CHAPTER IX. PUMPING, FLOODING, AND DRAINAGE THE present chapter deals with the methods adopted in ships of the Royal Navy for clearing water out of the ship, which has entered through damage or has accumulated in the bilges under the ordinary conditions of working; and also the means for voluntarily admitting water into certain portions of the ship to preserve stability, or to keep the ship upright or on an even keel after damage, or to flood the magazines, etc., in case of fire. By Drainage is meant the means of allowing water to pass from one compartment to another until it reaches a pump-suction by which it can be removed. By Flooding is meant the deliberate admission of water into the ship through a sea-cock. This may be necessary to correct heel or trim after damage, or in the event of fire. By Pumping is meant the general arrangements adopted to remove water from the ship by means of the fire and bilge pumps in the engine-rooms, or by the Downton pumps, worked by manual power. Before dealing generally with the subject, it will be advisable to see how far the pumps fitted to a ship are able to deal with the inflow of water. If A be the area of a hole in a ship's bottom in square feet, and d the distance of the centre of the hole below water, then the initial velocity of the water through the hole is given by 8 ft. per second, so that every second there would be 8A/a cubic ft. of water entering, or about 14A/a tons per minute. If the hole is 16 ft. below the surface, about 56 tons will enter in a minute for every square foot of area. The following is the specified capacity in tons per hour of the pumps available for dealing with such a leak in a recent large ship, viz.--- Four centrifugal pumps (used ordinarily for circulating` Four fire and bilge pumps..... ... Four Downton pumps ... 5600 tons 400 tons 100 tons 6100 tons1 That is about 102 tons per minute. But we have seen above that the water through 1 square ft. amounts to 56 tons a minute, so that a hole only 2 square ft. in area (19 in. diameter), 16 ft. below surface, is sufficient to overpower the whole pumping capacity of a large ship. Such a hole is small in comparison with what would result from a collision, and this illustrates the importance of efficient watertight subdivision, which has been dealt with in previous chapters. By this means the damaged compartments may be isolated, and a collision mat placed in position over the hole so that repairs of a temporary nature may be undertaken. In recent ships the arrangements for pumping and drainage are considerably simpler than formerly adopted; it is proposed only to deal with the arrangements in a battle-ship of the Duncan class, as being typical of recent practice. Main Drain.-Special arrangements are made for clearing the ship of large quantities of water for which the ordinary steam and hand pumps would be inadequate. For this purpose a main drain (Fig. 91) is worked above the inner bottom from the forward boilerroom, branching to either engine-room. This drain is 15 in. diameter in the middle boiler-room, and 20 in. x 15 in. in the after boiler-room. By means of this drain, water can be passed from either boiler-room into one or both engine-rooms. Sluice valves, with non-returns, are fitted as shown to control the flow of water to the engine-rooms; the non-return valves automatically prevent the passage of water from the engine-rooms or from one boiler-room to another. In each engine-room, suctions are taken down from the circulating pumps of the condensers, so that these pumps can be made to draw from the engine-room bilge if desired instead of from the sea. These circulating pumps work independently from the main engines, and their engines are placed as high in the engine-rooms as possible, in order that they may continue working even if the engine-room is flooded to a considerable depth. The sluice valves on the main drain are worked from below and also from the main deck. In addition to the main drain, the forward compartments likely This is an extreme assumption, as it is unlikely that the water could get to the engine-room sufficiently fast to enable the centrifugal pumps to be fully occupied. to have large quantities of water are drained into the forward boiler-room (Fig. 91). Similar drains are fitted aft, draining into the engine-rooms. At the forward end we notice that two pipes, 8 in. diameter, are used, and into these we have pipes leading from barbette, submerged torpedo-rooms, torpedo-tubes, chain lockers,1 MAIN SUCTION TO BILGE PUMP→→ COAL HOSE DOWNTON PUMP WT FLAT COAL WIN FIG. 93.-Pumping section. etc. The forward and after drains, and also the main drain, each have connection to a sea valve for flushing purposes. The wing compartments and inner coal-bunkers are drained on to the top of the inner bottom, as shown in Figs. 91 and 93. 1 In recent ships other means are adopted for clearing cable lockers of water and mud. |