Extended Operational and Trade Vocabulary

Marine Bunker Fuels, Lubricants and Bunkering Operations glossary

The chemistry and handling of marine fuels and lubricants: flash point, viscosity, acid number, and additive packages, catalyst fines (Al+Si) capped under ISO 8217, fuel stability and accelerated aging, ullage and air gap in tank gauging, and bunkering operations with the BDN and mass flow metering. Covers the test methods and quality parameters that govern bunker quantity and quality disputes.

301 defined terms.

Showing 250 on this page (page 1 of 2).

A

Abel flash point: Closed-cup flash point test method used historically for light distillates, largely superseded by Pensky-Martens for marine fuels.
Absolute viscosity: Dynamic viscosity expressed in centipoise (cP) or millipascal-seconds (mPa.s), distinct from kinematic viscosity.
Accelerated stability test: Laboratory aging procedure such as ASTM D4625 used to predict long-term fuel stability.
Acid number: Milligrams of KOH required to neutralize the acids in one gram of oil; measured per ASTM D664 for lubricants.
Additive package: Engineered chemical blend (detergents, dispersants, anti-wear, anti-foam) added to base oil to produce a finished lubricant.
Aeration: Forced air movement through cargo to control temperature, gas, or moisture.
Aft peak bunker tank: Stern-located ballast or fuel tank used in some vessels for trim and fuel storage.
Air gap: Vertical distance from the fuel surface to the top of the tank, used in ullage measurement.
Aluminum plus silicon (Al+Si): Combined concentration of catalyst fines in residual fuel, capped at 60 mg/kg under ISO 8217:2017 for most residual grades.
Ammonia, Anhydrous: Carried refrigerated (-33 C) on fully refrigerated LPG/ammonia carriers; toxic.
AMP (Alternative Maritime Power): Shore-supplied electrical power to a berthed ship, also called cold ironing or OPS.
Annex VI: Regulations for the Prevention of Air Pollution from Ships.
API Gravity: American Petroleum Institute density scale; higher API = lighter crude.
Apparent viscosity: Viscosity of a non-Newtonian fluid at a stated shear rate, relevant for waxy or high-asphaltene fuels.
Aromatic content: Concentration of aromatic hydrocarbons; influences CCAI and ignition behavior.
Aromaticity index: Calculated indicator of aromatic character used in ignition quality assessment.
Ash content: Inorganic residue after combustion of a fuel sample, measured per ISO 6245, capped at 0.100% m/m for most residual grades.
Asphaltene: High-molecular-weight polar fraction insoluble in n-heptane, central to fuel stability and incompatibility.
ASTM D4294: Energy-dispersive X-ray fluorescence (EDXRF) test for sulphur in petroleum products.
ASTM D445: Standard test method for kinematic viscosity of transparent and opaque liquids.
ASTM D4740: Spot test for fuel cleanliness and compatibility using a filter paper procedure.
ASTM D7619: Particle count by optical microscopy for cat fines and other solids in middle distillates and residual fuel.
Autoignition temperature: Lowest temperature at which a fuel ignites without external spark, distinct from flash point.

B

Backloading: Return of unused or off-spec bunkers from ship to barge or shore tank.
Barge: Tank vessel used for bunker delivery alongside ocean-going ships in port and at anchorage.
Base number (BN): Total alkalinity reserve of a cylinder or system oil in mg KOH/g, measured per ASTM D2896.
BDN (Bunker Delivery Note): Mandatory document under MARPOL Annex VI Reg 18 listing fuel particulars, retained on board for three years.
Beam loading: Loading bunkers across the vessel's beam from an opposite-side barge.
Bell-mouth: Flared suction inlet at the bottom of a bunker tank.
Bend angle: Geometry of bunker hose lay that must avoid kinking during transfer.
Bias: Systematic error in custody-transfer measurement, addressed by MFM calibration under TR48.
Bio-VLSFO: Very low sulphur fuel oil blended with bio-components such as FAME or HVO.
Biodiesel: Fatty acid methyl ester (FAME) blendstock, restricted in legacy ISO 8217 grades but permitted in 2024 revisions.
Black oil: Trade term for residual fuels distinguishing them from clear distillates.
Blending on board: Mixing two fuels in ship tanks, generally discouraged due to stability risk.
Blending ratio: Volumetric proportion of distillate to residual used to achieve a target viscosity or sulphur content.
Boil-off gas (BOG): Vapor from LNG cargo or fuel tanks managed by reliquefaction or use.
Bottom sample: Sample drawn from the lowest accessible point of a tank.
Brookfield viscosity: Viscosity measured with a rotational viscometer, used for very viscous oils.
BS&W: Bottom sediment and water, an old quality indicator for residuals.
BSC (Bunker Survey Certificate): Independent surveyor's certificate quantifying ROB and delivered quantities.
Bunker barge captain: Master of the delivering barge, signs the BDN and JDI on the seller side.
Bunker claim: Formal commercial dispute alleging off-specification or short delivery.
Bunker hose: Reinforced flexible hose used between barge manifold and ship manifold during transfer.
Bunker plan: Pre-transfer document specifying tanks, sequence, rates, and ullages.
Bunker survey: Quantity and quality measurement at delivery and redelivery.

C

CAS number: Chemical Abstracts Service identifier used on MSDS for marine fuels and additives.
Cat fines: Aluminosilicate catalyst particles from refinery FCC units, abrasive to liners, rings, and fuel pumps.
Catalytic fines: Synonym for cat fines, measured as Al+Si per ISO 10478 or ICP-OES.
CCAI (Calculated Carbon Aromaticity Index): Ignition quality indicator for marine fuels.
CCR (Conradson Carbon Residue): Carbon residue test per ASTM D189, largely replaced by MCR.
Centistoke (cSt): Unit of kinematic viscosity, 1 cSt = 1 mm2/s.
Centrifuge: Purifier or clarifier separating water and solids from fuel and lube oil.
Cetane index: Calculated ignition quality indicator for distillate fuels, per ASTM D976 or D4737.
Cetane Number: Ignition quality indicator for diesel-type fuels.
Change-over: Operational switching between fuels of different sulphur or type, with controlled temperature and viscosity ramping.
Charterer's fuel: Bunkers supplied and paid for by the time charterer during the charter period.
Chief engineer's BDN review: Verification by the C/E of bunker quantities and specifications before signing.
CII (Carbon Intensity Indicator): IMO operational efficiency rating influenced by fuel type and consumption.
Class A methanol: IMPCA reference grade for marine methanol bunkering.
Cloud point: Temperature at which wax crystals first appear in a distillate, per ASTM D2500.
Coalescer: Filter element that merges fine water droplets for separation.
Cofferdam: Temporary watertight enclosure for construction.
Cold filter plugging point (CFPP): Lowest temperature at which a measured volume of distillate passes through a standardized filter, per EN 116.
Cold flow properties: Combined behavior of distillate fuels at low temperatures, including pour, cloud, and CFPP.
Cold Ironing: Onshore power supply enabling ships to shut down engines in port.
Combined sulphur: Total sulphur in fuel, measured per ISO 8754 or ASTM D4294.
Compatibility: Ability of two fuels to be mixed without precipitation of asphaltenes, assessed by spot test (ASTM D4740).
Composite sample: Continuous drip sample collected throughout the bunker transfer.
COQ (Certificate of Quality): Document issued by the supplier or testing lab stating measured fuel properties.
Cryogenic hose: Vacuum-insulated transfer hose for LNG bunkering.
Custody Transfer: Quantity measurement event when cargo title passes ship/shore.
CWA 15375: CEN Workshop Agreement for LNG as marine fuel quality.
Cylinder oil: High-BN lubricant feeding the cylinder liners of two-stroke crosshead engines.
Cylinder oil feed rate: Lubricant consumption expressed in g/kWh, typically 0.6 to 1.2 g/kWh on modern slow-speed engines.

D

Dead freight: Charge for unused bunker capacity reserved but not delivered.
Debunkering: Removal of off-spec or unwanted fuel from ship tanks back to barge or shore.
Delivered density at 15 C: Mass per unit volume at the reference temperature, reported on the COQ.
Density at 15 C: Reference density used in petroleum volume corrections.
Detergent: Lubricant additive that neutralizes acidic combustion products and keeps deposits in suspension.
Dispersant: Chemical applied to oil spills to break oil into smaller droplets.
Distillate fuel: Fraction produced by atmospheric or vacuum distillation, including DMA, DMB, DMX, and DMZ grades.
DMA: ISO 8217 distillate marine grade A, gas oil equivalent, sulphur limited per regional ECA rules.
DMB: Distillate grade B, blended distillate with limited residual contamination.
DMX: Distillate grade X with the highest flash point flexibility for emergency engines.
DMZ: Distillate grade with higher minimum viscosity than DMA for engines requiring lubricity.
DNV PS (Petroleum Services): Bunker fuel testing service operated by DNV.
Drip sample: Sample continuously drawn at constant rate during bunker transfer via a sampling cock at the ship manifold.
Drip tray: Containment beneath manifold connections to catch spills during bunkering.
Dry-break coupling: Self-sealing coupling preventing spillage on disconnection, common in LNG and methanol transfer.

E

ECA (Emission Control Area): Designated sea area with stricter sulphur (0.10% m/m) and NOx limits under MARPOL Annex VI.
EDXRF: Energy-dispersive X-ray fluorescence used for sulphur and metals analysis in fuels.
EEDI: Energy Efficiency Design Index, MARPOL Annex VI Chapter 4.
EEXI: Energy Efficiency Existing Ship Index, MARPOL Annex VI Chapter 4.
EGCS (Exhaust Gas Cleaning System): Scrubber technology allowing compliant operation on HSFO under MARPOL Annex VI.
Elemental analysis: Determination of trace elements such as V, Na, Al, Si, Ca, Zn, Fe by ICP-OES.
EN 14214: European standard for FAME used as automotive fuel; reference for marine biodiesel components.
EN 590: European standard for automotive diesel, sometimes used as a reference for DMA-like marine grades.
Equilibrium temperature: Storage temperature at which a residual fuel remains stable and pumpable.

F

FAME (Fatty Acid Methyl Ester): Biodiesel component; capped or allowed depending on ISO 8217 edition and grade.
FCC slurry oil: Refinery stream rich in cat fines, occasionally blended into residual fuels.
Filterability: Ability of fuel to pass through engine filters without clogging.
Final boiling point (FBP): Highest distillation temperature for a distillate fuel.
Fire point: Lowest temperature at which a fuel sustains burning after ignition.
Flash point: Lowest temperature at which fuel vapor ignites with a pilot flame; minimum 60 C for SOLAS marine fuels (Pensky-Martens closed cup, ISO 2719).
FOBAS: Lloyd's Register Fuel Oil Bunker Analysis and Advisory Service.
FONAR (Fuel Oil Non-Availability Report): Document submitted under MARPOL Annex VI Reg 18.2.4 when compliant fuel cannot be obtained.
Forward bunker tank: Forward-located fuel storage tank.
Fuel changeover procedure: Documented stepwise procedure to switch fuel grades within engine and boiler limits.
Fuel oil quality dispute: Commercial and regulatory process under MARPOL Annex VI Reg 18.
Fuel system cleanliness: Absence of sediment, water, and cat fines in the fuel after centrifuging and filtration.
Fuel treatment: Onboard processes including settling, centrifuging, filtration, and heating.

G

Gas oil: Distillate fuel including MGO and DMA grades.
GCMS (Gas Chromatography Mass Spectrometry): Analytical technique used to detect chemical contaminants in fuel.
General Terms and Conditions (GTC): Standard contractual terms governing bunker supply.
Glycerol: By-product of biodiesel manufacture, capped at trace levels in FAME-blended marine fuels.
Grade: ISO 8217 product designation such as RMG 380 or DMA.
Gravimetric analysis: Mass-based test method, used for sediment and ash determinations.

H

H2S (Hydrogen sulphide): Toxic gas in fuel vapor space; ISO 8217 limit 2 mg/kg in liquid phase per IP 570.
Heated tank: Bunker tank fitted with steam or thermal-oil coils to maintain residual fuel pumpability.
High Speed Diesel (HSD): Distillate used by high-speed engines, similar to road diesel.
HSFO (High Sulphur Fuel Oil): Residual fuel with sulphur above the 0.50% m/m global cap, usable only with an approved scrubber.
HVO (Hydrotreated Vegetable Oil): Renewable diesel produced by hydroprocessing fats and oils, fully compatible with conventional distillate systems.
Hydrogen, liquid (LH2): Cryogenic fuel under development, stored at -253 C.
Hydroprocessed renewable diesel: Synonym for HVO.

I

ICP-OES: Inductively coupled plasma optical emission spectrometry, used for trace metals.
IFO 180: Intermediate Fuel Oil with nominal viscosity 180 cSt at 50 C, residual blend.
IFO 380: Intermediate Fuel Oil with nominal viscosity 380 cSt at 50 C, historically the dominant residual grade.
Ignition delay: Time between fuel injection and combustion onset, measured on FIA fuel ignition analyzers.
Ignition quality: Combined behavior of ignition delay and combustion progression, indicated by CCAI for residuals and cetane for distillates.
IMPCA Methanol Reference Specifications: International Methanol Producers and Consumers Association quality reference for marine methanol.
In-line blending: Mixing components during transfer rather than in a static tank.
Inerting: Replacing tank atmosphere with inert gas (N2, IG) below 8% O2 for tankers, 5% for chemicals.
Initial boiling point (IBP): Lowest distillation temperature for a distillate fuel.
Inspector: Independent surveyor representing buyer or seller during bunker transfer.
Intermediate Fuel Oil (IFO): Older trade term for residual blends 180 and 380 cSt.
IP 375: Manual sampling procedure for petroleum liquids.
IP 501: ICP-OES method for trace metals in residual fuel oil.
IP 570: Test method for H2S in liquid phase of residual fuel.
ISO 10307-1: Total sediment by hot filtration (TSP).
ISO 10307-2: Total sediment after thermal aging (TSA).
ISO 10478: Determination of aluminum and silicon in fuel oil by ICP-OES or AAS.
ISO 12185: Density by oscillating U-tube.
ISO 3104: Kinematic viscosity by capillary viscometer.
ISO 3675: Density by hydrometer.
ISO 3733: Water content by distillation.
ISO 4259: Statistical interpretation of test data for petroleum products, used to assess spec compliance with precision.
ISO 8216-1: Classification of petroleum products for marine use.
ISO 8217: International standard for marine fuel oil specifications.
ISO 8754: Sulphur in petroleum products by EDXRF.

J

JDI (Joint Declaration of Inspection): Pre-transfer checklist signed by master and barge officer covering hose connection, communications, and safety.
Jetting agent: Slop or fines-removal product used in fuel tank cleaning, not in fuel itself.
Joint sampling: Drip sampling witnessed by both supplier and receiver representatives.

K

K-value: Olefin Floc test indicator of asphaltene stability used in marine fuel laboratories.
Kappa number: Refinery term, not applicable to marine fuels but sometimes confused with K-value.
Kinematic viscosity: Ratio of dynamic viscosity to density, expressed in cSt; ISO 8217 specifies viscosity at 50 C for residuals and at 40 C for distillates.

L

Lab sample: Portion of the bunker drip sample sent to a testing laboratory.
Layered loading: Condition in which incompatible fuels form distinct strata in the tank.
Lead time: Notice period between bunker nomination and delivery.
LFL (Lower Flammability Limit): Lowest vapor concentration that supports combustion in air.
Light Cycle Oil (LCO): Refinery cargo, dirty product.
Liner wear: Cylinder liner abrasion accelerated by cat fines or insufficient BN.
LLOSP: Lowest level of suction at the bunker tank during stripping.
LNG bunker spec: Quality requirements drawn from ISO 23306 and CWA 15375 for LNG used as marine fuel.
LNG Bunkering: Process of supplying liquefied natural gas as marine fuel.
Loss control: Procedures and instrumentation to minimize quantity disputes.
Low Speed Diesel (LSD): Slow-speed crosshead engine driving the propeller directly.
LSFO: Low Sulphur Fuel Oil, generic term for residuals at or below 1.00% m/m sulphur.
Lubricator: Mechanical or electronic device feeding cylinder oil through quills into the liner.

M

Manifold: Pipe assembly at the ship side where bunker hoses connect.
Marine Diesel Oil (MDO): Blend of distillate and a small fraction of residual, similar to DMB.
Marine gas oil (MGO): DMA distillate fuel per ISO 8217.
MARPOL Annex VI Reg 14: Sulphur content of fuel oil global cap (0.50% m/m) and ECA cap (0.10% m/m).
MARPOL Annex VI Reg 18: Fuel oil availability and quality, BDN, sampling, and FONAR.
Mass Flow Meter (MFM): Bunkering meter used in Singapore and elsewhere for accurate measurement.
Master's protest letter: Formal note of disagreement issued by the master at delivery, often on quantity or sample handling.
MCR (Micro Carbon Residue): Carbon residue test per ISO 10370, modern replacement for CCR.
MEPC.182(59): IMO Guidelines for sampling of fuel oil for determination of compliance with MARPOL Annex VI.
MEPC.320(74): 2019 IMO Guidelines for consistent implementation of the 0.50% sulphur limit.
MEPC.96(47): IMO Guidelines for in-use fuel oil sampling.
Methanol IMPCA grade A: Reference specification used for marine methanol bunkering.
MFM bunkering: Bunker delivery using Coriolis mass flow meters under Singapore TR48 procedures.
Micro-organisms in fuel: Bacteria and fungi that grow at fuel-water interfaces, causing sludge and corrosion.
Microscopic examination: Test for water-in-fuel emulsion droplets and solids.
Middle distillate: Refinery fraction between kerosene and vacuum gas oil, encompassing marine distillates.
Minimum ignition energy: Lowest spark energy igniting a vapor mixture, critical for methanol and LNG safety.
MSDS (Material Safety Data Sheet): Document accompanying each bunker delivery describing hazards and handling.

N

Naphthenic acid: Carboxylic acid present in some crudes, contributing to TAN and corrosivity.
Nominal viscosity: Trade reference viscosity such as 380 or 180 cSt at 50 C.
Nomination: Buyer's request to a supplier for a specified quantity and grade of bunkers at a stated port.
Non-availability claim: Buyer claim against supplier when compliant fuel is not delivered.
NOR (Notice of Readiness): Ship's notification at port that it is ready to bunker.
NOx Technical Code: Issued under MARPOL Annex VI.

O

Off-spec bunker: Fuel found to deviate from contractual or ISO 8217 limits after testing.
Off-take meter: Meter at the bunker barge measuring delivered volume or mass.
Oil Record Book Part I: Machinery space operations on all ships of 400 GT and above.
Olefin content: Unsaturated hydrocarbons in fuel, contributing to instability.
Onboard sampling point: Approved location on the receiving line for collecting MARPOL samples.
OPS (Onshore Power Supply): Shore power connection enabling main and auxiliary engine shutdown at berth.
Oxidation stability: Resistance of fuel to degradation by oxygen, measured by ASTM D2274 for distillates.

P

Particulate matter (PM): Solids emitted in exhaust, influenced by fuel ash and residue.
Pensky-Martens flash point: Closed-cup test per ISO 2719, the SOLAS reference for marine fuel flash point.
Phosphorus: Element measured in lubricants as anti-wear additive (ZDDP) indicator; restricted in marine fuels.
Pilot Fuel: Small amount of conventional fuel igniting alternative fuel in dual-fuel engines.
Pipe stripping: Final draining of bunker hose into ship tank at end of transfer.
Pour Point: Lowest temperature at which oil flows; key to heating decisions.
Pour point depressant: Additive lowering pour point of waxy distillates.
Pre-arrival fuel oil sampling: Sampling required when entering ECAs to confirm compliant changeover.
Pre-transfer conference: Discussion between master, C/E, and barge captain before bunkering begins.
Pressure surge: Hydraulic shock during transfer that can rupture hoses or manifolds.
Pump stack: Vertical arrangement of transfer pumps on a bunker barge.
Purifier: Centrifuge with water seal removing free water and solids from fuel oil.

Q

Quality claim: Commercial dispute alleging the fuel does not meet contractual or ISO 8217 limits.
Quantity claim: Dispute over delivered mass or volume, often resolved by surveyor measurements.
Quenched sample: Fuel sample cooled rapidly to preserve volatile properties.

R

Receiving tank: Ship tank designated to take bunkers in the bunker plan.
Renewable Diesel: Drop-in diesel produced from biomass-derived oils.
Residual fuel: Heavy residual marine fuel grades RMG/RMK.
Retain sample: Sample retained by a party for future analysis or arbitration.
RMA 10: ISO 8217 residual grade with maximum viscosity 10 cSt at 50 C.
RMB 30: Residual grade with maximum viscosity 30 cSt at 50 C.
RMD 80: Residual grade with maximum viscosity 80 cSt at 50 C.
RME 180: Residual grade with maximum viscosity 180 cSt at 50 C, low residue.
RMG 180: Residual grade with maximum viscosity 180 cSt at 50 C.
RMG 380: Residual grade with maximum viscosity 380 cSt at 50 C, the workhorse pre-2020 HSFO.
RMG 500: Residual grade with maximum viscosity 500 cSt at 50 C.
RMG 700: Residual grade with maximum viscosity 700 cSt at 50 C.
RMK 380: Higher-density residual grade, max density 1010 kg/m3 at 15 C.
RMK 500: RMK grade at 500 cSt nominal viscosity.
RMK 700: RMK grade at 700 cSt nominal viscosity.
ROB (Remaining On Board): Quantity of fuel in tanks at the moment of survey.
Round trip sample: Sample handed to supplier and returned unopened, used in some custody-transfer regimes.

S

Sample seal: Tamper-evident seal applied to bunker samples with unique numbering.
Sampler: Person or device collecting bunker samples at the receiving manifold.
Sampling cock: Valve installed in the receiving line for drip sampling.
Sampling probe: Device extending into the flowing fuel for representative sampling.
Saybolt color: Color rating for distillate fuels, per ASTM D156.
Scavenge drain analysis: Quantification of iron, BN, and Al+Si in cylinder scavenge oil to tune feed rate.
Sediment by extraction: Older sediment determination by hot solvent washing.
Sediment by hot filtration: Total sediment determined per ISO 10307-1 (TSP).
Sediment, total existent: Sediment present at time of test before aging.
Settled water: Free water in tank bottom available for stripping.
Settling tank: Heated tank that allows water and solids to fall out before centrifuging.
SFOC (Specific Fuel Oil Consumption): Engine fuel consumption in g/kWh corrected to ISO conditions.
Shipboard incinerator: Approved unit for burning sludge, oily waste, and ROB cleaning residues.
Short delivery: Quantity of fuel received less than the BDN figure.
Singapore TR48: Technical Reference for bunker mass flow metering in the Port of Singapore.
Sludge: Water, sediment, and cat fines discharged from purifiers, logged in Oil Record Book.
Sodium: Element in fuel acting alongside vanadium to cause high-temperature corrosion.
Soot: Carbonaceous solid from incomplete combustion, contaminant of system oil.