SCALE EFFECTS WITH FIRE EXPOSURE OF PRESSURE-LIQUEFIED GAS TANKS

When a tank carrying a pressure-liquefied gas (PLG) is exposed to fire impingement, there is a risk of thermal-induced rupture of the tank. If the tank ruptures, the potential hazards include blast, projectiles, fire and toxic exposure. These hazards are associated with all possible scales of PLG containers from small handheld lighters to huge storage spheres. Over the years, many researchers have conducted scale fire-testing of tanks to improve understanding of the failure process and the associated hazards. These tests have been done at various scales from glass tubes and spheres containing a few cubic cm to full-scale rail tank cars carrying 130000 litres or more. These tests have been used to improve models for fireball diameters, duration, and blast and projectile effects. They also highlight very interesting features of the heating process and the failure mechanisms. One of the most strongly debated scale issues relates to the Rash evaporation of pressure-liquefied gases upon sudden depressurization. If the conditions are right, a tank failure may lead to sudden depressurization of the PLG and this may trigger an explosive phase change resulting in a boiling liquid-expanding vapour explosion (BLEVE). This topic has been an active area of research for many years. The objective of this paper is to provide an overview of scale issues as they relate to the heat-up and failure of a PLG container. It is hoped that this material will be useful for emergency responders, so they can understand better the issues of scale when dealing with accident situations.