HAZARDS OF LNG SPILLAGE IN MARINE TRANSPORTATION

Abstract : An investigation of the hazard of spillage of liquefied natural gas onto water is described. About 2000 gallons of LNG were consumed in various tests. The initial vaporization rate of LNG following spillage was found to be 0.037 lbs/sq ft sec; when the spill was confined, this vaporization rate was moderated after about 20 seconds by the growth of an ice layer on the water surface; when the spill was unconfined, a coherent ice floe was not observed and the vaporization rate was essentially time-dependent. Downwind of a natural gas source, time-averaged methane concentrations were given in good approximation by standard air pollution equations. However, peak concentrations were as much as twenty fold higher than average, adding an additional factor to the assessment of hazard. The effect of layering by the cold vaporized natural gas was similar to the effect of a temperature inversion on normal gases in the atmosphere. Small- scale explosions were observed on pouring LNG onto a water surface. These explosions are discussed but no single explanations seems pertinent to all of the incidents observed.