R

A toothed bar that meshes with a pinion to convert rotary to linear motion, used for example in some steering gears and jack-up leg systems.

A wire used in a racking (cross-bracing) arrangement to restrain container stacks or other structures against distortion.

A system that detects objects and measures their range and bearing by transmitting radio pulses and timing the echoes, an essential aid to navigation and collision avoidance required under SOLAS chapter V. IMO-grounded

The superimposition of the radar picture on an electronic chart display, combining sensed targets with charted information.

The tracking of radar targets to determine their course, speed, and risk of collision, done manually or automatically by ARPA.

A tank-level system that measures the distance to the liquid surface by radar, giving a closed, non-contact measurement suited to hazardous cargoes. IMO-grounded

Equipment for communicating by radio waves, central to ship safety communications under the GMDSS. IMO-grounded

Equipment that determines the bearing of a radio transmission, formerly a common navigation and homing aid.

A person qualified to operate the ship's radio equipment, holding the appropriate certificate under the Radio Regulations and STCW. IMO-grounded

The international regulations of the International Telecommunication Union governing the use of the radio spectrum, including maritime frequencies and procedures used within the GMDSS. IMO-grounded

A transmitter that emits a signal for position finding or homing; distress radiobeacons such as EPIRBs form part of the GMDSS. IMO-grounded

The bridge position equipped with the GMDSS radio equipment for distress, safety, and general communications. IMO-grounded

A non-destructive test using X-rays or gamma rays to reveal internal defects in welds on film or a detector, used to verify the soundness of structural welds.

Covered areas providing protection from rain, for example at access or working positions.

A short raised deck at the stern, one step up from the main deck, that increases stern buoyancy and space, common on smaller cargo ships.

The inclination of a mast, funnel, stem, or other member from the vertical or from a reference line.

A deliberate slope of the keel line so that the design draught aft differs from that forward, giving a built-in trim.

A steering gear in which hydraulic rams, powered by electrically driven pumps, move the tiller to turn the rudder, a common arrangement on large ships.

A distinctive broad, triangular stern hull form used on seismic survey vessels to deploy and tow wide arrays of streamers.

Inclined structures, fixed or movable, that allow vehicles to be driven on, off, and between the decks of ro-ro ships.

A steering-gear linkage (Rapson's slide) that connects the actuator to the tiller, converting the actuator's motion into rudder movement.

A digital chart that is a scanned image of a paper chart, used in ECDIS where electronic vector charts are not available, in raster chart display mode. IMO-grounded

The rotational speed at which an engine is designed to deliver its rated power.

A connection point at which a fluid, such as bunkers or cargo, is received aboard.

To move back and forth in a straight line, as a piston does in a cylinder.

A positive-displacement pump that moves fluid by the back-and-forth motion of a piston or plunger.

An organisation authorised by a flag administration to carry out security assessments, approve security plans, and verify compliance on its behalf under the ISPS Code. IMO-grounded

A logbook recording an engine's operating parameters, used in particular to demonstrate compliance with the nitrogen-oxide requirements of MARPOL Annex VI. IMO-grounded

A device that converts alternating current to direct current.

Subdued red or low-level white lighting used on the bridge at night to preserve the watchkeepers' night vision.

Structural dimensions reduced below the normal standard where permitted, for example in return for higher-strength steel or enhanced corrosion protection.

A valve that automatically lowers and controls the downstream pressure of a fluid to a set value.

Gearing that reduces the high rotational speed of an engine or turbine to the lower speed suited to the propeller.

The provision of duplicate or alternative equipment so that a function can continue after a failure, important for essential systems and dynamic positioning.

The provision of more than one means or path of propulsion so that the ship can still proceed if one fails, increasingly required or encouraged for safety. IMO-grounded

A traditional unit of oil viscosity, the time for a measured volume to flow through a standard Redwood viscometer.

A ship with refrigerated holds for carrying perishable cargo such as fruit, meat, and fish at controlled temperatures.

A system for monitoring and controlling refrigerated containers aboard a container ship.

A datum line used in drawings and calculations, such as the base line or a moulded reference.

A period of repair, renewal, and upgrading of a ship's structure, machinery, and equipment.

Heat-resistant material lining furnaces, boilers, and incinerators to withstand high temperatures.

The working fluid of a refrigeration system that absorbs and releases heat as it changes state; many older refrigerants are being phased out for environmental reasons. IMO-grounded

A freight container with its own refrigeration unit for carrying temperature-controlled cargo.

Ships with refrigerated holds for carrying fish and fish products at low temperature.

Insulated, cooled spaces for storing perishable cargo or the ship's provisions.

The process of removing heat to lower and maintain temperature below ambient, used for cargo and provisions.

The spaces housing refrigeration plant; where they contain certain refrigerants they attract particular safety and ventilation requirements. IMO-grounded

The arrangement of compressor, condenser, expansion device, and evaporator that provides cooling.

A self-contained refrigeration assembly, such as that fitted to a reefer container.

The density of a liquid compared with that of fresh water, used in cargo measurement and pump and stability calculations.

The probability that equipment will perform its function without failure for a given period under stated conditions.

A valve that opens automatically to release excess pressure from a system and protect it from overpressure.

The operation of machinery or equipment from a distance, such as engine controls on the bridge.

Valves that can be operated from a distance, hydraulically, pneumatically, or electrically, used for example to isolate tanks and lines in an emergency. IMO-grounded

Unmanned underwater vehicles controlled from the surface through a tether, used for subsea inspection, survey, and intervention.

A tethered, unmanned submersible operated from a surface vessel to carry out work and observation underwater.

An intermediate deck that can be installed or removed to divide a hold's height to suit different cargoes.

A pre-arranged meeting of vessels at a place and time, for example for transfer or escort.

Selected spaces examined during a survey as representative of similar spaces, so that conclusions can be drawn about the whole. IMO-grounded

The launch height for which a free-fall lifeboat must be certified to demonstrate safe water entry and acceptable occupant accelerations, under SOLAS and the LSA Code. IMO-grounded

A proprietary marine evacuation system for transferring people from a ship into survival craft.

A basket device used to lift a person from the water or transfer them in a rescue.

The davits used to launch and recover a rescue boat quickly, designed to operate even with the ship making headway, under SOLAS and the LSA Code. IMO-grounded

A fast, manoeuvrable boat carried to rescue persons from the water and to marshal survival craft; required and regulated under SOLAS and the LSA Code. IMO-grounded

A shore centre responsible for organising and coordinating search-and-rescue operations within a defined region, following the IAMSAR system. IMO-grounded

The crew members organised and trained to carry out rescues aboard, such as recovering a person from an enclosed space or the water.

Vessels equipped for scientific work at sea, such as oceanographic, fisheries, or geophysical research.

The buoyancy available above the waterline, in the watertight volume of the hull and enclosed superstructure, which keeps a ship afloat when it heels, pitches, or is partly flooded.

The stability remaining after damage and flooding, assessed against the survival criteria of the damage-stability requirements under SOLAS. IMO-grounded

Flexible mounts that support machinery while isolating its vibration and noise from the ship's structure.

The film-forming polymer that is the binder of a coating, or a material used in composites and adhesives.

Model tests in a towing tank to measure the resistance of a hull form at various speeds, used to predict the power required.

An ultrasonic method of measuring material thickness by detecting resonance, used to assess corrosion and wastage of structure.

An area of a ship or port to which access is controlled, for example for security under the ISPS Code or for safety. IMO-grounded

A tank-gauging device that limits the escape of cargo vapour to the atmosphere during measurement, permitted for cargoes of intermediate hazard. IMO-grounded

Conditions such as fog, mist, heavy rain, or snow that reduce visibility, in which special navigation rules and sound signals of the COLREGs apply. IMO-grounded

Delaying the timing of fuel injection in a diesel engine to lower peak combustion temperature and reduce nitrogen-oxide formation.

A thruster that can be lowered for use and withdrawn into the hull when not needed, used for manoeuvring and dynamic positioning.

Protection that disconnects a generator if it begins to take power from the system instead of supplying it, preventing motoring of the prime mover.

A process that forces water through a semipermeable membrane against the osmotic gradient to remove dissolved salts, used to produce fresh water from seawater.

A liferaft designed to be boarded and used either way up, so it functions whichever side lands uppermost on inflation. IMO-grounded

A system using fins, interceptors, or other devices to reduce the motions of a fast craft and improve comfort and safety.

The operation of relocating a mobile offshore drilling rig from one site to another.

The system of ropes, wires, and fittings used to support masts and to work cargo gear, boats, and other equipment; also the act of setting it up.

The horizontal distance between the lines of action of the weight and the buoyancy of a heeled ship, the lever that produces the righting moment; its curve against heel defines the ship's stability. IMO-grounded

A rigid slide forming part of a marine evacuation system, down which people descend from the ship to a liferaft or platform. IMO-grounded

A thruster in which the propeller blades are driven from a motor built into the surrounding rim or duct, without a central hub motor.

A propulsor in which a permanent-magnet motor integrated into the duct rim drives the propeller, offering a compact, efficient unit.

The upward slope of the bottom of the hull from the keel toward the bilge; see deadrise.

A vertical or near-vertical pipe; in offshore work, the pipe connecting a surface facility to the seabed.

A vessel designed to operate both on inland waterways and in coastal sea areas, meeting the requirements of both.

A ship combining roll-on/roll-off and lift-on/lift-off cargo handling, with ramps for wheeled cargo and hatches for lifted cargo.

Roll-on/roll-off, describing ships and cargo handled by driving wheeled units on and off over ramps.

Spaces for wheeled cargo that is driven on and off; their large open volumes pose particular fire and stability risks addressed by SOLAS. IMO-grounded

A passenger ship with roll-on/roll-off cargo spaces, subject to enhanced damage-stability and safety requirements under SOLAS following past casualties. IMO-grounded

The vehicle and cargo spaces of a roll-on/roll-off ship, subject to particular ventilation, drainage, and fire-protection requirements. IMO-grounded

A road tanker carried as cargo on a ro-ro ship, subject to dangerous-goods stowage rules where applicable. IMO-grounded

A wheeled vehicle carried as cargo, driven on and off a ro-ro ship.

The use of a layer of rock or aggregate to absorb and dampen loads, for example over a seabed pipeline.

The mustering and counting of persons aboard at assembly stations in an emergency or drill.

The use of devices such as bilge keels, fins, tanks, or gyros to lessen a ship's rolling.

The active or passive reduction of roll to improve comfort, safety, and operability.

A heavy-duty low trailer used to carry cargo on and off ro-ro ships, towed by a terminal tractor.

A cargo system in which wheeled units are driven on and off the ship over ramps, allowing rapid handling without cranes.

Guides for locating and restraining containers, formed from rolled sections.

Cargo carried on wheels, such as vehicles, trailers, and roll trailers, handled by roll-on/roll-off methods.

Hatch covers that open by rolling along rails on the coaming.

A proprietary cargo-handling system using cassettes moved without their own wheels.

Ferries carrying both roll-on/roll-off cargo and a substantial number of passengers, subject to the full passenger-ship safety regime under SOLAS. IMO-grounded

A roll-on/roll-off passenger ferry combining vehicle decks with passenger accommodation.

A guard around the propeller shaft where it leaves the hull that prevents ropes and lines from fouling and entering the stern tube.

A bow steering arrangement using a rotating unit to provide directional control at the forward end, as on double-ended ferries.

A positive-displacement pump using rotating elements such as gears, screws, or vanes to move fluid.

The rotating platform on a drilling rig that turns the drill string through the kelly.

Positive-displacement pumps using sliding vanes in a rotor to move fluid.

A steering gear in which hydraulic pressure acts on vanes to rotate the rudder stock directly, a compact arrangement.

A highly manoeuvrable tug with multiple azimuthing units arranged to give thrust and steering in any direction.

The bridge position used for planning the ship's intended voyage, increasingly integrated with the electronic chart system.

Vessels equipped to deploy, operate, and support remotely operated vehicles for subsea work.

An international professional body for naval architects and marine engineers, promoting standards and knowledge in the profession.

The hinged or rotatable surface at the stern used to steer the ship by deflecting the water flow; its size, strength, and steering gear are governed by class rules and SOLAS. IMO-grounded

The mechanism, usually hydraulic, that turns the rudder stock in response to the steering command.

An instrument showing the actual angle of the rudder, displayed at the steering position.

The flat or foil-shaped part of the rudder that acts on the water flow to steer the ship.

The area of the rudder blade, chosen in relation to the underwater profile to give adequate steering and manoeuvring.

The bearing that supports the weight of the rudder and rudder stock and allows it to turn.

The fixed structural support from which a semi-spade rudder is hung, carrying part of the rudder loads.

A steerable propulsion unit, such as an azimuthing thruster, that both propels and steers the ship.

A technique that uses rapid, controlled rudder movements to reduce a ship's roll as well as to steer it.

Cavitation occurring at the bottom (sole) of the rudder, which can cause erosion of the rudder surface.

A device that limits the maximum angle to which the rudder can be turned, protecting the steering gear and structure.

The shaft that transmits the turning torque from the steering gear to the rudder blade.

A rough, practical guideline based on experience rather than precise calculation.

A proprietary reference tool for finding classification or regulatory rules.

The navigation lights a vessel shows when underway to indicate its presence and aspect, as prescribed by the COLREGs. IMO-grounded

The reddish iron oxide formed when steel corrodes in the presence of oxygen and moisture, the visible product of corrosion.