Implosion
Also if workers use live steam to steam clean a tank car, inside, and outside, and then seal the airtight hatch, the air cools and a vacuum builds up until catastrophic failure. Most tankers have ceramic pressure inserts in the dome, so the ceramic breaks before pressure gets out of hand. Hard coupling also tends to break the ceramic inserts, when the liquid sloshes upwards in a crash. Never stand around a hump yard and watch tankers slam into eachother, you can get sprayed with caustic liquids !