ASTM D6895 Standard Test Method for Rotational Viscosity of Heavy Duty Diesel Drain Oils at 100°C
8. Sampling, Test Specimens, and Test Units
8.1 Ensure the test specimen is homogeneous. Engine sampling is generally specified in the test method, for example, Test Method D5967. Manual sampling from the container can be done in accordance with Practice D4057.
9. Preparation of Apparatus
9.1 Prepare the apparatus in accordance with manufacturers directions. The apparatus shall be capable of viscosity measurement to within 5 % of the standard Newtonian reference oil viscosity and a rate index value of 0.98 to 1.02 indicating a Newtonian fluid.
10. Calibration and Standardization
10.1 A Newtonian viscosity standard in the range 12 to 35 mPa·s at 100°C shall be used to verify instrument calibration. Run the procedure as in Section 12. A plot of shear stress (Pa) versus shear rate (s(-1)) shall be linearly regressed to yield a slope and intercept. Results shall be:
Intercept, < 0.1 Pa
Slope = viscosity value within 5 % of certified value, mPa·s
Correlation coefficient, r2 > 0.9998
This calibration procedure should be repeated if any criteria are not met
The instrument manufacturer should be contacted if the criteria cannot be met
The operator shall not proceed with this procedure if the calibration criteria are not met
NOTE 1 - It has been determined that use of a specific reference oil in the aforementioned viscosity range did not improve the precision. For laboratory to laboratory consistency, it is suggested to use Cannon S200 as the standard calibration fluid.
10.2 New SAE 15W-40 oil shall be used as a daily control chart standard. Run the procedure (see Section 12) and perform an analysis (see Section 13). Results shall be a rate index between 0.98 to 1.02 and a viscosity value at 100 s(-1), mPa·s, VIS100. Control chart the values of VIS100 and rate index. The procedure shall be checked and the instrument calibration rechecked if the reference oil does not fall within control limits. Practice D6299 shall be used as a guide in this area.
10.3 Some instruments and geometries will exhibit significant instrument/electronic noise at low shear stress or low shear rate levels, or both. This may be determined by plotting viscosity versus shear rate or viscosity versus shear stress for measurements of the standard oil. A horizontal line is obtained in regions far from noise. Annex A1 shows two examples of this type of plot. The minimum shear rate or shear stress to use in the analysis of data can then be determined for the particular instrument and geometry.
11. Conditioning
11.1 Shake all new and used oil samples using the following procedure. Do not prepare more than two samples at one time for one instrument.
11.2 Ensure cap is tight on container.
11.3 Shake vigorously by hand for 30 s. Wait 60 s for air bubbles to dissipate.
11.4 A specimen of the sample shall be taken for analysis promptly following the shaking and dissipation procedure of 11.3.
