They are. When I lived in Houston they happened all the time, and there would be at least a couple of really big explosions (i.e., shake the windows for miles around) every year.
Well, really spectacular industrial explosions like this one, while certainly not very rare, aren't all THAT common.
What has happened in the past on FR is that you do get one of these every few months, but then when it happens, people start frantically digging all over the place in the media, including local news, for ANY industrial fires or explosions of ANY kind, including small non-fatal ones in obscure places (and those ARE really common at chemical plants and refineries) and posting them to FR when they normally wouldn't be mentioned..and THEN you get the "what's up with all these industrial "accidents?" recently posts.