French Develop VLCC Design With Intermediate Deck

A double-hull crude carrier design incorporation an intermediate deck has been developed by the French participant in the pan-European E-3 tanker program.

The very large crude carrier (VLCC) proposed by Chantiers de l'Atlantique offers 6-meter (about 19.6 feet) spacing between inner and outer shells. This is more than twice the minimum stipulated in the 1990 Oil Pollution Act requirements for double skinned tankers trading to the U.S.

The 6-meter double bottom created by the intermediate deck will act as a void when operating to the U.S. But it has also been designed to enable oil to be carried when trading to those parts of the world not subject to double-bottom legislation.

The extra width and depth of the double hull spacing, the French yard believes, affords a much greater measure of protection for the cargo section in the event of high-energy collisions and groundings.

The design applies the principle of hydrostatic balance as a means of minimizing or obviating oil outflow if the cargo tanks are breached.

When used for cargo-carrying purposes, the double bottom tanks will not be fully loaded, so as to maintain an air gap above the cargo.

In the event of the bottom being holed, oil loss should be minimized because of the relatively low head of oil ensured by the low, intermediate deck. The air gap will ensure that seawater forced into the tanks by the difference in hydrostatic pressure, will act as a seal at the bottom of the ship, reducing or preventing cargo losses.

There will also be provision for transferring cargo to the main tanks or side shell spaces in an emergency situation.

Other stories from November 1991 issue


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