Oil Refinery Blow-Ups

What causes them? Turnarounds? Do we ever get to have any decent explanation- or is it covered up?
like last years explosion- at about this time of year- at the same place?

Texas City Refinery- BP

www.reuters.com...

Well, when the BP Oil Refinery around here blew it was the Iso-Cracker that went. Damn, thought it was an earthquake, but later mom(was working as a security guard there at the time) told me it was the Iso-Cracker going. Sure this was like 10 years ago though, but still one hell of a boom.