Ore-bulk-oil carrier

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).

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.

The idea of the OBO was that it would function as a tanker when the tanker markets were good and a bulk / ore carrier when these markets were good. It would also be able to take "wet" cargo (oil) one way and "dry" cargo (bulk cargoes / ore) the other way, thus reducing the time it had to sail in ballast (i.e. empty).

The first OBO carrier was Naess Norseman, built at A. G. Weser for the company Norness Shipping, controlled by the Norwegian shipowner Erling Dekke Næss. Næss was instrumental in conceiving the new type of vessel, together with his chief naval architect Thoralf Magnus Karlsen. Naess Norseman was delivered in November 1965 and was 250 m (820 ft) long with a beam of 31.6 m (104 ft), a draft of 13.5 m (44 ft), and a gross register tonnage of 37,965 tonnes.

The OBO carrier quickly became popular among shipowners around the world and as of today several hundreds of this type of vessel have been built. The ship type had its glory days in the early 1970s. In the 1980s, it became clear that the type required more maintenance than other vessels. Also, it was expensive to "switch" from wet to dry cargoes, and it took valuable time. If you had carried oil, you could switch to carrying ore or other dirty bulk cargoes, but not grain or other clean bulk cargoes. As the 1970s-built OBO vessels become older, most of them were used either as pure tankers or as pure ore carriers.

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Wikipedia