(197a) Blast Waves Produced by Rapid Phase Transition of Lng on WATER

Massive offshore storage of fuels have let international community arising questions about the hazards on the surrounding installations and people. Among the possible accidental scenarios, when cryogenic gas as Liquefied Natural Gas is spilled on water at a very fast rate, the phenomenon of Rapid Phase Transition (RPT) may occur: Large amounts of energy are released during phase transition and explosions can occur. The related consequences should be added to the possible consequences of fire in terms of flash fire, fireball, pool fire, and vapour cloud explosion for confined and congested geometry surrounding the release point.

In this paper, an acoustic analysis of blast waves produced by RPT of LNG on water was performed. Maximum overpressures as calculated at the source point and along the blast pathway are compared with results of large scale experiments. Safety distances are given for the sake of comparison with threshold distances reported in the open literature and international guidelines.

Results have showed that RPT explosion are able to produce damages only to very close equipment and for release rate larger than 10 m3/min, provided that 0.07 bar is considered as the threshold value for structural integrity. Rapid decay of pressure is observed for larger distances.