Originally Posted by HONDAMAN174
What was really shocking to me was how many propane tanks that did not go boom. There were some explosions from tanks letting go but about 90% of the damaged units still had tanks intact.
2014 Evo 2850 "Woodstock"
2011 Toyota Tundra "Clifford"
All propane tanks have pressure relief valves to prevent a BLEVE (pronounced bulevee) or a Boiling Liquid Expanding Vapor Explosion. In other words, applying enough heat to a propane tank will cause the liquid propane to boil, and that pressure will build up till something has to give.
Without the pressure relief, the tank would explode, with the classic fireball and shrapnel everywhere. but with a relief valve, the valve opens at a pressure lower than the tank failure point. You will wind up with a jet of propane out the valve that will usually ignite. Usually by the time the tank vents, the area is on so much fire that it can go unnoticed.
The other think to consider is that tank level greatly impacts the pressure that can build up. IIRC, a under 1/2 empty tank can vaporize its whole load and stay under the relief valve pop-off pressure.
These days, its exceedingly rare for a consumer propane tank to explode in a fire. If one does, it usually turns out its an older one without the relief valve.