The Coulombi Egg Tanker - The 'Limburg' Accident Better protection, safer and more economical than Double Hull

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The double hull VLCC 'Limburg', b. 2000, suffered an explosion in the double hull on 6 October 2002, outside a load port in Yemen. The vessel was 20% part-loaded with cargo in some wing tanks at the time and the weather was good. The draught of the ship may have been about 7-8 meters. This was the first time that a serious explosion occurred in a double hull VLCC and the question is of course what caused it? The damage in the starboard side shell is a big opening - hole - about 10 meters long and about 5 meters high above the waterline at 7-8 meters above the keel. The extent below waterline is not known - 6 meters?. The damage is situated slightly aft of mid-length between vertical web frames, web spacing about 5 meters, i.e. the side shell has been ripped off from one intermediate vertical web frame. The inner shell - about 3 meters from the outer shell - appears to be intact but is fractured and deformed inboard. Some edges of the damaged hole in the outer side shell are bent outboard.

It seems that the cargo tank boundary inside the damage was fractured and that cargo oil later leaked out and started to burn - see the picture above. The cargo oil flowed out on the sea and for a while the tanker was surrounded by burning crude oil. However, after a further while the fire burnt itself out and , e.g.the engine room is still intact. Apparently the crew did not try to extinguish the fire. What caused > 50 m² of stiffened 20 mm thick side shell plate (right) to disappear. Some 'experts' argue that it was a terrorist attack like the 'Cole' (remote right) two years earlier, but it was lightly built warship with a very thin shell plate (10 mm). Heiwa Co is at loss to see how you blow off > 50 m² of 20 mm thick shell plate from the outside of a tanker? An internal explosion inside a cell in the double hull seems also a likely cause. Hydrocarbon gas may have collected in one or two cells in the double hull bounded by vertical webs and horizontal stringers and the gas had exploded. The 'Limburg' The 'Cole' The reason why the explosion did not expand upwards and blow up the deck of the tanker is that there are two horizontal stringers between the damage and the deck. Thus the side shell blow out from inside, where the resistance was the least. 12 seamen on deck preparing to moor the 'Limburg' panicked (she was three miles from the port) and jumped overboard but were quickly picked up by boats assisting with the mooring. The double hull VLCC was quite new and it is a well known fact that structural defects occur early in the life of a tanker. It could simply have been due to a minor leak - fracture - in the inner hull resulting in crude oil collecting in the bilge of the double hull. The gas filled some cells in the double hull and ignited. Leaks between cargo tanks and double hull spaces in VLCCs have occurred previously. The leak may be due to pitting of the inner bottom or a fracture. Such leaks have caused big problems as it has been extremely difficult to clean the oil and gas filled double hull compartment and it is one of the major disadvantages and risks of double hull tankers. These risks have been highlighted on another Heiwa Co webpage operations. A careful inspection of the 'Limburg' before repairs will no doubt determine the exact cause and events of the accident. Latest news (13 October 2002) is that the initial damage was caused by a criminal attack of a small boat with explosives - a terrorist attack. It rammed the tanker and delivered the explosives that exploded both inside and outside the double hull - and blow the side shell outboard probably destroying the attackers. Very strange indeed. Where did this boat come from? What was the purpose of such a stupid attack? The damage was thus a big hole in the outer shell and a fracture in the inner shell. Water then flowed into the empty side ballast tank and the fracture in the inner shell allowed all the oil in the damaged cargo wing tank, which happened to be loaded, to flow out where it caught fire. First the oil above the waterline flowed out by gravity, later the last bottom oil in the cargo wing tank was forced out by water flowing into the cargo tank. The double side hull ballast tank was empty and it should first have been flooded and the tanker should have heeled a little towards the damage. It was apparently not possible to extinguish the fire by the tanker's own fire extinguishing means. One idea would have been to fill the ruptured double hull side ballast tank with foam and to see what happened. Maybe the foam would just have flowed out into the sea but it would have been good to have tried. It would be interesting to know if the 'Limburg' crew actually tried to fight the fire and how, and, if not, why? Had the same initial event happened to a partly loaded COULOMBI EGG tanker all cargo had been loaded in the upper centre tanks and nothing had happened - no fire, no oil spill. The same thing would have happened if the COULOMBI EGG tanker was fully loaded. This was not one of the design conditions of the COULOMBI EGG tanker but is a logical consequence of the COULOMBI EGG tanker design. However, the COULOMBI EGG tanker fire extinguishing system provides for the top side ballast tank being filled with foam due to the risk of a fire there. Had the 'Limburg' by chance carried the part oil cargo in the centre tanks there would have been no fire or oil spill. Contact anders.bjorkman@wanadoo.fr