If you use a converted keg (keggle) as your boil pot or HLT, check the bottom rim to make sure there are vent holes in it. Turns out that some may not have them (most do) and can explode when heated. Check out this thread and click on the pictures to see what happens when they explode. The burner is mangled, but luckily no one was injured in this incident.
http://forum.northernbrewer.com/viewtopic.php?p=389681#389681