How long before an engine or cab fire begins to affect the pressure of the gas stored as a liquid inside the tank though?
From the pictures and the descriptions I understand that there is a vent on top, either heat or pressure activated, which allows gas to blow off vertically upwards so as to prevent a build up of pressure to the point where the tank fails and ruptures, which is when you get this devastating BLEVE.
The last time I saw that acronym was in the Iain Banks novel Complicity where a man is murdered sadistically by Bleve, apparently a favourite method of the Welsh nationalists who burned English holiday cottages in the 70s and 80s.