H

The suitability of the crew and passenger spaces for living and working, in terms of comfort, noise, vibration, ventilation, and amenities; standards for crew habitability are set under the Maritime Labour Convention. IMO-grounded

An enclosed, environmentally controlled space provided for workers, for example a welding habitat that gives a safe atmosphere for hot work in a hazardous area.

A halogenated gas formerly widely used as a fire-extinguishing agent; its production has been phased out under environmental rules because it depletes the ozone layer, and existing systems are being replaced. IMO-grounded

A technique that humidifies an engine's combustion air with water vapour to lower combustion temperature and reduce nitrogen-oxide emissions.

A vessel restricted in its ability to manoeuvre by the nature of its work or its draught, which under the collision regulations may be entitled to particular consideration. IMO-grounded

A reference manual giving operating, maintenance, or safety information for equipment or procedures.

The formal transfer of responsibility, for example of the navigational watch from one officer to another, with a proper briefing on the situation.

A grip provided for holding on or for operating equipment, contributing to safe movement about the ship.

A rail provided along stairs, walkways, and openings for people to hold for safety.

A class of dry bulk carriers of moderate size, typically around 40,000 to 60,000 deadweight tonnes, versatile and able to use a wide range of ports.

The smallest main class of dry bulk carriers, typically up to around 40,000 deadweight tonnes, suited to smaller ports and varied cargoes.

Charges levied on a ship for the use of a harbour and its facilities.

The official responsible for the safe and efficient operation of a harbour, including the movement and berthing of ships.

A sheltered area of water where ships can anchor or berth in safety.

A protective coating that cures to a hard film, as distinct from a soft coating, used in tanks and assessed in coating-condition surveys.

The component of a two-pack coating or adhesive that reacts with the base to cause it to cure and harden.

A heat treatment or process that increases the hardness of a metal; also the curing of a coating.

A measure of how hard and resistant to indentation a cured coating film is, indicating its durability.

Components of a signal or vibration at multiples of a fundamental frequency; electrical harmonics from power converters can disturb a ship's electrical system and must be controlled.

The raised rim around a cargo hatch that strengthens the opening and keeps out water, its height set by the Load Line Convention. IMO-grounded

The weathertight closure over a cargo hatch, designed to keep out the sea; its strength and weathertightness are required by the Load Line Convention. IMO-grounded

The gaskets and sealing arrangements that make a hatch cover weathertight against its coaming.

The resilient rubber gasket that seals a hatch cover against its compression bar to keep out water.

Adhesive tape applied over hatch joints as a supplementary measure to improve weathertightness.

The opening in a deck through which cargo is loaded into and discharged from a hold.

A container ship designed without hatch covers over some or all holds, speeding cargo handling but requiring enhanced bilge pumping and structural arrangements.

Removable or fixed rails fitted around an open hatch to protect people working nearby from falling in.

The pipe through which the anchor cable passes from the deck down the ship's side to the water (hawse pipe) or down to the chain locker (spurling pipe).

A large rope or wire used for mooring or towing.

Air pollutants known or suspected to cause serious health or environmental effects, the control of which is part of wider efforts to limit emissions.

An area where a flammable or explosive atmosphere may be present, in which only certified safe equipment may be used and special precautions apply, as on tankers and gas carriers. IMO-grounded

Materials that present a risk to health, safety, or the environment; their carriage and handling are regulated by the IMDG Code and the bulk chemical and gas codes. IMO-grounded

Mooring lines led forward from the bow to hold the ship's head to the berth.

A small tank mounted high in a system that maintains a head of liquid, makes up for losses, and allows expansion, as in a cooling-water circuit.

An accounting of the heat input to and output from a system, used to analyse the efficiency of engines and plant.

A fire detector that responds to a rise in temperature or to a set temperature, part of the fixed fire-detection system.

A device that transfers heat between two fluids without mixing them, such as a cooler, condenser, or heater.

The raising of temperature, for example of cargo, fuel, or accommodation, by means of heating coils, heaters, or steam.

Pipe coils fitted in a tank through which steam or thermal oil is passed to heat the contents, used for heavy fuel oil and certain cargoes.

The vertical up-and-down motion of a ship as a whole in a seaway.

A light line with a weighted end thrown ashore or to another vessel to haul across a heavier mooring rope.

Crude oil of high density and viscosity, which may need heating to be pumped and handled.

A derrick of high capacity fitted to handle heavy or outsized cargo items.

Ships designed and equipped to carry exceptionally heavy or large items, often with high-capacity cranes or a submersible deck for float-on loading.

A system for moving very heavy loads aboard or between vessels, such as self-propelled modular transporters or skidding arrangements.

A condition in which a fixed-pitch propeller absorbs more torque than designed at a given speed, for example because of hull fouling or heavy weather, loading the engine.

Damage to a ship, its structure, or cargo caused by severe sea conditions, a recognised category of casualty and insurance claim.

The transverse inclination of a ship from upright caused by an external force such as wind or turning.

A coefficient used in a hull-resistance or propulsion estimation method.

The arrangements on a ship for helicopter operations, ranging from a winching area to a full landing deck, subject to safety requirements and IMO guidance. IMO-grounded

A helicopter landing deck fitted to a ship or offshore installation, designed and marked for safe helicopter operations.

The steering wheel or tiller of a ship, and by extension the act of steering.

The crew member who steers the ship under the direction of the officer of the watch.

A proprietary enclosed-habitat system providing a safe environment for carrying out repairs such as welding in hazardous areas.

A proprietary water-mist fire-extinguishing system that discharges very fine high-pressure water droplets to cool and smother a fire while using little water.

A proprietary buoyancy or marking device.

Fire-fighting foam expanded to a very high ratio of air to liquid, producing a large volume of light foam used to fill enclosed spaces such as machinery spaces.

The gross calorific value of a fuel, the total heat released by complete combustion including the heat recovered by condensing the water vapour produced.

A cargo-tank vent valve that releases vapour at high velocity to carry it well clear of the deck, reducing the risk of a flammable cloud forming, as required in tanker venting arrangements. IMO-grounded

An epoxy coating formulated to be applied in thick films per coat, building protective thickness quickly, used in tanks and on demanding surfaces.

See high expansion foam: a low-density fire-fighting foam expanded at a high ratio, used to flood enclosed spaces.

Hydraulic cylinders providing a long stroke, used for example to operate ramps, hatch covers, or lifting platforms.

A hydraulic drive operating at high pressure to deliver large forces from compact equipment.

A cutting method using a high-pressure jet of water carrying abrasive particles, used to cut metal and other materials without heat.

A diesel engine running at high rotational speed, compact and light for its power, used in fast craft, generators, and auxiliary drives.

A proprietary device that attaches to a tanker to provide dynamic-positioning offloading at offshore terminals.

The condition in which a ship's hull is bent so that the middle is higher than the ends, for example when supported by a wave crest amidships; the opposite of sagging.

A device for lifting loads, or the act of lifting; also the lifting of a signal flag.

A movable vehicle deck that can be raised and lowered to adjust the clear height for different vehicles on car carriers and ro-ro ships.

A space below deck for the carriage of cargo.

The volume of a cargo hold available for cargo.

A tank for temporarily retaining liquids such as sewage or bilge water until they can be discharged or treated in accordance with pollution rules. IMO-grounded

The bolts that secure a machine, such as a main engine, to its seating and the ship's structure.

A loading condition in which all cargo holds are filled to a similar degree, distributing the cargo evenly, as distinct from alternate or block loading.

A device that breaks up and disperses the components of a fluid uniformly, for example to treat fuel or process sludge.

A barge with a hopper hold that can be opened or that discharges by other means, used to carry and dump dredged material or aggregates.

The sloping tanks at the lower sides of a bulk carrier's holds that guide cargo toward the centre for discharge and provide ballast space.

A funnel-shaped container or structure that holds and channels bulk material toward an outlet.

A pipe-welding test position in which the pipe is horizontal and cannot be rotated, requiring welding all around it.

A pipe-welding position in which the pipe is horizontal and rotated during welding so the weld is made in the easier downhand position.

A welding position in which a fillet weld is made on a roughly horizontal joint on a vertical surface.

A flexible hose fitted with end couplings, used for transferring fluids such as cargo, bunkers, or water.

A weathertightness test in which a jet of water from a hose is directed at joints and closures, such as hatch covers, to check that they keep out water.

Cranes at a tanker's manifold used to lift and connect the cargo hoses or loading arms.

Work involving sources of heat or ignition, such as welding, cutting, or grinding, which requires strict permit-to-work controls, especially in or near tanks and hazardous areas. IMO-grounded

A craft supported on a cushion of air contained by a flexible skirt, able to travel over water and land; as a high-speed craft it may come under the High-Speed Craft Code. IMO-grounded

A method developed by a hydrodynamics institute for analysing ship speed-trial results to derive performance in standard conditions.

The main body of a ship, the watertight structure that provides buoyancy and contains the spaces.

Parts projecting from the main hull, such as the rudder, bilge keels, and shaft brackets, which add resistance; see appendages.

A factor in propulsion analysis expressing how the hull's wake and thrust deduction affect the propeller's effectiveness behind the hull.

The texture of the hull surface, which increases frictional resistance as it grows through fouling and corrosion; maintaining a smooth hull saves fuel.

A system of sensors that measures the stresses, motions, and slamming experienced by the hull and warns the crew, helping avoid overloading in heavy weather.

Damage to the hull or machinery, a category used in casualty reporting and insurance.

The amount of water vapour in the air, controlled in spaces and cargo holds to prevent condensation, corrosion, and cargo damage.

A storm of a severity expected on average once in a hundred years, used as a design condition for offshore structures and extreme-load assessment.

The visible hollows in thin plating between stiffeners, a cosmetic deformation that does not necessarily affect strength.

A valved outlet on the fire main to which a fire hose is connected.

A motor driven by pressurised hydraulic fluid, used to power deck machinery, thrusters, and other equipment.

A steering-gear or actuating mechanism in which hydraulic power drives a rack engaging a pinion to produce rotary motion, for example to turn the rudder stock.

Refrigerants used as interim replacements for CFCs, themselves being phased out under environmental rules because they still deplete ozone and are greenhouse gases. IMO-grounded

Surface preparation using high-pressure water jets to remove coatings, rust, and contaminants without abrasive grit.

Compounds of hydrogen and carbon that make up petroleum oils and gases, the principal liquid and gas cargoes and fuels.

The study of the forces and flows associated with liquids in motion, fundamental to predicting a ship's resistance, propulsion, and manoeuvring.

A hybrid craft combining a submerged hull and a foil to lift a slender surface-piercing strut, giving high speed and good seakeeping.

A craft fitted with foils that lift the hull clear of the water at speed, reducing resistance; as a high-speed craft it may come under the High-Speed Craft Code. IMO-grounded

A vessel equipped to survey the depth and nature of the seabed and to gather data for nautical charts.

A set of curves giving a ship's hydrostatic properties, such as displacement, centres of buoyancy and flotation, and metacentric data, against draught.

A system in which pressure is produced or controlled by the head of a column of liquid.

A device that automatically releases a liferaft or EPIRB when a sinking ship reaches a set depth, allowing the equipment to float free; required for certain equipment under SOLAS. IMO-grounded

A tanker loading method that keeps the cargo level low enough that the internal pressure at any leak is balanced by the external sea pressure, reducing the outflow of oil if the hull is breached. IMO-grounded

A large cavitation tunnel used for testing model propellers and studying cavitation.

A system for evacuating divers who are under pressure (in saturation), keeping them pressurised in a chamber or lifeboat until they can be safely decompressed.

A pressurised installation, such as a chamber complex, used to compress, accommodate, and decompress divers during saturation diving.

A lifeboat incorporating a pressure chamber so that saturation divers can be evacuated while remaining under pressure.

A pressurised capsule used to evacuate divers under pressure from a diving system in an emergency.