ASTM D6811 Standard Test Method for Measurement of Thermal Stability of Aviation Turbine Fuels under Turbulent Flow Conditions (HiReTS Method)
6. Apparatus (see Annex A1)
6.1 General - (See Fig. A1.2.) Fuel contained in the sample vessel is drawn through the sample filter by a pump. The temperature of the fuel is checked by the input fuel electronic thermometer. The fuel is pumped at a constant rate, at pressure set by the back pressure valve, through an electrically heated capillary tube which has a blackened outer surface to give a high thermal emissivity. The heating of the capillary tube is controlled to maintain a constant fuel temperature, as measured by the capillary exit electronic thermometer, at the exit of the capillary tube. The waste fuel is then cooled to a temperature of less than 20°C above ambient, as measured by the waste fuel electronic thermometer, before being discharged to a waste container. During the test, the temperature of the outside of the capillary tube is scanned, checked and recorded every 5 min at 12 points along the exit end of the capillary tube using a contactless pyrometer which is located on a computer-controlled elevating platform.

6.2 The thermal stability apparatus and capillary tube is specified in detail in Annex A1.

6.3 Sparger, of porosity 40 to 80 µm, which allows an air flow of approximately 1.5 L/min.

NOTE 1 - The porosity ofthe sparger can be checked using Test Method E 128.

6.4 Sample Filter, 20-µm stainless steel.

6.5 Aeration Dryer, glass or other suitable transparent material, minimum height 250 mm, minimum diameter 50 mm, filled with dry calcium sulfate and cobalt chloride (see 7.4), which is used in conjunction with an air supply and the sparger (see 6.3) to aerate the test sample.

7. Reagents and Materials
7.1 Heptane, CH3·(CH2)5·CH3, technical grade 95 % purity, for cleaning the apparatus tubeways, and sampling vessels. (Warning - Extremely flammable; harmful if inhaled.)

7.2 Trisolvent, for cleaning sampling vessels. (Warning - Each of the components and the trisolvent is flammable; harmful if inhaled; irritating to skin, eyes and mucous membranes.) It consists of equal volumes of the following:
7.2.1 Acetone, CH3·CO·CH3, technical grade, 95 % purity.

7.2.2 Toluene, C6H5·CH3, technical grade, 95 % purity.

7.2.3 Propan-2-ol, (CH3)2·CH·OH, technical grade, 95 % purity.

7.3 Cleaning Solvent, technical grade, 95 % purity, for cleaning sampling vessels. (Warning - Extremely flammable; harmful if inhaled.) It consists of one of the following:
7.3.1 2-methylpentane.

7.3.2 3-methylpentane.

7.3.3 2,2,4-trimethylpentane.

7.4 Drying Components, to dry the air used for aeration and to indicate the absorption of water by changes from blue to pink color. Use a mix, by volume or weight of the following:
7.4.1 Calcium Sulfate Anhydrous Powder, CaSO4 (97 %).

7.4.2 Cobalt Chloride Anhydrous, CoCl2 (3 %) granules.

7.5 Air, 1.5 L/min for aeration of the test sample.