Aut cum scuto aut in scuto
The old "rule of thumb" I was taught when I was on a company emergency chemical transport accident response team for the chemical plant I worked at, was that if you held up your thumb at arms length and couldn't completely cover the damaged railcar/tanker, you were too close.
Oh, yeah. Time to employ emergency back up procedures. Back up, back up, back waaaaaaaay the heck up.
Flying Karamazov Brothers, before doing the flaming batons of death juggling act, would inform everybody that they have a backup plan. "Everybody - backup!"
you can almost make it out but, it appeared the tow operators survived the blast and were seen running away from the flame front. looks like static electricity in the open tank got it. our rule of thumb is a closed tank doesn't have air to combust. if it does blow, an open scupper won't help mitigate the blast anyway. grounding the tank before working on it is critical. fuels sloshing around in the tank or moving thru a hose generates enough energy to make a spark. and yes, back away. a lot of back away. think about that next time you are gassing up your ride