THE EQUIPMENT OF DOCKS Railways and Roads.—In order to deal expeditiously with the cargoes and goods brought into and despatched from docks, numerous sidings communicating with the railways of the district are arranged along the quays. In ports where a large railway traffic is dealt with it is necessary to provide, within or near the dock area, marshalling yards and standage sidings if congestion of traffic on the quays is to be avoided.
The "lay-out" of the railways in a dock area calls for much skill and ingenuity, both in planning and in the arrangement of gradients, to secure economical and rapid working. Moreover, in busy ports of modern construction it is usual to provide at least three lines of rails on those quays where goods are worked direct from ship to railway truck, or vice versa, and not through transit sheds. This arrangement allows two roads to be used for standing wagons while one is a running road. The growth of motor road transport has made it necessary to afford liberal accommodation for heavy lorries both on quays and at the side of transit sheds and warehouses, and the provision of adequate road access has become a matter of primary importance. The tendency in all modern dock construction is, in fact, to provide much wider quay spaces than was formerly the practice. Even in the port of New York where the old long, narrow pier is the characteristic feature of the quay accommodation, wide piers are now being built.
Warehouses, etc.—The arrangement and nature of store and transit sheds, warehouses, etc., varies at every port, depending largely on the local trade and traffic conditions. At Liverpool three-storey sheds with roof cranes have been built at the new Gladstone docks (fig. 28). At the Manchester docks there are large quay-side warehouses of five floors and in some North American ports transit sheds with as many as 8 and 9 floors. Where double sided piers and quays are constructed, widths of from 3oo to over 5ooft. are usual in order to provide ample space for sheds and warehouses which frequently have rail and road tracks on both sides. A typical example of such construction in northern Pacific ports is the Ballantyne pier at Vancouver (fig. 18). The piers. at New York and in some of the other Atlantic ports of the United States are, however, usually built without open Quay spaces on the water fronts. Often the transit sheds cover practically the whole surface, and roadways and rail tracks, when provided, are constructed inside the building. Piers with open quay-side spaces and rail tracks are, however, becoming more common in the Atlantic ports.
Oil Export and Import.—The transport of oil in bulk (see PETROLEUM) is a product of the 2oth century. At all ports where tank steamers discharge, the oil berths are isolated and the arrangements for storage on shore must be such as to minimize the risk of fire and its spreading. The sea transport of petroleum in barrels is on a very small scale compared with bulk cargoes. The latter are loaded by being pumped from large storage tanks to the ship through mains.
Ports such as Los Angeles in California, Corpus Christi in Texas and Abadan in the Persian Gulf have been created since the beginning of the century for the shipment of bulk oil cargoes. Los Angeles has been made, as a port, since the opening of the Panama canal and the bulk of its seaborne trade of over 23 million tons annually is the export of oil. According to official statistics it is now the second port of the United States in point of tonnage.
Continuous quayage being unnecessary, the berths at which tankers load and discharge are usually alongside isolated jetties or dolphins connected with the shore by light piled structures on which the pipe mains are carried. Provision for the bunkering of ships using oil fuel is made at many ports, special oil jetties being set apart for this purpose.
In ports such as London, situated at a considerable distance from the mouth of a tidal river, oil berths are usually isolated in the lower reaches seaward of the dock areas. In some ports, however, this is not possible and at Stanlow, near Ellesmere, on the Manchester ship canal, a special petroleum dock, provided with a floating isolating gate or boom across the entrance, has been constructed with the object of preventing the flow of oil beyond the limits of the dock. Similar provision is made in other ports.
Coal Shipping Ports.—At docks whose principal export trade is coal, the arrangement of quays and berths is planned with special reference to the running of coal wagons to and from the shipping points. (For bunkering of ships see BUNKERING OF SHIPS.) In the ports of north-east England high level coal "staiths" are much used, mainly on account of the high elevation of the ground in the neighbourhood of the shipping berths, as, for in stance, on the river Tyne. At many high-level staiths such as those at Dunston on the Tyne and at Blyth, which are built parallel to the river bank, trains of wagons are brought on to the staith and discharged successively by means of shoots into vessels lying alongside. In situations where the elevation of the sur rounding ground is insufficient to provide for gravity discharge from staiths to the hatchways of large modern vessels, hydraulic hoists (electric hoists are sometimes used in American and con tinental ports, but in Great Britain hydraulic hoists are almost exclusively employed) are often provided, as in the docks of South Wales and Scotland as well as at north-east coast ports. Wagons are brought to the shipping points at quay level, or over a graded gantry structure raised sufficiently high above the quay to avoid obstruction of the quay space.
The coal hoist is contained in a steel latticework tower erected on the dock side. The tower may be either fixed in position or capable of limited movement along the quay so as to suit the position of a ship's hatchway. The loaded wagon is raised on a cradle or platform to the required height for the discharge of the coal through adjustable steel shoots into the ship's hold. In some ports the practice is for wagons to discharge through bot tom doors ; in others the wagons are fitted with end doors and are tipped on a cradle in the hoist. The running of wagons to and from the staith or hoist is, wherever possible, assisted by suitable grading of the tracks. Empty wagons are sometimes run off from the hoist at a higher level than the loaded wagon roads and run by gravity to the empty sidings. Electric and hydrau lic capstans are also used for working the wagons at shipping places.
Electric conveyors are much used in the shipment of coal, in some cases raising it from quay-level, as at Hull and Manchester. They are also used at some coal staiths in order to increase the height of the point of delivery of the coal. In this way they are employed at Dunston and other Tyne shipping places. Some of the modern coal shipping appliances in British ports, as at New port, are capable of loading coal into a ship at the rate of 85o tons per hour and at elevations of over 7 5f t. above high water.
In a few English ports, including Liverpool and Cardiff, some coal is shipped by means of cranes lifting wagons or containers and emptying them over the ship's hatchway. At Goole (see CANALS and CANALIZED RIVERS) small compartment boats con taining coal are raised by hoists and discharged into the waiting ships.
The wharf or jetty on which the coaling staith or hoist is erected is frequently constructed over and in front of a stone pitched slope in order to avoid the necessity of building a con tinuous deep water wall. This plan has been adopted at Swansea, Barry Dock, Newport and at many of the Tyne staiths. At the King's dock, Swansea, and at the King George dock, Hull, some of the coaling jetties are arranged en echelon; thus, in effect, increas ing the length of available berthing space by permitting one vessel partially to overlap that of another in the adjoining berth.
Up to about 1910 the use in the United Kingdom of high capacity coal wagons carrying 20 tons was uncommon, the usual maximum load being 1 o tons. The large wagon is, however, slowly replacing the older, uneconomical, small wagon at coal shipping ports. Practically all coal hoists and other shipping appliances constructed in Great Britain since the war have been designed for the 2o-ton wagon. Anti-breakage appliances, designed to mini mize the breakage of coal in falling from the shoot into the ship's hold, are often used at ports where grades of coal, the value of which is seriously deteriorated by breakage, are shipped. Their use reduces the speed of loading.
In America railway freight cars are of much larger capacity than in Europe and coal cars carrying up to 120 tons are in use. The shipment of coal is effected both by hoists and conveyor belts as in the United Kingdom, but the tipping arrangements provided for the cars are on a much larger scale ; and it is cus tomary to discharge them by means of revolving "tipplers" or "dumpers" into large hoppers whence the coal is delivered to the ship, either direct or over conveyor belts, through shoots as re quired. The large hoppers serve as reservoirs to equalize the rate of supply. In some cases the coal is dumped from railroad cars on the low level into very large pier cars which are raised by hoists and are tipped over hoppers at a high level. A coal shipping installation on the belt system, put into service at Baltimore in 1918 by the Baltimore and Ohio Railway, employs self-trimming loaders which shoot the coal at high velocity in any desired direction between decks. Somewhat similar mechanical trimmers are in daily use at the several other coal ports of the American continent.
By these means, in conjunction with highly developed ar rangements for dumping cars and belt feeding, the rate of ship ment of coal has been largely augmented. The Baltimore pier is double-sided, 7ooft. long and has four main coal loading towers. Over 40,000 tons have been loaded at it in one day. The use of the American type of large coal cars and mechanical trimming enables ships to be loaded with coal at some of the best equipped U. S. A. ports more rapidly than in British ports where the time rate for a complete cargo does not often exceed 600 tons per hour and is usually less on account of delays in trimming the coal between decks. The best American shipping plants have, in this respect, an advantage of at least 50% over the Tyne and South Wales ports.
Power for Dock Machinery, etc.—Though different sources of power are sometimes made use of at different parts of the same port, it is generally most convenient to work the various installations by one form of power from a central station. This applies in particular to installations of dock-side cranes. The adaptability and flexibility of electric power has led to its general adoption, and its use for cranes and other mechanical appliances at docks has become almost universal. Even at numerous other important ports where hydraulic power is available at the docks, electric appliances are now being installed side by side with hydraulic equipment.
Hydraulic power for dock appliances is more commonly used in Great Britain than in American ports and on the continent of Europe. It possesses undoubted advantages for operating gate opening machinery, large sluices, coal hoists, capstans, swing bridges and some other forms of dock equipment.
Appliances for Loading and Unloading Ships.—In addi tion to the provision of high speed electric cranes or cargo hoists on quays and wharves in most European and North American ports, the equipment of warehouses and transit sheds with elec tric "run about" and overhead cranes, runways, loaders, conveyors and hoists is becoming general. (See Proceedings XIIIth Inter national Navigation Congress, London, 1923.) In the Far East, however, even at ports handling a large volume of trade, cargo is still generally discharged by means of ships' derricks and dealt with on shore by manual labour. Again, in some ports, notably those of London, Rotterdam and Amsterdam, a large proportion of the cargoes is loaded or discharged overside from or into light ers and barges, and at Rotterdam sea-going ships lying at moor ings in the river or basins frequently take in or discharge the whole of their cargo from or to large Rhine barges without going alongside a quay.
The rapid loading and discharge of ships, thus enabling a quick "turn round" of the ship to be made, is of the utmost im portance both to the ship owner and the dock authority. The capital sum represented by a modern cargo ship and a dock berth is very large, and if the average time of loading or discharge of a ship can be reduced from, say 4 to 2 days, by the installation of appropriate mechanical appliances, the revenue earning capacity of the berth is increased theoretically by 100%, and that of the ship in proportion to the reduction effected in the time required for the voyage.
At quays working general cargo in busy ports a liberal but not extravagant provision of cranes is one for every 10o or 120 feet of quay. The traffic capacity of docks varies within very wide limits and depends largely on the nature of the principal exports and imports and on seasonal variations of traffic. In a well equipped port through which a large volume of mixed traffic passes, it is not too much to aim at a traffic intensity of 30o tons of cargo per foot of quay per annum. During the last 18 months of the war the ports in northern France operated by the British army passed an import tonnage of well over I ton per day per foot of quay frontage.
Cranes.—Dockside cranes for general cargo purposes are frequently of the portal type, travelling on rails laid upon the quay with space between the legs (which carry the crane plat form) for railway wagons to pass under. In some docks where warehouses are near to the face of the dock wall, travelling cranes of semi-portal type are employed : one pair of the crane legs travels on rails laid near the quay edge and the other pair on elevated rails fixed to the wall of the building. As a result this leaves nearly the whole quay space free for the passage of trans port.
Cargo cranes must be raised high enough above the quay sur face to enable their jibs to command the hatchways of ships rising high above the water level. For general purposes cranes of II, 3 and 5 ton lifting capacity are most commonly used, but for special purposes much more powerful travelling cranes are pro vided. Floating and fixed cranes of great capacity are employed for dealing with exceptional loads. Some floating cranes lifting tons are in use and at least one fixed crane, that at the Philadelphia Navy yard, is capable of lifting 35o tons.
Some modern dockside warehouses have been equipped with electric cranes travelling on the flat roof of the building and ar ranged to work cargo to and from the several floors of the ware house through hatchways formed in them and in the roof as at the Gladstone docks, Liverpool.
In New York and some other ports of the United States, par ticularly on the Atlantic coast, quay-side cranes are in use to a limited extent only. The bulk of the working of general cargo is effected by a process called "Burtoning." This consists of the joint working of the load by means of a ship's derrick and a fixed cargo mast or hoist attached to the wall of the pier shed which is built out close to the water front.
Electric current for dock side cranes is taken either from con ductors in conduits laid below the quay surface or fixed to the walls of quay-side buildings, or by means of flexible cables from plug boxes at points on the quay. (See also CRANES.) A useful and modern survey of the subject of Cargo Handling at Ports is H. A. Reed's Vernon-Harcourt Lecture 1928, Inst. of Civil Engineers.