Extended Operational and Trade Vocabulary

Marine Fuel Quality and ISO 8217 glossary

The fuel-quality vocabulary anchored in ISO 8217: abrasive wear from catalyst fines, accelerated and aged total sediment (ISO 10307-2), total acid number, additive treatment, and the stability and ignition parameters that grade a residual or distillate. Grounds each term in the ISO test method and the specification limit it reports.

321 defined terms.

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

A

Abrasive wear: Mechanical wear of liners, rings, and fuel injection equipment caused by hard particles such as catalytic fines in residual fuel.
Accelerated total sediment (TSA): Sediment content of a residual fuel measured by ISO 10307-2 Procedure A after aging at 100 C, used as a stability indicator.
Acid number: Milligrams of KOH required to neutralize the acids in one gram of oil; measured per ASTM D664 for lubricants.
Additive treatment: Dosing of cold flow improvers, stability dispersants, or combustion catalysts into bunker fuel to modify handling or burning characteristics.
Aged sediment: Sediment that develops in a fuel sample after thermal or chemical aging, distinguishing unstable fuels from those merely carrying existing solids.
Air release: Time taken for entrained air to escape from a fuel under controlled conditions, governed by ISO 9120 for hydraulic fluids and adapted informally for marine distillates.
Alcap: Alfa Laval self-monitoring separator system that adjusts discharge intervals based on water transducer signal at the clean oil outlet.
Alfa Laval: Swedish manufacturer of marine centrifugal separators including the MAB, MAPX, MMPX, MOPX, S, and P-Flex ranges.
Aluminum + silicon: Combined mass fraction of Al and Si in residual fuel, expressed in mg/kg, used as the ISO 8217 proxy for catalytic fines.
Ammonia bunker: Anhydrous ammonia (NH3) supplied as marine fuel for dual-fuel two-stroke engines, with a quality standard under development at ISO TC 28.
Anti-foaming agent: Silicone or polyacrylate additive used to suppress foam during bunkering and tank stripping.
API Gravity: American Petroleum Institute density scale; higher API = lighter crude.
Aromatic hydrocarbons: Ring-structured molecules abundant in residual fuel that raise CCAI and reduce ignition quality.
Asphaltenes: High molecular weight polar fractions of residual fuel insoluble in n-heptane, central to fuel stability and sludge formation.
ASTM D1298: Density, relative density, or API gravity by hydrometer.
ASTM D1796: Water and sediment in fuel oils by centrifuge.
ASTM D189: Conradson carbon residue test method.
ASTM D240: Bomb calorimeter test method for gross heat of combustion.
ASTM D2622: Sulfur in petroleum products by wavelength dispersive X-ray fluorescence.
ASTM D2709: Water and sediment in middle distillate fuels by centrifuge.
ASTM D287: Hydrometer method for API gravity of crude and petroleum products.
ASTM D3279: Standard test method for n-heptane insolubles.
ASTM D4052: Density and relative density of liquids by digital density meter.
ASTM D4176: Free water and particulate contamination in distillate fuels by visual inspection.
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 D4530: Micro method for determining carbon residue.
ASTM D473: Sediment in crude oils and fuel oils by extraction.
ASTM D4737: Calculated cetane index by four-variable equation.
ASTM D4739: Base number determination by potentiometric titration.
ASTM D4740: Spot test for fuel cleanliness and compatibility using a filter paper procedure.
ASTM D482: Standard test method for ash from petroleum products.
ASTM D4870: Determination of total sediment in residual fuels.
ASTM D524: Ramsbottom carbon residue test method.
ASTM D5291: Instrumental determination of carbon, hydrogen, and nitrogen.
ASTM D6304: Karl Fischer coulometric water determination.
ASTM D6469: Standard guide for microbial contamination in fuels and fuel systems.
ASTM D664: Standard test method for acid number of petroleum products by potentiometric titration.
ASTM D7039: Sulfur in gasoline and diesel fuel by monochromatic wavelength dispersive XRF.
ASTM D7094: Flash point by modified continuously closed cup tester.
ASTM D7212: Low-sulfur determination by energy dispersive XRF.
ASTM D86: Standard test method for atmospheric distillation of petroleum products, used for distillate marine fuels.
ASTM D93: Pensky-Martens closed cup test method for flash point of petroleum products.
ASTM D97: Standard test method for pour point of petroleum products.
ASTM D976: Calculated cetane index method for distillate fuels.
Atmospheric residue: Bottoms fraction from atmospheric distillation that forms the backbone of most heavy fuel oil blends.
Auto Ignition Temperature: Minimum temperature at which a substance ignites without external flame.

B

Back-end loss: Heat loss through exhaust gas attributable to incomplete combustion or low fuel quality.
Barge nomination: Operational instruction confirming the bunker barge and supply window agreed under the bunker contract.
BDN: Bunker delivery note required under MARPOL Annex VI.
Bicycloalkanes: Saturated two-ring hydrocarbons present in middle distillates affecting cold flow behavior.
BIMCO Bunker Terms 2018: Standard contractual terms published by BIMCO governing bunker sales, sampling, claims, and quality disputes.
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.
Biofouling of fuel: Microbial growth at the fuel-water interface in storage tanks, particularly in distillates with FAME content.
Biofuel grade: Marine fuel containing biogenic blendstocks, addressed in ISO 8217:2017 by allowing up to 7 percent FAME in DF grades.
Blending: Combining base stocks of differing properties to meet a sales specification, performed at refinery, terminal, or in-line during bunkering.
Boiling range: Temperature interval over which a fuel distills, controlled in distillates by ASTM D86 cut points.
Bomb calorimetry: Measurement of gross calorific value by combustion in an oxygen-pressurized bomb per ASTM D240 or ISO 1928.
Bottom Water: Water occupying the lowest layer of the ocean above the seabed.
Bunker barge: Tanker delivering fuel oil, MGO, or LNG to a cruise ship at berth or at anchor.
Bunker contract: Sale and purchase agreement covering grade, quantity, price, delivery location, and quality terms for marine fuel.
Bunker Delivery Note (BDN): Required under MARPOL Annex VI Regulation 18.
Bunker Quantity Survey: A measurement exercise to determine the quantity of fuel oil on board before and after bunkering, including soundings, temperature, and density corrections.
Bunker sample: MARPOL sample sealed at the manifold during bunkering, retained for 12 months.
Bunker survey: Quantity and quality measurement at delivery and redelivery.
Bunker Tanker: Small tanker delivering fuel to ships.
Bureau Veritas Fuel Testing: Marine fuel testing service operated by Bureau Veritas providing ISO 8217 conformity reports.
Burning quality: General term for the ease and completeness with which a fuel ignites and burns, captured for distillates by cetane index and for residuals by CCAI.
Butyl rubber: Elastomer used in some fuel handling hoses, compatible with hydrocarbons but degraded by aromatic-rich residues.

C

Calculated carbon aromaticity index (CCAI): Indicator of residual fuel ignition quality derived from density at 15 C and kinematic viscosity at 50 C, with values typically 800 to 870.
Calculated cetane index (CCI): Distillate fuel ignition quality estimate calculated from density and distillation data per ASTM D976 or D4737.
Calculated ignition index (CII): Alternative residual fuel ignition quality index using density and viscosity, related to but distinct from CCAI.
Calibrated tank table: Tank capacity table relating sounding to volume, prepared by a class-approved surveyor and used in bunker quantity surveys.
Calorific value: Heat released on complete combustion of a unit mass of fuel, reported as gross or net.
Carbon residue: Carbonaceous deposit remaining after evaporation and pyrolysis of a fuel, measured by Conradson, Ramsbottom, or micro methods.
Cat fines: Aluminosilicate catalyst particles from refinery FCC units, abrasive to liners, rings, and fuel pumps.
Centrifugal separator: Rotating bowl device that uses density difference to remove water and solids from fuel, with disc stack configurations dominating marine practice.
Cetane index: Calculated ignition quality indicator for distillate fuels, per ASTM D976 or D4737.
Cetane Number: Ignition quality indicator for diesel-type fuels.
Changeover procedure: Sequence for switching engine and boiler fuel between residual and distillate grades, controlling temperature gradient and viscosity.
Clarifier: Centrifugal separator configured for solids removal only, with a sealed bowl and no water outlet.
Cleanliness: Combined assessment of compatibility, stability, and absence of foreign matter in a fuel sample.
Cloud point: Temperature at which wax crystals first appear in a distillate, per ASTM D2500.
Cold filter plugging point (CFPP): Lowest temperature at which a measured volume of distillate passes through a standardized filter, per EN 116.
Cold flow improver: Additive that modifies wax crystal size to lower CFPP and pour point.
Combustion catalyst: Metallic additive intended to improve burnout of carbon-rich residual fuels in main engine cylinders and boilers.
Compatibility: Ability of two fuels to be mixed without precipitation of asphaltenes, assessed by spot test (ASTM D4740).
Compatibility spot test: ASTM D4740 procedure assessing residual fuel compatibility by depositing a heated drop on filter paper and rating against reference spots.
Conradson carbon residue (CCR): Carbon residue measured per ASTM D189 or ISO 6615 after destructive distillation.
Continuous drip sampler: In-line sampling device taking a small flow from the bunker hose throughout delivery to build a representative composite sample.
CORDOR sampler: Brand of fuel oil drip sampler used during bunker deliveries.
Corrosion: Electrochemical deterioration of metals through interaction with their environment.

D

Density at 15 C: Reference density used in petroleum volume corrections.
Disc stack: Series of conical separator discs in a centrifugal purifier creating thin layers for efficient phase separation.
Distillation curve: Plot of temperature against recovered volume during ASTM D86 distillation of a fuel sample.
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 VPS: See VPS.
Doctor test: Qualitative test for sulfur-containing mercaptans in distillate fuel.
Drip sampler: Sampling device that collects a continuous proportional fraction of the bunker stream throughout delivery.
Dual-fuel changeover: Operational switch between fuel grades for SECA compliance or engine reliability, requiring viscosity and temperature management.

E

Elemental analysis: Determination of trace elements such as V, Na, Al, Si, Ca, Zn, Fe by ICP-OES.
Emulsified water: Water dispersed as fine droplets in fuel, stabilized by surfactant components, resistant to settling and gravity separation.
End point: Highest temperature recorded during ASTM D86 distillation, indicating heavy tail content of a distillate.
Energy density: Heat released per unit mass or per unit volume of fuel, central to bunker economics.
Engine room daily log: Record of bunker consumption, tank levels, and fuel quality observations maintained under ISM requirements.
EPA Tier: US regulatory tiers for marine engine emissions parallel to IMO NOx Tiers, requiring fuel quality compatible with aftertreatment.
Equivalent black carbon: Soot emission indicator influenced by aromatic content and combustion completeness.
Ethylene-vinyl acetate: Common base polymer for cold flow improver additives.
Existent gum: Non-volatile residue formed in a distillate during accelerated evaporation, indicating oxidation tendency.

F

FAME: See Biodiesel.
Fingerprint analysis: Use of GC-MS or FTIR to identify chemical signatures distinguishing contaminated bunker fuel from compliant material.
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).
Fluid catalytic cracker (FCC): Refinery unit that produces gasoline and gas oil while shedding alumina-silica catalyst particles into slurry oil used in residual fuel blending.
FOBAS: Lloyd's Register Fuel Oil Bunker Analysis and Advisory Service.
Foreign water: Water in fuel arriving in addition to that present at the refinery, often from barge tanks, hoses, or condensation.
Free water: Visible water phase distinct from fuel, settling at tank bottoms.
Fuel changeover calculator: Tool computing time and temperature profile for safe transition between HFO and MGO around viscosity and thermal stress limits.
Fuel cleaning system: Complete settling, purifier, clarifier, and filter train preparing residual or distillate fuel for engine use.
Fuel oil treatment plant: Combined heating, separating, and filtering installation upstream of the fuel injection system.

G

Gas oil: Distillate fuel including MGO and DMA grades.
GC-MS: Gas chromatography mass spectrometry used to identify trace chemical contaminants in off-specification bunker fuel.
GEA Westfalia: German manufacturer of marine centrifugal separators including the OSE, OSD, and Unitrol ranges.
Gear oil contamination: Used lubricant intentionally or accidentally blended into marine fuel, detectable by elevated calcium, zinc, and phosphorus.
Gravity disc: Sized ring in a conventional purifier that defines the position of the oil-water interface based on fuel density.

H

Heating coil: Steam or thermal-oil coil in a fuel tank used to maintain residual fuel at pumpable viscosity.
Heating value: See calorific value.
HFO: Heavy fuel oil, residual marine fuel grade per ISO 8217 RMG and RMK.
High-pressure fuel pump: Engine-driven plunger pump delivering fuel to injectors at injection pressure, sensitive to viscosity and cat fines.
Homogeniser: In-line device using shear or ultrasonic energy to disperse asphaltenes and reduce settling in residual fuel.
Hot filter test: Filtration check at elevated temperature used to detect sediment that precipitates during fuel heating.
Hydrogen content: Mass fraction of hydrogen in fuel, correlating with calorific value and CO2 emission factor.
Hydrogen sulfide (H2S): Toxic gas dissolved in residual fuel, capped at 2 mg/kg in the liquid phase by ISO 8217 to limit occupational exposure.
Hydrotreated Vegetable Oil (HVO): Renewable diesel often used as drop-in marine fuel.

I

ICP-OES: Inductively coupled plasma optical emission spectrometry, used for trace metals.
Ignition delay: Time between fuel injection and combustion onset, measured on FIA fuel ignition analyzers.
IMO 2020: 0.50% sulfur cap on marine fuels; not a GHG measure but driving fuel mix changes.
IMO data collection system (DCS): Reporting framework that captures fuel oil consumption and CO2 emissions by fuel type, intersecting with bunker quality records.
In-line blender: Equipment that combines base streams during loading to achieve a sales specification without batch tank mixing.
Inspectorate: Bureau Veritas group company providing bunker quantity survey and sampling services worldwide.
Intertek Lintec: Marine fuel testing service within the Intertek group offering ISO 8217 analysis.
IP 15: Pour point test method published by the Energy Institute.
IP 309: Cold filter plugging point determination.
IP 336: Sulfur determination by energy dispersive XRF.
IP 34: Pensky-Martens closed cup flash point test method.
IP 380: Determination of total sediment in residual fuel oils, equivalent to ISO 10307-1.
IP 470: Aluminum, silicon, vanadium, nickel, iron, calcium, sodium, and zinc determination by ICP-OES.
IP 501: ICP-OES method for trace metals in residual fuel oil.
IP 570: Test method for H2S in liquid phase of residual fuel.
IP 575: Acid number of residual fuels by potentiometric titration.
IP 71: Kinematic viscosity test method aligned with ISO 3104 and ASTM D445.
ISO 10307-1: Total sediment by hot filtration (TSP).
ISO 10307-2: Total sediment after thermal aging (TSA).
ISO 10370: Determination of carbon residue by micro method.
ISO 10478: Determination of aluminum and silicon in fuel oil by ICP-OES or AAS.
ISO 12185: Density by oscillating U-tube.
ISO 12937: Water in petroleum products by coulometric Karl Fischer titration.
ISO 14596: Sulfur determination by wavelength dispersive XRF.
ISO 20846: Sulfur determination by ultraviolet fluorescence.
ISO 20884: Sulfur determination by wavelength dispersive XRF.
ISO 3104: Kinematic viscosity by capillary viscometer.
ISO 3675: Density by hydrometer.
ISO 3733: Water content by distillation.
ISO 3735: Sediment in crude oils and fuel oils by extraction.
ISO 3837: Hydrocarbon group analysis by fluorescent indicator adsorption.
ISO 3924: Boiling range distribution of petroleum fractions by gas chromatography.
ISO 4259: Statistical interpretation of test data for petroleum products, used to assess spec compliance with precision.
ISO 4264: Calculation of cetane index of middle distillate fuels by four-variable equation.
ISO 6245: Determination of ash from petroleum products.
ISO 6296: Water in petroleum products by potentiometric Karl Fischer titration.
ISO 6615: Conradson carbon residue determination.
ISO 8217: International standard for marine fuel oil specifications.
ISO 8217:1987: First edition of the marine fuel standard establishing the RM and DM grade framework.
ISO 8217:1996: Second edition refining viscosity classes and introducing tighter cat fines control.
ISO 8217:2005: Third edition aligning sulfur limits with then-current MARPOL Annex VI provisions.
ISO 8217:2010: Fourth edition introducing the 60 mg/kg aluminum plus silicon cap and revised stability requirements.
ISO 8217:2012: Fifth edition addressing biofuel allowance in distillate grades and adding hydrogen sulfide control.
ISO 8217:2017: Sixth edition with renumbered distillate grades, DFA/DFZ/DFB FAME-containing grades, and updated stability/cleanliness requirements.
ISO 8754: Sulphur in petroleum products by EDXRF.

K

Karl Fischer titration: Coulometric or volumetric water determination per ISO 12937 or ASTM D6304.
Kinematic viscosity at 40 C: Equivalent measurement for distillate fuels per ISO 3104 or ASTM D445.
Kinematic viscosity at 50 C: Resistance to flow under gravity of a residual fuel at 50 C, reported in cSt or mm2/s and defining RM grade classes.

L

LCO: Light cycle oil from FCC, a refinery blendstock contributing aromatic content to VLSFO blends.
LFO: Light fuel oil, an informal regional term broadly equivalent to MDO or RMA grades depending on market.
LIMS: Laboratory information management system used by bunker testing laboratories to handle sample logistics and reporting.
LNG bunker: Liquefied natural gas supplied at approximately minus 162 C as marine fuel, with quality addressed in ISO/TS 18683 and ISO 23306.
Low sulfur fuel oil: Residual fuel meeting a defined sulfur cap below the global 0.50 percent limit but above the 0.10 percent SECA limit.
Low sulfur marine gas oil (LSMGO): Marine gas oil with sulfur content at or below 0.10 percent for SECA compliance.
Lubricity: Capacity of a fuel to reduce friction in close-tolerance metal pairs, measured by ISO 12156-1 high frequency reciprocating rig.

M

Manual Sounding: Tape based liquid measurement when remote gauging is unavailable.
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: Air pollution and energy-efficiency annex.
MARPOL retained sample: Sealed sample of delivered fuel retained on board for at least 12 months for compliance verification, minimum volume 400 mL.
Mass flow meter: MFM, custody transfer meter required for bunkering in Singapore and other ports.
MCR: Maximum continuous rating, the highest power for continuous operation.
MEK 11: Designation associated with Mitsubishi self-cleaning centrifugal separator models in marine fuel and lube oil service.
MEPC.182(59): IMO Guidelines for sampling of fuel oil for determination of compliance with MARPOL Annex VI.
MEPC.184(59): IMO Marine Environment Protection Committee resolution setting the 2009 Guidelines for exhaust gas cleaning systems, complementary to bunker quality controls.
MEPC.320(74): 2019 IMO Guidelines for consistent implementation of the 0.50% sulphur limit.
Mercaptan: Reactive curing agent class used in fast-cure epoxy primers for low-temperature application.
Methanol bunker: Methanol (CH3OH) supplied as marine fuel for dual-fuel engines, with quality covered by IMPCA reference and informed by ISO TC 28 work in progress.
Microbial contamination: Bacteria, yeasts, and molds growing at the fuel-water interface, particularly in distillates and FAME blends.
Microcarbon residue (MCR): See MCR.
Mid-cut: Distillation fraction taken from the middle of a crude tower, the basis for many marine distillate grades.
Mitsubishi Selfjector: Mitsubishi Kakoki self-cleaning marine centrifugal separator range used for residual fuel and lube oil treatment.
Mol percent: Composition expression used for gaseous fuels such as LNG bunker, with methane number derived from molar composition.

N

n-Heptane addition: Reagent step in spot test or sediment procedures used to precipitate asphaltenes.
Naphthalene: Two-ring aromatic compound contributing to combustion soot in residual fuels.
Nickel: Trace metal in residual fuel, generally non-corrosive but indicative of crude origin and significant for SCR catalyst poisoning.
Non-compliant fuel: Bunker that fails to meet the agreed grade or a statutory limit such as the 0.50 percent sulfur cap.
NOx Tier: IMO emission tiers for marine engines, set by build date and operating area, dependent on fuel and engine tuning.
Nuclear magnetic resonance (NMR): Spectroscopic technique used in some advanced bunker laboratories for asphaltene structural characterization.

O

Off-specification fuel: Bunker that does not meet a specified parameter on test, triggering claims under the bunker contract.
Oily water separator (OWS): 15 ppm separator per MEPC.107(49).
On-line viscometer: Continuous viscosity sensor mounted in the engine fuel supply controlling viscotherm fuel heater output.
Operational manual sounding: Daily ullage check used to track ROB and verify consumption against engine room logs.
Origin certificate: Document accompanying some bunker deliveries declaring the refinery or terminal source.
Oxidation stability: Resistance of fuel to degradation by oxygen, measured by ASTM D2274 for distillates.

P

P615: Westfalia / GEA designation for a class of self-cleaning marine separator bowls.
PAH: Polycyclic aromatic hydrocarbon, a class of multi-ring aromatics enriched in residual fuels.
Paraffinic crude: Crude oil rich in saturated chain hydrocarbons producing distillates with high cetane and low aromaticity.
Pensky-Martens closed cup: Reference flash point apparatus for ISO 2719, ASTM D93, and IP 34 tests.
PIANO analysis: Detailed hydrocarbon group analysis breakdown into paraffins, isoparaffins, aromatics, naphthenes, and olefins.
Pin and lug coupling: Standard hose end used on bunker hoses, common in IMO standardized bunker manifolds.
Pour Point: Lowest temperature at which oil flows; key to heating decisions.
Power-based blending: In-line blending controlled by ratio control loops to deliver a fixed power equivalent specification.
Pre-combustion chamber: Engine feature improving ignition of low-cetane fuel, common in some medium speed designs.
Preheating: Raising residual fuel temperature toward 120 to 150 C before injection to reach 10 to 15 cSt at the engine inlet.
Pressure drop test: Filter and strainer performance check, used to flag onset of fouling from sediment or unstable fuel.
Pumpability: Cargo property reflecting viscosity at handling temperature.
Purifier: Centrifuge with water seal removing free water and solids from fuel oil.
Pyrolysis oil: Liquid product of biomass thermal decomposition, an emerging blendstock for bio-VLSFO.

Q

Quality claim: Commercial dispute alleging the fuel does not meet contractual or ISO 8217 limits.
Quality control sample: Reference fuel of known composition run alongside customer samples in a bunker laboratory to verify analytical performance.
Quantitative determination: Numerical analytical result distinguished from qualitative observations such as spot test ratings.

R

Ramsbottom carbon residue: Carbon residue method per ASTM D524, alternative to Conradson.
Reactivity: Combined ignition and combustion behavior of a fuel, qualitatively expressed by CCAI for residual grades.
Reformate: High-octane refinery stream not normally found in marine fuel except in trace blending excursions.
Reid vapor pressure: Vapor pressure of light petroleum products at 37.8 C, not normally specified for marine fuel.
Remaining on board (ROB): Fuel quantity present in ship tanks before or after a bunkering, central to bunker quantity surveys.
Representative sample: Sample whose composition matches the parent batch, achieved by continuous drip sampling throughout delivery.
Residual fuel oil: Heavy refinery bottom stream forming the RM grades of ISO 8217.
Retained sample: See MARPOL retained sample.
Reverse-osmosis water: Treated freshwater used for cooling fuel coolers, not for fuel dilution.
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.