Estimation of plate thickness deduction of oil tanker for domestic area - Indonesia waterwaysTahun 2018
The requirement of plate thickness of classification society is taking into account the net thickness, corrosion
allowance and additional extra margin as owner request. Corrosion allowance is an additional constant value that is
related to the environmental condition which shall be added in the formulae to calculate the requirement plate
thickness and profile of the ship construction in accordance with the classification society rules. It is known that
major Classification Societies rules are based on the North Atlantic Ocean enviromental condition. However, if the
ships are operated in local domestic area, i.e. Indonesia waterways, the rules requirements become very conservative.
These condition make the ship design be coming over design. This study aims to develop time-dependent corrosion
allowance formulation. The statistical analysis of thickness diminution carried out using measurement records that
are documented from 23 Oil Tankers during her voyages in Indonesian waterways. The age of target ships was
ranging from 5 to 23 years. The thickness measurements were located in the deck plate, bottom plate, inner bottom
plate and side shell plate which are located on ballast tank, fresh water tank, void tank, fuel oil tank, slop tank and
cargo tank. It is found that the Weibull distribution could be used for estimation the time dependent plate thickness
deduction. In general, for design life of 25 years the greatest deduction of plate thickness is in deck area of 2.4 mm,
followed by bottom plate of 1.8 mm, 1.6 mm side plate and the smallest is in inner bottom plate which is 1.1 mm.
Generally, the results show that the thickness diminutions in Indonesian waterways are smaller than IACS CSR
requirements, but greater than Sone’s results.
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