ISO 6249 pdf download.Petroleum products — Determination of thermal oxidation stability of gas turbine fuels — JFTOT method
1 Scope
This International Standard 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 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.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative references indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 31 70:1 988, Petroleum liquids — Manual sampling. ISO 31 70:1 988/Amd. 1 :1 998. ISO 31 71 :1 988, Petroleum liquids — Automatic pipeline sampling .
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply. 3.1 heater tube aluminium tube controlled at an elevated temperature, over which the test fuel is pumped; the tube is resistively heated and temperature controlled by a thermocouple positioned inside it NOTE The critical test area is the 60 mm thinner portion between the shoulders of the tube. The fuel inlet to the tube is at the 0 mm position, and the fuel exit is at 60 mm. 3.2 decomposition product oxidative product laid down on the heater tube in a relatively small area of the thinner portion of the tube, typically between the 30 mm and 50 mm position from the fuel inlet,and that trapped in the test filter
4 Principle
The jet fuel thermal oxidation tester (JFTOT) subjects the test fuel to conditions which can be related to those occurring in gas turbine engine fuel systems. The fuel is pumped under pressure at a fixed volumetric flow rate through a heater, after which it enters a precision stainless-steel filter where fuel degradation products may become trapped. The differential pressure across this filter is continuously monitored and an excess, indicating significant deposition on the filter, will cause a premature shut-down of the apparatus before the expiry of the normal test period. At the end of the test period, or after an earlier shut-down, the amount of deposit on the heater tube is rated with reference to a standard colour scale (see B.4.1 ).
5 Reagents and materials
5.1 Water, distilled or deionized, for use in the spent sample reservoir as required for JFTOT models 230 and 240. 5.2 Trisolvent, consisting of an equal mix of acetone, toluene and propan-2-ol. 5.3 Cleaning solvent, methylpentane, 2,2,4-trimethylpentane or heptane, of technical grade and 95 % minimum purity. 5.4 Drying agent: self-indicating silica gel, for use in the aeration dryer. NOTE This granular material changes colour gradually from blue to pink indicating that its capacity to absorb water is exhausted. 5.5 Filter paper, of general purpose grade, retentive and qualitative. NOTE Filter paper of 8 µm retention has been found satisfactory. 5.6 Membrane filter, with a diameter of approximately 25 mm, porosity 0,45 µm, and made of mixed esters of cellulose. NOTE Filters of type HA manufactured by Millipore have been found satisfactory. 5.7 Sparger, of porosity 40 µm to 60 µm, which allows an air flow rate of approximately 1 ,5 l/min. NOTE The sparger is supplied with the JFTOT apparatus. The porosity of the sparger may be checked using ASTM E 1 28