Ore-bulk-oil carrier

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An Ore-bulk-oil carrier, also known as combination carrier or OBO, is a ship designed to be capable of carrying wet or dry cargoes. The idea is to reduce the number of empty (ballast) voyages, in which large ships only carry a cargo one way and return empty for another. These are a feature of the larger bulk trades (e.g. crude oil from the Middle East, iron ore and coal from Australia, South Africa and Brazil).

Combination carriers found themselves specialising in one trade or the other, and their flexibility went very much unused. Very few were built after the 1980s, and the idea has rather fallen out of fashion. One of the more famous OBOs was the Derbyshire MV Derbyshire of 180,000 deadweight tonnes, which in September 1980 became the largest British ship ever lost at sea. It sank in a Pacific typhoon while carrying a cargo of iron ore from Sept-Îles in Canada to Japan.

A fleet of smaller, "river-sized" (several thousand tonnes) ore-bulk-oil carriers have been used for some decades on European Russia's waterways, primarily by Volgotanker. The Russian word for 'ore-bulk-oil carrier', nefterudovoz (нефтерудовоз, literally 'oil/ore carrier'), in combination with a number, is often used as a proper name for a ship, e.g. Nefterudovoz-51M'.