大型タンカーの座礁時油流出減少対策の研究
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概要
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Negative pressure system, which keep the ullage of cargo oil tanks urder negative pressure, was studied as the measures to mitigate oil outflow at stranding in 1990. This system for single hull tankers, however, was not adopted as the alternative of double hull tankers in the 30th MEPC. This report throws light upon negative pressure system again and shows this system for double hull tnankers is very effective to reduce the oil outflow. Firstly, the experiment of oil outflow from cargo oil tank was carried out, using two dimensional cargo oil tank model of scale 1/100. Conventinal (non negative pressure) system and negative pressure system were compared with. Needless to say, negative pressure system retains more oil on the damaged cargo oil tank. Furthermore, it was proven that conventional system allows the inflow of water to double hull and retain less oil in it, but negative pressure system fills the double hull with oil by 100% and retains more oil in double hull. Secondary, mean oil outflow at stranding were calculated for the IMO reference tankers of 150,000 DWT and 283,000 DWT with/without negative pressure system, according to the IMO INTERIM GUIDELINE (1995). This guiedline shows the calculaion method of oil outflow at collision and strading, where flooded volume of the double hull at equilibuium is assumed to contain 50% oil and 50% sea water. However, in this report, the double hull is assumed to be filled with oil by 100% for nagative pressure system at stranding. Negative pressure is assumed -0.5kg f/cm^2 as the allowable limit of hull strength. Caluculated result shows that mean oil outflow reductions due to negative pressure system are 71% for 150,000 DWT and 58% for 283,000 DWT tanker at stranding.
- 1998-09-04