ASTM D2070 Standard Test Method for Thermal Stability of Hydraulic Oils
8. Procedure
8.1 Place a representative 200-mL sample of test oil obtained per D4057 - 88 sampling procedure in a clean 250-mL Griffin beaker containing one each of the cleaned and polished iron and copper rods.
8.2 Place the rods totally below the surface of the oil and crossed. Place them in contact with each other at one point only.
8.3 Place the beaker and its contents in the pre-heated aluminum block test fixture in the oven.
8.4 Maintain the test fixture at 135°C +/- 1°C for 168 h. Start the time when the test sample is placed in the oven.
8.5 Keep the oven doors closed during the entire test period. Monitor the temperature continuously via thermocouple in the center of the test block.
8.6 At the completion of 168 h, remove the beakers from the oven and allow to cool to room temperature before proceeding. Individually remove the rods from the oil sample. Remove any loose sludge clinging to the rods with a plastic or rubber policeman and return the sludge to the oil.
8.7 Copper Rod Analysis - Wash the rod with heptane to remove all oil and allow to air dry. Discard the heptane wash. Make a visual evaluation of the condition of the rod against the Cincinnati Milacron color chart (available from Cincinnati Milacron) and record.
8.8 Steel Rod Analysis - Wash the steel rod with heptane to remove all oil and allow to air dry. Discard the heptane wash. Make a visual evaluation of the rod against the Cincinnati Milacron color chart and record.
8.9 For each sample, dry a #41 Whatman filter for 1 h in an oven at 70°C and cool in a dessicator. Weigh to the nearest 0.1 mg. Vacuum filter at a nominal 200 mm of Hg vacuum oil through the pre-weighed #41 Whatman filter. Do not rinse the beaker at this time. Remove the oil filtrate and set aside. Replace the filter flask with a clean one and wash all remaining residue from the beaker with heptane. Wash the residue on the filter paper with heptane until all evidence of oil is removed. Oven dry the residue and filter paper at 70°C, 1 h, allow to cool and weigh to nearest 0.1 mg. For each sample pre-weigh an 8 micron Millipore filter pad to the nearest 0.1 mg. From the oil filtrate, pipet 25 mL of oil and vacuum filter at a nominal 200 mm of Hg vacuum through the pre-weighed 8 micron Millipore filter pad. Wash residue with heptane, air dry, and weigh to the nearest 0.1 mg.
9. Calculation
9.1 Total Sludge Determination - The weight of the sludge on the No. 41 Whatman paper is reported as milligrams per 100 mL of oil. Therefore, the weight of the original filter paper is subtracted from the dried filter paper plus residue and the difference divided by two. The weight of the sludge on the 8 micron Millipore filter pad is also reported as milligrams per 100 mL. The weight of the original filter pad is subtracted from the weight of the dried residue plus filter pad and the difference multiplied by four. Total sludge is the summation of the sludge from the No. 41 Whatman filter paper plus the sludge from the 8 micron filter pad. Weight of total sludge (mg/100 mL of oil)
T - W x 0.5 + M x 4
where:
W = weight of sludge on Whatman filter in mg
M = weight of sludge on 8 micrometer millipore filter in mg
T = total weight of sludge in mg/100 mL
