ASTM D5972 Freezing Point of Aviation Fuels (Automatic Phase Transition Method)
4. Summary of Test Method
4.1 A specimen is cooled at a rate of 15 +/- 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.
5. Significance and Use
5.1 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.
5.2 Petroleum blending operations require precise measurement of the freezing point.
5.3 This test method produces results which have been found to be equivalent to Test Method D2386 and expresses results to the nearest 0.1°C, with improved precision over Test Method D2386. This test method also eliminates most of the operator time and judgment required by Test Method D2386.
5.4 When specification requires Test Method D2386, do not substitute this test method or any other test method.
