Crane Glossary: Definitions of Nautical Terms: Shipping and Tonnage Measurement

Discussion in 'The War at Sea' started by dbf, Jan 17, 2012.

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    TNA Catalogue Ref: WO 202/671
    Courtesy of Drew

    Gallery Album
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    I. Quay or Wharf Cranes
    II. Overhead Travelling and Gantry Cranes
    III. Cantilever Cranes
    IV. Floating Cranes
    V. Derricks
    VI. Sheer-Legs
    VII. Transporters & Telphers
    VIII. Specialised Hoisting and Stacking Machinery
    Cranes in the Port of London, 1931

    Figs. 1 - 5
    Figs. 6 - 10
    Figs. 11 - 15
    Figs. 16 - 18


    1. Displacement Tonnage
    2. Deadweight Tonnage
    3. Gross and Net Tonnage
    4. Gross Tonnage
    5. Net Tonnage
    6. Relations between Tonnage Figures
    7. Importance of Distinguishing Types of Measurement Employed
    8. Measurement Capacity

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    The variety of cranes is so great that it is not easy to classify them systematically.

    The terminology of cranes is not altogether free from ambiguity, partly owing to the variation of the local and national usage of technical term.
    (W.H. ATHERTON, Hoisting Machinery, pp. 1, 178.)

    The following glossary attempts to define the main types of crane and hoisting gear, especially those likely to be found in a port. When names are self-explanatoryy, e.g. locomotive breakdown crane, light mobile crane, no description is given.
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    According to their structure and uses cranes are capable of various motions. For convenience these motions may be described as follows:

    1. Hoisting: lifting the load.

    2. Slewing: rotation of the jib about a vertical axis; or revolving.

    3. Luffing: alteration of the angle of the jib, which carries the hoisting rope, and thus of the radius from within the load can be raised or lowered.

    4. Travelling: movement of the bridge of an overhead or gantry crane within the limits of the crane structure, or movement from time to time of a crane running on rails.

    5. Racking: movement of a hoisting trolley or hoisting crab transversely on the bridge of a travelling crane, or on the jib of a cantilever crane.
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    Usually of the jib type, i.e. an upright structure on which is mounted an arm extending at an angle. In most jib cranes the jib can be luffed, and nowadays most luffing cranes are "level-luffing cranes", i.e. they are fitting with a compensating gear to maintain the suspended load at a constant height while luffing is in progress, and thus reduce the power required. Without this the load would change in height. Level-luffing may be effected either by articulating the jib, as in Wylie gear (Fig. 2), or by a device for paying out cable, as in a Stothert and Pitt crane, to compensate for the raising and lowering of the jib (Fig. 3).

    In a luffing jib crane balance weights are employed: in a fixed jib crane the tendency to instability may be obviated either by a balance weight or merely by the rigidity of the structure.

    Quay or Wharf cranes may be conveniently described as follows:


    These may be further subdivided into:

    - (i) Simple; running on rails, usually at 10 - 15 feet gauge. (Fig. 1)

    - (ii) Portal; standing on an arched base wide enough to allow to the passage of railway trucks underneath. The gauge may allow for one railway track, as shown in the diagram, or for two or three tracks. (Fig. 2)

    - (iii) Semi-portal; Screen shot 2012-01-17 at 15.17.44.png shaped, mounted partly on a quayside rail and partly on a rail along a shed roof, so as to allow free passage of traffic along the quay. (Fig. 3)

    - (iv) Gantry-crane; a bridge structure (gantry) running on rails, with gauge allowing up to three tracks, and carrying a jib crane with transverse travel (Fig. 18)

    (c) ROOF CRANE.
    These vary considerably in structure.

    All these types can have either luffing or fixed jibs; the great majority are luffing.

    Most quay cranes have a lift of up to 3 tons, though many lift 3 - 10 tons (these may be portal, but probably more frequently are gantry-cranes, at which the capacity may reach 30 tons (Fig. 18)); in every big port certain larger quay cranes are installed, e.g. the 80-ton crane at DURBAN, various powerful coaling cranes, or the fixed crane at BIRKENHEAD, which has a capacity of 150 tons at 28 feet radius. (Fig. 4)
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    (i) Overhead Traveller (frequently called Electric Overhead Traveller). Widespread in use and employed in erecting-shops, warehouses, foundries, and power stations. Parallel rails are mounted near the top of each of two opposite walls, the rail and supporting structure being known as a gantry. A cross structure, the bridge, is carried by wheels running on each gantry rail, and a trolley carrying the hoisting gear runs on rails along the bridge at right angles to the gantry rails. Two movements are possible, therefore, the travelling of the bridge and the racking of the trolley, and a load can be raised from or lowered at any point within the space bounded by the walls. Capacity may reach 120 tons. Such cranes, when used in foundries, are sometimes called Foundry Cranes. (Fig. 5)

    For outside work, as in timber yards, an overhead traveller requires the erection of gantries specially to carry the overhead rails.

    (ii) A much less expensive crane for outdoor work is the Goliath or Bridge Crane consisting of a bridge standing on vertical legs which usually run on ground-rails. Usually operated by electricity. Capacity may reach 200 tons. (Fig. 6)

    In both of these types of crane a trolley is strictly a hoisting gear which is moved to and fro along the bridge (or racked) by a system of pulleys; a self-moving gear (i.e. fitted with an independent motor) is known as a crab. (This distinction applies also to the hoisting gear of cantilever cranes and transporters.)
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    In a cantilever crane the arm or jib extends horizontally from a base or tower structure and is counterbalance.

    (i) Block-setting or Titan Crane. The Titan is a specialised crane used solely for block-setting in harbour works. It is nearly always steam-driven. As the work proceeds rails are laid forward, along which the base structure of the crane (the truck), carried by wheels, is moved onwards. The cantilever jib carries a trolley and never a crab, which is too heavy. The trolley holds the hoisting pulleys. By means of the travel of the trolley and the slewing of the jib, a block may be set in any desired position. The truck is wide enough to act as a portal structure, through which the blocks can pass on railway wide enough to act as a portal structure, through which the blocks can pass on railway trucks. Capacity ranges from 20 to 100 tons (depending largely on the length of the jib), but the majority lift 30 - 40 tons (the enormous blocks of the breakwaters at MARSEILLES require to be handled by a floating crane). The Titan crane constructed by Stothert and Pitt for the harbour works at FISHGUARD and PETERHEAD handled 40-ton blocks at a maximum radius of 125 feet. (Fig. 7.) Its weights were:

    Screen shot 2012-01-18 at 11.48.47.png

    (ii) Giant Hammerhead. Similar to the Titan except that the cantilever is mounted on a tall tower which is fixed. There are a few giant-hammerhead cranes in existence; they are normally found in fitting-out berths, being capable of handling such heavy objects as gun turrets. Capacities range up to 250 tons at 105 feet radius. The jib often carries a small auxiliary jib crane working along the top. (Fig. 8)

    The Titan is better described as a Block-setting Titan, and the Giant as a Giant Hammerhead crane so as to avoid confusion (e.g. in French a titan electrique is a hammerhead).

    (iii) Cantilever Tower Crane. A similar machine, but of much lighter construction; it is used in shipyards, and consists of a cantilevered jib with trolley, mounted on a tall tower. In this country the tower is usually fixed, in continental yards it is more often movable. Capacity usually 5 tons at 100 feet or 10 tons at 30 feet. (Fig. 9.)
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    By mounting a crane on a pontoon a powerful crane can be made transportable. The crane itself is usually of the slewing and luffing jib type (Fig. 10). The largest made for port use is in JAPAN, with a capacity of 350 tons at 100 feet, although larger floating cranes are employed on the MARSEILLES breakwater extensions. An interesting floating crane, used by the U.S. NAVY, has a bridge girder of cantilever form with a capacity of 100 tons and an extreme travel of the trolley of 190 feet; the total weight is 1,200 tons. Modern large ones are usually self-propelled (steam or diesel-electric); older and smaller types are usually dumb.
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    A derrick consists of an upright which is stayed by cables or beams anchored to the ground. This mast carries a luffing jib and is slewing. In a guyed derrick the stays are cables; in a stiff-leg or Scotch derrick they are rigid beams. (Fig. 12). Many derricks are temporary structures for construction work. A ship's derrick is really a guyed derrick in type. Shipbuilding derricks are of the guyed type, but obstruction near the ground is avoided by making the jib short and fixing its pivot at a height on the mast. A tower derrick is a stiff-leg derrick standing on a tower.
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    When referred to as part of the lifting equipment of a port or shipyard sheer-legs usually consist of one long and two shorter rigid legs, standing tripod fashion, and hinged at the apex, which is fitted with pulleys. The two shorter legs are fixed to the ground but pivoted; the longer leg is fixed by movable within a traverse along a straight line which bisects at right angles the line joining the bases of the two shorter legs. By moving the longer leg inwards, therefore, the apex can be made to reach beyond the line joining the bases of the shorter legs. By moving the longer leg outwards the load can be brought within the triangle formed by the three legs. (Fig. 11)

    A sheer-legs can be used for handling heavy objects such as engines and boilers. The outreach may be as much as 35 feet, and the lift, as with the large sheers at ANTWERP, 120 tons (now removed). In some ports sheers are fitted to pontoons.

    The term "sheers" is also applied to a great variety of more or less temporary apparatus, either to rigid tripod (like the contractor's tackle) or to an apparatus permitting lift only outside the triangle. In the latter type the place of the longer leg is taken by a cable.
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    A variety of lifting and conveying machines are included in this category, and the terminology is extremely vague. All are designed to handle particular commodities.

    Broadly speaking, a transporter consists of a straight beam erected at a height above the ground, along which runs a trolley which lifts the load, carries it the required distance, and lowers it. There is only one trolley or crab. The load is usually light, up to 3 tons, but may exceed 6. Transporters may be called Bridge-Type Transporters when the beam is carried by an upright structure at each end. (Figs. 13, 16, 17.) A special class of the bridge type is the Temperley Transporter, in which the bridge need not be horizontal. In a Tower-Type Transporter the beam is carried by a central structure extending on both sides, being cantilevered out. (Fig. 14.) Transporters are often mounted on wheels.

    On a waterside site the end projecting over the water is often pivoted so that it can be raised while a ship is being berthed.

    A Telpher is similar, except that the track may take up any shape, and many carry more than one trolley or crab. (Fig. 15.)

    In both transporter and telpher a crab is usually employed, which is operated by a driver in a cab attached to it.

    In this group of appliances grabs and buckets are normally used, owing to the nature of the commodities dealt with - coal, ore, etc.
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    Coal hoists, stackers, etc, are employed for dealing with individual commodities, and are usually designed for particular conditions in a shed or store. It is convenient to use the designation "Elevator" to describe unloading plant such as Pneumatic Grain Elevators, Bucket (dredger type) Elevators, etc, and "Conveyor" for moving belts and similar appliances.

    MOTIVE POWER OF CRANES. Cranes may be steam, hydraulic, electric, motor, or manual - each form of power is employed in particular cases. For quay cranes hydraulic power is giving way to electric power, but seems likely to be used for some time. In fixed cranes, especially when the load does not vary much and is fairly large, hydraulic power is best. Electric cranes have obvious advantages, but in the smaller types the capital outlay is relatively high compared with hydraulic cranes. Electric motors are practically essential for self-moving crabs.
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    CRANES in the PORT of LONDON, 1931

    Screen shot 2012-01-17 at 15.52.25.png

    Kempe's Engineering Dictionary, 1942, 17, 39 (by J.H. HUNTLEY) (London, 1942).

    B. CUNNINGHAM: Cargo Handling at Ports (London, 1923).

    W.H. ATHERTON: Hoisting Machinery (London, 1940).

    H.H. BROUGHTON, Electric Cranes, being vol. 3 of The Electrical Handling of Materials (London, 1922).
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    Fig. 1. Quay crane with fixed jib, non-portal, travelling (left).

    Fig. 2. Quay crane, level-luffing, portar, travelling (right).

    Fig. 3. Quay crane, level-luffing, semi-portal, travelling.

    Fig. 4. Heavy quay crane, luffing, fixed; 150 tons at 28 feet radius, 50 tons at 88 feet; weight of counterweight 162 tons. At BIRKENHEAD.

    Fig. 5. Foundry crane (electric overhead traveller); 120 tons.

    Note: These illustrations are not drawn on a uniform scale

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    Fig. 6. 35-ton electric Goliath, for use in a railway yard.

    Fig. 7. 40-ton Titan or Block-setting crane.

    Fig. 8. 250-ton Giant Hammerhead crane for fitting out.

    Fig. 9. 10-ton fixed Tower crane for ship-building.

    Fig. 10. Floating crane, 150 tons at 98 feet, 30 tons at 125 feet.

    Note: These illustrations are not drawn on a uniform scale

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    Fig. 11. Side elevation of sheer-legs.

    Fig. 12. Scotch Derrick crane.

    Fig. 13. Travelling Bridge Transporter for coal; total reach 290 feet, capacity of skip, 25 cwt. (A skip is a bucket, which has to be filled by hand, as distinct from a grab.)

    Fig. 14. Non-slewing travelling-tower coal transporter, horizontal beam, with automatic 25-cwt. grab.

    Fig. 15. Telpher.

    Note: These illustrations are not drawn on a uniform scale.

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    Fig. 16. Travelling transporter with travelling jib crane, both slewing and luffing; capacity 6 1/2.

    Fig. 17. Travelling transporter with slewing travelling crane (fixed jib).

    Fig. 18. 12-ton gantry crane (slewing), with fixed jib.

    Note: These illustrations are not drawn on a uniform scale.

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    Note: Most (but not all) of the following definitions have been adopted in compiling Hydrographic publications. Most of the terms are used in varying senses by scientific workers; it is not claimed that the definitions given below are valid for all purposes, but merely that they show the sense in which the terms are used in I.S.T.D. publications.

    Awash: A rock or shoal is described as awash when its height is less than 1 foot above, or its depth less than 1 foot below, chart datum. (Note: In descriptive writing it is legitimate to refer to a rock or a shoal as being awash at certain states of the tide; e.g. "at low water this rock, which dries 10 feet, forms a useful leading mark, but at half-tide it is awash and forms a great danger in the approach from the eastward".)

    Bank: A detached shoal, the depths on which may or may not constitute a danger, or a similar shoal area connect with the shore. May be of sand, mud, or gravel. Generally used for a considerable detached area with depths less than those surrounding it, which may or may not be dangerous to shipping. (See "Shoal", "Spit", and "Sand".)

    Basin: An area of water artificially enclosed which may be tidal or not. If tidal is referred to as Tidal Basin, if not it sometimes called a Wet Dock (See "Wet Dock"). Geographically it may refer to an almost land-locked area of water leading off a fjord, inlet, etc.

    *Bay: An inlet of the sea formed by the curvature of the land between two capes or headlands.

    Beach: Sand, pebbles, shingle, smooth boulders, etc, above high water. Extends inland as far as cliffs, dunes, etc. Not used for jagged reefs, rocks, or coral. (See sketch)

    *Bight: Similar to bay, but larger. (Usually crescent-shaped and not more pronounced that a 90 degree sector of a circle.)

    Breakers: Rough sea (or swell) breaking on shoals and banks. (See "Overfalls" and "Surf".)

    Breakwater: A solid structure, protecting a harbour or anchorage, alongside which ships do no generally lie. (See "Mole".)

    Camber: A small basin, usually with a narrow entrance and usually inside a harbour, used for berthing small craft.

    Canal: A ship or boat channel, dredged or cut through the dry land or through drying shoals or banks. (See "Cut".)

    Cape: A promontory facing the open sea. May be high or low. (See "Head" and "Point".)

    Channel: A narrow passage of deeper water, natural or dredged, which may lead into a harbour or through a sound or strait.

    Coast: The meeting of sea and land, considered as the boundary of the land (See "Shore"); the narrow strip immediately landward of the high-water line, or (sometimes) a much broader zone extending for some distance inland. (See sketch.)

    Coastline: High-water line. (See sketch.)

    *Cove: A small indentation in a cliffy coast, frequently with a restricted entrance, and often circular or semicircular in shape. (See "Inlet".)

    *Creek: A comparatively narrow inlet of fresh or salt water which is tidal through its whole course.

    Cut: Similar to a canal, but shorter. (Usually "cuts" straighten out bends in winding channels.)

    Deep: A detached area considerably deeper than the surrounding waters.

    Dock: An area of water artificially enclosed in which the depth of water is regulated. Also used loosely of any water area artificially enclosed (i.e. as an equivalent of "Basin").

    Dolphin: A built-up mooring post, usually of wood, erected on shore or in the water. Used for ships to secure to clear of quays, etc., or for hauling-off from alongside a quay, wharf, etc.

    Dry dock: Usually excavated and faced with masonry or concrete, and such that water may be admitted and pumped out, leaving the ship dry, resting on blocks, and supported by shores. The entrance is closed by either a sliding caisson, a floating caisson, or gates. Also called a Graving dock.

    Dyke (dike): A causeway; or a loose-rubble mound built over shallow water in a similar way to a training wall, but not necessarily for the same purpose. Sometimes built across a shallow bank on one side of an estuary to prevent silting, or to give some protection from wave action which might cause the bank to shift. Also a ditch.

    Eddies: See "Rips".

    Flat: A flat shelf of any material, usually joined to the land.

    Floating dock: A watertight structure, capable of being submerged sufficiently to receive a ship by the admission of water into the pontoon tanks. The pontoon tanks are then pumped out, the dock and ship rising until the latter is clear of the water.

    Foreshore: The area between the high- and low- water lines. (See sketch.)

    Graving dock: See "Dry dock".

    Gridiron: Usually consists of baulks of timber, placed parallel to one another on the foreshore below high-water mark, and in such a position that a ship can be moved over them at high water and left dry and resting on them at low water.

    Groynes: Small wooden or stone erections, usually built at right angles to the shore along a beach to prevent coast erosion; also frequently erected in estuaries and small harbours to prevent silting.

    *Gulf: An arm of the sea extending into the land, intermediate in size between a bay and sea. (See "Bay".)

    Gut: A natural narrow inlet of deep water in a bank or shoal (sometimes forming a channel through it). It may also refer to the main part of a channel.

    Harbour: An anchorage protected by the formation of the land or by artificial works. (See "Port" and "Roadstead".)

    Hard: A strip of stone or concrete built on a beach to facilitate landing and/or hauling up of small craft.

    Head: A comparatively high promontory with either a cliffy or a steep face. (See "Cape" and "Point".) An unnamed head is usually described as a headland.

    Hill: See "Mountain".

    *Inlet: A small indentation in the coast, tapering towards its head. (See "Cove".)

    Jetty: Similar to a pier, but may be of stone. Usually at right angles to the coast or to the structure from which it extends. Ships can lie alongside it.

    Knoll: Usually roundish and detached. (See "Mountain".)

    Lock: An excavation in the entrance to a dock or basin, fitted with a caisson or gates at each end, through which ships can be transported from tidal waters without materially altering the level of the water in the dock or basin. Some locks can be used as dry docks. (See "Basin") and "Wet dock".

    Marine railway: The term generally employed in some countries for a patent slip. The cradle is usually built up from the rail level, with the height gradually increasing towards the outer end instead of being parallel to the rails. The line of blocks thus conforms more or less to the usual run of a ship's keel when afloat. "Crandall type" marine railways are designed on this principle.

    (i) A breakwater alongside the sheltered side of which ships can lie.
    (ii) A stone structure within an artificial harbour, at right angles to the coast or to the structure from which it extends, alongside which ships can lie.

    Mountain: "Mountain", "hill", and "knoll" are comparative terms of height (in descending order) varying with the general configuration of the country. (See "Peak".)

    Overfalls: The irregular wave effect caused by currents or tidal streams passing over an uneven bottom.

    Patent slip: A cradle, supported on carriages, and running on rails or racks laid on an inclined beach or shore. The cradle is run out to receive the ship, and she is then hauled up in it until clear of the water.

    Peak: A hill or mouton with a comparatively sharp summit.

    Pens: A series of parallel jetties for berthing several destroyers, submarines, or small craft.

    Pier: Usually of wood or iron, and built at right angles to the coast. The head, alongside which ships can lie, is frequently wider than the body of the pier. Occasionally built solely as a promenade.

    Point: A sharp promontory.

    Port: A commercial part of a harbour, where the quays, wharves, facilities for landing cargo, docks, repair shops, etc are situated.

    Quay: Any stretch of wall alongside which ships can lie.

    Reef: An are of rocks or coral (detached or not) of considerable extent, which may dry, or nearly dry, in places. May also be used for a low rocky or coral area some of which is above water. (See "Shoal".)

    Rips: Rips and eddies are broken water crossed by the deflection of currents or tidal streams into areas of relatively still water, or by the encounter of opposing currents or tidal streams.

    River: A flow of fresh water which, except where affected by tide in its lower reaches, is always in the same direction.

    Roadstead: An open anchorage, which may or may not be protected by shoals, reefs, etc. (See "Harbour" and "Port".)

    Sand: A shoal area of sand, usually connected with the shore. (See "Spit" and "Bank".)

    Shoal: A detached area of any material, the depths over which usually constitute a danger. (Shoal areas connected with the shore are usually called spits, sands, banks or reefs.) (Note: "Reef" is usually used for shoals composed entirely of rock or coral.)

    Shore: The meeting of sea and land, considered as the boundary of the sea (see "Coast"; e.g. "the west coast of India forms the eastern shore of the Arabian Sea"); the strip of land between low water and the landward margin of the beach. Both "coast" and "shore" are also used in a wider sense to denote the land bordering the sea as seen from a ship. (See sketch).

    Shoreline: A term used by geologists. High-tide shoreline = High-water line. Low-tide shoreline = Low-water line.

    Sound: A passage between two sea areas.

    Spit: Below-water: a narrow shoal area (of any material) connected with the shore.
    Above-water: a low narrow tongue (of similar material to a beach) connected with the shore.

    Strait: See "Sound".

    Surf: The sea breaking on the shore or on a spit, bank, or reef connected with the shore, or on a detached reef, etc. (See "Breakers" and "Overfalls".)

    Swell: The state of the sea produced by distant or subsided wind; as opposed to waves, which are produced by present and existing wind.

    Training wall: A rubble mound, frequently submerged, built alongside the channel of an estuary or river so that the tides or currents may set through the latter and assist in keeping it clear.

    Wet dock: An artificial harbour in which water is retained by caissons or gates and kept at a certain level, so that ships always remain afloat, irrespective of the level of the water outside the dock or basin. The entrance is usually through a lock. (See "Basin".)

    Wharf: A structure, usually of wood and on the same line as the coast, alongside which ships can lie.

    * When describing the horizontal dimensions of bays, bights, coves, creeks, and gulfs, the words "shallow" and "deep" should never be used; e.g. "a long shallow bight" and "a bay 3 miles long and 1 mile deep" are incorrect "a bay 3 miles wide and 1 miles long" may be used, but owing to considerable diversity of opinion on Y, 3 miles northward, the coast recedes about 1 mile to form Y Bay ... " When describing creeks and inlets, the distance they extend inland and the width at the entrance should be given.

    Sketch showing relation between shore, coast, etc.
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    EXPLANATION OF TERMS (22 April 1943)

    The figures of tonnage quoted for ships are of four kinds: displacement, deadweight, gross register tonnage, and net register tonnage.

    Displacement tonnage and deadweight tonnage are measured in units of WEIGHT - avoirdupois tons in the country.
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    Displacement tonnage is employed invariably for warships, having been in use since 1872. It represents the actual weight of water displaced by the ship at a given draught, i.e. the actual weight of the fabric and everything aboard. It is evaluated by computing the volume of sea water displaced, in cubic feet, and by dividing by 35 to obtain tons. For displacement in fresh water the volume is divided by 36. Displacement represents the greatest tonnage figure which can be quoted against a ship. It is rarely employed for merchant ships. Since the Washington Conference of 1921-22, the actual figure for warships has been given as standard displacement, i.e. total weight except for fuel and reserve feed water.

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