Explosion (BLEVE). An excellent video showing BLEVE can be seen below.
Over the years Dr. Jerner has worked on several BLEVE investigations as can be seen in his vitae, the following are just two of the investigations noted in his vitae:
Lubbock City/County Health Department investigation of water heater/boiler explosion.
Star-Spencer Elementary, Spencer Oklahoma. Investigation of boiler explosion at elementary school.