Given the huge amount of reporting and 3rd party investigation that goes into every significant refinery, it would a rather foolish act to mislead.
What the heck is a flammable vapor thats similar to diesel?
A refinery has lots of process units and intermediate steps prior to making a finished product. It will be a vapor because it is so hot in the process. Likely once it cools down after spending time outside the pipe, it would coalesces into a liquid.
It really isn't diesel until all the additives are in sulfur removed and meets the ASTM specification. I read that the fire started in the Crude Unit. That is one of the early steps and essentially no finished refined product comes out of that unit. In a crude distillation tower, the fluid is heated between ~625°F to ~7000°F. Most of the crude oil is turned into vapor at this point.
I assume that making the unit small with high speed throughput lowers the amount of heat necessary for the process. Yet throughput at this kind of temperature means higher pressure and lots of complicated valving.
How high? I'd guess over a 1,000 psi.