How explosive is crude oil?

Look at what is in crude oil.. Light and heavy oils, tar, gasoline, diesel, propane, butane, either, and much more. They are all flammable and under the right condition explosive. To get to an explosive requirement you have your LEL lower explosive level.. ( to lean) and UEL .. Upper explosive level( to rich) if that is over or under it will not explode.. But if in between the two .. Boom. Just like your car when you flood it, or your to lean on the gas ratio. Solvents are used. The only thing at they flair off is hydrogen , as it is to unstable to do much with it. And most refineries can only put so much into the air. Now if you have a firecracker and break it in half.. Light it with a match.. Fizzles .. THen get one thats not broke.. It blows up.. Why because the good one contains the energy from the burn, just like an engine cylinder does. If the burnable what ever has its energy released... Burning gasoline in a open can, won't blow up. Ifits contained.. Lid on can sealed up, and starts to burn the energy is contained can blow up. It's that easy. That's why except on TV cars that are on fire normally don't blow up, hose from filler burned up, and gas station fires, because the gas can't build up pressure, as the energy is released. Through vents.

 

It might have been what fire fighters call a BLEVE. "Boiling liquid expanding vapor explosion". A sealed tank car filled with liquid, gets hot because of the fire on the outside, the liquid inside starts to expand, and at some point the expansion causes the tank to rupture, which is technically an explosion, but probably not in the sense you are thinking. I am sure that after it ruptured that crude burned long and hot though.

 

The tank cars are supposed to have pressure relief valves to keep that from happening.

 

If the heat gets too intense the relief valves cannot keep up with the increasing pressure. Eventually something has to give. That's why we try to flow massive amounts of water onto the cars to keep them cool enough so the relief valves can do their job.

 

The relief valves are designed and made for exactly that.. Relieving any pressure.. They have one for normal expansion, for everyday usage.. and what's called a busting disc. They blow out when x amount of psi is reached inside the tank. And that is well below any dangerous level.