steamers for storing drinking water, except that they occupied the entire hold of the vessel. The oil was pumped into these cisterns. In the same year he ordered in Sweden the tank steamer "Zoroaster." When delivered this steamer did not answer all requirements, but it was so improved by Nobel as to allow of its being used for the transportation of oil. Nobel was also the first who, to prevent the oil from penetrating into the boiler and engine rooms, and from becoming heated, separated the hold from the engine room by a partition filled with water the latter being constantly renewed. In case of leakage the oil can only reach the water, and, being specifically lighter, rises to the top. At the uppermost point apertures are provided through which the oil runs off. Figure 58 shows the dimensions and construction of a modern tank steamer as built in English ship-yards. A clear and comprehensive description of one of the more recently built steamers, the "Charlois," is found in The Marine Transport of Petroleum, by George Herbert Little, an English naval architect. "This vessel is 310 feet long, 39 feet beam, and 25 feet 3 inches deep, and is capable of carrying upwards of 3500 tons of petroleum, besides bunker coal, on a moderate draft. "The requisite subdivision into eight tanks of moderate size is obtained by the introduction of nine thwart-ship bulkheads, which are very heavily stiffened and made extra thick to withstand the pressure due to any one tank being full, while the others are empty. In addition to these there is a longitudinal bulkhead running the entire length of the oil compartments in the centre of the ship, which further subdivides each tank into two. Wells or water spaces are formed at each end of the oil compartments, which are filled with water when the vessel is loaded with oil, and thereby isolate the oil from the rest of the ship and boiler-room, to prevent risk of fire. Each tank is provided with a smaller tank above, running up through the 'tween-decks to the upper deck, which is fitted to allow for the expansion and contraction of the oil, due to the difference in temperature, without permitting the oil to ever fall below the level of the top of the tank proper, which is essential to the vessel's stability at sea. It is usual to carry these expansion tanks about half full of oil. The expansion tanks also serve the purpose of giving access to the tanks, proper man-holes and Jacob's ladders being provided. A special feature in this vessel, which the designers had particularly in view, is the fact that she could, with very slight alterations, be used for ordinary cargoes; the expansion tanks being arranged conveniently, and of extra size, for this purpose. This is, we think, an important point. The machinery and boilers are placed close aft, and clear of the oil compartments, and the saloon and officers' and engineers' cabins and gallery are abaft this, and therefore well clear of the tanks. The crew are berthed in the forecastle, and there is a long bridge amidships, with a shade or awning deck, connecting it to the poop. The shade deck was especially introduced by the designers to make the vessel more seaworthy, as she is employed in the Atlantic trade, and this considerably reduces the amount of exposed deck. The internal fittings of this vessel are most complete, and, as a further precaution against fire, she is lighted throughout by electric light on the incandescent principle, the engines and dynamos being placed in the engine room directly under the control of the engineers. There are also steam heaters for all the cabins and the crew. Two powerful pumps are fitted in the 'tween-decks with very complete piping arrangements, each pump being capable of discharging the entire cargo of oil in 30 hours. There is no double bottom for water ballast, but tanks are provided on both ends for trimming purposes. For ballasting the ship when light, two or more of the oil tanks are run up with water, special means being provided for this purpose; and when so laden the vessel is much steadier at sea than if carrying ballast in the ordinary double bottom; and as these vessels have to make one out of every two trips across the Atlantic light ship, this is very important." Experience has suggested some minor improvements sincə the "Charlois" was built. The vessels of later construction have a somewhat greater carrying capacity. The expansion tanks are not so large, but extend the whole length of the oil tanks they are designed to relieve. The strength of the hull has been still further increased by the addition of another deck or horizontal partition running through the oil tanks, dividing each into an upper and lower tank. This iron partition, with its braces, adds materially to the stability of the ship both when empty and full. An American firm has recently undertaken the construction of tank-vessels according to MacDugall's patent, and which are claimed to form the future basis of a new tank transport of petroleum. However, thus far the matter has not progressed beyond the experimental stage. The vessels are designed to be towed. They are cigar-shaped, with a deck resembling a whaleback. In 1892, 59 tank-steamers were engaged in carrying petroleum from the United States, 27 of which took their cargoes from Philadelphia. The appended table, from the Annual Report of the Secretary of Internal Affairs of the Commonwealth of Pennsylvania. Part III, Industrial Statistics, 1892, gives the names of the tank steamers that were engaged in carrying petroleum from the United States in 1892. There were fifty-nine in all. Those that carried cargoes from Philadelphia are designated by a star. The table shows the tonnage of each ship, her capacity to carry bulk oil, her length, breadth of beam and depth, and the flag under which she sails. A second table gives similar information in regard to the bulk sailing vessels that took cargoes, in 1892, from the United States. |