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    "source_title": "Encyclopaedia Britannica (1926)",
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    "title": "(HI. 1. P.) SALVAGING",
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    "verified_text": "salvage work, or the raising and recovery of suike1 shins and cargoes, has alwavs had a fascina- tion, first for the reason that very little is known of the subject by the outside public, and secondly the spirit of adventure appeals to us to-day, although possibly in a modified degree compared with that which sent our forefathers out to search for hidden treasures in far-off lands. it is still one of the professions which retains a spice of romance in this commonplace world. salvage engineering has alwavs been confined to a small num- ber of the enginecring profession, although it is a highly tech- nical business, where skill, experience and determination are pitted against wind and sea. it necessitates trained men and snecial annliances and is a work that must be carried on night and day whenever the elements permit. divisions of the subject—marine salvage may be divided up under a few principal headings:— salvaging (1) the raising of vessels sunk in deep water by means of pon- toons, etc. @) raising by the application of compresscd air to expel the water. (3) refloating of ships stranded on rocks or sand where the bot- tom is damaged and temporary repairs have to be made by divers, and where pumping plant of different descriptions is used to free the vessel of water. (4) uprighting of capsized vessels, etc. the salvage ship.—the salvage ship is one of the most impor- tant factors in salvage operations, and, although generally a small vessel, carries a very complicated equipment of appliances for use in the work with a view to rendering her as independent as possible of assistance from ashore, and enable her to make repairs, etc., in out-of-the-way places where it would be difficult to obtain other assistance. as an example, one of the most modern type is composite built and her dimensions are 170 ft. long by 30 ft. wide, fitted with triple expansion engines, and has a speed of 14 knots. she accommodates about 80 officers and men, consisting of engineers, artisans, divers, motor engineers, electrical engineers and others. her equipment consists of portable pumping plant of 5,000 tons per hour which can be transferred to the wrecke.! vessel, portable oil driven air compressors, portable electric lizhting plant and electric submersible pumps which work under water, the vessel has powerful electric arc lamps at the mastheads of 5,000 c.p., with sufficient length of water-tight cables to allow of them being placed on the wrecked ship and opcrated by the salvage ship’s dynamos; also searchlights, submarine arc and incandescent lamps for the divers, submarine oxyacetylene burning plant for cutting plates under water, also a complete equipment of submarine neumatic drilling machines up to 3 in. in diameter, pneumatic ammers, rock-boring drills and submarine photographic appara- tus. she its fitted with long-range wireless telegraphy, and has a fully equipped workshop with electrically driven lathes, drilling machines, etc. in the store-room are all descriptions of blocks, shackles, ropes and other appliances necessary for discharging cargoes and other work in connection with the salvage of a wrecked vessel; she is also fitted as a first class and powerful tuz boat, and carries line-throwing guns. deing constructed of wood she is able to remain alongside a damazed ship in weather when the vessel of ordinary construction would have to leave. salvage pumps.—at one time steam pumps were entirely used in salvage operations, and were supplied with portable boilers so that they might be placed on board a wreck. they performed very excellent service, generally under most difficult conditions. to place such heavy gear on board a wrecked ship from a salvage craft rolling alongside on a winter night required a large amount of skill and care. when placed in position they had to be con- nected up to the portable boilers and steam raised before they were available for pumping. it was also necessary to place a supply of coal on board if the ship’s bunkers were not available, and this supply was often washed away. steam pumps are still retained on board the salvage ship, as they are able to perform work that the present type of pumping plant cannot do; for instance, sand, coal, grain and even copper and iron ore can be discharged by them from under water. the internal combustion engine (q.v.) went a great way to revolutionise salvage pumping plant. it was much lighter than the steam pump, required no boiler, and the fuel could be car- ried to the wreck in barrels or drums in an ordinary ship’s life- boat. further, when not required for work it can be stopped and started again in a few minutes, while steam has always to be kept on the portable boilers of the steam pumps. the advan- tages of the oil motor driven centrifugal pump will be obvious; it is just as efficient for pumping water as the steam pump, saves in cost of running, takes up less stowage space and uses paraffin as fuel, which can generally be obtained without difficulty. the sizes in general use are 12 in. and 6 inch. _ the latest type of pumping machinery is the electrically driven submersible. it has been well tried under all conditions and found more efficient than any of the older types. it can be placed aboard in boats and driven from the dynamos of the sal- vage ship lying off the wreck. there is no necessity to secure it, as it works practically without vibration and can be used from the derricks and lowered down into the water. its great advan- tage is that while the ordinary salvage pump has only a lifting 457 capacity of 30 ft. the submersible is able to raise the water to a height of 80 ft.; no priming is necessary, and no particular atten- tion need be paid to the discharge hose as far as making it air and watertight. former electric salvage pumps that were tried were fitted with watertight cases, and proved entirely unsuccess- ful for this particular kind of work. in the submersible pumy, water is allowed free access to the electrical parts. lifting operations from deep water with this somewhat brief description of salvage plant used particulars of actual salvage operations will be explained, com- mencing with the raising of sunken vessels from deep water by means of lifting barges dependent on the rise and fall of tide. —— e . : —_ = —? ss — eee eer ee ee, ee ee eee ee oe — pw wee ee se se be ee ee ee ee ee ee ee ee ee -—- ww ween ew eee ee eee eae ee oe ee ee vm oooo. mtt fic. 1.—lifting wires in position and buoyed. the method of procedure is to place lifting vessels of sufficient buoyancy over the wreck and pass a number of g in. steel wire ropes under the vessel, bringing the ends of the wires up and making them fast to the lifting ships at low water; then as the tide rises, if the calculations have been correct, the vessel is raised from the bottom the height of the rise of tide, and carried into shallower water where the wreck is grounded, and the operations are continued each tide until her decks are above water (see figs. 1, 2 and 3). the fractures are then patched by the divers, salvage pumps installed and the vessel pumped out and floated. the dimensions of lifting vessels vm ys fig.2 fiq.3 fic. 2.—lifting lighters in position. wires secured, and pinned at low tide. fic. 3.—wreck lifted. that have been employed in a large number of cases are: iength 165 ft.; breadth 36 ft., and each with a lifting capacity of 1,500 tons maximum. one of the principal difficulties with this method is the placing of the heavy wire cables under the bottom of the wreck, especially if she has sunk in the sand, mud or clay. if not too deeply embedded this is generally accomplished by towing them under with two ves- sels, one on each side, and the ends of the cables attached to them. where this is not found to be possible owing to the wreck having become too deeply embedded a system of hydraulic boring at nigh pressure is resorted to, by which method the wires are rove under the wreck in the required positions for lifting. in cases where there is little or no rise of tide submersible pontoons are used. these are really steel cylinders with a lifting capacity ranging from 50 tons each to 250 tons or more. they are divided into three watertight compartments and fitted with 458 low pressure air connections for expelling the water, and with high pressure air for opening the valves. the ends of the cyl- inders used at the lifting of h.m.s. “* gladiator ” were dome- shaped, and covered with collision mats to protect them against chafing. strong channel bars were riveted around the pontoons at intervals to carry the wire cables, and the whole of the cyl- inders between the channel bars were covered with 3-1n. fir plank- ing for protection against obstructions when lifting. double 6 in. strops of special extra flexible wire ropes were fitted in the required position around the pontoons, and to these were at- tached plate shackles to which the g-in. lifting wires were fas- tened. in this case the pontoons were used to uprighten the ves- sel, which lay over on her beam ends at an angle of 113 degrees. the g-in. wire cables were swept under the wreck and the out- side ends attached to the pontoons. these were filled with water and sunk alongside the ship; the other ends of the wires were then hove in as tightly as possible and made fast to massive steel bollards fastened to the upper side of the ship. the cyl- inders or pontoons were then emptied of water by means of compressed air and the vessel uprighted, assistance being also given by compressed air and pymping from some of the sound compartments. in this case pontoons were only used on one side, but in order to raise a vessel that is sunk and lying upright on the bottom two sets of cylinders are necessary, and the plan of lifting is as follows:— | a sufficient number of g-in. wire cables are placed under the ship, the pontoons are attached to the ends of the wires on one side of the ship and filled with water, and by heaving in on the opposite cables they are hauled down into the required positions alongside the wreck. a special form of hydraulic gripping ma- chines is attached to the pontoons on the other side of the wreck and the wire cables rove through these hydraulic grips. when everything is ready the pontoons are filled and allowed to slide down the wire cables to the bottom. the grips are then closed from the surface vessel and compressed air pumped down to all the pontoons, which expels the water, and if sufficient buoy- ancy has been given by the pontoons the vessel is brought to the surface. lifting by compressed air.—al\\l openings are closed by the divers, and compressed air pumped down to connections made to all the different compartments from air compressors of the salvage ships. the water is then expelled through the fractures and the vessel rises to the surface. this method entails a very large amount of diving work, as funnels, etc., have to be cut away and the openings closed and made airtight. decks under air pressure have to be strongly shored up and supported. refloating stranded ships——the conditions of stranding are very varied. assuming a large vessel stranded on a rocky bottom on an exposed coast and sustaining such damage that all com- partments are filled with water and the vessel appears at first sight to be a hopeless wreck. a diver’s survey of the position is made as soon as possible, and at the same time a careful survey is made of all compartments to ascertain whether the water falls in each at the same rate as the tide. some compartments will generally be found to be holding water, that is to say the tide does not ebb and flow in them as it does outside. the amount of pumping plant required can thus be easily gauged for com- partments under these conditions. when the tide ebbs and flows as it does outside it shows considerable damage to the outer bottom, which neccssitates extra pumping plant and the patching of the fractures by divers. should the vessel have cargo on board a portion of it will probably have to be discharged to lighten the ship. after all this work has been done the vessel is pumped out and refloated. the patches used by divers to close up fractures are generally made of wood and secured into position by bolts drilled through the patches and through the plating of the ship. jagged or out- standing plating is cut away by explosives or by submarine oxyacetylene cutting plant to make a fair surface for the patches. if any rocks are in the way or have entered the hull of the wreck they are removed by drilling holes with submarine pneumatic rock drills and dispersing them by explosives. lf; ¥.) salvation army",
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