On Fri, 30 Sep 2005 09:10:25 -0400, wrote:

The weak spot on a tank is the long seam, not the circ seam for the
heads. A BLEVE will only happen when the pressure rise is so high as
to not allow the relief valve to vent properly, the long seam rips
open so fast that is runs the length the the tank due to the rising
pressure in the tank. Once the long seam hits the circ seam it will
run around the circ. If the pressure is still rising due to the high
heat imput the heads will come off. If the pressure rise has slowed
down due to the long seam being opened, no heads will fly off.

This is correct. The head is the strongest part, as is the weld. I've
seen the aftermath of two BLEVEs and seen many more photos. Most
opened up at the seam as you say, but one opened away from the seam.
In that case, it looked like the fire had been concentrated in that
area, undoubtedly weakening the metal.

John
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John De Armond
See my website for my current email address
http://www.johngsbbq.com
Cleveland, Occupied TN