ASTM D6351 Determination of Low Temperature Fluidity and Appearance of Hydraulic Fluids
7. Procedure
7.1 Pour the specimen into the test jar to the level mark.
7.2 To remove trace amounts of water, preheat the sample to 100°C for 30 min, then cover loosely and allow the sample to cool for 30 min. If the hydraulic fluid is water based, for example a water-glycol fluid, this drying step is to be omitted.
7.3 Close the test jar with the cork.
7.4 Prepare a temperature reference jar in accordance with 7.1 with a liquid that will remain fluid at the selected test temperature. Insert a thermometer through a centrally bored cork so that it fits tightly and is coaxial and the bulb is immersed so that the beginning of the capillary is 3 mm below the surface of the liquid.
7.5 Place the test jar and temperature reference jar in the bath. Be sure the sample is totally immersed in the cooling bath, paying particular attention if a liquid bath is used.
7.6 Keep the samples in the bath for 168 consecutive h.
7.7 Record the temperature of the thermometer in the reference jar prepared in accordance with 7.4 just before examining the samples per 7.8.
7.8 After 168 h, immediately examine the samples. Hold the jar in a horizontal position for 5 s and observe whether the sample flows. Note the presence of any crystals, particles, or separation and the appearance of the specimen.
