This never happened. It is a scenario: a collision at the LNG terminal in Zeebrugge tears open the cargo tanks of a 174,000 m³ LNG carrier lying at the jetty. We drew the hazard zones that Sandia National Laboratories calculated for LNG spills on water onto the real map of the port. With a hole of about 1 m² in one tank, the LNG burns as a pool fire on the water for about 40 minutes. The heat damages steel structures up to about 180 m away, wood can catch fire up to about 330 m, and bare skin burns within a minute up to about 550 m. With holes of 2 m² in three tanks those distances grow to about 400 m, 780 m and 1.4 km. The storage tanks on land are about 700 m from the ship and the nearest houses about 1.8 km. If the gas does not ignite at once, it drifts downwind as a cloud. For a larger hole of 5 m², Sandia found the cloud can stay flammable up to about 3 km in a light wind. With a north-westerly wind that reaches the edge of Heist. Damage to buildings comes from the heat. Close to the fire steel structures fail: the jetty, the unloading arms and the ship itself. Further out wood and plastic can catch fire. In the open there is no blast to push buildings over. Gas that drifts into a building or a sewer before it ignites can explode in there, on a local scale. A 2012 study by the Chinese People's Armed Police Force Academy took the worst case: the whole cargo of a 147,000 m³ carrier turns into one gas cloud and explodes at once. Their result: buildings heavily damaged up to 215 m, repairable damage to buildings up to 430 m, windows broken up to 1.1 km and one window in ten up to 2.9 km. That goes far beyond what Sandia calculated. The US energy regulator FERC states that LNG vapour mixed with air does not explode in the open, and a real leak boils off over minutes. The ship carries about 4 petajoules of energy, roughly as much as 0.9 million tonnes of TNT. LNG cannot release that energy in one go. It burns as fire over tens of minutes. A BLEVE, the explosion of a burning pressure tank, needs gas stored under pressure. The cargo tanks of a large LNG carrier are at almost atmospheric pressure and vent their gas. Small LNG ships and road tankers with pressure tanks can BLEVE. The distances are Sandia's general figures for LNG carriers, not a study of Zeebrugge itself. The wood distances (12.5 kW/m²) are our own estimate between Sandia's figures. The shape of the cloud is drawn for illustration.
Source: Hazard distances: Sandia National Laboratories (2004, 2008). Worst case: Li Jianhua and Huang Zhenghua, Procedia Engineering 45 (2012). LNG and explosions: US Federal Energy Regulatory Commission. Map: © OpenStreetMap contributors. Scenario and visualisation by The Moving Sea
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