Non-Structural Bulkheads to Control Tanker Oil Spills.
Abstract:
A system of non-structural transverse bulkheads, formed by transverse membranes enclosing the open space between transverse webs in the cargo tanks of a tanker, is presented. The system provides additional subdivision, which reduces the outflow of oil from a loaded cargo tank if the tank is ruptured in collision. The ability of the system to reduce collision outflows on a 75,000 DWT tanker is evaluated on the basis of the statistics of past collision damages. A design method for sizing sheet steel membranes is developed. Cost estimates, and Required Freight Rate to recover the increased investment, are included, predicated on Japanese construction. It is shown that a reduction of probable accidental discharge of approximately 9 can be achieved by an estimated annual increase in operating cost when non-structural bulkheads are fitted in wing tanks only and at every second frame. Finally, estimates are made of the overall effectiveness of the system in reducing the probable discharge of oil from all sources, operational as well as accidental. Author