EXPLANATION
The pour point of a petroleum product is an index of the lowest temperature of its utility for certain applications. Flow characteristics, like pour point, can be critical for the correct operation of lubricating systems, fuel systems, and pipeline operations. Test results from this method can be determined at either 1 or 3 ° C intervals. This test method yields a pour point in a method similar to Test Method ASTM D97 when the 3 ° C intervals are reported. This test method has better precision relative to Test Method ASTM D97 as measured in the 1998 interlaboratory test program. However, do not substitute this method when specifications require Test Method ASTM D97. This test method is designed to cover the temperature range from -57 to +51° C. This test method is not intended to use for crude oils nor its applicability verified for residual fuels.
TEST SUMMARY
After inserting the test jar containing the specimen into the automatic pour point apparatus and initiating the test program, the specimen is automatically heated to the designated temperature and then cooled at a controlled rate. At temperature intervals of 1 or 3 ° C, depending on the selection made by the user prior to the test, a slightly positive air pressure is gently applied onto the surface of the specimen which is contained in an air-tight test jar equipped with a communicating tube. Since one end of the communicating tube is inserted into the specimen, while the other end is maintained at atmospheric pressure, a small amount of downward movement or deformation of the specimen surface, as a result of the application of air pressure, is observed by means of upward movement of the specimen in the communicating tube. This upward movement of the specimen is detected by a pressure sensor which is installed at the atmospheric end of the communicating tube. The lowest temperature at which deformation of the specimen is observed upon application of air pressure is recorded as the pour point.
TEST PRECISION
Relative bias among certain samples was observed using 3 ° C intervals. However, it does not appear to be of a systematic nature. A relative bias of 1.1° C was observed when comparing testing at 1 versus 3 ° C intervals.