ASTM D4624 Measuring Apparent Viscosity by Capillary Viscometer
ASTM D4624 Standard Test Method for Measuring Apparent Viscosity by Capillary Viscometer at High-Temperature and High-Shear Rates
11. Report
11.1 Report the viscosity in millipascal seconds (mPa•s) to two decimal places and the test temperature (°C).
12. Precision and Bias
12.1 Precision - The precision of the test method was determined by the statistical examination of interlaboratory test results. The analysis did not use data from Laboratories P and Q because those two laboratories did not report data for a complete class of oils in the round-robin program. The precision calculated from the test results from the other seven laboratories is as follows:
12.1.1 Repeatability - The ratio of successive results (larger value divided by the smaller) 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 in only one case in twenty.
Repeatability = 1.05
12.1.2 Reproducibility - The ratio between two single and independent results (the larger value divided by the smaller), obtained by different operators working in different laboratories on identical test material would, in the long run, exceed the following value only in one case in twenty.
Reproducibility = 1.08
12.2 Bias - This test method uses standards of known viscosity to establish a calibration curve which is then used to determine the viscosities of test oils by interpolation. The standards are thereby forced to their correct values. As a result of this relative method of determining viscosities, this test method has no bias.
12.2.1 No justifiable statement can be made on the bias of the procedure described in this test method since all determinations are relative to the calibration fluids.
12.2.2 However, this test method will generally give higher values (about 0.1 mPa•s higher) for non-Newtonian oils than rotational viscometer test methods (Test Methods D4683 and D4741). This reflects the different operating conditions of the tests, and is not a bias.
13. Keywords
13.1 capillary method; shear testing–petroleum products; viscosity–apparent
