Drainage System of U.S.S. Monterey
By A.W. Stahl, Assist. Naval Constructor, U.S. Navy
The water-tight subdivision which is a prominent feature of all our new naval vessels involves, as a necessary consequence, a more or less elaborate pumping system for the purpose of removing water that may from any cause enter any of the separate compartments. It is not expected that any such pumping or, as it is usually called, drainage system will successfully cope against the volume of water that would be admitted through a large opening in the bottom or side of an unsubdivided vessel. But if the leak be slight, or if the water entering the bilges be that which is used to keep the crankpins or other parts of the machinery from heating, or that due to leakage of boilers, leakage of shaft tubes, or to any other of the many minor causes which exist in every ship, then the drainage system should be able to keep the vessel reasonably clear. In case of serious damage it is the function of water-tight subdivision to localize the effect of such damage and to set a limit to the volume of water that can enter the vessel. As soon as temporary or permanent repairs to the hull have been made, sufficient to prevent the further influx of water, that which has entered is to be pumped out.
Again, in some vessels, such as the Monterey, special arrangements are made for filling the double-bottom compartments with sufficient water to decrease the freeboard in action; and this large volume of water must be pumped out, if need be, with certainty and rapidity. A proper drainage system must then be able to clear any one of the many compartments into which modern ships are divided, and its manipulation and operation should not be interfered with by the fact of there being considerable water in the vessel. While the drainage system thus plays a necessary and important part in all naval vessels, it becomes specially important in vessels of the Monitor type. In such ships the small freeboard restricts the reserve of buoyancy to such an extent as to make it essential that all means provided for clearing the ship of water shall be of the most efficient character. In time of actual emergency the simplicity of such a system plays an important part in regulating its efficiency. A system which might work admirably on ordinary occasions might readily fail by reason of its complexity when the men detailed to operate it were excited by the danger due to the actual occurrence of some serious accident. It must also be borne in mind that in designing any such system, the weights of piping, valves, etc., must be kept within reasonable limits. The general arrangement of water-tight compartments and drainage of same adopted for U.S.S. Monterey, while not free from objections, yet seems to combine the elements of lightness, simplicity and efficiency to such an extent that a brief description of the same may prove interesting to officers of our service.
The Monterey, now nearing completion at the Union Iron Works, San Francisco, is a vessel of the Monitor type. She is 256 feet long, 59 feet beam, 17 feet in depth from bottom of keel to top of main deck at side. Her normal draft is estimated to be 14 feet 6 inches, so that her reserve of buoyancy is that due to a possible increase of draft of 2 feet 6 inches. She has 83 transverse frames, her inner bottom extending longitudinally from frame No. 5 to frame No. 77, and transversely to the armor shelf or upper longitudinal on both sides. The transverse frames within the limits of the double bottom consist of main angles riveted to the outside plating, reverse angles riveted to the inner bottom plating, and vertical floor plates connecting and riveted to main and reverse angles.
There are six longitudinals on each side of the vertical keel, consisting, like the latter, of a continuous series of plates connected to inner and outer bottom platings by means of long angles. The transverse frames and the longitudinals are firmly united at their intersections by means of angle clips.
Every third or fourth transverse frame and every alternate longitudinal are made solid and water-tight in their connection with each other as well as with the inner and outer bottom platings; the plates of the remaining frames and longitudinals are provided with large lightening holes.
The space between the inner and outer bottoms is thus subdivided into 107 separate water-tight compartments, the actual water-tightness of which has been determined by filling each compartment separately with water under the maximum head that it could have while the ship was still afloat.
Above the double bottom we find a central longitudinal bulkhead, also two longitudinal coal-bunkers and two wing-passage bulkheads. There are also, quite a number of transverse bulkheads, and by the intersection of these bulkheads this space is divided into 78 separate water-tight compartments. The fore and after peaks are similarly divided into eight compartments.
Access to the compartments in the double bottom is provided for by means of 99 manholes in the inner bottom plating, and 70 manholes in the water-tight longitudinals, all such manholes being fitted with hinged water-tight covers.
Communication between the other compartments above the double bottom and in the peaks is effected by 11 manholes and 73 water-tight doors, some of the latter being sliding and arranged to be operated from the berth deck, while others are hinged and can only be operated at the door itself.
We have thus a total of 193 separate water-tight compartments, each of which is to be so arranged and connected that it may be pumped clear of water.
The drainage system of this vessel is divided into two main parts: (1) The main drainage system which deals with all the water that is to be pumped from compartments above the inner bottom; (2) The secondary drainage system for pumping out the compartments between the inner and outer bottoms. The principal pipes of both systems extend practically the whole length of the ship, being located within the double bottom and close to the vertical keel, the 11-inch main drain-pipe on starboard side and the 4-inch secondary drain-pipe on port side. At intervals along the main drain-pipe are located five large non-return and stop-valves, each valve being secured by its flanges to the two sections of main pipe between which it lies. Each valve is also secured to the inner bottom plating, a large hole being cut in the latter to correspond to an opening in the top of the valve. These openings are provided with strainers, and it is through them that any free water above the inner bottom finds its way into the main drain-pipe. Certain of the various bulkheads above the double bottom are provided at their lower ends with sluice-gates which are operated from the berth deck, and by means of which any water accumulating beyond them may be sent to the nearest strainer leading to one of the non-return valves.
Along the engine and boiler rooms a short section of 11-inch main drainpipe also runs along port side of vertical keel, being provided with two non-return valves, so that no arrangement need be made for allowing water to pass through the center longitudinal bulkhead. All the main drain-piping empties into two large wells, one in each engine room, built between the inner and outer bottoms, pipes leading from these wells direct to main steam-pumps and also to the circulating pumps belonging to the main engines.
Between each two consecutive water-tight transverse frames in or near central part of vessel there are six separate water-tight compartments within the double bottom, three on each side of keel, this number being slightly reduced at the very ends of the double bottom. Alongside the vertical keel and at the lowest point of every such section of six compartments is located a strainer box, which is connected by a branch pipe to the secondary drain-pipe running close by. In this branch pipe is a common stop-valve, arranged to be operated from the berth deck, so that each strainer can be pumped from independently. A sluice-gate, also operated from berth deck, is fitted to the vertical keel and to each water-tight longitudinal within each section, so that water from any of the six compartments in the section may drain down to the strainer box. Thus the water from all the compartments of each section is handled by one branch pipe. The secondary drain-pipe is connected directly with two steam-pumps and four hand deck-pumps; but means are also provided for connecting the secondary and main drain-pipes at three points, so that the secondary drainage water may enter the main drain-wells and be pumped out thence by the four steam-pumps connected therewith, and conversely the four hand-pumps can thus be used to assist in pumping from the main drain-pipe. The drainage from the crank pits ordinarily empties by a small special drain-pipe directly into the main wells; but when much oil is being used the crank-pit drainage may be pumped out separately by two small steam-pumps arranged for that purpose.
Sounding tubes are fitted to every compartment, so that the amount of water therein may be at any time ascertained from berth deck. It is to be noticed that the moving of all valves, sluice-gates, etc., and all other operations connected with the drainage are performed at the level of the berth deck, so that the presence of water in or above the double bottom does not interfere with the efficiency of the pumping system. The upper ends of all the rods coming to berth deck are provided with deck sockets, which automatically indicate at all times whether the valves, gates, etc., are open or closed. All pipes make water-tight joints with the water-tight plating through which they pass, and are provided with expansion joints between each two of such watertight joints.
In the Monterey it was essential to keep the weight of piping, etc., down to the smallest practicable amount, and in view of this fact the system actually adopted and just described seems to combine the various factors of efficiency to a very considerable degree.
The Kuro-Siwo or Current of Japan
By J.J. Mahlmann, Harbor Master of Kobe, Japan
(Translated from Annalen der Hydrographie und Maritimen Meteorologie, by H. G. Dresel, Ensign, U.S. Navy.)
It is generally known that the Kuro-Siwo (black current) has its origin in the equatorial current of the Pacific Ocean. The latter, in reaching the Philippine Islands and islands immediately to the southward of these, breaks up into two branches, of which one turns towards the south along the Australian coast and towards the east. The other branch, called Kuro-Siwo farther to the north, sets towards the northward, passing along the east coasts of the Philippine and Loo Choo Islands, after which it takes a northeast direction, passing along the south and southeast coasts of Japan, continuing its course to the west coast of America. Having its origin in the equatorial stream, the temperature of the Kuro-Siwo is considerably higher than that of the ocean through which it flows. Its limits can therefore be ascertained by temperature measurements. The boundaries, breadth and rate of the current, however, are not constant, being greatly influenced by the monsoons of the China Sea. The storms in the Pacific also exert a considerable influence on the Kuro-Siwo, frequently causing very marked changes in its direction. During fair weather the Kuro-Siwo runs in a nearly straight line from Van Uiemens Straits to Rock Island, touching Osima on the way. During the winter months the current is seldom met with on this line, nor even at some distance to the southward of it, but in the summer during fair weather it can be surely depended upon, with the line from Osima to Rock Island as its northern limit. It is easily distinguished by the presence of seaweed, drift-wood, tide-rips, as well as by the dark color of the current (from which the name Kuro-Siwo) which contrasts vividly with the color of the surrounding sea. From Rock Island the Kuro-Siwo takes a more northerly direction, passes by Nosima Saki, and turns into the northern part of the Pacific Ocean.
For the most part no currents are met with in the waters adjacent to the northern limits of the Kuro-Siwo, but a counter current has been at times observed, as was the case in February, 1879, at which time the sailing ship Sumanura-maru, Captain Spiegelthal, which had lost her masts when distant about 10 sea miles from Osima, drifted 25 sea miles to the west in four days during a dead calm.
The width of the zone lying between the Kuro-Siwo and the coast of Japan varies with the direction and force of the wind. With heavy northern blows it increases; with southerly and easterly blows it decreases. Should the latter winds be of considerable force and long duration, the Kuro-Siwo departs from its regular ENE direction and sets more or less directly towards the coast, where it causes unusually high flood-tides. As under these circumstances the current sets on shore with an appreciably high rate, it has been observed that steamers have been carried 16 sea miles towards the shore in as many hours, so as to make Osima on the port hand instead of on the starboard.
As the south and east winds are generally accompanied by thick weather, the greatest possible vigilance is necessary on passages between Osima and Rock Island. Neglect of this may easily lead to the loss of the vessel, as is shown by the loss of the French mail steamer Nile with nearly every soul on board, on the coast of Idsu. In fair weather vessels have seldom been set on shore by the current.
The zone along the coast in which the local tidal currents occur does not have the same width at all places or at all times. It extends seaward for 5 or 6 miles, and at the capes and promontories its width is only half a mile. As a rule, the velocity of these tidal currents varies inversely as the breadth of the zone; the smaller the width the greater is the rate of the current. At times the flood-tide has not occurred at Osima, probably because the Kuro-Siwo in striking this cape sets directly across the path of the flood, or because at this time the flood sets through the channel between Osima and the main island.
The flood-tide runs along the coast in a westerly direction and enters the deep bays along their west shores, while the ebb sets out along their east shores.
While running along the coast between Osima and Rock Island, one should try as often as possible to discover whether the vessel is being set on shore, especially with northerly and easterly winds and falling barometer. On the passage from Yokohama to Kobe, in case the weather permits it to be done, the course after passing Rock Island should be laid near enough to the coast so as to skirt the boundaries of the zone of tidal currents. The danger of being set on shore is thus avoided, and the advantage obtained of being able to fix the vessel's position before the weather becomes thick. The distance of the course along the coast line varies but slightly from the distance corresponding to the direct course. The former course approaches the great circle arc between Rock Island and Osima.
In case the inshore course cannot be made, one should steer from Rock Island so as to make Matoya Light. Bearings of the latter will show whether the vessel is being set ashore. If the weather becomes thick, after sighting Matoya, there is no longer any danger of being set on shore, as the distance from Matoya to Osima is short. As soon as Matoya Light is made, which is visible at a distance of 16 miles, the course must be laid so as to clear Osima.