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Ukraine: BLEVE it or not; Part two of the Mystery at Saki Airbase [1]

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Date: 2022-08-12

Possible fuel trucks that could be the cause of the explosions.

This is diary is a follow up to my previous diary: Ukraine: It was 3 fuel trucks, in Crimea, with a cigarette butt. The main thesis of it was that the primary explosions at the airbase were from exploding fuel trucks. The main objection voiced by some was that exploding fuel trucks could not leave a crater. While I thought the video of a fuel truck exploding and dropping a bridge span was sufficient, to some it was not. The basic objection is that fuel-air explosions do not leave a crater. Which I generally agree with. However, the example fuel truck explosion I provided and the proposed mechanism for the blasts at Saki Airbase are not simple fuel-air explosions. It is a combination of a fuel-air explosion and a BLEVE.

BLEVE is the acronym for Boiling Liquid Expanding Vapor Explosion. BLEVE is caused when a pressure vessel holding a liquid is brought above boiling temperature. The liquid is unable to fully phase change to gas which increases pressure on the pressure vessel. With continued heating, pressure increases until the pressure vessel fails. At this point the liquid violently (and I do mean violently) vaporizes as the pressure can longer be maintained. This expansion is energetic enough to be considered an explosion. The liquid does not need to be combustible. My favorite example of BLEVE is the Mythbuster’s episode “Exploding Water Heater” where they essentially turn a water heater into a rocket.

Most fuel trucks do not explode in massive fireballs destroying everything around them. They merely go up in terrifying infernos making anyone nearby wet their pants. The video below is a common example. A truck crashes, tearing open the fuel tank and a spark lights it all up.

While big and impressive there is no cratering of the road or massive damage comparable to what we see at the airbase. Sometimes, the tank is intact enough that the gas inside is not yet on fire, but as it drains the fuel air mix reaches the balance to allow an energetic explosion. More explosive than above, but still not crater worthy.

So what conditions do we need to achieve a fuel truck BLEVE? Let’s walk through the video of a truck that massively explodes in Italy.

Skipping over the quick teaser of the full explosion at the start we see the fuel truck going down the road and fails to stop. It crashes into the truck in front of it and catches on fire. There is a critical aspect here which is not immediately apparent. The fire is started by the semi’s own fuel tanks rupturing and catching on fire. The fuel trailer tank is still intact. But we do not see an immediate BLEVE. Instead the fire continues long enough for the traffic to be cleared out around it. After the edit, we see the truck smoking away until a sudden, violent explosion strong enough to collapse the bridge span that it was on.

Let’s compare that bridge damage to a HIMARS attack on a bridge.

x ❗️First video of Antonovsky bridge over Dnipro river after Ukrainian strikes! #Kherson #Ukraine pic.twitter.com/3YDKK2hK14 — Special Kherson Cat 🐈🇺🇦 (@bayraktar_1love) July 27, 2022

For my money, the fuel truck BLEVE wins. But the BLEVE is not easy to achieve. The fuel tank MUST remain intact while it builds up enough pressure. This is why we don’t see every fuel truck being blown up by Ukraine turning into cratering explosions. Most big fuel truck attacks or accidents seem to involve an immediate rupturing of the tank itself which prevents pressure build up. It’s sort of counter-intuitive that the fuel tank breaking apart is a good thing.

The next thing we need for a BLEVE is a heat source. The heat needs to be strong enough and long enough for pressure to build up inside the tank. Eventually the pressure builds enough for the fuel tank to rupture. If the heat source is open fire, then as the tank ruptures and the fuel violently expands, it gets another kick as the fuel vapor ignites further energizing the explosion.

Finally, some people noted the difference between the liquid propane the Italian truck was carrying and aviation fuel the Russian fuel trucks would be carrying. But the difference in boiling temp is less important due to the fire heating the tank up. Once the temperature inside the Russian fuel tank gets high enough to vaporize the fuel, it will start building up pressure until it ruptures. When it ruptures, the aviation fuel will instantly vaporize creating perfect conditions to burn it.

The BLEVE also provides a mechanism for the near instantaneous explosions of two fuel trucks. Both fuel trucks would be heating and pressurizing. Once the first one fails, shrapnel will be sent in all directions. Should a chunk strike the other fuel truck tank, the hit could weaken the tank enough to have it rupture as well, setting off the second explosion. The third fuel truck was behind a berm protecting it from shrapnel from the first two, letting it continue pressuring until it failed on its own.

So for this to be the cause, we need a large hot fire around at least two of the fuel trucks. The fuel trucks should have their tanks intact at this point allowing them to pressurize before erupting into a BLEVE/fuel-air double explosion. If it’s good enough to take down a bridge span, it should be good enough to make a big old crater.

As for what sets it off, go ahead and choose your own scenario. But your scenario needs to lead to heating two trucks without rupturing their tanks. A fuel spill lit on fire achieves this nicely. I’ll leave the Tom Clancy ideas to you all. ;)

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[1] Url: https://www.dailykos.com/stories/2022/8/12/2116062/-Ukraine-BLEVE-it-or-not-Part-two-of-the-Mystery-at-Saki-Airbase

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