ASTM D6749 for pour point of petroleum products (Automatic air pressure method)
1. Scope
1.1 This test method covers the determination of pour point of petroleum products by an automatic apparatus that applies a slightly positive air pressure onto the specimen surface while the specimen is being cooled.
1.2 This test method is designed to cover the range of temperatures from -57 to +51°C; however, the range of temperatures included in the (1998) interlaboratory test program only covered the temperature range from -51 to -11°C.
1.3 Test results from this test method can be determined at either 1 or 3°C testing intervals.
1.4 This test method is not intended for use with crude oils.
NOTE 1 - The applicability of this test method on residual fuel samples has not been verified. For further information on the applicability, refer to 13.4.
1.5 The values stated in SI units are regarded as standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D97 Test Method for Pour Point of Petroleum Products
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
2.2 IP Standard:
IP15 Test Method for Pour Point of Petroleum Products
3. Terminology
3.1 Definitions:
3.1.1 pour point, n - in petroleum products, the lowest temperature at which movement of the test specimen is observed under prescribed conditions of test.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 air pressure, n - a regulated slightly positive air pressure gently applied onto the specimen surface in the air-tight test jar that causes upward movement of the specimen in the communicating tube, which has one end inserted into the test specimen and the other end at atmospheric pressure.
3.2.2 no-flow point, n - in petroleum products, the temperature of the test specimen at which a wax crystal structure of the test specimen or viscosity increase, or both, impedes movement of the surface of the test specimen under the conditions of the test.
3.2.2.1 Discussion - The no-flow point occurs when, upon cooling, the formation of wax crystal structures or viscosity increase, or both, has progressed to the point where the applied observation device no longer detects movement under the conditions of the test. The preceding observation temperature, at which flow of the test specimen is last observed, is the pour point.
