Standard test methods (ASTM and others) and specifications for petroleum products

An overview of common test methods and specifications of petroleum fuels. What, why and how do the different test?

Due to commercial, safety, enviromental, quality and processing reasons, there is a huge number of specifications and related test methods for petroleum products. This document gives a short description of the main standard test methods for gasoline and diesel used for cars and jet (kerosine) for aviation fuel.

Typical specification limitations and ranges are also given. The specifications varies over time, from country to country and for different product classes. The given numbers are therefor only examples of the variation. For gasoline and diesel, the most strict limits represents markets with highly advanced requirements for emission control and fuel efficiency; enables technologies that can help increase vehicle and engine efficiency, in addition to enabling sophisticated NOx and particulate matter after-treatment technologies. The weakest limits represents markets with no or first level requirements for emission controls; based primarily on fundamental vehicle/engine performance and protection of emission control system. 

Detailed and updated versions of methods are avaliable for purchase at ASTM and other vendors. See also Standard test methods for crude oil properties.

Content:
(links directly to the tests)

Acidity, TAN - total acid number Corrosion, copper Heat of combustion Smoke point
Aromatics, total Corrosion, silver Hydrogen content Sulfur, doctor test
Aromatics, PAH - polycyclic aromatic hydrocarbons (di+, tri+) Density@15°C JFTOT - thermal stability and preheat code Sulfur, mercaptans
Ash Distillation Naphthalenes Sulfur, total
Benzene Ethanol and other alcohols Octane number, reserach (RON) Trace metals
Carbon residue Existent gum Octane number, motor (MON) Vapour pressure
Cetane Index FAME content Olefins Viscosity
Cetane number Flash point Oxidation stability Water content
Cloud point (CP) Foam volume Oxygen content Water separation (MSEP rating)
Cold finger plugging point (CFPP) Foam vanishing time Phosphorous content
Colour, Saybolt Freeze point Sediments (total particulate)
Conductivity Gravity Silicon content

Acidity, TAN - total acid number

What:
The determination of the sum of all acid compounds present in petrochemical samples. TAN is expressed in mg of KOH per g of sample.  The acid number is a measure of the amount of acidic substance in the oil.

Why:
New and used petroleum products and biodiesel may contain acidic constituents that are present as additives or as degradation products formed during service, such as oxidation products. Trace amounts of acid can be present in aviation turbine fuels and are undesirable because of the consequent tendencies of the fuel to corrode metals that it contacts or to impair the water separation characteristics of the aviation turbine fuel. The acid number is used as a guide in the quality control of lubricating oil formulations. It is also sometimes used as a measure of lubricant degradation in service.

How:
ASTM D3242  Standard Test Method for Acidity in Aviation Turbine Fuel:
The sample is dissolved in a mixture of toluene and isopropyl alcohol containing a small amount of water. The resulting single phase solution is blanketed by a stream of nitrogen bubbling through it and is titrated with standard alcoholic potassium hydroxide to the end point indicated by the color change (orange in acid and green in base) of the added p-naphtholbenzein solution.

ASTM D664  Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration:
The sample is dissolved in toluene and propanol with a little water and titrated with alcoholic potassium hydroxide (if sample is acidic). A glass electrode and reference electrode is immersed in the sample and connected to a voltmeter/potentiometer. The meter reading (in millivolts) is plotted against the volume of titrant. The end point is taken at the distinct inflection of the resulting titration curve corresponding to the basic buffer solution.

Alternative test methods: IP 354, ISO 6618, ASTM D974

Typical specifications:
Jet Kerosine:  Max  0.015 - 0.10  mg KOH/g   (by D3242)
Diesel:          
Max  0.08  mg KOH/g              (by D664)

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Aromatics, total and olefins

What:
The determination of hydrocarbon types.
D1319: Over the concentration ranges from 5 to 99 volume % aromatics, 0.3 to 55 volume % olefins, and 1 to 95 volume % saturates in petroleum fractions that distill below 315 °C.

D5186: The total amounts of monoaromatic (1 to 75 wt%) and polynuclear aromatic hydrocarbon compounds (0.5 to 50 wt%) in motor diesel fuels, aviation turbine fuels, and blend stocks.

Aromatics: Cyclic (ring-shaped), planar (flat) molecules with a ring of resonance bonds that exhibit more stability than other geometric or connective arrangements with the same set of atoms. The simplest of the aromatics have 6 carbon atoms and contains 3 double bounds.
Olefins: Unsaturated hydrocarbons that contain at least one carbon–carbon double bond, with the general formula CnH2n. Also called alkenes.

Why:
The determination of the total volume percent of saturates, olefins, and aromatics in petroleum fractions is important in characterizing the quality of petroleum fractions as gasoline blending components and as feeds to catalytic reforming processes. This information is also important in characterizing petroleum fractions and products from catalytic reforming and from thermal and catalytic cracking as blending components for motor and aviation fuels. This information is also important as a measure of the quality of fuels.
The aromatic hydrocarbon content of motor diesel fuels is a factor that can affect their cetane number and exhaust emissions. The aromatic hydrocarbon content and the naphthalenes content of aviation turbine fuels affect their combustion characteristics and smoke-forming tendencies. Regulations place limits on the total aromatics content and polynuclear aromatic hydrocarbon content of motor diesel fuel.

How:
ASTM D1319  Standard Test Method for Hydrocarbon Types in Liquid Petroleum Products by Fluorescent Indicator Adsorption:
A liquid petroleum sample, is introduced into a glass column packed with activated silica gel and a small layer of fluorescent dyed gel. After the sample has been adsorbed on the gel, alcohol is added to desorb the sample down the column to separate the hydrocarbons. The fluorescent dyes are selectively separated into aromatic, olefin, and saturate zones, which are visible under ultraviolet light. Each boundary in the column is calculated by volume percentage from the length of each zone in the column.

ASTM D5186  Standard Test Method for Determination of Aromatic Content and Polynuclear Aromatic Content of Diesel Fuels and Aviation Turbine Fuels by Supercritical Fluid Chromatography:
An aliquot of the fuel sample is injected onto a packed silica adsorption column and eluted using supercritical carbon dioxide mobile phase. Monoaromatics and polynuclear aromatics in the sample are separated from nonaromatics and detected using a flame ionization detector. 

Alternative test methods: IP 156 (for jet kerosine)and EN 12916 for aromatics. ASTM D1159 for olefins.

Typical specifications:
Gasoline:     
Aromatics:      Max 35.0 vol%             (by D1319)
Olefins:           Max 10-18 vol%           (by D1319)

Jet Kerosine:
Aromatics:      Max 25.0 - 50.0 vol%    (by D1319)
Olefins:           Max 5 vol%                 (by D1319)

Diesel:         
Aromatics:      Max  15 - 25  wt%        (by D5186)

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Aromatics, PAH - Polycyclic aromatic hydrocarbons (di+, tri+)

What:
The determination of the total amounts of monoaromatic (1 to 75 wt%) and polynuclear aromatic hydrocarbon compounds (0.5 to 50 wt%) in motor diesel fuels, aviation turbine fuels, and blend stocks.

Aromatics: Cyclic (ring-shaped), planar (flat) molecules with a ring of resonance bonds that exhibits more stability than other geometric or connective arrangements with the same set of atoms. The simplest of the aromatics have 6 carbon atoms and contains 3 double bounds.

Why:
The aromatic hydrocarbon content of motor diesel fuels is a factor that can affect their cetane number and exhaust emissions. The aromatic hydrocarbon content and the naphthalenes content of aviation turbine fuels affect their combustion characteristics and smoke-forming tendencies. Regulations place limits on the total aromatics content and polynuclear aromatic hydrocarbon content of motor diesel fuel.

How:
ASTM D5186  Standard Test Method for Determination of Aromatic Content and Polynuclear Aromatic Content of Diesel Fuels and Aviation Turbine Fuels by Supercritical Fluid Chromatography:
An aliquot of the fuel sample is injected onto a packed silica adsorption column and eluted using supercritical carbon dioxide mobile phase. Monoaromatics and polynuclear aromatics in the sample are separated from nonaromatics and detected using a flame ionization detector. 

Alternative test methods: EN 12916, ASTM D2425, IP391

Typical specifications:
Diesel:           Max  2.0 - 8.0  wt%      

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Ash

What:
Ash: The non-gaseous, non-liquid, solid residue after a complete combustion  with air.

The determination of ash in the range 0.001–0.180 mass %, from petroleum products. It is limited to petroleum products which are free from added ash-forming additives.

Why:
Knowledge of the amount of ash-forming material present in a product can provide information as to whether or not the product is suitable for use in a given application. Ash can result from oil or water-soluble metallic compounds or from extraneous solids such as dirt and rust.

How:
ASTM D482  Standard Test Method for Ash from Petroleum Products:
The sample contained in a suitable vessel is ignited and allowed to burn until only ash and carbon remain. The carbonaceous residue is reduced to an ash by heating in a muffle furnace at 775°C, cooled and weighed.

Alternative test methods: JIS K 2272, ISO 6245

Typical specifications:
Diesel:          
Max 0.001 - 0.01 wt%

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Benzene

What:
Test method covering the following concentration ranges for the preceding aromatics: benzene, 0.1 to 5vol%; toluene, 1 to 15vol%; individual C8 aromatics, 0.5 to 10vol%; total C9 and heavier aromatics, 5 to 30vol%, and total aromatics, 10 to 80vol%

Benzene: The most simple aromatic molecule, with the formula C6H6.

Why:
Regulations limiting the concentration of benzene and the total aromatic content of gasoline have been established in order to reduce the ozone reactivity and toxicity of automotive evaporative and exhaust emissions. Test methods to determine benzene and the aromatic content of gasoline are necessary to assess product quality and to meet fuel regulations.

How:
ASTM D5580  Standard Test Method for Determination of Benzene, Toluene, Ethylbenzene, p/m-Xylene, o-Xylene, C9 and Heavier Aromatics, and Total Aromatics in Finished Gasoline by Gas Chromatography:
The sample is separated into the different types of hydrocarbons
by packed column gas cromathography.

Alternative test methods: ASTM D3606, JIS K 2536, EN 238, EN 14517

Typical specifications:
Gasoline:           Max 1.0 - 5.0 vol%

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Carbon residue

What:
Determination of the amount of carbon residue ("coke") formed after evaporation and pyrolysis of petroleum materials.

Why:
he carbon residue value of the various petroleum materials serves as an approximation of the tendency of the material to form carbonaceous type deposits under degradation conditions similar to those used in the test method. It can be used to provide some indication of the relative coke forming tendency of such materials.

How:
ASTM D4530 Standard Test Method for Determination of Carbon Residue (Micro Method):
A weighed quantity of sample is placed in a glass vial and heated to 500°C under nitrogen atmosphere for a specific time. The sample undergoes coking reactions, and volatiles formed are swept away by the nitrogen. The carbonaceous-type residue remaining is reported as a percent of the original sample as “carbon residue (micro).”

Alternative test methods: ASTM D189, JIS K2270, ISO 10370

Typical specifications:
Diesel:              Max 0.2 - 0.3 wt%

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Cetane Index

What:
The method provides a means for estimating the ASTM cetane number (Test Method D613) of distillate fuels. It is a supplementary tool for estimating cetane number when a result by Test Method D613 is not available and if cetane improver is not used. Within the range from 32.5 to 56.5 cetane number, the expected error of prediction will be less than +/-2 cetane numbers for 65 % of the distillate fuels evaluated.

Why:
The Calculated Cetane Index is useful for estimating ASTM cetane number when a test engine is not available for determining this property directly and when cetane improver is not used. It may be conveniently employed for estimating cetane number when the quantity of sample available is too small for an engine rating.

How:
ASTM D4737 Standard Test Method for Calculated Cetane Index by Four Variable Equation:
Two correlations have been established between the ASTM cetane number and the density and 10 %, 50 %, and 90 % distillation recovery temperatures of the fuel. Procedure A has been developed for diesel fuels meeting the requirements of Specification D975 Grades No. 1–D S15, No. 1–D S500, No. 1–D S5000, No. 2–D S5000, and No. 4–D. Procedure B has been developed for diesel fuels meeting the requirements of Specification D975 Grade No. 2–D S500.

Alternative test methods: ASTM D189, JIS K 2280, ISO 4264

Typical specifications:
Diesel:              Min 48.0 -55.0

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Cetane Number

What:
A test method covering the determination of the rating of diesel fuel oil in terms of an arbitrary scale of cetane numbers. The cetane number scale covers the range from zero (0) to 100, but typical testing is in the range of 30 to 65 cetane number.

Why:
The cetane number provides a measure of the ignition characteristics of diesel fuel oil in compression ignition engines. The method is used by engine manufacturers, petroleum refiners and marketers, and in commerce as a primary specification measurement related to matching of fuels and engines.

How:
ASTM D613 Standard Test Method for Cetane Number of Diesel Fuel Oil:
Cetane number is determined at constant speed in a precombustion chamber type compression ignition test engine. It s using a standard single cylinder, four-stroke cycle, variable compression ratio, indirect injected diesel engine.

Alternative test methods: ASTM D7170 and D6890, ISO 5165, JIS K2280

Typical specifications:
Diesel:              Min 48.0 -55.0

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Cloud point (CP)

What:
Cloud point: The temperature of a liquid specimen when the smallest observable cluster of hydrocarbon crystals first occurs upon cooling. Test method covering petroleum products and biodiesel fuels that are transparent in layers 40mmin thickness, and with a cloud point below 49°C.

Why:
For petroleum products and biodiesel fuels, cloud point of a petroleum product is an index of the lowest temperature of their utility for certain applications

How:
ASTM D2500 Standard Test Method for Cloud Point of Petroleum Products and Liquid Fuels:
The specimen is cooled at a specified rate and examined periodically. The temperature at which a cloud is first observed at the bottom of the test jar is recorded as the cloud point.

Alternative test methods: ASTM D5771, D5772 and D5773, JIS K2269, ISO 3015

Typical specifications:
Diesel:              Equal to or lower than the lowest expected ambient temperature where used

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Cold finger plugging point (CFPP)

What:
CFPP: Highest temperature, at which a given volume of fuel fails to pass through a standardized filtration device in a specified time when cooled. The test method covering the determination of the CFPP temperature of diesel and domestic heating fuels, including those containing a flow-improving or other additive.

Why:
The CFPP of a fuel is suitable for estimating the lowest temperature at which a fuel will give trouble-free flow in certain fuel systems.

How:
ASTM D6371 Standard Test Method for Cold Filter Plugging Point (CFPP) of Diesel and Heating Fuels:
The sample is cooled under specified conditions and, at intervals of 1°C, is drawn into a pipet under a controlled vacuum through a standardized wire mesh filter.
The procedure is repeated, as the specimen continues to cool, for each 1°C below the first test temperature. Testing is continued until the amount of wax crystals that have separated out of solution is sufficient to stop or slow down the flow so that the time taken to fill the pipet exceeds 60 s or the fuel fails to return completely to the test jar before the fuel has cooled by a further 1°C.

Alternative test methods: IP 309, JIS K 2288, EN 116

Typical specifications:
Diesel:              Equal to or lower than the lowest expected ambient temperature where used

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Colour, Saybolt

What:
A method that covers the determination of the color of refined oils such as undyed motor and aviation gasoline, jet propulsion fuels, naphthas and kerosine, and, in addition, petroleum waxes and pharmaceutical white oils. An empirical definition of the color of a clear petroleum liquid based on a scale of −16 (darkest) to +30 (lightest).

Why:
Determination of the color of petroleum products is used mainly for manufacturing control purposes and is an important quality characteristic since color is readily observed by the user of the product. In some cases the color may serve as an indication of the degree of refinement of the material. When the color range of a particular product is known, a variation outside the established range may indicate possible contamination with another product.

How:
ASTM D156 Standard Test Method for Saybolt Color of Petroleum Products:
The height of a column of sample is decreased by levels corresponding to color numbers until the color of the sample, when viewed through the length of the column, is unmistakably lighter than that of the standard. The color number above this level is reported, regardless of whether the sample was darker, questionable, or a match at the higher level.

Alternative test methods: ASTM D1544

Typical specifications:
Jet kerosine:              The requirement to report Saybolt Colour shall apply at the point of manufacture, thus enabling a colour change in distribution to be quantified. Unusual or atypical colours should be noted and investigated.

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Conductivity

What:
Test methods  covering the determination of the electrical conductivity of aviation and distillate fuels with and without a static dissipator additive. The test methods normally give a measurement of the conductivity when the fuel is uncharged, that is known as the rest conductivity. Conductivities can be measured from 1 pS/m to 2000 pS/m, but some meters can only read to 500 or 1000 pS/m.

Conductivity: A measure of a material's ability to conduct an electric current.

Why:
The ability of a fuel to dissipate charge that has been generated during pumping and filtering operations is controlled by its electrical conductivity, which depends upon its content of ion species. If the conductivity is sufficiently high, charges dissipate fast enough to prevent their accumulation and dangerously high potentials in a receiving tank are avoided.

How:
ASTM D2624 Standard Test Methods for Electrical Conductivity of Aviation and Distillate Fuels:
A voltage is applied across two electrodes in the fuel and the resulting current expressed as a conductivity value. With portable meters, the current measurement is made almost instantaneously upon application of the voltage to avoid errors due to ion depletion. Ion depletion or polarization is eliminated in dynamic monitoring systems by continuous replacement of the sample in the measuring cell.

Alternative test methods: IP 274

Typical specifications:
Jet kerosine:    50 - 600 pS/m

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Corrosion, copper

What:
Determination of the corrosiveness to copper of aviation gasoline, aviation turbine fuel, auto-motive gasoline, cleaners solvent, kerosine, diesel fuel, distillate fuel oil, lubricating oil, and natural gasoline or other hydrocarbons having a vapor pressure no greater than 124 kPa at 37.8°C.

Why:
Crude petroleum contains sulfur compounds, most of which are removed during refining. However, of the sulfur compounds remaining in the petroleum product, some can have a corroding action on various metals and this corrosivity is not necessarily related directly to the total sulfur content. The effect can vary according to the chemical types of sulfur compounds present. The copper strip corrosion test is designed to assess the relative degree of corrosivity of a petroleum product.

How:
ASTM D130 Standard Test Method for Corrosiveness to Copper from Petroleum Products by Copper Strip Test:
A polished copper strip is immersed in a specific volume of the sample being tested and heated under conditions  of temperature and time that are specific to the class of material being tested. At the end of the heating period, the copper strip is removed, washed and the color and tarnish level assessed against the ASTM Copper Strip Corrosion Standard.

Alternative test methods: IP 154, SS-ISO 2160, ISO 2160, JIS K2513

Typical specifications:
Gasoline:           Max Class I
Jet kerosine:      Max 1
Diesel:              
Max Class I

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Corrosion, silver

What:
Detection of the corrosiveness of aviation turbine fuels on silver.

Why:
Crude petroleum contains sulfur compounds, most of which are removed during refining. However, of the sulfur compounds remaining in the petroleum product, some can have a corroding action on various metals and this corrosivity is not necessarily related directly to the total sulfur content. The effect can vary according to the chemical types of sulfur compounds present. The silver strip corrosion test is designed to assess the relative degree of corrosivity of a petroleum product towards silver and silver alloys.

How:
IP 227 Silver Corrosion by Aviation Turbine Fuels:
After a complete immersion of the silver strip in 250 ml of the sample to analyse at 50°C for 4 hours, this corroded strip is classified between 0 and 4.

Alternative test methods: ASTM D7671

Typical specifications:
Jet kerosine:              Max 1

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Density@15°C  (Gravity)

What:
Determination of the density or relative density of petroleum distillates and viscous oils that can be handled in a normal fashion as liquids at test  temperatures between 15 and 35°C. Its application is restricted to liquids with vapor pressures below 80 kPa and viscosities below about 15 000 cSt at the temperature of test.

Density: Mass of a substance per unit volume.

Why:
Density is a fundamental physical property that can be used in conjunction with other properties to characterize both the light and heavy fractions of petroleum and petroleum products. Determination of the density or relative density of petroleum and its products is necessary for the conversion of measured volumes to volumes at the standard temperature of 15°C. Density is important for consistency and good fuel economy. Higher density produces more power and more smoke.

How:
ASTM D4052 Standard Test Method for Density and Relative Density of Liquids by Digital Density Meter:
A small volume of liquid sample is introduced into an oscillating sample tube and the change in oscillating frequency caused by the change in the mass of the tube is used in conjunction with calibration data to determine the density of the sample.

Alternative test methods: ASTM D1298, IP 160 and IP 365, ISO 3675, ISO 12185, JIS K 2249

Typical specifications:
Gasoline:           Min 715-720  to Max 775-780 kg/m3
Jet kerosine:      Min 775 to Max 840 kg/m3   or 37-51 °API
Diesel:              Min 800-
820 to Max 845-860  kg/m3

Back to Content          Density - Gravity          API Gravity

Distillation

What:
Atmospheric distillation of petroleum products using a laboratory batch distillation unit to determine quantitatively the boiling range characteristics of such products as light and middle distillates, automotive spark-ignition engine fuels, aviation gasolines, aviation turbine fuels, diesel fuels, special petroleum spirits and naphthas. Test results are commonly expressed as percent evaporated or percent recovered versus corresponding temperature, either in a table or graphically, as a plot of the distillation curve.

Why:
Distillation (volatility) characteristics of hydrocarbons are important for their safety and performance. The boiling range gives information on the composition, properties and  behavior during storage and use. Volatility is the major determinant of the tendency of a hydrocarbon mixture to produce potentially explosive vapors. Distillation characteristics are critically important for gasolines, affecting starting, warm-up, and tendency to vapor lock at high operating temperature or at high altitude. High boiling point components in fuels can significantly affect the degree of formation of solid combustion deposits. Volatility is an important factor in the application of many solvents. Distillation limits are often included in petroleum product specifications. This basic test method of determining the boiling range of a petroleum product has been in use as long as the petroleum industry has existed. Then, a tremendous number of historical data bases exist for estimating end-use sensitivity on products and processes.

How:
ASTM D86 Standard Test Method for Distillation of Petroleum Products and Liquid Fuels at Atmospheric Pressure:
Based on its composition, vapor pressure, expected IBP and/or FBP, the sample is placed in one of four groups. Apparatus arrangement, condenser temperature,
and other operational variables are defined by the group in which the sample falls. 100-ml of the sample is distilled under prescribed conditions for the group in which the sample falls. The distillation is performed in a laboratory batch distillation unit at ambient pressure under conditions that provide one theoretical plate fractionation. Systematic observations of temperature readings and volumes of condensate are made. The volume of the residue and the losses are also recorded.

Alternative test methods:  ISO 3405, JIS K 2258, ASTM D2887

Typical specifications:

Gasoline: 
10% recovery:        Max 45-65 °C      (Max 113-149 °F)
50% recovery:        65-100 °C            (149-212 °F)
90% recovery:        130-175 °C          (266-347 °F)
Final boilig point:    Max 205 °C         (Max 401 °F)

Jet kerosine:
10% recovery:        Max 205 °C         (Max 401 °F)
Final boilig point:    Max 300 °C         (Max 401 °F)
Distillation residue: Max 1.5 vol%
Distillation loss:      Max 1.5 vol%

Diesel:
90% recovery:        Max 320-340 °C   (Max 608-644 °F)
95% recovery:        Max 340-370 °C   (Max 644-698 °F)
Final boilig point:    Max 350-365 °C   (Max 662-689 °F)

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Ethanol, methanol and other alcohols, and oxygen content

What:
Determination of ethers and alcohols in gasolines by gas chromatography. Specific compounds determined are methyl tert-butylether (MTBE), ethyl tert-butylether (ETBE), tert-amylmethylether (TAME), diisopropylether (DIPE), methanol, ethanol, isopropanol, n-propanol, isobutanol, tert-butanol, sec -butanol, n-butanol, and tert-pentanol (tert-amylalcohol). Individual ethers are determined from 0.20 mass % to 20.0 mass %. Individual alcohols are determined from 0.20 mass % to 12.0 mass %. Equations used to convert to mass % oxygen and to volume % of individual compounds are provided. The method includes a relative bias correlation for ethanol in spark-ignition engine fuels for the U.S. EPA regulations reporting based on Practice D6708 accuracy assessment between Test Method D4815 and Test Method D5599.

Alcohols: Organic compounds in which a hydroxyl functional group (–OH) is bound to a saturated carbon atom.
Ethers: Organic compounds that have the general group R-O-R'. R and R' can be smilar or different alkyl substituents.

Why:
Ethers, alcohols, and other oxygenates can be added to gasoline to increase octane number and to reduce emissions. Type and concentration of various oxygenates are specified and regulated to ensure acceptable commercial gasoline quality. Drivability, vapor pressure, phase separation, exhaust, and evaporative emissions are some of the concerns associated with oxygenated fuels..

How:
ASTM D4815 Standard Test Method for Determination of MTBE, ETBE, TAME, DIPE, tertiary-Amyl Alcohol and C1 to C4 Alcohols in Gasoline by Gas Chromatography:
Separation by gas chromatography.

Alternative test methods:

Typical specifications:
Gasoline:
Alcohols:             Max
10% ethanol and 3 vol% methanol
Oxygen content:  Max 2.7 - 3.7 wt%
Diesel:     
Alcohols:            Non-detectable

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Existent gum

What:
Determination of the existent gum content of aviation fuels, and the gum content of motor gasolines or other volatile distillates in their finished form, (including those containing alcohol and ether type oxygenates and deposit control additives) at the time of test.

Gum: Viscous material that is formed from degradation of oil

Why:
The primary purpose of the test method, as applied to motor gasoline, is the measurement of the oxidation products formed in the sample prior to or during the comparatively mild conditions of the test procedure. Since many motor gasolines are purposely blended with nonvolatile oils or additives, the heptane extraction step is necessary to remove these from the evaporation residue so that the deleterious material, gum, may be determined. With respect to aviation turbine fuels, large quantities of gum are indicative of contamination of fuel by higher boiling oils or particulate matter and generally reflect poor handling practices in distribution downstream of the refinery. It has been proved that high gum can cause induction-system deposits and sticking of intake valves, and in most instances, it can be assumed that low gum will ensure absence of induction-system difficulties.

How:
ASTM D381 Standard Test Method for Gum Content in Fuels by Jet Evaporation:
A measured quantity of fuel is evaporated under controlled conditions of temperature and flow of air or steam. For aviation gasoline and aviation turbine fuel, the resulting residue is weighed and reported as milligrams per 100 mL. For motor gasoline, the residue is weighed before and after extracting with heptane and the results reported as milligrams per 100 mL.

Alternative test methods: IP 131, IP 540

Typical specifications:
Jet kerosine:       Max 7  mg/100ml.

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FAME content

What:
Determination of the content of Fatty Acid Methyl Esters (FAME) biodiesel in diesel fuel oils. It is applicable to concentrations from 1.00 to 20 volume %. The procedure is applicable only to FAME.

Why:
The test method is applicable for quality control in the production and distribution of diesel fuel and biodiesel blends containing FAME.

How:
ASTM D7371 Standard Test Method for Determination of Biodiesel (Fatty Acid Methyl Esters) Content in Diesel Fuel Oil Using Mid Infrared Spectroscopy (FTIR-ATR-PLS Method):
A sample of diesel fuel, biodiesel, or biodiesel blend is introduced into a liquid attenuated total reflectance (ATR) sample cell. A beam of infrared light is imaged through the sample onto a detector, and the detector response is determined. Wavelengths of the absorption spectrum that correlate highly with biodiesel or interferences are selected for analysis. A multivariate mathematical analysis converts the detector response for the selected areas of the spectrum from an unknown to a concentration of biodiesel. Thetest method uses Fourier transform mid-IR spectrometer with an ATR sample cell. The absorption spectrum shall be used to calculate a partial least square (PLS) calibration algorithm.

Alternative test methods:

Typical specifications:
Diesel:        Non-detectable

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Flash point

What:
D56:Determination of the flash point, by tag manual and automated closed testers, of liquids with a viscosity below 5.5 mm2/s (cSt) at 40 °C (104 °F), or below 9.5 mm2/s (cSt) at 25 °C (77 °F), and a flash point below 93 °C (200 °F).

D93:Determination of the flash point of petroleum products in the temperature range from 40 to 360°C by a manual Pensky-Martens closed-cup apparatus or an automated Pensky-Martens closed-cup apparatus. NOTE 1—Flash point determination as above 250°C can be performed, however, the precisions have not been determined above this temperature. For residual fuels, precisions have not been determined for flash points above 100°C. Procedure A is applicable to distillate fuels (diesel, kerosine, heating oil, turbine fuels), new lubricating oils.

Why:
Flash point measures the tendency of the specimen to form a flammable mixture with air under controlled laboratory conditions. It is only one of a number of properties that shall be considered in assessing the overall flammability hazard of a material. Flash point is used in shipping and safety regulations to define flammable and combustible materials. Flash point can indicate the possible presence of highly volatile and flammable materials in a relatively nonvolatile or nonflammable material. For example, an abnormally low flash point on a sample of kerosene can indicate gasoline contamination.

How:
ASTM D56 Standard Test Method for Flash Point by Tag Closed Cup Tester:
The specimen is placed in the cup of the tester and, with the lid closed, heated at a slow constant rate. An ignition source is directed into the cup at regular intervals. The flash point is taken as the lowest temperature at which application of the ignition source causes the vapor above the specimen to ignite.

ASTM D93 Standard Test Methods for Flash Point by Pensky-Martens Closed Cup Tester:
A brass test cup of specified dimensions, filled to the inside mark with test specimen and fitted with a cover of specified dimensions, is heated and the specimen stirred at specified rates, by either of two defined procedures (A or B). An ignition source is directed into the test cup at regular intervals with simultaneous interruption of the stirring, until a flash is detected.

Alternative test methods: ASTM D3828, IP 170 and IP 523, EN 22719

Typical specifications:
Jet kerosine:             Min 28.0 °C  (-2 °F)   (ASTM D56)
Diesel:                     Min 55 °C (131 °F)     (ASTM D93)

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Foam volume and vanishing time

What:
A  determination of foam volume of diesel fuel, and the foam vanishing time when run in a standarized test equipment.

Why:
Foam in engines and prosessing units can cause severe troubles due to the large volume increase of the liquide. Foam can be stabilized by chemicals or particulates, and an increased foaming tendency can therefor be an indication of impurites in the fuel.

How:
NF M 07-075 Determination of the foaming tendency of diesel Fuels:
Testing of foaming tendency covers an injection of a given amount of diesel fuel under constant pressure into a graduated glass cylinder, where the foam volume and the vanishing time are measured.

Alternative test methods:

Typical specifications:
Diesel:
Foam volume:               Max 100 ml
Foam vanishing time:    Max 15 sec           

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Freeze point

What:
A method that covers the determination of the temperature below which solid hydrocarbon crystals form in aviation turbine fuels. The method is designed to cover the temperature range of −80 °C to 20 °C; however, 2003 Joint ASTM/IP Interlaboratory Cooperative Test Program has only demonstrated the test method with fuels having freezing points in the range of −42 °C to −60 °C.

Why:
The freezing point of an aviation fuel is the lowest temperature at which the fuel remains free of solid hydrocarbon crystals. These crystals can restrict the flow of fuel through the fuel system of the aircraft. The temperature of the fuel in the aircraft tank normally decreases during flight depending on aircraft speed, altitude, and flight duration. The freezing point of the fuel must always be lower than the minimum operational fuel temperature. Petroleum blending operations require precise measurement of the freezing point.

How:
ASTM D5972 Standard Test Method for Freezing Point of Aviation Fuels (Automatic Phase Transition Method):
A specimen is cooled at a rate of 15 6 5°C/min by a Peltier device while continuously being illuminated by a light source. The specimen is continuously monitored by an array of optical detectors for the first formation of solid hydrocarbon crystals. Once the hydrocarbon crystals are formed, the specimen is then warmed at a rate of 10 + 0.5°C/min until the last hydrocarbon crystals return to the liquid phase. The detectors are sufficient in number to ensure that any solid hydrocarbon crystals are detected. The specimen temperature at which the last hydrocarbon crystals return to the liquid phase is recorded as the freezing point.

Alternative test methods: ASTM D2386, D7153, D7154 and IP16, IP 435, IP 528, IP 529

Typical specifications:
Jet kerosine:              Max -50.0 - -45.5 °C  (-58 - -50 °F)

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Heat of combustion

What:
A test method that covers the estimation of the net heat of combustion (megajoules per kilogram or Btu per pound) of aviation gasolines and aircraft turbine and jet engine fuels.  This test method is purely empirical and is applicable to liquid hydrocarbon fuels that conform to the specifications for aviation gasolines or aircraft turbine and jet engine fuels of grades Jet A, Jet A-1, Jet B, JP-4, JP-5, JP-7, and JP-8. The empirical equations for the estimated net heat of combustion, sulfur-free basis, were derived by stepwise linear regression methods using data from 241 fuels, most of which conform to specifications for aviation gasolines and aircraft turbine or jet engine fuels.

Why:
The method is for use as a guide in cases where experimental determination of heat of combustion is not available and cannot be made conveniently and where an estimate is considered satisfactory. It is not intended as a substitute for experimental measurements of heat of combustion. The mean density for all fuels used in developing the correlation was 779.3 kg/m3 and that two thirds of the samples had a density between 721.4 and 837.1 kg/m3. The use of this correlation may be applicable to other hydrocarbon distillates and pure hydrocarbons; however, only limited data on non-aviation fuels over the entire range of the variables were included in the correlation. The calorimetric methods  measure gross heat of combustion. However, net heat is used in aircraft calculations because all combustion products are in the gaseous state. This calculation method is based on net heat, but a correction is required for condensed sulfur compounds.


ASTM D3338 Standard Test Method for Estimation of Net Heat of Combustion of Aviation Fuels:
A correlation in inch-pound units has been established between the net heat of combustion and gravity, aromatic content, and average volatility (10%, 50%, and 90% distillation recovery temperatures) of the fuel. This correlation was converted to SI units. To correct for the effect of the sulfur content of the fuel on the net heat of combustion, an correction equations containing the sulfur content is applied.

Alternative test methods: ASTM D1405 and D4529

Typical specifications:
Jet kerosine:         Min 42.8 MJ/kg

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Hydrogen content

What:
A test method that covers the estimation of the hydrogen content (mass percent) of aviation gasolines and aircraft turbine and jet engine fuels. The test method is empirical and is applicable to liquid hydrocarbon fuels that conform to the requirements of specifications for aviation gasolines or aircraft turbine and jet engine fuels of types Jet A, Jet A-1, Jet B, JP-4, JP-5, JP-7, and JP-8.

Why:
The method is intended for use as a guide in cases in which an experimental determination of hydrogen content is not available. The mean density for all fuels used in developing the correlation was 783.5 kg/m3 and that two thirds of the samples had a density between 733.2 and 841.3 kg/m3. The use of this correlation may be applicable to other hydrocarbon distillates similar to aviation fuels, but only limited data on nonaviation fuels were included in the correlation. Hydrogen content is required to correct gross heat of combustion to net heat of combustion. Net heat is used in aircraft calculation because all combustion products are in the gaseous state, but experimental methods measure gross heat.

How:
ASTM D3343 Standard Test Method for Estimation of Hydrogen Content of Aviation Fuels:
A correlation has been established between the hydrogen content of a fuel and its distillation range (10%, 50%, and 90% distillation recovery temperatures), API gravity, and aromatic content. This relationship is given by an equation.

Alternative test methods:

Typical specifications:
Jet kerosine:     Min 13.4 wt%

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JFTOT (thermal stability and preheat code)

What:
This test rates the tendency of gas turbine fuels to deposit decomposition products within the fuel system.

Why:
In flight, cold jet fuel and hot engine oil pass each other in a heat exchanger. This transfer warms up the jet fuel and cools the engine oil and hot parts that would otherwise overheat at the high temperatures encountered. The thermal stresses experienced in modern jet engines can lead to the formation of undesirable and possibly harmful insoluble materials, such as lacquers on heat exchangers and control surfaces. Thus, jet fuel must have a high thermal stability and must not break down and deposit coke and varnishes in the fuel system passages. The test results are indicative of fuel performance during gas turbine operation and can be used to assess the level of deposits that form when liquid fuel contacts a heated surface that is at a specified temperature.

How:
ASTM D3241 Standard Test Method for Thermal Oxidation Stability of Aviation Turbine Fuels:
During the test, fuel is pumped over a heated aluminum alloy tube and through a very fine, heated stainless steel screen at a constant flow rate. After contacting the tube, the fuel is filtered to collect any solid decomposition products. The pressure drop across the filter is monitored during the test. At the end of the test, the tube is removed and visually examined for any stain or discoloration. The operator utilizes a standardized Visual Tube Rater (VTR) to determine the color rating. The VTR is an internally lit black box with three 30 W incandescent bulbs and the color chart seen below on the left. The operator rates the tube deposits on a scale of 0 to 4.

Alternative test methods: IP 323

Typical specifications:
Jet kerosine:   
Delta pressure:   Max 25 mmHg
Preheat code:     Max 2-3

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Naphthalenes

What:
Determination, by ultraviolet spectrophotometry, of the total concentration of naphthalene, acenaphthene, and alkylated derivatives of these hydrocarbons in jet fuels. This test method is designed to analyze fuels containing not more than 5 % of such components and having end points below 315°C (600°F); however, the range of concentrations used in the interlaboratory test programs which established the precision statements for this test method were 0.03 to 4.25 volume % for Procedure A, and 0.08 to 5.6 volume % for Procedure B. This test method determines the maximum amount of naphthalenes that could be present.

Why:
This test method for naphthalene hydrocarbons is one of a group of tests used to assess the combustion characteristics of aviation turbine fuels of the kerosene boiling range. The naphthalene hydrocarbon content is determined because naphthalenes, when burned, tend to have a relatively larger contribution to a sooty flame, smoke, and thermal radiation than single ring aromatics.

How:
ASTM D1840 Standard Test Method for Naphthalene Hydrocarbons in Aviation Turbine Fuels by Ultraviolet Spectrophotometry:
The total concentration of naphthalenes in jet fuels is determined by measurement of the absorbance at 285 nm of a solution of the fuel at known concentration.

Alternative test methods:

Typical specifications:
Jet kerosine:      Max 3 vol%

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Octane number, research (RON)

What:
A laboratory test method covering the quantitative determination of the knock rating of liquid spark-ignition engine fuel in terms of Research O.N., except that this test method may not be applicable to fuel and fuel components that are primarily oxygenates. The sample fuel is tested using a standardized single cylinder, four-stroke cycle, variable compression ratio, carbureted, CFR engine run in accordance with a defined set of operating conditions. The O.N. scale is defined by the volumetric composition of PRF blends. The sample fuel knock intensity is compared to that of one or more PRF blends. The O.N. of the PRF blend that matches the K.I. of the sample fuel establishes the Research O.N. 1.2 The O.N. scale covers the range from 0 to 120 octane number but this test method has a working range from 40 to 120 Research O.N. Typical commercial fuels produced for spark-ignition engines rate in the 88 to 101 Research O.N. range. Testing of gasoline blend stocks or other process stream materials can produce ratings at various levels throughout the Research O.N. range.

Why:
Research O.N. correlates with commercial automotive spark-ignition engine antiknock performance under mild conditions of operation. Research O.N. is used by engine manufacturers, petroleum refiners and marketers, and in commerce as a primary specification measurement related to the matching of fuels and engines. Research O.N., in conjunction with Motor O.N., defines the antiknock index of automotive spark-ignition engine fuels, in accordance with Specification D 4814. The antiknock index of a fuel approximates the Road octane ratings for many vehicles, is posted on retail dispensing pumps in the U.S., and is referred to in vehicle manuals. Research O.N. is also used either alone or in conjunction with other factors to define the Road O.N. capabilities of spark-ignition engine fuels for vehicles operating in areas of the world other than the United States. Research O.N. is used for measuring the antiknock performance of spark-ignition engine fuels that contain oxygenates. Research O.N. is important in relation to the specifications for spark-ignition engine fuels used in stationary and other nonautomotive engine applications.

How:
ASTM D2699 Standard Test Method for Research Octane Number of Spark-Ignition Engine Fuel:
The Research O.N. of a spark-ignition engine fuel is determined using a standard test engine and operating conditions to compare its knock characteristic with those of PRF blends of known O.N. Compression ratio and fuel-air ratio are adjusted to produce standard K.I. for the sample fuel, as measured by a specific electronic detonation meter instrument system. A standard K.I. guide table relates engine C.R. to O.N. level for this specific method. The fuel-air ratio for the sample fuel and each of the primary reference fuel blends is adjusted to maximize K.I. for each fuel. The Engine Speed is set to run with 600 rpm.

Alternative test methods: ISO EN 5163

Typical specifications:
Gasoline:           Min 91 - 98

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Octane number, motor (MON)

What:
A laboratory test method covering the quantitative determination of the knock rating of liquid spark-ignition engine fuel in terms of Motor octane number, including fuels that contain up to 25 % v/v of ethanol. However, this test method may not be applicable to fuel and fuel components that are primarily oxygenates. The sample fuel is tested in a standardized single cylinder, four-stroke cycle, variable compression ratio, carbureted, CFR engine run in accordance with a defined set of operating conditions. The octane number scale is defined by the volumetric composition of primary reference fuel blends. The sample fuel knock intensity is compared to that of one or more primary reference fuel blends. The octane number of the primary reference fuel blend that matches the knock intensity of the sample fuel establishes the Motor octane number. The octane number scale covers the range from 0 to 120 octane number, but this test method has a working range from 40 to 120 octane number.

Why:
Motor O.N. correlates with commercial automotive spark-ignition engine antiknock performance under severe conditions of operation.Motor O.N. is used by engine manufacturers, petroleum refiners and marketers, and in commerce as a primary specification measurement related to the matching of fuels and engines. Motor O.N., in conjunction with Research O.N., defines the antiknock index of automotive spark-ignition engine fuels, in accordance with Specification D4814. The antiknock index of a fuel approximates the road octane ratings for many vehicles, is posted on retail dispensing pumps in the United States, and is referred to in vehicle manuals. Motor O.N. is used for measuring the antiknock performance of spark-ignition engine fuels that contain oxygenates. Motor O.N. is important in relation to the specifications for spark-ignition engine fuels used in stationary and other nonautomotive engine applications. Motor O.N. is utilized to determine, by correlation equation, the Aviation method O.N. or performance number (lean-mixture aviation rating) of aviation spark-ignition engine fuel.7.

How:
ASTM D2700 Standard Test Method for Motor Octane Number of Spark-Ignition Engine Fuel:
The Motor O.N. of a spark-ignition engine fuel is determined using a standard test engine and operating conditions to compare its knock characteristic with those of PRF blends of known O.N. Compression ratio and fuel-air ratio are adjusted to produce standard K.I. for the sample fuel, as measured by a specific electronic detonation meter instrument system. A standard K.I. guide table relates engine C.R. to O.N. level for this specific method. The fuel-air ratio for the sample fuel and each of the primary reference fuel blends is adjusted to maximize K.I. for each fuel. The Engine Speed is set to run with 900 rpm.

Alternative test methods: ISO EN 5163

Typical specifications:
Gasoline:           Min 82 -88

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Oxidation stability

What:
Test methods covering the determination of the stability of gasoline in finished form only (D525) and of middle distillate fuels such as No. 2 fuel oil (D2274), under accelerated oxidation conditions.

Why:
The induction period may be used as an indication of the tendency of motor gasoline to form gum in storage. It should be recognized, however, that its correlation with the formation of gum in storage may vary markedly under different storage conditions and with different gasolines.

How:
ASTM D525  Standard Test Method for Oxidation Stability of Gasoline (Induction Period Method)
The sample is oxidized in a pressure vessel initially filled at 15 to 25°C with oxygen pressure at 690 to 705 kPa and heated at a temperature between 98 and 102°C. The pressure is recorded continuously or read at stated intervals until the breakpoint is reached. The time required for the sample to reach this point is the observed induction period at the temperature of test, from which the induction period at 100°C can be calculated.

ASTM D2274 Standard Test Method for Oxidation Stability of Distillate Fuel Oil (Accelerated Method):
A 350-mL volume of filtered middle distillate fuel is aged at 95°C (203°F) for 16 h while oxygen is bubbled through the sample at a rate of 3 L/h. After aging, the sample is cooled to approximately room temperature before filtering to obtain the filterable insolubles quantity. Adherent insolubles are then removed from the oxidation cell and associated glassware with trisolvent. The trisolvent is evaporated to obtain the quantity of adherent insolubles. The sum of the filterable and adherent insolubles, expressed as milligrams per 100 mL, is reported as total insolubles.

Alternative test methods: ISO 7536 (for gasoline), ISO 12205 (for diesel)

Typical specifications:
Gasoline:         Min 360 - 480 minutes   (D525)
Diesel:             Max 25 g/m3                (D2274)

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Phosphorus content

What:
Determination of phosphorus generally present as pentavalent phosphate esters or salts, or both, in gasoline. This test method is applicable for the determination of phosphorus in the range from 0.2 to 40 mg P/litre or 0.0008 to 0.15 g P/U.S. gal.

Why:
Phosphorus in gasoline will damage catalytic convertors used in automotive emission control systems, and its level therefore is kept low.

How:
ASTM D3231 Standard Test Method for Phosphorus in Gasoline:
Organic matter in the sample is decomposed by ignition in the presence of zinc oxide. The residue is dissolved in sulfuric acid and reacted with ammonium molybdate and hydrazine sulfate. The absorbance of the Molybdenum Blue complex is proportional to the phosphorus concentration in the sample and is read at approximately 820 nm in a 5-cm cell.

Alternative test methods:

Typical specifications:
Gasoline:           No specifications  

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Sediment, total particulates

What:
Gravimetric determination by filtration of particulate contaminant in a sample of aviation turbine fuel (D5452) and middle distillate fuel (D6217) delivered to a laboratory. The mass change difference during filtration identifies the contaminant level per unit volume. Method D6217 using less quantities of fuel than D5452, and thus, is a faster method to perform.

Why:
These test methods provides a gravimetric measurement of the particulate matter present in a sample of aviation turbine fuels and diesel fuels delivered to a laboratory for evaluation. The objective is to minimize these contaminants to avoid filter plugging and other operational problems. Although tolerable levels of particulate contaminants have not yet been established for all points in fuel distribution systems, the total contaminant measurement is normally of most interest. The mass of particulates present in a fuel is a significant factor, along with the size and nature of the individual particles, in the rapidity with which fuel system filters and other small orifices in fuel systems can become plugged. The test methods can be used in specifications and purchase documents as a means of controlling particulate contamination levels in the fuels purchased. Maximum particulate levels are specified in several military fuel specifications.

How:
ASTM D5452 Standard Test Method for Particulate Contamination in Aviation Fuels by Laboratory Filtration:
A known volume of fuel is filtered through a preweighed test membrane filter and the increase in membrane filter mass is weight determined after washing and drying. The change in weight of a control membrane located immediately below the test membrane filter is also determined. The objective of using a control membrane is to assess whether the fuel itself influences the weight of a membrane. The particulate contaminant is determined from the increase in mass of the test membrane relative to the control membrane filter.

ASTM D6217 Standard Test Method for Particulate Contamination in Middle Distillate Fuels by Laboratory Filtration:
A measured volume of about 1 L of fuel is vacuum filtered through one or more sets of 0.8 µm membranes. Each membrane set consists of a tared nylon test membrane and a tared nylon control membrane. After the filtration has been completed, the membranes are washed with solvent, dried, and weighed. The particulate contamination level is determined from the increase in the mass of the test membranes relative to the control membranes, and is reported in units of g/m3 or its equivalent mg/L

Alternative test methods: ASTM D7321 (diesel with FAME), EN 12662

Typical specifications:
Gasoline:           Max 1 mg/l   (D5452)
Jet kerosine:      
Max 1 mg/l   (D5452)
Diesel:              Max 10 mg/l  (D6217)

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Silicon content

What:
Determination of total silicon by monochromatic, wavelength-dispersive X-ray fluorescence (MWDXRF) spectrometry in naphthas, gasoline, gasoline-ethanol blends, reformulated gasoline (RFG), ethanol and ethanol-fuel blends, and toluene at concentrations of 3 mg/kg to 100 mg/kg.

Why:
Silicone oil defoamer can be added to coker feedstocks to minimize foaming in the coker. Residual silicon in the coker naphtha can adversely affect downstream catalytic processing of the naphtha. Silicon contamination of gasoline, gasoline-ethanol blends, denatured ethanol, and their blends has led to fouled vehicle components (for example, spark plugs, exhaust oxygen sensors, catalytic converters) requiring parts replacement and repairs. Finished gasoline, gasoline-ethanol blends, and ethanol-fuel blends can come into contact with silicon a number of ways. Waste hydrocarbon solvents such as toluene can be added to gasoline. Such solvents can contain soluble silicon compounds. Silicon-based antifoam agents can be used in ethanol plants, which then pass silicon on to the finished ethanol-fuel blend. This test method can be used to determine if gasoline, gasoline-ethanol blends, and ethanol-fuel blends meet specifications with respect to silicon content of the fuel, and for resolution of customer problems. Volatile compounds may not meet the stated precision from this test method because of selective loss of light materials during the analysis.

How:
ASTM 7757 Standard Test Method for Silicon in Gasoline and Related Products by Monochromatic Wavelength Dispersive X-ray Fluorescence Spectrometry:
R
apid and precise measurement of total silicon in naphthas, gasoline, gasoline-ethanol blends, RFG, ethanol and ethanol-fuel blends, and toluene with minimum sample preparation. Typical analysis time is 5 min to 10 min per sample. Excitation by monochromatic X-rays reduces background, simplifies matrix correction, and increases the signal/background ratio compared to polychromatic excitation used in conventional WDXRF techniques.

Alternative test methods:    Inhouse ICP-AES methods with detection limit of 1 mg/kg.

Typical specifications:
Gasoline:             No specifications

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Smoke point

What:
Determination of the smoke point of kerosine and aviation turbine fuel. Smoke point: The maximum height, in millimetres, of a smokeless flame of fuel burned in a wick-fed lamp of specified design.

Why:
The smoke point is related to the hydrocarbon type composition of aviation fuels. Generally the more aromatic the fuel the smokier the flame. A high smoke point indicates a fuel of low smoke producing tendency. The smoke point (and Luminometer number with which it can be correlated) is quantitatively related to the potential radiant heat transfer from the combustion products of the fuel. Because radiant heat transfer exerts a strong influence on the metal temperature of combustor liners and other hot section parts of gas turbines, the smoke point provides a basis for correlation of fuel characteristics with the life of these components.

How:
ASTM D1322 Standard Test Method for Smoke Point of Kerosine and Aviation Turbine Fuel:
The sample is burned in an enclosed wick-fed lamp that is calibrated daily against pure hydrocarbon blends of known smoke point. The maximum height of flame that can be achieved with the test fuel without smoking is determined to the nearest 0.5 mm.

Alternative test methods: IP 57

Typical specifications:
Jet kerosine:     Min 18.00 - 25.00 mm

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Sulfur doctor test

What:
This test method is intended primarily for the detection of mercaptans in motor fuel, kerosine, and similar petroleum products. This method may also provide information on hydrogen sulfide and elemental sulfur that may be present in these sample types.

Why:
Sulfur present as mercaptans or as hydrogen sulfide in distillate fuels and solvents can attack many metallic and non-metallic materials in fuel and other distribution systems. A negative result in the doctor test ensures that the concentration of these compounds is insufficient to cause such problems in normal use.

How:
ASTM D4952 Standard Test Method for Qualitative Analysis for Active Sulfur Species in Fuels and Solvents (Doctor Test):
The sample is shaken with sodium plumbite solution, a small quantity of powdered sulfur added, and the mixture shaken again. The presence of mercaptans or hydrogen sulfide or both is indicated by discoloration of the sulfur floating at the oil-water interface or by discoloration of either of the phases.

Alternative test methods: IP 30

Typical specifications:
Jet kerosine:     Negative

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Sulfur, mercaptans

What:
Determination of mercaptan sulfur in gasolines, kerosines, aviation turbine fuels, and distillate fuels containing from 0.0003 to 0.01 mass % of mercaptan sulfur. Organic sulfur compounds such as sulfides, disulfides, and thiophene, do not interfere. Elemental sulfur in amounts less than 0.0005 mass % does not interfere. Hydrogen sulfide will interfere if not removed.

Why:
Mercaptan sulfur has an objectionable odor, an adverse effect on fuel system elastomers, and is corrosive to fuel system components.

How:
ASTM D3227 Standard Test Method for (Thiol Mercaptan) Sulfur in Gasoline, Kerosine, Aviation Turbine, and Distillate Fuels (Potentiometric Method):
The hydrogen sulfide-free sample is dissolved in an alcoholic sodium acetate titration solvent and titrated potentiometrically with silver nitrate solution, using as an indicator the potential between a glass reference electrode and a silver/ silver-sulfide indicating electrode. Under these conditions, the mercaptan sulfur is precipitated as silver mercaptide and the end point of the titration is shown by a large change in cell potential.

Alternative test methods: IP 342

Typical specifications:
Jet kerosine:     Max 0.003 wt%

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Sulfur, total

What:
A method covering the measurement of sulfur in hydrocarbons, such as diesel, naphtha, kerosine, jet fuels, crude oils, gasoline (all unleaded), and other distillates. In addition, sulfur in other products, such as M-85 and M-100, may be analyzed using this technique. The applicable concentration range is 0.0150 to 5.00 mass % sulfur.

Why:
The quality of many petroleum products is related to the amount of sulfur present. Knowledge of sulfur concentration is necessary for processing purposes. There are also regulations promulgated in federal, state, and local agencies that restrict the amount of sulfur present in some fuels. This test method provides a means of compliance with specifications or limits set by regulations for sulfur content of petroleum products. Compared to other test methods for sulfur determination,  D4294 has high throughput, minimal sample preparation, good precision, and is capable of determining sulfur over a wide range of concentrations. A typical analysis time is 2 to 4 min per sample.

How:
ASTM D4294 Standard Test Method for Sulfur in Petroleum and Petroleum Products by EnergyDispersive X-ray Fluorescence Spectrometry:
The sample is placed in the beam emitted from an X-ray source. The resultant excited characteristic X radiation is measured, and the accumulated count is compared with counts from previously prepared calibration standards that bracket the sample concentration range of interest to obtain the sulfur concentration in mass %.

Alternative test methods: ASTM D1266, D1552, D2622 and D5453, IP 107, IP 243, IP 336 and IP 373, ISO/DIS 14596

Typical specifications:
Gasoline:           Max 10 - 1000 mg/kg
Jet kerosine:     
Max 1000 - 3000 mg/kg
Diesel:              Max 10 - 2000 mg/kg

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Trace metal

What:
Determination of selected elements (Aluminum, Barium, Calcium, Chromium, Copper, Iron, Lithium, Lead, Magnesium, Manganese, Molybdenum, Nickel, Potassium, Sodium, Silicon, Silver, Titanium, Vanadium, Zinc) in middle distillate fuels by inductively coupled plasma atomic emission spectrometry (ICP-AES). The concentration range of this test method is approximately 0.1 to 2.0 mg/kg. Middle distillate fuels covered in this test method have all distillation fractions contained within the boiling range of 150 to 390°C. This includes, but is not limited to, diesel fuels and aviation turbine fuels.

Why:
Trace elemental analysis is used to indicate the level of contamination of middle distillate fuels. Trace metals in turbine fuels can cause corrosion and deposition on turbine components at elevated temperatures. Some diesel fuels have specification limit requirements for trace metals to guard against engine deposits. Trace level copper in middle distillate aviation turbine fuel can significantly accelerate thermal instability of the fuel leading to oxidation and production of detrimental insoluble deposits in the engine. There are several sources of multi-element contamination of naval distillate fuel. Sea water is pumped into the diesel fuel tanks (as ballast) to trim ships. Also, some of the oilers (fuel supply ships) have dirty tanks. Corrosion products come from unlined tanks, piping, pumps, and heat exchangers.

How:
ASTM D7111 Standard Test Method for Determination of Trace Elements in Middle Distillate Fuels by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES):
Calibration standards are prepared by mixing organometallic standard materials in kerosine. An internal standard material is added to the calibration standards and fuel samples. The calibration standards and the fuel samples are aspirated into the ICP-AES instrument. The concentrations of the elements in the fuel are calculated by comparing emission intensity ratios of the fuel and calibration standards to the internal standard.

Alternative test methods:

Typical specifications:
Gasoline:     Max 1 mg/kg or non-detectable, whichever is lower
Diesel:         Max 1 mg/kg or non-detectable, whichever is lower

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Vapour pressure

What:
A method covering the use of automated vapor pressure instruments to determine the total vapor pressure exerted in vacuum by air-containing, volatile, liquid petroleum products. This test method is suitable for testing samples with boiling points above 0°C (32°F) that exert a vapor pressure between 7 and 130 kPa (1.0 and 18.6 psi) at 37.8°C (100°F) at a vapor-to-liquid ratio of 4:1. Measurements are made on liquid sample sizes in the range from 1 to 10 mL. No account is made for dissolved water in the sample.

Why:
Vapor pressure is a very important physical property of volatile liquids. The vapor pressure of gasoline and gasoline-oxygenate blends is regulated by various government agencies. Specifications for volatile petroleum products generally include vapor pressure limits to ensure products of suitable volatility performance. This test method is more precise than Test Method D 4953, uses a small sample size (1 to 10 mL), and requires about 7 min to complete the test. 

How:
ASTM D5191 Standard Test Method for Vapor Pressure of Petroleum Products (Mini Method):
A known volume of chilled, air-saturated sample is introduced into an evacuated, thermostatically controlled test chamber, the internal volume of which is five times that of the total test specimen introduced into the chamber. After injection into the test chamber, the test specimen is allowed to reach thermal equilibrium at the test temperature, 37.8°C (100°F). The resulting rise in pressure in the chamber is measured using a pressure transducer sensor and indicator. Only total pressure measurements (sum of the partial pressure of the sample and the partial pressure of the dissolved air) are used in this test method, although some instruments can measure the absolute pressure of the sample as well.

Alternative test methods:

Typical specifications:
Gasoline:      Min 45-60  and max  85-105  kPa

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Viscosity

What:
A method that specifies a procedure for the determination of the kinematic and dynamic viscosity, n, of liquid petroleumproducts, both transparent and opaque. The method is intended for application to liquids for which primarily the shear stress and shear rates are proportional (Newtonian flow behavior). The range of kinematic viscosities covered by this test method is from 0.2 mm2/s to 300 000 mm2/s  at all temperatures.

Why:
Many petroleum products, and some non-petroleum materials, are used as lubricants, and the correct operation of the equipment depends upon the appropriate viscosity of the liquid being used. In addition, the viscosity of many petroleum fuels is important for the estimation of optimum storage, handling, and operational conditions. Thus, the accurate determination of viscosity is essential to many product specifications.

How:
ASTM D445 Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity):
The time is measured for a fixed volume of liquid to flow under gravity through the capillary of a calibrated viscometer under a reproducible driving head and at a closely controlled and known temperature. The kinematic viscosity (determined value) is the product of the measured flow time and the calibration constant of the viscometer. The dynamic viscosity, can be obtained by multiplying the kinematic viscosity by the density of the liquid.

ASTM D446  Standard Specifications and Operating Instructions for Glass Capillary Kinematic Viscometers
These specifications cover operating instructions for glass capillary kinematic viscometers, also some widely used viscometers suitable for use in accordance with Test Method D 445.

Alternative test methods: IP 71,  ISO 3104, JIS K2283

Typical specifications:
Jet kerosine:      Max 8.0 cSt @-20°C.                                 
Diesel:              Min 2.0  and  Max 4.0-4.5  mm2/s @40°C    

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Water content

What:
Direct determination of water in the range of 10 to 25 000 mg/kg entrained water in petroleum products and hydrocarbons using automated instrumentation. This test method also covers the indirect analysis of water thermally removed from samples and swept with dry inert gas into the Karl Fischer titration cell.

Why:
A knowledge of the water content of lubricating oils, additives, and similar products is important in the manufacturing, purchase, sale, or transfer of such petroleum products to help in predicting their quality and performance characteristics. For lubricating oils, the presence of moisture could lead to premature corrosion and wear, an increase in the debris load resulting in diminished lubrication and premature plugging of filters, an impedance in the effect of additives, and undesirable support of deleterious bacterial growth.

How:
ASTM D6304 Standard Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration:
An aliquot is injected into the titration vessel of a coulometric Karl Fischer apparatus in which iodine for the Karl Fisher reaction is generated coulometrically at the anode. When all of the water has been titrated, excess iodine is detected by an electrometric end point detector and the titration is terminated. Based on the stoichiometry of the reaction, 1 mol of iodine reacts with 1 mol of water; thus, the quantity of water is proportional to the total integrated current according to Faraday’s Law.

Alternative test methods: ISO 12937,  JIS K 2275

Typical specifications:
Diesel:             Max 200 - 500 mg/kg

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Water separation (MSEP rating)

What:
A rapid portable means for field and laboratory use to rate the ability of aviation turbine fuels to release entrained or emulsified water when passed through fiberglass coalescing material.

Why:
This test method provides a measure of the presence of surfactants in aviation turbine fuels. Like Test Methods D 2550 and D 3602, this test method can detect carryover traces of refinery treating residues in fuel as produced. They can also detect surface active substances added to or picked up by the fuel during handling from point of production to point of use. Certain additives can also have an adverse effect on the rating. Some of these substances affect the ability of filter separators to separate free water from the fuel.

How:
ASTM D3948  Standard Test Method for Determining Water Separation Characteristics of Aviation Turbine Fuels by Portable Separometer:
TA water/fuel sample emulsion is created in a syringe using a high-speed mixer. The emulsion is then expelled from the syringe at a programmed rate through a standard fiber-glass coalescer and the effluent is analyzed for uncoalesced water by a light transmission measurement. The results are reported on a 0-to-100 scale to the nearest whole number. High ratings indicate the water is easily coalesced, implying that the fuel is relatively free of surfactant materials. A test can be performed in 5 to 10 min.

Alternative test methods:

Typical specifications:
Jet kerosine:     Min 70 - 85

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Related Topics

  • Standard Organizations - National and International organizations producing codes and standards - ANSI, ISO, DIN, BSi and more
  • Material Properties - Material properties for gases, fluids and solids - densities, specific heats, viscosities and more
  • Miscellaneous - Engineering related topics like Beaufort Wind Scale, CE-marking, drawing standards and more

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