Will Single Hull VLCs Adopt HBL?
 
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Will Single Hull VLCs Adopt HBL?

      4/12/1999

Following the grounding of the Exxon Valdez 10 years ago, the US Congress pushed through the Oil Pollution Act (OPA 90) in the following year. Basically it brought in mandatory double hulls for tankers and stipulated phase-out times for existing single hull tankers.
The International Maritime Organisation (IMO) then amended the International Convention for the Prevention of Pollution from Ships (Marpol). As amended Marpol requires all single hull tankers, of any substantial size, to comply with one of a number of alternatives once they have reached the age of 25. These alternatives are to: fit double hulls, fit segregated ballast tanks, fit protectively located wing or double bottom tanks or adopt hydrostatic balance loading (HBL). Once those ships reach the age of 30, they can no longer be used to carry oil.
The industry has, since the early nineties, built a substantial number of double hull tankers while it is now starting to adopt HBL for older tankers. HBL involves partially loading tanks so that, if the hull is pierced near the bottom of the ship in a grounding, water flows into the vessel rather than oil flowing out.
A double hull configuration, as is now required in new tankers, gives extra protection by making it less likely that the cargo tanks would be opened up to the sea in the event of a grounding. It is worth remembering though that, if a double hull tanker's tanks are ruptured, oil outflow will be greater than with a single hull ship.
But there are problems which were not addressed at the time Marpol was changed and are likely to become more apparent over the next few years. Many experts were skeptical about the inherent suitability and safety of the double hull design for tankers. Those concerns were dismissed at the time but the first generation of double hull tankers have suffered problems which are likely to become more acute as time goes by. Considerable concern has been caused by the incidence of pitting in the bottoms of cargo tanks which raise the possibility of leakage of oil into those void spaces with the obvious associated dangers.
However, the question of how to treat existing vessels is an even thornier issue. In recent weeks a controversy has been raging over the wisdom of using HBL to keep older tankers, and especially very large crude carriers (VLCCs), going for their last five years before being barred from carrying oil by Marpol. Certain charterers, including BP, have apparently decided not to charter tankers using HBL.
That has, of course, worried the owners of older tankers. It has also worried the International Association of Independent Tanker Owners (Intertanko). In the meantime a recent recommendation stated by Stena Bulk calls for all single hull tankers to adopt HBL.
It would be in the best interests of the tanker industry if HBL is adopted for all single hull tankers. That would, in effect, mean that all tankers, single and double hull, offered roughly the same environmental protection in the event of a grounding.
Full article: Shipping Times


 


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