GLOSSARY

Absolute pressure
The sum of gauge pressure and ambient atmospheric pressure.

Accommodation
The section or area of the ship in which the crew quarters, cargo control room and navigation bridge are located; also called the superstructure.

Acute toxic effect
The effect on a man of a single exposure of short duration to high concentrations of poisonous compounds or vapours.

Agent
A person or business holding a limited agency authority from a shipowner or master to act on behalf of the ship in arranging and facilitating a visit to a port.

API gravity
An empirical scale used for measuring the density of liquid petroleum. The unit is called the 'degree API'. It was established by the American Petroleum Institute in 1892 as a standard for the American petroleum industry. The conversion from specific gravity to API gravity is: API gravity = (141.5/specific gravity - 131.5.)

Approved
Approved by a flag state authority, government department, classification society or other appropriate authority, such as by the Commandant of the US Coast guard.

Arm
An articulated cargo pipe device used to connect the shore terminal piping to a tanker's manifold flange connection for the transfer of cargo.

Aromatic
Containing little or no wax.

ARPA
Automatic radar plotting aid - an electronic device incorporated in or operating with a radar set to provide an automatic indication of the tracks of approaching vessels and also their courses, speeds and CPA's. Sometimes called a 'collision avoidance system' (CAS).

Asphalt
Black, solid or semi-solid bitumens which occur in nature or are obtained as residues during petroleum refining.

ASTM
American Society for Testing Materials.

Balance tanks
Cargo tanks which are reserved to receive the final amounts of cargo when loading.

Ballast
Sea water carried aboard vessels to provide adequate draft for safe manoeuvring and seakeeping, or to adjust the trim of the vessel.

Barrel
A unit of liquid measurement equal to 42 US gallons at 60 °F, or about 0.159 cubic meters.

Black oils
Dark coloured petroleum liquids, including such products as fuel oils, some diesel fuels, and some gas oils, but excluding refined lubrication oils.

Blank flange
A circular flat plate bolted to the flanged end of a section of cargo piping (as at the amidship manifold) to close off the line. Blind flange.

Bleeder valve
A small valve used for draining off air or liquid from a pipeline.

Blends
Intentional mixtures of two or more products or cargoes.

Block valves
Valves in the main cargo lines used to isolate sections of the cargo piping system.

Blower
A portable fan used for cargo tank ventilation.

Boiling point
The temperature at which the vapour pressure of a substance is equal to the ambient atmospheric pressure.

Bonding cable
An electrical cable intended to ground (earth) the ship to the pier it is moored to.

Bunkering
The process and procedures of loading fuel on board a vessel.

Butterworth
A proprietary name for Butterworth Systems Inc., manufacturers of tank washing machines, equipment and systems.

Cargo handling
The loading, discharging and transferring of cargo.

Cathodic protection
A method of preventing wastage or corrosion of a vessel's steel structure using sacrificial (zinc) anodes or a system of impressed electrical current.

CAV
Computerised and automated vessel.

CBT
Clean ballast tank system, which uses reserved tanks for ballasting, but employs the ship's cargo pumps and piping for filling and emptying the ballast tanks.

CCR
Cargo control room — the control space on the ship from which cargo operations are directed and cargo valves and cargo pumps are controlled.

Certified gas free
Indicates that a confined space has been inspected and tested by a licensed marine chemist using calibrated equipment and approved procedures and found to be free of toxic or explosive concentrations of petroleum vapour. A certificate is issued indicating the type of work which can be performed in the tank and protective equipment required for entry.

Charter
A contract for the use or employment of a vessel for a period of time or for one or more voyages.

Checklist
A summary reminder list of tasks to be completed in preparing for and conducting an operation or procedure. The properly completed checklist serves as a record of correct performance.

Chemical absorption indicator
An instrument used for detecting the presence of and measuring the concentration of gasses or vapours by means of discolouration of a chemically treated material contained in a glass tube.

Chronic toxic effect
The cumulative effect on a man of prolonged exposures to low concentrations, or of intermittent exposures to higher concentrations, of a poisonous compound or vapour.

Clean oils
Refined oils with little or no colour; also known as 'clean petroleum products', 'white oils', or 'white products'.

Closed gauging
A method of measuring the contents of a tank without opening the tank or permitting the escape of tank atmosphere, by use of a fixed device, or a portable device which can be connected to a vapour-tight fitting at the measurement point.

Cloud point
The temperature at which wax crystals begin to precipitate out from suspension in a paraffinic oil.

C02
Carbon dioxide.

Cofferdam
A narrow empty space between two bulkheads, intended to prevent leakage between adjacent compartments, as between a cargo tank and the engine room.

COLREGS
A US acronym for the international rules for the prevention of collisions at sea.

Combination carrier
A ship designed to carry either petroleum or dry bulk cargo.

Combustible gas indicator
An instrument used for detecting a combustible gas/air mixture. The measurement is usually presented as a percentage of the lower explosive limit (LEL).

Commingling
The intentional mixture of two oil cargoes with the intention of forming one homogeneous mixture.

Compatibility
The degree to which petroleum cargoes can be mixed without detriment to the quality of either component. Compatible cargoes can tolerate mixtures with small quantities of the other cargo without affecting required quality.

Condensate
A light crude oil obtained from the condensation of heavy vapours from a natural gas well.

Containment
Permanent and temporary arrangements intended to prevent the spread or flow of cargo overflows or spills if they should occur.

Contaminated ballast
Clean or segregated ballast containing free oil or dissolved oil in concentrations above an acceptable level.

Contamination
Unintentional mixture of two petroleum cargoes with the result that one of the cargoes no longer has the required quality or cannot be used for its intended purpose.

Contingency plan
A prepared program of actions, personnel duty assignments and important information prepared in advance of an incident and implemented to contain or reduce its effects.

COW
Crude oil washing.

Crossover
Cargo pipe sections and associated valves which connect two adjacent cargo piping systems.

PA
The 'closest point of approach' of another vessel passing one's own vessel. A full PA description includes time, bearing and distance off of the closest point while passing.

Crude oil
A naturally occurring petroleum liquid, consisting principally of different types of hydrocarbons and containing varying proportions of other substances. Unrefined petroleum.

Decant
To carefully remove the bottom water layer from a slop tank or cargo tank.

Deepwell pump
A type of centrifugal pump, installed at the bottom of a cargo tank in a large diameter vertical pipe ('deep well') which permits its removal for service or replacement.

Dehumidify
To remove part of the water vapour from air by mechanical means.

Discharge
The process of removing a petroleum cargo from a tanker to a shore terminal using the ship's pumping equipment.

Displacement
Replacing the contents of a pipeline by pumping through it an amount of cargo equal to (or nearly equal to), the total internal volume of the line.

Draft
The depth of the lowest part of the ship below the surface of the water; or the depth of the ship at a particular point along its length.

Drop
Lowering a portable tank washing machine from one washing level to the next washing level in a cargo tank.

Drop line
A cargo pipe extending from above the main deck downward to the bottom of the ship, connecting the ship's deck cargo piping to the cargo piping in the ship's tanks, used while loading to avoid flowing cargo through the pumproom.

DWT
Deadweight tonnage; the maximum amount of tonnage which can be safely carried aboard a ship at the governing loadline. DWT includes fuel, crew, water, stores and cargo.

Earthing
The electric connection of equipment to the main body of the earth to ensure that it is at earth electrical potential. On board ship, the connection is made to the main metallic structure of the ship; also called 'grounding'.

ECDIS
Electronic chart display and information system.

ECR
Engine control room.

EDG
Emergency diesel generator.

Eductor
A device which uses Bernoulli's principle to create a suction for tank stripping by means of a stream of drive fluid (usually supplied by the cargo pump discharge stream).

Emulsion
A mechanical mixture of two liquids which do not naturally mix, such as an oil-in-water emulsion. An emulsion has an internal (smaller fraction) phase and an external (larger fraction) phase. 'Mousse' which often forms as a result of a crude oil spill is an oil-in-water emulsion.

ESD
Emergency shut down - a system or process by which cargo transfer can be stopped suddenly without hazard or detriment to the vessel or terminal.

Experience factor
An average ratio of the volume of cargo on board a ship compared to the volume of cargo received from/by the corresponding shore terminal for cargoes which meet certain agreed criteria. Also known as vessel experience factor or 'VEF'.

Explosimeter
See 'Combustible gas indicator'.

Explosion proof
Electrical equipment or fixtures which are enclosed in a case which is capable of withstanding an explosion of a flammable hydrocarbon vapour/air mixture occurring within it and of preventing the ignition of an explosive vapour surrounding the fixture by sparks, flashes, external heating or explosions from the vapour within.

Explosive limits
The limits of the explosive (flammable) range of a hydrocarbon vapour and air mixture. The range between the maximum and minimum concentrations of hydrocarbon vapour in air which form explosive flammable mixtures. The limits are usually abbreviated LEL for lower explosive limit, and UEL for upper explosive limit.

Fix
A determination of the navigational position of a vessel by electronic, visual or celestial means.

Flag state
The national authority under whose jurisdiction a vessel is registered and which issues its certificate of inspection.

Flame arrester
Any device or assembly of a cellular, tubular, pressure or other type used for permitting the passage of a gas while preventing the passage of flames into an enclosed space.

Flame screen
A fitted screen of corrosion resistant wire of at least 30-by-30 (wires per inch) mesh, or two screens of 20-by-20 mesh spaced 1/2 to 3/2 inches apart, installed to permit the passage of gas but to prevent the passage of a flame into a space. 'Gauze screen'.

Flammable
Capable of being ignited and of burning in air. A 'flammable liquid' is any liquid which gives off flammable vapours at or below a temperature of 80 °F.

Flammable range
The range of conditions between the minimum and maximum concentrations of vapour in air which form explosive or burnable mixtures. The limits are usraally defined as LFL (lower flammable limit) and UFL (upper flammable limit). See 'explosive limits'.

Flange
The face plate of the end of a pipe or hose to which another hose or pipe flange can be bolted.

Flashlight
A battery operated hand lamp; a 'torch'.

Flash point
The lowest temperature at which an oil gives off sufficient vapour to form a mixture which will ignite under standard conditions.

Flushing
Cleaning a cargo or ballast pipeline of its previous contents by pumping through it an amount of fluid several times the volume of the pipeline.

Foam
The aerated solution of chemicals and water which is used for fire prevention and fire fighting.

Free fall
The uninhibited, open fall of liquid into a tank.

Gas
Hydrocarbon and other vapours from petroleum; see also 'inert gas'. A term used to cover all vapour/air mixtures.

Gas free
The condition of a confined space which has been tested using an appropriate gas indicator and found to be sufficiently free, at the time of the test, of toxic or explosive gases for a specified purpose such as manned entry, cold work, hot work, etc.

Gas oil
A fuel oil intermediate between the light distillates and heavy diesel fuels.

Gas freeing
The process of replacing a hazardous tank atmosphere with air.

Gasoline
A volatile petroleum liquid principally used as a fuel in internal combustion engines with spark ignition.

Gate valve
A valve with a sliding disc mounted perpendicular to the direction of flow in the pipeline. Gate valves provide full, unobstructed flow when fully open.

GMDSS
Global marine distress and safety system.

Gravitation
The natural flow of oil or water from one tank to another by the force of gravity alone.

Gun
A fixed (not portable) tank washing machine.

H2S
Hydrogen sulphide.

Halon
A halogenated hydrocarbon used in fire fighting; acts by inhibiting flame propagation.

Hazardous area
An area in which vapour may be present continuously or intermittently in sufficient concentrations to create a dangerous (flammable and/or toxic) atmosphere.

Heating coils
A system of small-diameter piping in the bottom of a cargo tank through which steam is admitted to heat the cargo.

Heel
A small amount of liquid intentionally left in a tank, to reduce measurement errors due to tank bottom shape, or to maintain certain tank conditions (such as the temperature of an LNG tank).

Hogging
A loaded condition of a ship in which there is an excess of weight over buoyancy at the ends and an excess of buoyancy over weight at the middle. The ship is slightly arched, with the main deck under tension and the keel under compression. The normal condition of a tanker in ballast.

Hot work
Work involving flames or temperatures likely to be sufficiently high to cause ignition of flammable gas. Includes welding, burning, soldering, grinding and use of internal combustion engines, electrically driven tools or non-explosion proof electrical equipment.

Hot work permit
A document used to control a hot work activity. It approves specified work which could produce a source of ignition at a specific location and time under controlled conditions.

Hydrocarbon gas
A gas mixture composed entirely of hydrocarbons.

Hydrometer
An instrument for determining the specific gravity of a liquid at observed temperature.

ICS
International Chamber of Shipping, London.

Impinging
Releasing a liquid or vapour under pressure in the form of a spray or stream which is directed against a surface.

IMO
International Maritime Organisation, 4 Albert Embankment, London SE1 7SR.

Incendive spark
A spark of sufficient temperatui ; and energy to ignite a flammable gas.

Incident
An event which causes, or which may have caused but for the timely intervention of the crew or good fortune, injury to the crew, vessel, or cargo, or a financial loss to the owner. Also called a 'near miss'.

Inert gas
A gas or mixture of gasses incapable of supporting combustion of hydrocarbons or otherwise react with the cargo.

Inert condition
A tank is in an inert condition when the oxygen content of the atmosphere throughout the tank does not exceed 8% by volume.

Innage
The depth of a liquid in a tank.

Insulating flange
An electrical insulating device or method of connection placed between the metallic flanges of a hose or cargo arm assembly to prevent passage of electrical current through the hose string or cargo arm.

Intrinsically safe
An electrical device or circuit which is incapable of producing a spark or thermal effect (during normal operation or by accident) with sufficient energy to ignite a prescribed gas or vapour under test conditions.

ISGOTT
International safety guide for oil tankers and terminals, as published by the ICS and OCIMF.

Lashing
A short length of small diameter natural fibre line tied between a manual valve handwhecl and the valve body or support to indicate that the valve is closed.

Lightering
Offloading cargo from a deeply laden vessel to a barge or ship to permit the vessel to enter harbour, go alongside a berth, or assist removal after stranding.

Lines
May refer either to cargo pipelines, or to vessel mooring lines, depending on the usage.

List
The tilt or inclination of a vessel to port or starboard, measured in degrees from the vertical.

Loading
Receiving cargo on board a tanker from a shore terminal, at a SPM or from another vessel.

Loading overall
Loading through hatches or deck openings by means of portable, open ended pipes or hoses, resulting in a free fall of liquid into the tank.

LOT
Load on top procedures employed for the reduction of oceanic pollution by loading crude oil cargoes on top of the residues of the previous cargo.

Lower explosive limit
The minimum concentration of vapour in air which forms a flammable or explosive mixture. (LEL).

Main suction valve
Large valves located in each cargo tank used to admit cargo from the tank into the bottom cargo lines (or from the lines into the tank whe loading).

Manifold
The cargo piping arrangement at each side of a tanker's main deck, where the inlet/outlet ends of the cargo piping, fuelling lines, and other piping are placed for connection to the shore terminal or lightering vessel piping by means of hoses or articulated arms.

Manifold valve
The cargo piping valve immediately inboard of the flange at the amidship manifold connection point.

Manning
The planning and assignment of the correct number and qualificatioi of personnel to perform a task or procedure.

MARPOL 73/78
The International Convention for the Prevention of Pollution from Ships, 1973, as modified by the protocol of 1978 adopted by the International Conference on Tanker Safety and Pollution Prevention (TSPP Conference).

MARPOL line
A small-diameter pipeline used to discharge the final cargo residues from ship's tanks and pipelines into the shore pipeline.

MCP
Main cargo pump - large centrifugal pumps used to discharge the major part of the cargo.

MSD
Marine sanitation device - a ship's sewage treatment plant.

MSDS
Marine safety data sheet - an information sheet for chemicals used on board.

MTBF
Mean time between failures.

Naked lights
Open flames or fires, exposed incandescent material or other unconfined sources of ignition.

NOR
Notice of readiness.

NPSH
Net positive suction head.

OBO
An ore-bulk-oil vessel.

OBQ
Cargo on board a tanker before loading begins.

OCIMF
Oil Companies International Marine Forum, London.

ODM
Oil discharge monitor.

Off-test
The condition of a petroleum product which does not meet its quality requirements, possibly through improper refining or contamination.

Oil
Petroleum,in crude or refined liquid form.

Oil tight
Rivetted, caulked, gasketed or welded connections or seams which prevent any leakage of oil.

Open gauging
A system which does nothing to minimise or prevent the escape of vapour from cargo tanks while the contents are being measured.

Overboard discharge
A through-hull piping connection, located above the waterline of the ship, used to discharge dirty ballast or slop water under controlled conditions.

Overflow
The accidental escape of oil cargo from a cargo tank onto the deck of the tanker.

Paraffinic
Crude oils containing significant quantities of wax in suspension.

Person in charge
The crew member (or shore terminal employee) designated by the master (or terminal executive) as the person responsible for the safe and non-polluting conduct of oil transfer operations; also called the 'responsible officer'.

Petroleum
Crude oil and liquid hydrocarbon products derived from it.

PFD
Personal flotation device, or 'life preserver'.

P&l
Protection and Indemnity; a mutual insurance organisation.

PM
Preventive maintenance.

PPE
Personal protective equipment.

Port state
The national authority of the port in which a tanker finds itself.

Potable
Water suitable for crew consumption.

Pour point
The lowest temperature at which an oil will flow or can be poured under specified test conditions.

Prime
To physically remove air or vapour from a pump, replacing it with liquid, so that the pump will operate properly.

Protest
A Note of Protest as a formal, written notification of disagreement, prepared by the master, regarding an action or situation affecting a marine venture.

PSI
Pressure measured in the English (imperial) units of pounds per square inch.

Pumproom
A compartment or space in the ship where cargo pumps and other cargo transfer machinery is located.

Purging
The removal of a tank atmosphere containing hydrocarbon vapours by use of mechanical blowers and normally by replacement with inert gas.

P/V valve
Pressure/vacuum relief valve - a dual purpose valve incorporated in the cargo tank venting system which automatically prevents excessive pressure or vacuum in the tank or tanks to which it is connected.

Reducer
A short section of tapered pipe with a large diameter opening and flange face on one end and a smaller diameter opening and flange face on the other.

Residual oil
The bottoms product from the distillation of petroleum; 'resid'.

Riser
A vertical cargo pipe extending from the bottom to the pumproom to the main deck.

ROB
Cargo 'remaining on board' when a tanker has finished discharging.

RVP
Reid vapour pressure - the vapour pressure of a liquid determined by laboratory testing in a standard manner in the Reid apparatus at a standard temperature of 38 °C.

SABA
Surface air breathing apparatus.

Sacrificial anode
A piece of metal, usually an alloy of zinc or aluminum, installed on the interior surface of a cargo or ballast tank, or on the exterior surface of the hull, for the purpose of reducing corrosion of the ship structure. See 'cathodic protection'.

Sagging
A condition of loading in which the middle portion of the ship is lower then the ends due to excess of weight over buoyancy amidship. The standard condition of a tanker when fully loaded. When a tanker is sagged, the main deck is in compression and the keel is under tension.

Salinity
The density of the water in which the ship is floating compared to the density of fresh water.

SBT
Segregated ballast tanks - a system of ballast tanks, piping and pumps which is independent of (segregated from) the cargo systems of a tanker.

Sealing
Securing a closed valve or other cargo control device with a numbered seal as a means of proving at a later time or date that the valve or device has not been opened or operated.

Sea suction
The connection or valve in a cargo or piping system which is connected to the sea chest. Used for transferring sea water into the ship (ballasting or tank washing) or for pumping clean ballast out of the ship.

Sediment
Solid or semi-solid material which settles out from water or petroleum and accumulates in the bottoms of the cargo or ballast tanks.

Segregation
Physical separation of different cargoes or products within a tanker by using separate piping systems or by maintaining designated valves closed.

Set
A group of cargo tanks loaded or discharged simultaneously.

Shut down
The immediate stop of cargo transfer operations due to malfunction, incident or uncertainty.

Slops
Residual oil which has been transferred to a collecting tank (slop tank), usually mixed with other recovered oils and/or water.

Slop tank
A tank designated to store oily waste for subsequent ecologically approved disposal.

Sludge
Deposits in the bottom of a cargo tank which may include sediment, petroleum waxes, rust scale, sand and other foreign material.

Sour crude
Crude oil containing at least 0.05 cubic feet of dissolved hydrogen sulphide (H2S), per 100 gallons of crude oil; capable of producing dangerously toxic vapours.

SOLAS
(International convention for the) Safety of Life at Sea, 1974 and its 1978 Protocol, and the 1981 and 1983 amendments.

Specific gravity
The ratio of the weight of a given volume of material at a standard temperature to the weight of an equal volume of distilled water at the standard temperature (usually 4 °C).

Spill
An accidental, uncontrolled discharge of oil from a tanker into the surrounding water due to a cargo overflow, hull leak, pipeline failure, or improper procedure.

SPM
Single point mooring - an offshore mooring buoy used for loading or discharging deep-draft vessels.

Spontaneous combustion
Ignition of a combustible material by means of accumulated heat generated by a chemical reaction within the material.

Spool piece
A short section of pipe of constant diameter with a flange face fitted to each end.

Squad
A small group of crew members selected and trained for a particular emergency or incident task.

Squat
The increase in draft of a ship in proportion to its speed through the water and the depth of the water it is in.

Stand-by
The notice time (normally 10 to 20 minutes) given by a person in charge prior to requiring stoppage of an oil transfer operation.

Static accumulator
An oil with an electrical conductivity less than 100 picoSiemens/meter (pSm), so that it is capable of retaining a significant electrostatic charge.

Static electricity
The electric charge accumulated in a material or on the surface of a material through rapid physical contact and separation of dissimilar materials (ie. oil flowing in cargo piping).

STCW
(International convention on) Standards of Training, Certification and Watchkeeping for Seafarers, 1978.

Stripping
The operation which removes the last pumpable cargo from a cargo tank or cargo pipeline; also called 'draining'.

Stripping pump
A small capacity reciprocating (or rotary) pump used to empty or drain cargo tanks after the main cargo pumps become ineffective.

Strum
A bell-shaped fitting on the end of a cargo suction pipe.

Surging
An unsteady fore-and-aft movement of a vessel in a seaway or at a berth.

Surge pressure
A sudden increase in pressure in a cargo line caused by starting a pump or by shutting off the outlet of the cargo line against flow.

Swash plate
A baffle plate or open bulkhead in a cargo tank designed to prevent excessive forces from the movement of the liquid cargo.

Terminal
Shore facilities where tankers load or discharge petroleum cargoes.

Thiefage
The amount of water under the cargo at the bottom of a cargo tank, measured as a vertical dimension (or innage).

Thieving a tank
Measuring the amount of water innage at the bottom of a tank of petroleum cargo.

TLV
Threshold limit value - the highest concentration of a harmful substance in air to which it is believed a person may be exposed for eight hours per day for an indefinite period without danger to health.

Ton
A long ton of 2240 pounds avoirdupois (16 ounces per pound).

Tonne
A metric tonne of 1000 kilograms.

Toxic
A material which has a poisonous effect on a person who inhales or ingests it.

TPI
Ton(ne)s per inch of immersion - the number of ton(ne)s which must be loaded into or removed from a ship to change the amidship draft by one inch. This may also be expressed as TPC (tonnes per centimetre).

Topping off
The operation of completing the loading of a tank to a desired ullage.

Transfer
The intentional movement of cargo, ballast, or fuel from one tank to another within a vessel.

Trim
The arithmetic difference between the forward draft and after draft of a vessel.

Trim tanks
The final tanks to be filled when loading a tanker; the levels in the tanks being adjusted to achieve the desired trim at the completion of loading.

TVP
The true vapour pressure, or absolute pressure exerted by the gas produced by evaporation from a liquid when gas and liquid are in equilibrium at ambient temperature.

UHF
Ultra-high frequency radio transmission.

Ullage
The vertical distance from the surface of the cargo in a cargo tank to the measurement or datum point for that cargo tank. Outage.

Ullage space
The space or distance between the upper surface of the cargo in a tank and the underside of the deck, or top of the tank.

UMS
Unmanned machinery space.

Vacuum pump
A pump used to evacuate air from equipment of tanks, commonly used to prime main cargo pumps and in oil spill recovery operations.

Vapour
One or more components of petroleum when in the vapour or gaseous phase.

Vapour pressure
The force exerted when a solid or liquid is in equilibrium with its own vapour at a stable temperature. May refer to the vapour pressure of one component of a mix of vapours, or to the total of the vapour pressures in a mixture at ambient temperature.

VEF
Vessel experience factor; see 'experience factor'.

Ventilation
The replacement of the atmosphere in a confined space by natural or mechanical means.

Venting
Controlled release (or intake) of gas (or air) from (into) a cargo tank by manual or mechanical action, such as by the manual opening or automatic action of a P/V valve.

Vent lines
The piping system fitted to relieve excessive pressure of vacuum conditions in a cargo tank.

VHF
Very-high frequency radio transmission.

Viscosity
The property of liquids which causes them to resist instantaneous change of shape, or instantaneous rearrangement of their parts due to internal friction. Viscosity of oils is usually express as the number of seconds required for a standard quantity of oil to from through a standard apparatus at a specified temperature. Scales and ratios of measurement include Saybolt Furol, Saybolt Universal, Engler, Redwood and Kinematic.

Volatility
The tendency of a liquid to vapourise.

VRP
Vessel response plan.

VTS
Vessel traffic service.

Watch
The group of ship's personnel assigned to perform routine duties for a specified time period. A set time period of the day during which various crew members perform their duties. A particular duty ('gangway watch'), to which a crew member has been assigned.

Work permit
A document or form which when completed authorises a specified person to perform defined work in a limited area under prescribed conditions while observing required precautions. Any variation or departure from the conditions set forth voids the permit, requiring suspension of work and amendment of the permit.