Ore-bulk-oil carrier
When tank - bulk cargo carriers refers to various bulk cargo ship types for simultaneous or alternate transportation of crude oil and ores, as well as some other bulk materials.
The ore / oil cargo ship, or O / O Carrier ( from the English Oil / Ore for oil and ore) is the older version for certain services with mixed cargo volume of crude oil and ores.
The oil / bulk / ore freighter, or OBO carriers ( from the English Oil Bulk Ore oil, bulk and ore) is, in particular for highly flexible services with mixed cargo volume of crude oil, suitable ore and other bulk cargoes in regions where otherwise only a one-sided load use would be possible.
History
Although at the end of the 19th century, first simple combination of oil - ore ships were, as they developed the first specialized ore carriers and tankers, tried, the development direction was at first but still rather uncertain (see also the ships Vaderland and Neptune). In particular ore carriers were made with trim and stability reasons, equipped in relation to cargo holds, ballast water large capacity, the use of which is offered to the oil transportation in order to avoid uneconomic ballast voyages.
The G. Harrison Smith of 1921 can be regarded as one of the first to be assigned consistently as combined shipping for ore and oil drive. The shipping company International Petroleum Company took the G. Harrison Smith ores of the South American west coast to Maryland on the North American east coast, thence in ballast to Mexico, where she invited oil for the west coast again. Because, among other things, higher fees in the Panama Canal ( tankers had a higher, ie unfavorable survey ), but not worth this service, after which the ship was further operated as a conventional ore carriers.
Another early example were the engine driven, designed as an oil / ore freighter Svealand and America country ( 15357 GRT) belonging to the Swedish shipping company Broström Group Angfartygs A / B Tirfing. The 1925 -built at the German shipyard in Finkenwerder ships transported ore from Cruz Grande in Chile to Baltimore. They were chartered for 20 years at Bethlehem Steel. A theoretically possible crude oil transport was not carried out as a tanker because of the high channel passages, if approved.
Around the mid-1950s began to develop ore / oil ships that are no longer exclusively in the Erzladeräume enclosing tanks, but also in the actual cargo holds loaded the transportable oil itself.
One of the first ships of this valid in principle to the last design, was rebuilt in 1954 in the United States for the New York shipping company Ore Transport Company Californian.
Another innovation in 1957 was the first time built tank - bulk ships, fitness for dry cargo larger Granted. These ships could also transport oil or lighter solids, instead of exclusively ore and oil for the first time.
The last major step in the development of a real OBO Carrier was done by the Bremen AG Weser shipyard to build the Naess - Norseman in November 1965. The key figures in developing the new type of ship were Erling Næss dekke, the owner of the shipping company Norness Shipping and its Chief Naval Architect TM Karlsen.
With the advent of real OBO carriers a short phase of increase in ship sizes of these types of vessels was accompanied, which ended early as the 1970s. The numerical evolution of the OBO carriers took place in the early 1970s, culminating and sounded in the 1980s rapidly again, as the already higher than the price of pure tankers during construction about 10% of ships not only as a much more demanding in maintenance and turned out in the technical maintenance, but also a relatively long time to switch from one cargo to another need. The vast number of these ships were therefore with age as a pure bulk carriers (and then usually as pure ore carriers ) down or tankers. A greater percentage of these ships was sold for the stated reasons quickly as unprofitable again to cancel.
Only in the 1990s, some Scandinavian shipowners began again to order a number of smaller, about the Aframax segment to be resettled OBO carriers.
Cargo space arrangement
Combined tank - bulk vessels must comply due to their interpretation of some criteria that go beyond those of the conventional tank or bulk carriers. Firstly, it must cope with the demanding loading and unloading operation of dry cargo, in particular the ore handling, on the other hand, the oil cargoes must be transported clean and gas-tight. The numerous pipes for the tank operation must be so placed that they can not deteriorate during drying charging mode. In early designs, the bulk materials were loaded into the central cargo holds, the cargo and ballast tanks were located laterally and below. In later designs, such as the 1950s oil was transported in the central cargo holds, which gas-tight hatch cover made it necessary. In the further development of the O / O Carrier to OBO carriers, the shape and the size of the dry cargo holds modified ( see illustrations).