Forensic analysis on bursting accident of buffer tank in liquefied natural gas bus

In December 2019, a buffer tank burst accident occurred in the maintenance of liquefied natural gas (LNG) bus in China. Failure analysis revealed the bus-mounted buffer tank had been subjected to an excessive internal pressurization, although the tank material met the specifications for engineering practice. The physical evidence related to the failed tank showed that a chemical explosion was impossible. As water was used to pouring the frozen pipeline prior to the accident, according to the consequences observed, the rapid phase transition (RPT) explosion of the residual LNG due to external heat from water was regarded as the main causation of incident. The explosion energy was inversely estimated by the TNT equivalent method, and the rapid expansion of natural gas produced excessive pressure, thus causing the buffer tank to explode.