The International Association of Independent Tanker Owners (Intertanko), Oslo, is promoting a new tanker design it believes will provide better environmental protection than double hulled designs.
Intertanko said trials and tank tests showed the performance of a horizontal bulkhead/rescue tank concept is better than double hulls in accidents involving high energy impacts.
The new design uses single hulls but has a system of pipes and valves that are activated after a grounding or collision. It uses hydrostatic balance to automatically transfer the cargo from a damaged tank into empty rescue tanks.
The tests by Intertanko and Lloyds Register showed the rescue tank concept minimized oil outflow even when a vessel was exposed to strong tides.
Intertanko said in the event of a high energy collision, the horizontal bulkhead/rescue tank design could reduce a spill by as much as 75% from that of a double hull. Taking an average of low, medium, and high energy collision scenarios, the mid-deck rescue tank design model test results showed almost six times less spillage than the double hull.
Intertanko said the new design offers significant advantages during salvage of a wrecked tanker because the hydrostatic balance siphon effect could be used for safe transfer of cargo.
Philip Embiricos, chairman of Intertanko's safety and technical committee, said it would be a grave error to focus all attention on double hulls, given the existence of more promising solutions to spills.
"A technological freeze would be shortsighted," Embiricos said.
"In effect it would severely restrict the ship designer's ability to minimize oil outflow in the event of a serious grounding, collision, or other type of incident."
The Intertanko official added, "it also would be inconsistent and unfair to tanker owners who face unlimited liability in U.S. waters without the freedom to adopt the best possible design option to minimize pollution."
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