ASTM D5985 Test Method for Pour Point of Petroleum Products (Rotational Method)
4. Summary of Test Method
4.1 After inserting the test specimen into the automatic pour point apparatus, and initiation of the program, the test specimen is heated and then cooled by maintaining a constant temperature differential between the cooling block and the sample. The test specimen is continuously tested for flow characteristics by rotating the test specimen cup at approximately 0.1 rpm against a stationary, counter-balanced, sphere-shaped pendulum. The temperature of the test specimen at which a crystal structure or a viscosity increase, or both, within the test specimen causes the displacement of the pendulum is recorded with a resolution of 0.1°C. The test specimen is then heated to the original starting temperature.
5. Significance and Use
5.1 The pour point of a petroleum product is an index of the lowest temperature of its utility for certain applications. Flow characteristics, such as pour point, can be critical for the correct operation of lubricating systems, fuel systems, and pipeline operations.
5.2 Petroleum blending operations require precise measurement of the pour point.
5.3 This test method can determine the temperature of the test specimen with a resolution of 0.1°C at which either crystals have formed or viscosity increases sufficiently to impede movement of the petroleum product.
5.4 This test method yields a D97/IP15 equivalent pour point when the 3°C interval results are reported.
NOTE 2 - Since some users may wish to report their results in a format similar to Test Method D97 (in 3°C intervals) the precisions were derived for the temperatures rounded to the 3°C intervals. The term equivalent is intended to mean in the same format. For statements on bias relative to Test Method D97, see 13.3.
5.5 This test method has better repeatability and comparable reproducibility relative to Test Method D97 as measured in the 1992 interlaboratory program.
