ASTM D7279 Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids by Automated Houillon Viscometer
7. Sampling and Test Specimens
7.1 Obtain a representative test specimen in accordance with Practice D4057 or Practice D4177.
7.2 Instructions for Residual Fuel Oils - (Warning - Exercise care as vigorous boil-over can occur when opaque liquids that contain high levels of water are heated to high temperatures. Wear appropriate personal protective equipment for handling hot materials.)
7.2.1 Place the first batch of resid samples to be analyzed for the day in their original containers in a sample pre-heat apparatus that is held between 60 °C and 65 °C for 1 h. Ensure the cap on each container is tightly closed.
7.2.2 Rigorously stir each sample for approximately 20 s with a glass or steel rod of sufficient length to reach the bottom of the container.
7.2.3 Remove the stirring rod and inspect for sludge or wax adhering to the rod. If there is sludge or wax adhering to the rod, continue stirring until the sample is homogeneous.
7.2.4 Recap each container tightly and shake vigorously for 1 min. Then loosen the cap, retighten to finger tight, then back off 3/4 turn to a full turn and place back into the sample pre-heat apparatus.
7.2.5 Upon completion of 7.2.4 for all samples in the batch, increase the sample pre-heat apparatus temperature to between 100 °C and 105 °C and continue heating for 30 min.
7.2.6 Remove each container from the sample pre-heat apparatus, close tightly, and shake vigorously for 60 s.
7.2.7 Using a volume delivery device such as a micropipette, introduce sufficient volume of the sample into the selected Houillon tube. The volume to be used is a function of the viscometer tube constant. The volume delivery device may be pre-warmed to facilitate transfer of highly viscous samples. (See Section 10.)
7.2.8 Analysis of all samples in the batch must be completed within 1 h from completion of 7.2.6.
8. Preparation of Apparatus
8.1 Place the automated viscometer on a stable and level horizontal surface. Make appropriate piping, drainage, and vacuum connections. Refer to the manufacturer's instructions.
8.2 If not already mounted, install the detection cells.
8.3 After installing and securing all viscometer tubes in the bath, fill the bath with appropriate amount of bath fluid (see 6.4).
8.4 Add the appropriate amount of solvent(s) to the solvent reservoir(s).
8.5 Follow the manufacturer's instructions for the operation of the instrument.
8.6 Select a clean, dry, and calibrated viscometer tube having a range covering the estimated kinematic viscosity of the specimen to be tested, if known. The appropriate viscometer tube to use depends on the estimated viscosity of the sample to be tested. The calculation in 8.6.1 may be used to decide which tube to use.
8.6.1 Using Eq 1, the viscometer tube should be chosen so that its constant C falls between ν/200 < C < ν/30 to give flow times, T, between 30 s and 200 s.
NOTE 1 - In the interlaboratory study conducted for the development of this test method, the flow times were between 30 s and 200 s.
8.6.2 If a viscosity estimate is not known, a second analysis may be necessary using a different viscometer tube after a first trial analysis.
9. Calibration
9.1 Calibrate according to the manufacturer's instructions. Calibrated tubes may be purchased but shall be verified as per 9.4.
9.2 Use certified viscosity reference standards (see 6.1).
9.3 Refer to Section 10 for general operation of the automated viscometer and to the manufacturer's instructions.
9.4 The determined kinematic viscosity should match the certified value within +/- 0.5 %. If it does not, then reanalyze the standard. If the value is still out of range, then check all control system settings for the viscometer tube, and recheck each step in the procedure, including the temperature measuring device, and viscometer calibration to locate the source of error.
NOTE 2 - The most common sources of error are caused by particles of dust lodged in the capillary bore of the viscosity tube (particularly for used oils) and temperature measurement errors. Modification of the cleaning constants by increasing the number of cycles and increasing the aspiration time before and after passage of the solvent (see Section 11) may be required.
