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Hull Survey Definitions, Terms & Terminology

Updated: Dec 25, 2021

Terminology for Marine Surveyors and other Maritime Professionals & Seafarers

Reference Material & Definitions incorporated, as applicable, in Marine Appraisals & Marine Survey Reports, prepared by Karatzas Marine Advisors & Co.

Abaft: A point beyond the midpoint of a ship’s length, towards the rear or stern.

ABS (American Bureau of Shipping): a vessel classification agency that also assigns international loadlines.

ABS Load Line Certification: An International load line certificated vessel that meets the requirements of the International Maritime Organization’s International Convention on Load Lines.

Abrasion: The removal of material by mechanical, i.e. rubbing or frictional, means.

Abrasion Test: A laboratory test to evaluate drilling-grade weighting material for potential abrasiveness. The test measures weight loss of a specially shaped, stainless-steel mixer blade after 20 minutes at 11,000 rpm running in a laboratory-prepared mud sample. Abrasiveness is quantified by the rate of weight loss, reported in units of mg/min. Mineral hardness, particle size and shape are the main parameters that affect abrasiveness of weighting materials. Some crystalline forms of hematite grind to a higher percentage of large particles than do other forms and are therefore more abrasive. Hematites are harder than barites, grind courser and are more abrasive. Thus, a hematite that is proposed as a weighting material for mud is typically a candidate for abrasion testing.

Access Holes: Holes cut in ship’s structure to permit entering or leaving various compartments.

Active Corrosion: Gradual chemical or electrochemical attack on a metal producing loose scale, by atmosphere, moisture or other agents.

Admeasure: To measure, calculate, and certify; for the purpose of registration, certain dimensions of a vessel as well as its gross and net tons.

Affreightment, Contract Of, (COA): An agreement by an ocean carrier to provide cargo space on a vessel at a specified time and for a specified price to accommodate an exporter or importer.

Aft: Movement toward the stern (back end) of a ship.

After Rake: The part of the stern which overhangs the keel.

AHP (Above Head of Passes): used with mileage designations on the Mississippi River, the Head of Passes being mile zero.

AIWW: Atlantic Intracoastal Waterway.

All Fast: he time during which the Vessel is completely moored, which includes gangway down and secured (for all Vessels other than Inland Barges), at the Cargo Transfer Point.

All Hands: The entire crew.

All In: The total price to move cargo from origin to destination, inclusive of all charges.

All Standing: To bring to a sudden stop.

Alleyway: A vessel’s internal passageway or corridor.

Allowable Corrosion or Wastage Limit: The acceptable thickness diminution of structural elements.

Aloft: Above the upper deck (above).

Alongside: A phrase referring to the side of a ship. Goods delivered “alongside” are to be placed on the dock or barge within reach of the transport ship’s tackle so that they can be loaded.

Alteration: Change that does not affect the basic character or structure of the ship to which it is applied.This is typically a limited change to the ship's structure, equipment or functions, such as change of components, change of local structure, change of draught or change of class notations not affecting ship's purpose/type.

AMVER: Automated Mutual-Assistance Vessel Rescue System

Anchor Watch: The detail on deck at night, when at anchor, to safeguard the vessel (not necessarily at the anchor; a general watch).

Anchor Handling Tug Support Vessels (AHTS): Specialist vessels designed for towing and/or anchor handling. Predominantly employed in the movement of rigs and platforms, and for the handling and laying of their anchors. Anchor Handling Tug Supply (AHTS) vessels combine the role of supply vessels and anchor handling tugs. They are the backbone of offshore operations and constitute the largest proportion of offshore vessels. Not only do they deliver supplies such as deck cargo, water, fuel, dry bulk and mud to oil rigs and platforms, they are specially designed to provide anchor handling services, towage duties and in some cases also serve as an Emergency Towing Rescue and Recovery Vessel (ETRRV). Some modern AHTS vessels are also equipped for fire fighting, rescue operations and oil recovery to enable them to have a more multi-role capability.

Anode: The positively charged metal surface and the corroding part of an electrochemical corrosion cell at which the oxidation or loss of electrons occurs. Sacrificial anode or impressed current anode. Also, Sacrificial Anode.

Antifouling: Paint for use on underwater areas on hulls. Antifouling contains agents who prevent the adhesion and growth of organisms on the hull.

API-MPMS: The American Petroleum Institute Manual of Petroleum Measurement Standards, as such may be amended and/or updated from time to time.

Arkansas River Lock and Dam 1 (Located in Tichnor, AR at mile 10 on the Arkansas River): This is a single chamber lock that is 600 ft. by 110 ft. in dimension (also called Norrell Lock).

Asdem Pumping Performance Formula: The formula maintained by Asdem and used to assess underperformance by a tanker’s pumps during discharge of cargo. The formula can be found on Asdem’s website at:

Astern: Behind a vessel; or, move in a reverse direction.

Atlantic: A grain export region that includes export elevators in Brunswick, GA, Albany, NY, and Chesapeake, VA.

ATDNSHINC: Any Time Day or Night Sundays & Holidays Included.

ATUTC: Actual Times Used to Count

Athwartship: Transverse or across a vessel from side to side or a direction across the width of a vessel.

Automated Identification System (AIS): An electronic instrument placed on regulated powered vessels to automatically provide their identity, location and other navigational data to a central receiving base to facilitate navigational control and safety.

Auxiliary Lock: The smaller chamber of a double lock that transfer vessels from one water level to another water level. The advantage of this two-lock facility is that both chambers can be working at the same time, and more importantly while one chamber is closed for repairs, the other chamber can handle the traffic. See Main Chamber Lock.

Avast: An order to stop or cease hauling (stop action at once).

Avoirdupois weight (n): the series of units of weight based on the pound of 16 ounces and the ounce of 16 drams

Awash: Level with the water (water ready to, or slightly covering decks).

AWWL: Always Within Institute Warranties Limits (insurance purpose).

Backhaul: To haul a shipment back over part of a route it has traveled.

Bacterial Corrosion or Microbially Influenced Corrosion (MIC) is corrosion which is induced or accelerated by the presence of micro organisms.

Ballast: Any substance, other than cargo, which is usually placed in the inner compartment of a vessel to produce a desired draft or trim.

Bareboat Charter (Demise Charter): A form of vessel rental in which the charterer assumes total responsibility for the vessel and its operations, as if the vessel was owned by the charterer.

Barge: A large, flat-bottomed, rigged or unrigged, craft of full body and heavy construction, specially adapted for the transportation of bulk freight such as grain, ethanol, fertilizer, coal, lumber, oil etc. from a port to shallow-draft waterways. Barges have no locomotion and are pushed by towboats. A single, standard barge can hold 1,500 tons of cargo or as much as either 15 (jumbo hopper) railroad car or 58 large grain hopper semi-trailers or 60 truckloads. A barge load of grain, as a unit of measure is 52,500 bushel . A jumbo covered hopper barge is the type of barge most frequently used for moving grain on the rivers. A barge is 200 feet long, 35 feet wide and has a draft of 9 feet. Barges carry dry bulk (grain, coal, lumber, gravel, etc.) and liquid bulk (petroleum, vegetable oils, molasses, etc.).

Barge, Inland: A USCG- or American Bureau of Shipping-inspected and approved tank barge that is restricted to operations in the inland waterways of the US.

Barge, Jumbo Covered Hopper: Type of barge most frequently used for moving grain on the rivers. Older barges held 52,500 bushels, but some newer barges have larger capacities.

Ocean Barge or Ocean-Going Barge: A USCG- or American Bureau of Shipping-inspected and approved tank barge that has an ABS Load Line Certification and is certified to operate in offshore waters.

Barges Unloaded: The number of barges of grain unloaded in the area between Baton Rouge New Orleans, LA.

Barrel (and BBL): 42 US Gallons measured at 60 degrees Fahrenheit (60°F).

Base Rate / Freight Rate: A tariff term referring to ocean rate less accessorial charges, or simply the base tariff rate.

Beam: The breadth of a vessel.

BENDS: Both Ends (Load & Discharge Ports)

BEP: Best Environmental Practice.

Bentonite: A material composed of clay minerals, predominantly montmorillonite with minor amounts of other smectite group minerals, commonly used in drilling mud. Bentonite swells considerably when exposed to water, making it ideal for protecting formations from invasion by drilling fluids. Montmorillonite forms when basic rocks such as volcanic ash in marine basins are altered.

BIMCO: Baltic & International Maritime Council

Blasting or Shot-Blasting: The cleaning of a metal surface by a stream of abrasive particles.

Blister: A raised area, often dome shaped, resulting from loss of adhesion between a coating or deposit and the substrate.

BNWAS: Bridge Navigational Watch Alarm System

Bollard Pull: The static pulling force of a tugboat measured in pounds/tons.

Bone in her teeth: A colloquial phrase implying that a boat is moving through the water at considerable speed. The "bone" is the bow wave thus produced.

Bosom: The inside of an angle bar.

Bound (Fogbound): Immobilized by heavy fog.

Bound (Windbound): When a tow stops due to high wind and the boat does not have enough power to keep the tow moving.

BPG: Bridge Procedures Guide

BPQ: Barge Particulars Questionnaire

Breakbulk Cargo: Non-containerized general cargo stored in boxes, bales, pallets or other units to be loaded onto or discharged from ships or other forms of transportation. (See also: bulk and container.) Examples include iron, steel, machinery, liner-board and wood pulp.

Breaming: Cleaning the barnacles, paint, etc., from a ship’s bottom with a blow torch.

Bridge Transit Decision Points: Decision points in passage plans describe places or times when vessels must take action to avoid hazardous conditions. Such decision points should allow enough time and distance to safely execute a contingency plan. Passages that include lift and swing bridges must anticipate and account for delayed openings, especially in high-current scenarios.

Bridle: A V-shaped chain, wire, or rope attached to a vessel being towed to which the towline is connected. A short length of wire with a line attached at the midpoint. A bridle is used to distribute the load of the attached line. Often used as boom travelers and for spinnaker down hauls.

Bright Work: Varnished woodwork or polished metal.

Brittle Fracture is the separation of a solid accompanied by little or no macroscopic plastic deformation. Typically, brittle fracture occurs by rapid crack propagation with less expenditure of energy than for ductile fracture. Brittle tensile fractures have a bright, granular appearance and exhibit little or no necking.

Buckling: a bulge bend or other wavy condition of the structure caused by in plane compressive stresses and /or shear stresses.

Bulk Cargo: Loose cargo (dry or liquid) that is loaded (shoveled, scooped, forked, mechanically conveyed or pumped) in volume directly into a ship’s hold; e.g., grain, coal and oil.

Bulwark: The side of a vessel that extends above the upper deck.

Buoy: A stationary floating object used as an aid for navigation.

Buoyancy: Ability to float, lifting power when immersed.

Burr Edge: The rough uneven edge of a punched or burnt hole or plate.

Bushel: A unit of measure containing 2,150.42 cubic inches, 56 pounds of corn, or 60 pounds of wheat or soybeans.

Butt Joint: A joint between two structural members lying in the same plane. Typically a butt joint is used to describe the welded connection between two plates in the transverse direction.

Butt Strap: A bar or plate used to fasten two or more objects together with their edges butted.

Butterworth: A washing process used to gas free or clean a cargo tank, by means of hot water or chemicals, sprayed through a patented rotating nozzle.

Butterworth Opening: A deck access opening with bolted cover, designed for butterworth operations.

By the Head: Deeper forward (front end deepest in water).

By the Lee: Sailing downwind with the wind blowing over the leeward side of the boat, increasing the possibility of an unexpected jibe.

Cable Laying Vessel: A Cable Laying Vessel (cable layer or cable ship) is a sea going vessel specially designed to lay underwater cables (telecommunications, electric power transmission, or other). Р’ The newest design of cable layers is a combination of cable-laying and repair ships, so they are also able to retrieve broken or damaged sub-sea cables and repair them on board. Depending on water depth and the risk of potential damage, sub-sea cables are buried in the sea floor by the cable layer using a special plough. A DP 2 system enables the vessel to remain in a precise position above the defined cable route.

Cabotage: Shipment of cargo between a nation’s ports is also called coastwise trade. The U.S. and some other countries require such trade to be carried on domestic ships only.

Camber: The upward slope of a vessel’s deck, occurring when the centerline is higher than the gunwale.

Cant: The inclination of an object from the perpendicular. As a verb, to turn anything so that it does not stand square to a given object.

Cant Beam: Any of the beams supporting the deck plating or planking in the overhanging part of the stern of a vessel. They radiate in fan shape from the transom beam to cant frames.

Cant Body: The portion of a vessel’s body either forward or aft in which the planes of the frames are not at right angles to the center line of the ship.

Cant Frame: Hull side frame not aligned perpendicular to the vessel’s centerline.

Cant Frames: The frame (generally bulb angles) at the end of a ship which are cented, that is, which rise obliquely from the keel.

Car, Jumbo Hopper: A rail car with a 3,500-bushel capacity, and a 100 ton grain capacity.

Cargo Quantity: The volume or quantity of the Cargo that is either loaded or discharged at the Cargo Transfer Point and that is specified in the charterparty and/or B/L. Cargo Transfer Point: The location specified in the charterparty where custody of the Cargo is transferred from Seller to either Buyer or Buyer’s designee.

Cathode: The negatively charged metal surface and the non-corroding or protected part of an electrochemical corrosion cell.

Cathodic Protection: The partial or complete protection of a metal from corrosion by making it a cathode, using either a galvanic or an impressed current to bring a metal to a potential where it is thermodynamically stable.

Cavitation: The formation of bubbles on an aerofoil section in areas of reduced pressure. Can occur on heavily loaded ship propellers.

Cavitation Damage: Degradation of metal surfaces, characterized by pitting, in which the pit profile is irregular, occurring when very turbulent fluids are in contact with the metal surface, and associated with the formation and collapse of cavities in the liquid at the solid – liquid interface.

Center of Buoyancy (CB): The point through which the buoyancy force acts. It is defined in space by its longitudinal, vertical and transverse (respectively, LCB, VCB and TCB) position relative to a set of orthogonal axes. It is also the centroid of volume of the displaced water. Center of Flotation (CF): The centroid of area of a waterplane. A small weight added, or removed, from the ship vertically in line with the CF will cause a change of draught without heel or trim. For a symmetrical ship the CF will be on the centerline and its position is given relative to amidships. Center of Gravity (CG): The point through which the force due to gravity, that is the weight of the body, acts. Its position is defined in a similar way to the center of buoyancy and is very important in calculations of stability. The point of equilibrium of the total weight of a containership, truck, train or a piece of cargo. Centerline: The longitudinal vertical plane of a vessel.

CERCLA (Comprehensive Environmental Response, Compensation and Liability Act): The U.S. federal statute that establishes the legal and financial responsibilities of those persons or companies that discharge or dispose of hazardous substances on or into land, air, and navigable waters of the U.S. Primarily administered by the U.S. Environmental Protection Agency.

Certification: The act of attesting that a vessel has met specific legal requirements by the issuance of various certificates or validation of documents by certain governmental or private agencies.

CFR: The US Code of Federal Regulations. U.S. Code Title 46 - Shipping and CFR: Title 33. Navigation and Navigable Waters.

Chain of Rocks Locks (Located in Granite City, IL at mile 186 on the Upper Mississippi River): This double lock includes a 1200 ft. by 110 ft. main lock chamber and 600 ft. by 110 ft. auxiliary lock (also called Mississippi River Locks 27).

Channel: That portion of a waterway that is naturally or artificially deepened to permit safe navigation within certain limits.

Charter Party: A contractual agreement between two entities for the purpose of renting, hiring, or leasing the exclusive use of a vessel.

Charterer: The person or entity hiring the performing Vessel.

Chock: A piece of wood or other material put next to cargo to prevent it from shifting.

CIF (Cost, Insurance, and Freight): Cost of transportation and insurance to be paid by the seller of goods to the named point of destination.

Classification: The certification process, as administered by certain international agencies, whereby a vessel is designed, constructed, and maintained, in accordance with an agency’s requirements.

CLC: Civil Liability Convention of 1969, as such has been amended from time to time.

Clip: A small steel bracket used for securing or reinforcing.

Clipper Bow: A bow with an extreme forward rake, once familiar on sailing vessels.

Close-up Survey: A survey where the details of structural members are within the close visual inspection range of the surveyor, i.e. normally within the reach of hand.

COACP: Contract of Affreightment Charter Party

Coating Evaluation Criteria: Normally an assessment of the extent of damage registered in terms of coating breakdown area and/or rust scales in % of area under consideration, normally the complete tank, with additional information on coating damage to edges and weld connection. Typical coating failures may be given as additional information.

Coating, often synonymous with Painting, i.e. a protective film of thickness usually about 0,2 - 0,5 mm, applied to prevent corrosion mainly via a three main mechanisms; the barrier effect, the cathodic effect or by inhibition / passivation.

COC: Certificate of Compliance.

Coefficients of Fineness: These relate to the underwater form and give a broad indication of the hull shape. They are the ratios of certain areas and volumes to their circumscribing rectangles or prisms.

Cofferdam: The space in a vessel between two closely located parallel bulkheads.

Collision Damage: Damage caused by physical impact between two or more ships used for navigation.

Collision Mat: A large mat used to close an aperture in a aperture in a vessel’s side resulting from a collision.

Comehome: A convex curvature of the rake sides of a barge that produces a narrower beam at the headlog than the beam of the hull.

Common Carrier: A federally licensed company that offers to the general public, under published tariffs, to engage in the interstate or foreign transportation of commodities of various types.

Companionway (Sailing Boat): The main entrance to the cabin, usually including the steps down into the cabin. A passageway through which a ladder or stairs lead from the deck down to the cabin.

Compartment: An interior space of a vessel’s hull formed by bulkheads.

Condition Assessment Program (CAP): A voluntary system, which gives a detailed assessment of a tanker’s actual condition at the time of inspection and is available to both charter-parties and owners. CAP is a voluntary program, initially developed by the oil industry, to assess the continued fitness of older ships to carry their cargo safely. CAP involves a detailed survey, including gauging of the vessel’s structure and a sophisticated strength and fatigue engineering analysis. It also includes extensive testing of the vessel’s machinery, equipment and cargo systems. A CAP rating is assigned to the vessel. A CAP 1 (Very Good) or CAP 2 (Good) rating is required by most charterers. Both of these ratings suggest that the vessel has been maintained to a standard in excess of Classification Society and Statutory minimums.

Condition Survey: A survey normally of limited scope and time and intended to identify any anticipated structural or corrosion related deficiencies and give an overall visual impression of the structural integrity.

Condition Rating Terms:

* ABOVE AVERAGE (GOOD): Condition unimpaired without significant wear of deviation from original strength and operating efficiency. No maintenance or repair required.

* AVERAGE (FAIR) : Condition with tear and fear and other deficiencies of minor nature not requiring correction or repair.

* BELOW AVERAGE (POOR): Condition in which the adequacy of strength and/or operational efficiency if marginally below acceptable limits or is in doubt. Remedial action is required.

* UNSATISFACTORY: Condition of undoubtedly inadequate strength or operational efficiency immediate extensive repair or renewal required to reinstate serviceability.

Confirmed Letter of Credit: A letter of credit, issued by a foreign bank, whose validity has been confirmed by a domestic bank. An exporter with a confirmed letter of credit is assured of payment even if the foreign buyer or the foreign bank defaults.

Contact Damage: Damage caused when the ship strikes something other than another ship. (see also ‘Grounding’).

Container: An intermodal uniform, sealed, reusable metal “box” (generally 40 feet in length, able to hold about 40,000 pounds) in which merchandise can be moved by either, rail, barge, truck or vessel. The use of containers (or containerization) in trade is generally thought to require less labor and reduce losses due to breakage, spoilage, and pilferage, compared to more traditional methods of shipment. Containers come in 53, 48, 45, 40 and 20 foot lengths, and are anywhere between 8, 8.5, 9 and 9.5 feet in height. Width is eight foot. Container Load: A load sufficient in size to fill a container either by cubic measurement or by weight. Containerizable Cargo: Cargo that will fit into a container and result in an economical shipment. Containerization: Stowage of cargo in a container for transport in the various modes. See Container.

Contour Line: A line on a chart connecting points of equal depth or elevation.

Contract Carrier: A federally licensed company that offers, under individual contracts, to engage in interstate or foreign transportation of commodities of various types.

Conversion: Change that substantially alters the main dimensions (L, B, D), watertight subdivision, carrying capacity, engine power or ship type. Increased draught is normally not regarded as a conversion. However, precaution should be taken if the increase in draught is major.

COFR (Certificate of Financial Responsibility): a document issued by U.S.C.G. to a company for a vessel or a fleet of vessels, giving evidence that the vessel owner/operator has met the financial requirements for oil spill clean-up costs as contained in the Oil Pollution Act of 1990.

COGSA (Carriage of Goods by Sea Act): U.S. federal codification passed in 1936 which standardizes carrier’s liability under carrier’s bill of lading. U.S. enactment of the Hague Rules.

Corn: Corn varieties include: U.S. No. 1-5 and Sample Grade, Yellow, White, and Mixed Corn as defined by USDA's Grain Inspection, Packers and Stockyards Administration. Corn #1: The highest grade of corn, distinguished by the highest minimum test weight, lowest moisture and foreign material, and the fewest damaged kernels. Marketed primarily as food. Corn #2: Most frequently traded of all grades (about 60 percent of all corn sold), and the grade on which the traded price is based. It is used primarily for animal feed. Grades 3, 4, 5, and Sample are lower grades than #2. Sample Grade is the lowest grade available.

Corrosion Fatigue: The process in which a metal fractures prematurely in a trans- crystalline manner under conditions of simultaneous corrosion and repeated cyclic loading of lower stress levels or fewer cycles than would be in the absence of a corrosive environment

Corrosion is the chemical or electrochemical reaction between a material, usually a metal and its environment that produces a deterioration of material and its properties, usually an oxide is formed.

Corrosion Prevention System is considered a full hard coating; alternatively a full hard coating supplemented by cathodic protection.

COTP: Captain of the Port.

Crack: A fracture type discontinuity without complete separation characterized by a sharp tip and high ratio of length and width to opening displacement.

Craft: A boat, ship or airplane.

Crevice Corrosion: Localized corrosion of a metal surface at, or immediately adjacent to, an area that is shielded from full exposure to the environment because of close proximity between the metal and surface of another material. It is usually associated with small volumes of stagnant water; within lapped joints, under heads of fastenings, under gaskets and packings, under marine organisms and porous deposits.

Critical Structural Areas: Locations which have been identified from calculations to require monitoring or from the service history of the subject ship or from similar ships to be sensitive to cracking, buckling or corrosion which would impair the structural integrity of the ship.

Crossing the Line: Crossing the Equator.

Cumulative Damage: An aggregation of damage due to various physical causes, specifically applied to fatigue under various stress ranges and frequencies.

Customary Anchorage: The recognized anchorage for or within the designated port for the Cargo Transfer Point (that may be specified in the charterparty).

Customs: A duty or tax on imported goods. The Customs Department also works to prevent the importation of illegal drugs and contraband.

Customs Broker: This person prepares the needed documentation for importing goods (just as a freight forwarder does for exports). The broker is licensed by the Treasury Department to clear goods through U.S. Customs. Performs duties related to documentation, cargo clearance, coordination of inland and ocean transportation, dockside inspection of cargo, etc. (Also known as a customhouse broker.)

D & A Policy: Any applicable Drug and Alcohol abuse policy.

Damage Survey: A survey requested as a result of hull damage or other defects.

Daymark: A marker used as an aid to navigation and which is visible in daylight.

DCV: Debris (or Drift) Collection Vessel

Dead Ahead: Directly ahead on the extension of the ship’s fore and aft line.

Deadhead: One leg of a move without a paying cargo load. Usually refers to repositioning an empty piece of equipment.

Deadman: An object, such as an anchor, piling, or concrete block, buried on shore.

Deadrise: The upward slope of a vessel’s bottom occurring when the centerline is deeper than the bilge knuckle; provided to facilitate removal of liquid cargo.

Deadweight: The number of tons of 2,240 pounds that a vessel can transport of cargo, stores and bunker fuel. It is the difference between the number of tons of water a vessel displaces “light” and the number of tons it displaces when submerged to the “load line”. The carrying capacity of a ship in metric tons, including the weight of fuel and stores as well as the cargo. The cargo capacity of a ship is generally estimated as 95 percent of deadweight capacity for large tankers and 85 percent of deadweight capacity for dry cargo container ships.

Deadweight Cargo: A long ton of cargo that can be stowed in less than 40 cubic feet.

Deadweight Tonnage: The cargo capacity of a vessel.

Deck Barge: Transports heavy or oversize cargoes mounted to its top deck instead of inside a hold. Machinery, appliances, project cargoes and even recreational vehicles move on deck barges.

Deck Button: A round, steel fitting affixed to a vessel’s deck, designed to secure or guide cables for making up barge tows.

Dedicated Tow: Movement of barge(s) between two points by the use of a boat exclusively assigned to that movement. A “dedicated” boat offers greater control of barge movements than a “tramp” tow, but generally at a higher cost.

Deepwater Construction Vessel (DCV): DCV vessel is capable of executing complex infrastructure and pipeline projects in ultra deep water, while offering sufficient lifting capacity to install platforms in relatively shallow water. These vessels are capable of operating in waters beyond 3,000 meters. They used for the installation of foundations, moorings, SPARs, TLPs, and integrated topsides, as well as pipelines and flowlines. As a rule, deepwater construction vessels are outfitted with DP2 or DP3 technology for operations in very harsh environments. DCV are equipped with powerful offshore cranes and ROV work class systems. On biggest DCVs the living quarters can accommodate up to 500 persons in single and double cabins or even up to 700 (like on DCV “Thialf”, Heerema).

Delivery Window: The period during which the Vessel nominated by or on behalf of Buyer or Seller under the Agreement is to present itself at the Cargo Transfer Point, as established by the charterparty and is within the contract delivery date range set forth in the Agreement.

Demurrage: A charge assessed for detaining a vessel beyond the free time stipulated for loading or unloading. A penalty fee assessed when cargo isn’t moved off a wharf before the free time allowance ends.

Detention: The period of time that an owner or charterer is deprived of the use of his vessel as a result of actions of another party (usually a party with statutory authority such as the Coast Guard.

Deformation: A change in the form of a structure due to stress, thermal change, change in moisture, or other causes.

Delamination: Peeling from undercoat or substrate.

Deposit Attack: An attack under, or around, the edge of a local deposit formed on a metal surface in the presence of an electrolyte.

Derelict: A vessel abandoned and drifting aimlessly at sea.

Derrick [Drilling]: The structure used to support the crown blocks and the drillstring of a drilling rig. Derricks are usually pyramidal in shape, and offer a good strength-to-weight ratio. If the derrick design does not allow it to be moved easily in one piece, special ironworkers must assemble them piece by piece, and in some cases disassemble them if they are to be moved.

Diameter - Outside Diameter (OD): Outside or outer diameter. Casing and tubing are commonly described in terms of inside diameter (ID) and outside diameter. Diameter - Inside Diameter (IS): Inside or inner diameter. Casing, tubing and drillpipe are commonly described in terms of inside diameter and outside diameter.

Differential: An amount added or deducted from base rate to make a rate to or from some other point or via another route.

Dinner Bucket Boat (also Lunch Bucket Boat): A boat that does not have a galley or only has limited crew quarters. These boats generally work daylight hours only.

Displacement: The weight, in tons of 2,240 pounds, of the vessel and its contents. Calculated by dividing the volume of water displaced in cubic feet by 35, the average density of sea water. Weight of the Ship = Volume of Water Displaced (Displacement) × Density of Water. The water that is displaced by the ship equals the volume of the ship that is submerged, and we can rewrite the equation as, Weight of the Ship = Submerged Volume of the Ship (Displacement) × Density of Water.

Ditty Bag: A bag used by sailors to hold gear needed for repairs on sails or rigging.

Diving Support Vessel (DSV): Diving Support Vessel (DSV) is designed for diving operations carried out below and around oil production platforms and related installations in open waters. These vessels are used for underwater repair, inspection, construction works, well intervention and etc. Most of the modern DSV vessels designed for efficient diving operations in harsh environments.

Dock: (verb) - To bring in a vessel to tie up at a wharf berth. (One parks a car, but docks a ship.) (noun) - A dock is a structure built along, or at an angle from, a navigable waterway so that vessels may lie alongside to receive or discharge cargo. Sometimes, the whole wharf is informally called a dock.

Dockage: A charge by a port authority for the length of water frontage used by a vessel tied up at a wharf.

Docking Plan: Detailed structural plan and profile of the lower hull structure required for correct location of the vessel in dry docking.

Docking Tug: A tugboat that assists a large seagoing vessel to and from its berth.

Documentation: The process of licensing a vessel in either enrollment or registry, resulting in the issuance of a vessel’s official document.

Dog Shores: The last supports to be knocked away at the launching of a ship.

Doldrums: The belt on each side of the Equator in which little or no wind ordinarily blows.

Dolphin (Mooring Dolphin): A cluster of piles driven into the bottom of a waterway and bound firmly together for the mooring of vessels.

DOS: A Declaration of Security as provided for under the ISPS Code.

Double-rake Barge: A barge that neither its bow or stern is square. Double-skin Barge: A barge with a void space between the cargo tanks and the hull.

Doubler: A steel plate installed on an existing structural plate and used as a strengthening base for deck fittings or as a repair of a damaged area. A wood or metal plate bolted beneath a mounting surface for reinforcement.

Downwind: Sailing in the same direction as the wind.

Draft: The depth of a vessel’s keel below the waterline; often expressed as light-draft; or, conversely, loaded draft.

Draft Marks: The numerical markings on the sides of a vessel at the bow and stern, which indicate, at the lower edge of the number, the amount of water the vessel draws.

Drayage: Transport by truck for short distances; e.g. from wharf to warehouse.

Dredge (Backhoe Dredge)

A backhoe is a type of grab crane dredging pontoon. It consists of a hydraulic grab crane mounted on a dredging pontoon. The dredging pontoon is usually held in place by three spud poles. Backhoes are used to dredge heavy clay, soft stone, blast rock and soil thought to contain boulders, for example in foreshore protection operations.

Dredge (Cutter Suction Dredge (CSD))

A cutter suction dredge (CSD) sucks dredged material through the intake pipe at one end and then pushes it out the discharge pipeline directly into the placement site. Since a CSD pumps directly to the placement site, it operates continuously and can be very cost-efficient. Most CSDs have a cutterhead on the suction end. A cutterhead is a mechanical device that has rotating blades or teeth to break up or loosen the bottom material so that it can be sucked through the dredge. Some cutterheads are rugged enough to break up rock for removal. A CSD is mounted (fastened) to a barge, not usually self-powered, towed to the dredging site, and then secured in place by special anchor piling, called spuds (see sidebar).

A CSD is able to work in a range of water depths and has the ability to dig its own flotation if the existing ground is very shallow or above water. It’s very efficient in areas with thick shoals, where the cutterhead is buried in the bottom. Water pumped with the dredged material is generally contained in the placement site until the solids settle out. Once settled, the water is generally returned to the waterway.

A CSD comprises the cutterhead, the spuds, the pipeline and the pontoons to float the pipeline. The connection of the spuds and cutterhead to the waterway floor, along with the floating pipeline, may sometimes limit a CSD’s ability to maneuver during inclement weather conditions.

CSD operators can adjust their approach to projects depending on the season by using anchors to help “walk” the vessel forward and efficiently utilize the floating pipeline. Dredge (Cutter Suction Dredge)

A cutter suction dredger is a stationary or self-propelled vessel that uses a rotating cutter head to loosen the material in the bed (‘cutting’). A suction inlet located beneath the cutter head (known as the suction mouth) is connected by a suction tube directly to one or more centrifugal pumps. The vacuum force at the suction inlet sucks up the loosened material. The suction tube and cutter head are attached to a ladder. The ladder with cutter head is positioned at the fore of the vessel. On the aft side, the cutter generally has two spud poles. One spud pole (the auxiliary spud) passes straight through the vessel, while the other is mounted on a movable spud carriage, which can be moved lengthwise along the vessel or pontoon. Steel cables are used to move the ladder or cutter head back and forth, with the spud in the spud carriage as the center of each concentric circle that it describes. Moving the spud carriage causes the cutter suction dredger to move as well (‘stepping’). The cutter suction dredger discharges the dredged material directly to shore via a floating pipeline or into a barge with a special loading system.

Dredge (Hopper Dredge)

A hopper dredge is well-suited for dredging materials ranging from soft mud and silt to dense sands and clay. It can maintain operations in relatively rough seas and because of its mobility be used in high-traffic areas. It is often used at ocean entrance channels and is very productive in deep water and wide open spaces. A hopper dredge is nimble and can transit quickly to dredged material placement sites under its own power without the need for tug assist or towing.

Dredge (Hydraulic Dredge)

A hydraulic dredge works by sucking a mixture of dredged material and water from the channel bottom. The amount of water sucked up with the material is controlled to make the best mixture. Too little water and the dredge will bog down; too much and the dredge won’t be efficient in its work. There are two main types of hydraulic dredges – hopper dredges and cutter suction dredges.

Dredge (Mechanical Dredge)

A mechanical dredge removes material by scooping it from the sea floor and placing it into a barge or an approved placement area. Dipper, backhoe and clamshell dredges are types of dredges that are suitably named in accordance with their scooping buckets.

Mechanical dredges are rugged and can work in tightly confined areas. They are mounted on a large barge, towed to the dredging site, and secured in place by anchors or anchor pilings (otherwise known as spuds). Mechanical dredges are often used in harbors, near docks and piers, and in relatively protected channels. Usually two or more disposal barges, called scows, are used in conjunction with a mechanical dredge. The operation generally consists of a series of barges. While one barge is filled with material, another barge transits to the placement site and then returns to repeat the cycle, allowing for near continuous and uninterrupted operations. Mechanical dredges are particularly efficient on dredging projects where the placement site is several miles away.

Clamshell dredges are designed to handle loose to medium dense soils and dredge materials, while backhoe and dipper dredges are used to remove consolidated or hard-packed materials and can also be used to clear rock and debris. Hooded or enclosed buckets are utilized to control the flow of water and to prevent contaminated sediments from seeping back into the water column.

Dredge (Trailing Suction Hopper Dredge)

A trailing suction hopper dredger has large, powerful pumps and engines that enable it to suck up sand, clay, sludge and even gravel from ocean or river beds. One or two suction pipes run from the vessel to the bed. A draghead is attached to the end of the pipe and lowered to just above the bed, making it possible to regulate the mixture of sand and water that it takes in. A trailing suction hopper dredger generally stores the dredged material in its own hopper and discharges the left-over water overboard. A trailing suction hopper dredger can empty its hopper in a variety of different ways: a) Depositing - Opening doors or valves on the bottom of the vessel so that the hopper contents drop out. b) Pumping - Using jet pumps or water jets to pump water into the hopper at high pressure so that the sand becomes ‘fluid’ again. The dredge pumps can then pump the resulting mixture through a pipeline which is connected to the vessel. c) Rainbowing - This method is the same as pumping, except that the hopper contents are not pumped through a pipeline, but are sprayed over the vessel’s bow directly at the desired location.

Dredge (Water Injection Dredge)

Water injection dredgers are often used in small, shallow ports and marinas because they have good manoeuvrability and can dredge very close to embankments and quay walls. An injection beam located underneath the vessel injects large volumes of water under low pressure into silt or fine sand in order to resuspend it. The sediment mixture turns into a density current, which is then removed with the help of gravity. Some water injection vessels are built as demountable pontoons.