ASTM D4741 Measuring Viscosity at High Temperature and High Shear Rate by Tapered-Plug Viscometer
12. Report
12.1 Report the apparent viscosity to the nearest 0.01 cP (mPa.s) at 150°C and 1 x 10(6)s(-1) shear rate.
13. Precision and Bias
13.1 The following criteria should be used for judging the acceptability of results:
13.1.1 Repeatability - The difference between successive test results, obtained by the same operator with the same apparatus under constant operating conditions on identical test material, would in the long run, in the normal and correct operation of the test method, exceed the following value only in one case in twenty:
2.8 % of the mean
Twelve laboratories were used in a program to obtain the precision statement. Statistical analysis was obtained using 12 ASTM engine oils in the range from 2.4 to 4.8 mPa-s. The test series included SAE 0W-30, 5W-20, 5W-30 (4) 10W-30, 10W-40 (2), 15W-40, 20W-50, and 30 grade oils.
13.1.2 Reproducibility - The difference between two single and independent results, obtained by different operators working in different laboratories on identical test material, would in the long run, in the normal and correct operation of the test method, exceed the following value only in one case in twenty:
5.0 % of the mean
13.2 Bias - No justifiable statement can be made on the bias of the procedure described above, since all determinations are relative to the calibration fluid.
13.3 Relative Bias - Results from this method were found, in an interlaboratory study, to agree with those from Test Methods D4683 and D5481. They can be expected to give, on average in the long run, the same results for the same oil.
13.4 A revised procedure has been developed which shows improved precision. This procedure is being tested in an interlaboratory round robin to ensure continued agreement with Test Methods D4683 and D5481, and will be balloted as a revision to this test method when available.
14. Keywords
14.1 dynamic viscosity; high temperature; high shear viscosity; rotational viscometer
