Structural Degradation of Oil Tanker Operating in Indonesian Waterways

Corrosion is one of the significant factors for decreasing strength in floating marine structures. In general, rules of classification society use the North Atlantic Ocean located in the sub-tropical region as a reference area in the formulation of the structural strength. If the sub-tropical area compare with tropical region such as Indonesia waterway, Indonesia waterway has high salinity and humidity. This makes marine environment in Indonesia more corrosive. One example of the effects of corrosion is the reduction in plate thickness. This leads to decrease in ship strength. Using measured thickness data collected from 25-thickness measurement reports from 24 Oil Tankers that sailing in Indonesian waterways, the diminution of ship structural thickness has been analysed. The age of Oil Tankers, whose data was taken, ranges from 5 to 23 years. Data analysis was carried out by using statistical approach based on Weibull distribution. Using 95% cumulative probability, it was found that the thickness diminution of Oil Tanker with design life of 20 years is 2,07 mm for deck plate, the side plate is 2,06 mm, the bottom plate is 1,81 mm and the inner bottom plate is 1,53 mm.