ASTM D6749 for pour point of petroleum products (Automatic air pressure method)
11. Procedure
11.1 Pour the sample specimen into the test jar to the scribed mark. When necessary, heat the sample in a bath or oven until it is just sufficiently fluid to pour into the test jar. Samples with an expected pour point above 36°C or samples which appear solid at room temperature can be heated above 45°C, but shall not be heated above 70°C.
11.2 Insert the charged test jar into the metallic block bath and install the test jar cap assembly snugly.
11.3 Select the desired test mode, including the pour point testing interval, according to the manufacturer's instructions. Should the user wish to provide results with a similar format to Test Method D97/IP15, then testing at a 3°C interval shall be selected. Start the automatic sample preheating function, and then enter the expected pour point (EPP). When the 3°C testing interval is chosen, the EPP needs to be a multiple of 3°C.
11.4 Start the test program. The sample is automatically preheated by the automatic apparatus to 45°C or to EPP + 9°C, whichever is higher, but no higher than 70°C, by maintaining the bath temperature at 48°C or EPP + 12°C, whichever is higher.
11.5 After the preheating is completed, the specimen is cooled down automatically.
11.5.1 The metallic block bath is cooled down at a rate of 3 to 4°C/min, to the EPP + 40°C.
11.5.2 From the EPP + 40°C to the no-flow point, the metallic block bath is cooled at a rate of 0.8 to 1.1°C/min.
11.6 As the specimen temperature reaches a predetermined temperature, which is dependent on the EPP, the automatic apparatus starts testing for no-flow state by applying air pressure to the specimen surface at the programmed testing interval. When the specimen is still in a fluid state, the specimen level moves up in the glass tube as air pressure is applied on the specimen surface; when the specimen reaches a no-flow state, the specimen level does not move at all in the glass tube. Upon detecting the no-flow point, the automatic apparatus computes and displays the pour point, which is t97he sum of the no-flow point temperature and the testing interval. Also, the automatic apparatus stops cooling and starts heating the specimen.
11.6.1 Specimen Having Expected Pour Point Equal To or Above +36°C - The automatic apparatus starts testing for the no-flow state at EPP + 9°C.
11.6.2 Specimen Having Expected Pour Point Equal To or Between +31°C and +35°C - The automatic apparatus starts testing for the no-flow state at 45°C.
11.6.3 Specimen Having Expected Pour Point Equal To or Below +30°C - The automatic apparatus starts testing for the no-flow state at EPP + 15°C.
11.7 Remove the test jar cap assembly and clean the test jar and test jar cap assembly.
NOTE 4 - Residual fuels have been known to be sensitive to thermal history. In the case where a residual fuel sample is tested, refer to Test Method D97 for sample treatment.
12. Report
12.1 Report the temperature recorded in 11.6 and the testing interval as the pour point in accordance with Test Method D6749.
