B

The return leg of a voyage, often carrying cargo at a lower rate than the outbound (head haul) leg because it runs against the dominant direction of trade.

A qualified officer designated to support and monitor the navigator on watch, providing redundancy and an independent check during critical navigation such as pilotage or restricted visibility.

The removal of metal from the root side of a weld, by grinding, machining, or air-arc gouging, to reach sound metal before depositing a backing or sealing run on the reverse side.

A dredger fitted with a hydraulic backhoe excavator mounted on a pontoon, used to dig out and remove seabed material, typically in harbours and confined areas.

Material or a run of weld placed at the root of a joint to support the molten pool and ensure full penetration during welding.

A bracket fitted on the reverse side of a connection to reinforce it and help distribute load into the surrounding structure.

A weld run deposited on the root side of a joint, either first to support subsequent runs or last to seal the root after backgouging.

A ring placed inside a pipe joint at the root to support the weld metal and assist full penetration when welding pipe sections together.

Pressure that resists flow in the direction of normal discharge, for example exhaust backpressure acting against an engine's exhaust flow, which if excessive reduces efficiency.

Corrosion influenced or accelerated by the activity of microorganisms, such as sulphate-reducing bacteria, often found in stagnant water in tanks and bilges; also called microbiologically influenced corrosion.

A plate fitted to direct, deflect, or restrict the flow of a fluid or to reduce the free movement of liquid in a tank.

Cargo carried in sacks or bags, such as grain, cement, or sugar, requiring particular stowage and dunnage to prevent damage and shifting.

For a balanced rudder, the proportion of the rudder area placed forward of the turning axis, which reduces the torque needed to turn the rudder.

The cubic capacity of a cargo hold measured to the inside of the frames, spar ceiling, and beams, representing the space available for bagged or baled (non-bulk) cargo, as distinct from the larger grain capacity.

See bale capacity: the volume of a hold available for baled or packaged cargo, measured to the inboard faces of frames and beams rather than to the shell.

Weight, normally seawater carried in dedicated tanks, taken on to adjust a ship's draught, trim, stability, and stress when it is carrying little or no cargo. Its management to control the transfer of harmful aquatic organisms is regulated by the BWM Convention. IMO-grounded

The transfer of ballast water between tanks, or the loading and discharging of ballast, carried out to adjust draught, trim, heel, or hull stresses during cargo operations and passage.

Pumps dedicated to filling and emptying ballast tanks, sized to move large volumes of water to control the ship's draught and trim within the time required for cargo operations.

The arrangement of tanks, pumps, piping, and valves used to carry, transfer, and discharge ballast water for control of draught, trim, heel, and stress.

A tank dedicated to carrying ballast water. Dedicated seawater ballast tanks are subject to a protective-coating performance standard under SOLAS to combat corrosion. IMO-grounded

A ballast water management method in which water taken on in coastal waters is replaced with open-ocean water during the voyage, to reduce the transfer of coastal organisms. It must achieve the efficiency set by the D-1 standard of the BWM Convention. IMO-grounded

The BWM Convention standard requiring ships that manage ballast water by exchange to achieve at least 95 percent volumetric exchange, set out in regulation D-1. IMO-grounded

The mechanical, physical, chemical, or biological processes used to remove, render harmless, or avoid the uptake or discharge of harmful aquatic organisms and pathogens in ballast water, as required by the IMO BWM Convention. IMO-grounded

A ship-specific plan, required under the BWM Convention, describing the procedures and arrangements the ship uses to manage its ballast water and sediments in compliance with the Convention's standards. IMO-grounded

The BWM Convention standard, set out in regulation D-2, specifying the maximum permitted concentrations of viable organisms and indicator microbes in discharged ballast water, met by treatment rather than exchange alone. IMO-grounded

The processing of ballast water, by methods such as filtration combined with disinfection, to reduce living organisms to the levels required by the D-2 performance standard of the BWM Convention. IMO-grounded

Installed equipment that treats ballast water to meet the BWM Convention's D-2 standard; such systems require type approval, and those using active substances need additional IMO approval. IMO-grounded

The operation of taking ballast water into tanks to increase draught and adjust trim and stability when cargo is light or absent.

A swivel ball-joint coupling used in bow-loading arrangements on tankers and offshore terminals to connect the cargo hose or loading arm while allowing relative movement.

The largest international shipping association, which represents shipowners and operators and is well known for developing standard contract forms and clauses widely used in the industry.

Brakes that apply friction through a flexible band tightened around a drum, used for example on mooring and anchor-handling winches to control the rendering of line.

A unit of pressure approximately equal to atmospheric pressure at sea level. The term also denotes a shoal of sand or silt across a harbour or river entrance.

A charter under which the charterer takes the vessel without crew or provisions and assumes responsibility for operating, manning, and maintaining it for the charter period, effectively as a temporary owner.

A flat-bottomed craft, usually without its own propulsion, used to carry cargo on inland waters or to be towed or pushed, and to load or discharge ships at anchor.

A carrier arrangement in which loaded barges are floated into and carried aboard a catamaran-type mother vessel for ocean transport, then floated out at destination.

Ships designed to carry loaded barges (lighters) that are loaded and discharged afloat, allowing cargo to be transferred without port cranes, as in LASH-type vessels.

A hard-shelled marine crustacean that attaches to submerged surfaces; barnacle growth on a hull is a major form of fouling that increases drag and is countered by anti-fouling coatings.

An instrument that measures atmospheric pressure, used aboard to help forecast changes in the weather.

A range of engine and shaft speeds that must be passed through quickly and not run in continuously, because torsional vibration of the shafting reaches dangerous levels there.

A unit of volume used for crude oil and petroleum products, equal to 42 US gallons (about 159 litres). The term also denotes a cylindrical container.

The horizontal reference line, usually at the top of the keel, from which vertical hull dimensions and draughts are measured in ship drawings and calculations.

A measure of the reserve alkalinity of a lubricating oil, indicating its capacity to neutralise acids formed during combustion; important when burning high-sulphur fuel.

The early stage of ship design in which the main dimensions, form, capacity, powering, and general arrangement are established to meet the owner's requirements, before detailed design.

A device used to secure hatch covers or tarpaulins in place so that they remain weathertight under working conditions.

Strips of wood or metal used for various purposes, including securing hatch tarpaulins (battening down), spacing cargo from the ship's side (cargo battens or spar ceiling), and stiffening.

The principal aluminium ore, carried as a dry bulk cargo. Some forms can liquefy if too wet, so it is addressed among cargoes that may behave dangerously under the IMSBC Code. IMO-grounded

The former Code of Safe Practice for Solid Bulk Cargoes, the IMO instrument governing the safe stowage and shipment of dry bulk cargoes, since developed into the mandatory IMSBC Code. IMO-grounded

Billion cubic feet, a unit of volume used for natural gas.

A fixed navigational mark, lit or unlit, erected on land or on the seabed to guide or warn mariners; also an electronic device that transmits a signal for position-finding or distress alerting.

A bracket connecting a deck beam to a frame, transferring loads and stiffening the connection between the transverse beam and the side framing.

A component that supports a rotating or sliding part while allowing relative motion with low friction, such as the main bearings of an engine or the shaft bearings. In navigation, a bearing is the direction of one object from another.

The load-carrying segments of a bearing, particularly the tilting pads of a thrust or journal bearing that form a supporting oil film.

An empirical scale that relates wind force to observable sea and land conditions, running from force 0 (calm) to force 12 (hurricane), widely used in weather reporting at sea.

The large base structure of a marine diesel engine that supports the crankshaft main bearings and ties the engine to the ship's foundations.

A commercial term referring to the time before cargo discharge begins; certain payments or conditions, such as freight, may fall due before breaking bulk.

A ship's bell, used for time-keeping and as a sound signal, notably to indicate a vessel at anchor in restricted visibility as required by the collision-avoidance rules (COLREGs). IMO-grounded

A pivoted lever bent at an angle that changes the direction of a motion or force transmitted through a linkage.

A flexible, corrugated element that can expand, contract, or flex to absorb movement, vibration, or thermal expansion in piping and ducting.

A pipe fitting incorporating a flexible bellows to accommodate thermal expansion, vibration, and slight misalignment between connected pipe sections.

A self-unloading arrangement using conveyor belts to carry dry bulk cargo from the holds to a discharge boom, allowing the ship to discharge without shore equipment.

A bulk carrier fitted with internal conveyor belts and a boom so that it can discharge its cargo by itself, independent of shore facilities.

A mechanical test in which a specimen, often a welded joint, is bent to a specified angle or radius to reveal soundness and ductility and to detect cracks or lack of fusion.

A load that tends to bend a structural member, producing tension on one side and compression on the other.

The internal moment at a section of a beam or hull girder that tends to bend it; the longitudinal bending moment of the hull, in hogging and sagging, is fundamental to assessing a ship's structural strength.

To bring a ship alongside a quay or to a mooring; also the place where a ship is moored, or a sleeping place for a person on board.

The operation of bringing a ship alongside a berth and securing it, often with the assistance of tugs and mooring lines.

An angled edge prepared on plate or pipe before welding so that the joint can be filled with weld metal to the required penetration.

The larger end of a connecting rod, which is bored to fit around the crankpin of the crankshaft.

A loop or slack part of a rope between its ends; also a wide, gently curving indentation of a coastline.

A monitoring device that measures the oil content of water being discharged from machinery-space bilges and gives an alarm, and stops discharge, if it exceeds 15 parts per million, as required by MARPOL Annex I. IMO-grounded

Supporting blocks arranged under the bilge of a ship in dry dock to help carry and steady the hull alongside the central keel blocks.

Long fins fitted along the turn of the bilge on each side of the hull to damp rolling motion; a simple, passive form of roll reduction.

The principal piping run of the bilge system to which the branch suctions from the various compartments connect for pumping out accumulated water.

The system of pipes through which water collecting in the bilges is drawn to the bilge pumps for removal; its arrangement is governed by classification and SOLAS requirements. IMO-grounded

The shell plating at the rounded turn of the bilge, where the bottom meets the side of the hull.

Pumps used to remove water that accumulates in the bilges and to dewater compartments; the number and capacity of bilge pumps are set by SOLAS and classification rules. IMO-grounded

The radius of the rounded turn of the bilge between the flat of bottom and the side shell.

The course of shell plating that runs along the curved turn of the bilge.

The complete arrangement of wells, suctions, pipes, valves, and pumps for collecting and removing water from the ship's compartments; required for safety under SOLAS. IMO-grounded

Tests carried out to demonstrate that the bilge pumping system can draw from each required suction and dewater compartments at the design rate.

The water, often mixed with oil and other residues, that collects in the lowest internal spaces of a ship and must be managed and discharged in accordance with pollution-prevention rules. IMO-grounded

The body of regulation, principally MARPOL Annex I, governing the treatment, monitoring, and discharge of oily bilge water, including the 15 ppm discharge limit and required equipment. IMO-grounded

Equipment that separates oil from bilge water so that the water can be discharged within the permitted oil content; required under MARPOL Annex I for machinery-space bilges. IMO-grounded

A recess at the low point of a compartment where water collects so that it can be drawn off by the bilge suction.

A document issued by or for the carrier that acknowledges receipt of cargo for shipment, serves as evidence of the contract of carriage, and acts as a document of title to the goods.

The legal document that transfers ownership of a ship from seller to buyer.

Transition pieces joining two different metals, such as aluminium and steel, used where direct welding is impractical and galvanic corrosion must be controlled, for example between an aluminium superstructure and a steel deck.

The film-forming component of a paint that holds the pigment together and bonds the coating to the surface, largely determining the coating's properties.

A substance incorporated in anti-fouling paints and treatment systems to kill or deter marine organisms; the use of harmful biocides in anti-fouling systems is controlled under the AFS Convention. IMO-grounded

Fuels derived from biological sources, considered as lower-carbon alternatives or blend components for marine engines, with combustion and emission characteristics that may differ from conventional fuel oil.

The inboard end of an anchor cable or rope, the last part secured within the ship.

Paired vertical posts fixed to the deck around which mooring or towing lines are made fast.

A bitumen-based protective coating compound used to protect steel surfaces, such as the insides of tanks and chain lockers, against corrosion.

A heavy, viscous residue of petroleum refining, carried as a hot liquid cargo and used for protective coatings and road making.

Cargoes derived from bitumen, carried in heated tanks because they are solid or highly viscous at ambient temperature.

Cargo that dockworkers refuse to handle, typically because of an industrial dispute; also used loosely for dark, dirty petroleum cargoes.

A traditional informal term for the engine-room crew of a steamship, derived from the coal dust and grime of the stokehold.

The darker, heavier petroleum cargoes such as crude oil and fuel oils, as distinct from the lighter clean (white) products.

A total loss of electrical power on board when the generators are off the bus, leaving the ship without power until supply can be restored; recovery arrangements are an important safety consideration. IMO-grounded

The propelling of abrasive against a surface to clean and prepare it; see abrasive blasting. Also a short sound signal given on the whistle.

Recognised visual standards that define the degree of cleanliness and surface preparation achieved by abrasive blasting before coating, used to specify and inspect surface preparation.

Surface preparation by propelling abrasive or steel shot at a surface to remove rust, scale, and old coatings and to produce a profile suited to new coating.

Materials used as the abrasive medium in blast cleaning, such as grit, shot, or mineral abrasives, selected according to the surface and finish required.

A proprietary automated or semi-automated blast-cleaning installation used in shipyards to prepare steel surfaces efficiently.

A small valve or fitting used to release trapped air or to drain off fluid from a system or pipeline.

Fuel produced by mixing components, for example residual and distillate fractions, to achieve a target viscosity, density, and sulphur content for use in marine engines.

Arcs around a ship where the view, or a radar's coverage, is obstructed by structure such as masts or cargo, creating areas that cannot be seen or scanned. Bridge sightline obstructions are limited by SOLAS bridge visibility requirements. IMO-grounded

A localised raised bubble in a coating where it has lost adhesion, often caused by trapped moisture or solvent or by underfilm corrosion.

The formation of blisters in a paint or coating film, a common mode of coating breakdown that exposes the substrate to corrosion.

A measure of hull fullness, the ratio of the underwater hull volume to the volume of the enclosing rectangular block defined by length, breadth, and draught; fuller hulls have higher values.

A bulk-carrier loading arrangement in which a group (block) of adjacent holds is loaded while others are empty; like alternate loading, it is specifically assessed for structural strength. IMO-grounded

The practice of loading a bulk carrier with cargo concentrated in certain holds rather than evenly, which must be checked against permissible local and global hull loads.

The controlled removal of water from a boiler to discharge accumulated sludge and dissolved solids and to maintain water quality.

A fan or compressor that delivers air, for example for engine scavenging, combustion air, or ventilation.

In ship stability, the metacentric radius, the vertical distance from the centre of buoyancy to the metacentre, a geometric quantity used in calculating metacentric height.

The means provided for persons to board and leave a ship safely, such as gangways, accommodation ladders, and pilot ladders, the safe rigging of which is required under SOLAS. IMO-grounded

The maximum speed at which it is safe for a pilot or other person to board or leave a ship, taking account of the ladder arrangement and sea conditions.

A fixed support on which a ship's boat rests when stowed on deck.

A practice mustering and operation of survival craft and their launching arrangements, required at regular intervals under SOLAS to ensure crew and passengers are prepared for an emergency. IMO-grounded

The rope or wire rove through the blocks of a davit by which a boat is hoisted and lowered.

The winch used to hoist and lower a boat on its davit falls in a controlled manner.

The senior member of the deck ratings, responsible under the deck officers for the day-to-day deck work, maintenance, and supervision of the deck crew.

A ship-lines drawing showing the transverse sections (frame lines) of the hull, with forebody sections on one side of the centreline and afterbody sections on the other.

The transverse cross-sectional shapes of the hull at successive stations, defining its form in the body plan.

The vapour that forms as a liquefied gas cargo, such as LNG, slowly warms and evaporates in its tanks; it is managed by being used as fuel, reliquefied, or otherwise handled. Carriage of such cargoes is governed by the IGC Code. IMO-grounded

Equipment that safely burns boil-off gas from liquefied gas cargo, either as fuel in the propulsion plant or boilers, or in a gas-combustion unit, to dispose of excess vapour.

The rate, expressed as a percentage of cargo volume per day, at which a liquefied gas cargo evaporates through heat ingress into the tanks.

A pressure vessel in which water is heated to generate steam for propulsion, cargo heating, or auxiliary services; boilers are subject to design approval, survey, and safety-valve requirements.

The valves and fittings attached to a boiler that are essential for its safe operation, such as safety valves, water-level gauges, stop valves, and feed check valves.

Hard deposits that form on boiler heating surfaces from impurities in the feed water, impairing heat transfer and risking overheating if not controlled by water treatment.

The chemical conditioning of boiler feed and boiler water to control scale, corrosion, and carryover, maintaining safe and efficient boiler operation.

The temperature at which a liquid changes to vapour at a given pressure.

A strong post on a quay or on deck around which mooring lines are secured.

The pulling force a tug can exert measured at zero speed against a fixed point, the standard rating of a tug's towing capability.

Supports or padding fitted to spread load and protect cargo or structure, for example beneath stowed pipes or large items.

Imported goods held under customs control on which duty has not yet been paid, kept in a bonded store until cleared.

A locked store aboard ship, under customs seal, holding dutiable goods such as spirits and tobacco for issue only when permitted.

Curves giving the cross-sectional area of the immersed hull at each station as a function of draught, used to calculate buoyancy, trim, and longitudinal strength for any waterline.

A storeroom, usually forward, holding the deck department's gear such as ropes, paints, and tools, in the boatswain's charge.

The plating forming the bottom of the hull, between the bilges, which together with the side and deck plating makes up the watertight envelope and contributes to longitudinal strength.

The thin layer of water close to the hull in which friction slows the flow relative to the surrounding stream; its behaviour governs frictional resistance and flow into the propeller.

The forward end of a ship's hull.

A fitting at the bow that grips and holds the chain or chafe chain of a mooring or towing connection, used in single-point mooring and offshore operations.

A control position located forward, for example on some offshore or specialised vessels, from which bow loading or thruster operations can be supervised.

Hinged or visor doors in the bow of a ro-ro ship giving vehicle access; their security and the watertight integrity behind them are subject to strict SOLAS requirements following past casualties. IMO-grounded

The outward curvature of the hull above the waterline at the bow, which adds reserve buoyancy and deck area but can increase impact loads in waves.

A tool or system used to assess the slamming and impact loads associated with bow flare in a seaway.

An arrangement on shuttle tankers for loading crude oil through a connection at the bow from an offshore facility, with the necessary mooring, hose, and control equipment.

A rudder fitted at the bow of certain vessels, such as double-ended ferries, to improve manoeuvring when moving in that direction.

The heavy impact of the bow against the sea surface as it re-enters after pitching in waves, producing high transient loads on the structure.

A self-contained bow unit combining steering and thrust on certain vessels, providing manoeuvring control at the forward end.

A transverse propeller in a tunnel near the bow that produces sideways thrust to assist berthing and low-speed manoeuvring.

A large upward-opening bow door on some ro-ro ships that lifts to allow vehicle access; its locking and integrity are safety-critical under SOLAS. IMO-grounded

A hollow, box-section structural member of high stiffness and strength, used for example in hatch coamings, cranes, and certain hull structures.

A cooling arrangement in which cooling coils are mounted in a sea chest so that seawater cools the system by natural or induced circulation, avoiding separate seawater pumps.

A triangular or shaped plate used to connect and stiffen the junction of two structural members and to transmit load between them.

The power actually delivered at the engine output (the crankshaft or coupling), measured at the brake, as distinct from the indicated power developed in the cylinders.

The mass of fuel an engine consumes per unit of brake power output over time, a key measure of engine fuel efficiency.

An alloy of copper and zinc, used aboard for fittings, valve parts, and heat-exchanger components where moderate corrosion resistance is needed.

The width of the hull, usually quoted as the moulded breadth measured to the inside of the shell plating at the widest point.

General cargo carried in individually handled units such as cartons, crates, drums, or bags, rather than in bulk or in containers.

A maintenance approach in which equipment is repaired only after it fails, as opposed to planned or condition-based maintenance.

A structure on the forward deck that deflects and breaks up water shipped over the bow, protecting deck cargo and fittings; also a coastal structure protecting a harbour.

A horizontal plate connecting the side structure across the stem at the bow, tying the two sides together.

Mooring lines led roughly at right angles to the ship's side to hold it close against the berth.

A cylinder of compressed breathable air supplying a breathing apparatus for use in spaces where the atmosphere is hazardous or oxygen-deficient.

Equipment that supplies clean air to the wearer for entry into smoke-filled, toxic, or oxygen-deficient spaces; self-contained breathing apparatus is required fire-fighting and rescue equipment under SOLAS. IMO-grounded

The deck on which the navigating bridge is situated, from which the ship is conned and controlled.

The field of view available from the navigating bridge; SOLAS sets minimum requirements for the view of the sea surface and the limits on blind sectors ahead of the ship. IMO-grounded

A control position on the bridge wing equipped with the instruments and controls needed to manoeuvre the ship during berthing and close-quarters operations.

The extensions of the navigating bridge to each side of the ship, giving a clear view down the ship's side for manoeuvring and berthing.

Direct VHF radio communication between the bridges of vessels in sight or proximity of one another to coordinate their movements and avoid collision.

A planned exchange of information before an operation, such as a navigation or safety briefing, to ensure all involved understand the plan and their roles.

Sudden fracture of a material with little plastic deformation, a particular concern for steel at low temperature, which is guarded against by selecting steels with adequate notch toughness.

A dangerous loss of heading control when a ship running before large following or quartering seas is slewed broadside to the waves, risking a severe heel or capsize.

The cargo space that is lost and cannot be filled because of the shape of the holds and of the cargo units, reducing the cargo that can be loaded.

An intermediary who arranges transactions between parties, such as a shipbroker who fixes charters or sales, or an insurance broker who places cover.

The commission earned by a broker for arranging a transaction such as placing insurance or fixing a charter.

An alloy based on copper and tin, valued for corrosion resistance and strength and used for propellers, bearings, and valve and pump components.

A standard published by the British Standards Institution setting requirements for freight containers.

The temperature and pressure at which the first bubble of vapour forms in a liquid mixture as it is heated, marking the start of boiling.

The formation of bubbles in a coating film during application or curing, a defect that can impair the protective film.

A dredger that excavates the seabed with an endless chain of buckets running over a ladder, bringing up material continuously.

A self-unloading system using a rotating wheel fitted with buckets to dig into and lift dry bulk cargo onto a conveyor for discharge.

A cover or plate fitted to close the hawse pipe or spurling pipe to keep out sea and weather around the anchor cable.

The sudden sideways collapse or wrinkling of a structural member under compressive load when it becomes unstable, an important failure mode for plating and stiffeners.

The compressive load at which a structural member becomes unstable and buckles.

The characteristic shape into which a member deforms when it buckles, such as column buckling of a stiffener or plate-panel buckling.

The berths, slipways, or building docks in a shipyard where ships are assembled and constructed.

A rolled stiffener section with a bulbous edge that provides bending stiffness efficiently, widely used to stiffen plating in ship structures.

A protruding bulb at the forefoot below the waterline that modifies the bow wave system to reduce wave-making resistance and improve efficiency at design speed.

Unpackaged cargo carried loose in the holds, either dry (such as ore or grain) or liquid (such as oil); the safe carriage of solid bulk cargoes is governed by the IMSBC Code. IMO-grounded

A single-deck ship designed to carry unpackaged dry bulk cargoes in large holds; bulk carriers are subject to additional structural and safety requirements under SOLAS. IMO-grounded

A freight container designed to carry dry bulk commodities, loaded through hatches in the top and discharged through openings at the end or bottom.

The uppermost deck up to which the transverse watertight bulkheads are carried; it is a key reference for a ship's subdivision and damage stability under SOLAS. IMO-grounded

Doors fitted in watertight bulkheads to allow passage while maintaining watertight integrity when closed; their type, control, and operation are regulated by SOLAS. IMO-grounded

The vertical partition walls dividing a ship into compartments; watertight bulkheads provide subdivision and contribute to strength, with their number and spacing governed by SOLAS. IMO-grounded

The plating that extends above the weather deck at the ship's side as a protective barrier, fitted with freeing ports to clear shipped water.

A built-in bed in a ship's cabin.

To supply a ship with fuel; bunkers are the ship's fuel, and bunkering is the operation of taking it on.

A document provided when fuel is supplied, recording the quantity and characteristics of the bunkers delivered, including sulphur content; its provision and retention are required under MARPOL Annex VI. IMO-grounded

The deck connection points at which fuel is received aboard, fitted with the necessary couplings, drip trays, and controls to prevent spillage.

A charter-party provision dealing with the supply, quantity, quality, and cost of bunkers and the responsibilities of the parties for them.

A small tanker or barge used to deliver fuel to other ships, at a berth or at anchor.

A floating, moored marker used to indicate channels, hazards, or positions, or to provide a mooring; navigational buoys are part of the system of aids to navigation.

A frame structure on a buoy-handling vessel used to lift and handle navigational buoys over the side.

A crane on a buoy tender designed to lift, deploy, and recover heavy navigational buoys and their sinkers.

A vessel equipped to lay, recover, service, and reposition navigational buoys and their moorings.

The upward force exerted by water on a floating or immersed body, equal to the weight of the water displaced, which supports the ship and underlies stability and reserve buoyancy.

A device that mixes fuel with air and ignites it to produce a controlled flame, for example in a boiler or incinerator.

A conductor in a switchboard to which the generators and outgoing circuits are connected, distributing electrical power within the system.

A weld joining two members aligned in the same plane, edge to edge, the common joint for joining plates and pipes end to end.

A joint in which two members meet edge to edge in the same plane, typically completed by a butt weld.

A quarter-turn valve in which a disc rotates within the pipe to control flow, compact and quick-acting, widely used in ballast and cooling-water systems.

The longitudinal curves formed by the intersection of vertical fore-and-aft planes with the hull surface, shown in the sheer plan to describe the hull form, especially aft.

The International Convention for the Control and Management of Ships' Ballast Water and Sediments, the IMO treaty requiring ships to manage ballast water to the D-1 or D-2 standard to limit the spread of harmful aquatic organisms. IMO-grounded

An alternative path that allows flow to go around a component such as a filter, cooler, or valve, used for control or to maintain flow when the component is isolated.

A filter arrangement through which only part of the flow passes for fine cleaning, while the main flow continues, gradually cleaning the whole volume over time.