ASTM D5706 Standard Test Method for Determining Extreme Pressure Properties of Lubricating Greases Using a High-Frequency, Linear-Oscillation (SRV) Test Machine
9. Procedure
9.1 Using solvent-resistant gloves, clean the test ball and disk by wiping the surfaces with laboratory tissue soaked with the cleaning solvent. Repeat wiping until no dark residue appears on the tissue. Immerse the test ball and disk in a beaker of the cleaning solvent under ultrasonic vibration for 10 min. Dry the test ball and disk with a clean tissue to ensure no streaking occurs on the surface.
9.2 Ensure that the test load unit is in the release position (refer to the operating manual for details).
9.3 Procedure A and B:
9.3.1 Procedure A - Place a small amount (approximately 0.1 g to 0.2 g, the size of a pea) of lubricating grease to be tested on the cleaned test disk in an area such that overlapping with previous wear scars will not occur.
9.3.2 Procedure B (since 2005) - Place the grease caliper with 1 mm in height on the cleaned disc. Fill the opening of the grease caliper with grease. Remove any excess grease by means of a spatula. Remove the grease caliper by lifting it upwards. Fasten the disc in the specimen holder.
9.4 Place the cleaned ball, using the tweezers, in the disassembled, cleaned, and dried ball holder. Tighten the fastening screw until resistance just begins. Place the cleaned test ball on the top and in the middle of the lubricating grease specimen so that the lubricating grease makes a circular symmetric pad between the test ball and disk.
9.5 Ensure the machine is unloaded (indicated by a load reading of -13 N or -14 N) and carefully place disk containing the lubricating grease specimen and test ball on the test area platform.
9.6 Tighten both the ball and disk clamps until resistance to tightening just begins. Then load unit to 100 N and tighten the ball and disk clamps to a torque of 2.5 N·m. Reduce the load to 50 N for break-in.
9.7 Turn on the heater control and set to the desired temperature.
9.8 Set the load charge amplifier to the setting that corresponds to the 400 N load.
9.9 Change the load charge amplifier at each load in accordance with the manufacturer's instructions when the coefficient of friction at each test load is to be studied.
9.10 When the temperature has stabilized, turn on the chart recorder and depress the drive start toggle switch until the timer begins to count and then adjust the stroke amplitude knob to 1.00 mm for Procedure A and to 1.5 mm for Procedure B.
9.11 When the digital timer reaches 30 s, increase the load to 100 N using the slow ramp speed rate and maintain this load for 2 min for Procedure A and 15 min for Procedure B. The 2 min or 15 min interval includes the loading ramp sequence. Increase the load by 100 N every 2 min using the slow ramp until a load of 1200 N (or 1400 N) is reached, or the load limit of the test apparatus is attained, or failure occurs.
9.12 The test is ended when the last test load step has been passed or when failure occurs. Failure is indicated by a rise in coefficient of friction of greater than 0.2 over steady state for over 20 s or a stoppage in the oscillating of the test machine (see Test Method D7421). If no stoppage occurs, the O.K./pass load needs to be determined manually by reading the recording chart for the coefficient of friction (and stroke).
NOTE 10 - Because a 30 s break-in at 50 N is used, the load increase times will occur on the half minute of even minutes.
NOTE 11 - The SRV II test machines available after 1992 have a maximum load of 1400 N, and SRV III test machines after 1995 of 2000 N, as well as the SRV model IV of 2000 N. Optimol Instruments supplies an upgrade kit to allow SRV I/II machines to operate with 1600 N, if needed.
9.13 When the 1200 N load run or maximum load of the test apparatus is completed or failure occurs, turn off the heater control, release the load to minimum setting, (typically -13 N or -14 N), and remove the test ball, disk, and lubricating grease test specimen.
