ASTM D4425 for oil separation from lubricating grease
ASTM D4425 standard test method for oil separation from lubricating grease by centrifuging (Koppers Method)
6. Apparatus
6.1 High-Speed Centrifuge capable of developing a G value of 36000. Mount the unit on a flat level surface to allow unrestricted air flow to the motor. This is essential for long motor life. The centrifuge should be equipped with:
6.1.1 Fixed Angle Rotor, multiple place, which can sustain a G value of 36000.
6.1.2 Thermometer, preferably of a dial type, installed so that the temperature in the vicinity (5 to 15 mm) of the rotor can be measured. (For Sorvall centrifuge, see Fig. 1.)
6.1.3 Air Choke, installed at the air inlet of the centrifuge chamber (for Sorvall centrifuge, see Fig. 2), and used to control the temperature if the unit lacks an automatic temperature control. Some designs require outlet choking as well.
6.1.4 Centrifuge Tubes made of transparent material, capable of withstanding a G value of 36000 for 100 h minimum (Note 1).
NOTE 1 - Polypropylene tubes were found to be the most durable.
6.2 Balance, having a capacity of about 100 g with a minimum sensitivity of 0.1 g.
7. Sampling
7.1 The sample presented for analysis should be large enough to make possible the selection of a representative portion for testing. Each run will require approximately 0.5 g for each cubic centimetre of tube capacity. Examine for any indication of non-homogeneity such as oil separation, phase changes, or gross contamination. If any abnormal conditions are found, obtain a new sample.
7.2 The sample temperature at time of loading is to be between 15°C and 35°C.
8. Preparation of Apparatus
8.1 Inspect the centrifuge unit paying particular attention to the cleanliness of the rotor which will be unbalanced by any surface deposits.
8.2 Examine the required number of tubes to be used for the test, rejecting any with surface scratches or imperfections.
