ISO/TC 28/WG 27 - Stability, cleanliness and compatibility

This document specifies a procedure for rating the tendencies of gas turbine fuels to deposit decomposition products within the fuel system. It is applicable to middle distillate and wide-cut fuels and is particularly specified for the performance of aviation gas turbine fuels. The test results are indicative of fuel thermal oxidation stability during gas turbine operation and can be used to assess the level of deposits that form when liquid fuel contacts a heated surface at a specified temperature. This method is also applicable to aviation turbine fuel that consists of conventional and synthetic blending components as defined in the scope of for instance ASTM D7566[1] and Def Stan 91-091[2]. NOTE For the benefit of those using older instruments, non-SI-units and recalculated numbers are given in between brackets where they are more suitable.

This document specifies a method for the determination of the cloud point of petroleum products which are transparent in layers 40 mm in thickness and have a cloud point below 49 °C, amongst which are diesel fuels with up to 30 % (V/V) of fatty acid methyl ester (FAME)[2], paraffinic diesel fuels with up to 7 % (V/V) FAME[3], 100 % FAME[5] and lubricants. NOTE For the purposes of this document, the term "% (V/V)" is used to represent the volume fraction (φ) of a material.

This document specifies a method for the determination of the pour point of petroleum products. A separate procedure suitable for the determination of the lower pour point of fuel oils, heavy lubricant base stock, and products containing residual fuel components is also described. The procedure described in this document is not suitable for crude oils. NOTE There is equipment available that uses an automated procedure similar to the one described in this document. However, the precision thereof has not been established[1]. [1] ISO develops an automated test method standard.

This document specifies a method to determine cloud point using a step-wise cooling technique that is executed by means of automated equipment types with optical detection mode. The method is applicable to distillate fuels, fatty-acid methyl esters (FAME) and paraffinic diesel fuels, including blends thereof, as well as those containing flow-improvers or other additives, intended for use in diesel engines and domestic heating installations. The method can be applied to other products such as vegetable oils or lubricants, but these kinds of products have not been evaluated during the interlaboratory study (ILS), no precision data are available.

This document specifies a procedure for the calculation of the cetane index of middle-distillate fuels from petroleum-derived sources. The calculated value is termed the "cetane index by four-variable equation". Throughout the remaining text of this document, the term "cetane index" implies cetane index by four-variable equation. This document is applicable to fuels containing non-petroleum derivatives from tar sand and oil shale. It is not applicable to pure hydrocarbons, nor to distillate fuels derived from coal. Cetane index calculations do not take into account the effects from additives used to enhance the Cetane number. NOTE 1 This document was originally developed using a matrix of fuels, some of which contain non-petroleum derivatives from tar sands and oil shale. NOTE 2 The cetane index is not an alternative way to express the cetane number; it is a supplementary tool, to be used with due regard for its limitations. NOTE 3 The cetane index is used to estimate the cetane number of diesel fuel when a test engine is not available to determine this property directly, or when insufficient sample is available for an engine rating. The most suitable range of fuel properties for application of this document is as follows: Fuel property Range Cetane number 32,5 to 56,5 Density at 15 °C, kg/m3 805,0 to 895,0 10 % (V/V) distillation recovery temperature, °C 171 to 259 50 % (V/V) distillation recovery temperature, °C 212 to 308 90 % (V/V) distillation recovery temperature, °C 251 to 363 Within the range of cetane number (32,5 to 56,5), the expected error of the prediction via the cetane index equation will be less than ±2 cetane numbers for 65 % of the distillate fuels examined. Errors can be greater for fuels whose properties fall outside this range of application. As a consequence of sample-specific biases observed, the expected error can be greater even when the fuel's properties fall inside the recommended range of application. Therefore, users can assess the required degree of prediction agreement to determine the fitness-for-use of the prediction. NOTE 4 Sample specific biases were observed for distillate fuels containing FAME (fatty acid methyl ester).

ISO 20844:2015 specifies a method to assess the resistance to shear stresses applied to mineral oils, synthetic oils, and other fluids containing polymers, when passed through a specified diesel injector nozzle. The shear stability is measured by the change in viscosity of the fluid under test, brought about by the polymer degradation during stress. Under normal circumstances, this International Standard is applied to hydraulic fluids of categories HR and HV as defined in ISO 6743‑4[1] and specified in ISO 11158 [2], but it may also be applied to fire-resistant hydraulic fluids within categories HFA, HFB, HFC, and HFD, with modified conditions as specified in ISO 12922[3]. No formal correlation has been established between the viscosity loss, or the absence of viscosity loss, obtained using the procedures described in this International Standard and that of oils and fluids in actual service. However, it provides standardized conditions for the evaluation of polymer stability under minimized thermal and oxidative stresses. It is normally used by manufacturers of fluids and additives, and users, as a means of ranking existing and potential formulations. NOTE Changes to properties other than viscosity are specified in some specifications, but these are not covered by the procedures specified in this International Standard.

ISO 10370:2014 specifies a method for the determination of the amount of carbon residue, in the range 0,10 % (m/m) to 30,0 % (m/m), left after evaporation and pyrolysis of petroleum products under specified conditions. NOTE 1 The carbon residue value serves as an approximation of the tendency of petroleum products to form carbonaceous deposits under similar degradation conditions, and may be useful in the assessment of relative carbon-forming tendencies of products within the same class. In this case, care should be taken in the interpretation of results. For products which yield a residue in excess of 0,10 % (m/m), the test results are equivalent to those obtained by the Conradson carbon residue test (see ISO 6615[1]) in the range of 0,10 (m/m) to 25,0 (m/m) (for details see Annex A). This International Standard is also applicable to petroleum products which consist essentially of distillate material, and which may yield a carbon residue below 0,10 % (m/m). On such materials, a 10 % (V/V) distillation residue is prepared by the procedure described in 7.3.1 and 7.3.2 before analysis. Both ash-forming constituents, as defined by ISO 6245[2] and non-volatile additives present in the sample add to the carbon residue value and are included in the total value reported. NOTE 2 The presence of organic nitrates incorporated in certain distillate fuels will yield abnormally high values for the carbon residue. The presence of alkyl nitrate in the fuel may be detected by ISO 13759.[3]

ISO 10307-2:2009 specifies two procedures — A (thermal) and B (chemical) — for the accelerated ageing of residual fuel oils. When combined with the hot filtration method specified in ISO 10307-1, these procedures permit the prediction of fuel oil stability, as affected by sedimentation, during storage and handling of the fuel oils.

ISO 10307-1:2009 specifies a method for the determination of total sediment in residual fuel oils having a maximum viscosity of 55 mm2/s at 100 °C, and for blends of distillate fuels containing residual components.

This International Standard specifies a method for the determination of the particulate content of middle distillate fuels with a closed flash point of 38 °C or higher, determined in accordance with ISO 2719, ISO 3679 or ISO 13736. It is not applicable to light distillate fuels (gasolines) or to aviation fuels. A gravimetric limitation of the contamination of middle distillate fuels used in diesel engines and domestic applications should be used for the control of filter plugging and other operational problems, and this procedure is applicable up to 25 g/m3. The precision of this procedure is only valid if the results are obtained strictly in accordance with the provisions of this International Standard, particularly in respect of the material used for the filter (see the note in 6.9), sample size and filtration of the complete sample.

This International Standard specifies a method for the laboratory determination of the sum of water
and sediment in residual fuel oils using the centrifuge method. With some oils it is difficult to
obtain water or sediment contents using this method. When this situation is encountered, IS0 3733
and IS0 3735 should be used.
NOTE - It has been observed that centrifugal methods of determination of water and sediment may, in many
cases, give erroneous results. This is especially so when use of a high-speed mixer has been employed to obtain a
representative sample. The method is therefore not entirely satisfactory and the amount of water determined is
almost always lower than the actual water content.
Significant quantities of water and sediment can cause operational problems in handling equipment
and in engines and burners, particularly when the water present contains mineral salts. Design of
residual fuel oil treatment facilities, such as filters or centrifuges, is based on a maximum quantity
of material to be removed before combustion. Residual fuel oils destined for further refinery
processing also require low levels of water and sediment to minimize corrosion problems.

Describes a procedure for the measurement of inherent stability under accelerated oxidizing conditions. The method provides a basis for the estimation of the storage stability, under the conditions of this test, of middle-distillate fuels with an initial boiling point above approximately 175 °C and a 90% (V/V) recovery point below 370 °C. Is not applicable to fuels containing residual components, or any significant component from a non-petroleum source.

Specifies a procedure for determination of the ageing characteristics of petroleum-based lubricating oils. Applicable to those oils which have an evaporation loss of less than 15 % mass fraction.

The principle of the method specified is oxidizing the sample in a pressure bomb initially filled at 15 °C to 25 °C with oxygen at 690 kPa, heating at a temperature between 98 °C and 102 °C, reading the pressure at stated intervals or recorded continuously 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 may be calculated. The method is applicable for aviation and motor gasolines in their finished form only.

The principle of the method specified is placing a weighed test portion in a crucible and subjecting to destructive distillation. The residue undergoes cracking and coking reactions during a fixed period of severe heating. At the end of the specified heat period, the test crucible containing the carbonaceous residue is cooled in a desiccator and weighed. The residue remaining is calculated as a mass percentage of the original test portion. The method may be used to determine amounts of carbon residues in the range of 0,01 % (m/m) to 30,0 % (m/m), left after evaporation and pyrolysis.