What is Roll Stability Test?
Table of Contents
To check the lubricant quality, we normally did different tests using different types of lubricants tester or tribometers. We have already discussed the Pin on Disc Tester and Four-Ball Tribometers. We will discuss the grease roll stability testing method and the Roll Stability Tester.
To determine the grease’s mechanical stability, oil separation, and consistency change, we usually do the roll stability testing of all lubricants following ASTM D1831.
The grease is evenly distributed on the inside walls of the test cylinders. A weighted roller is then placed inside the cylinder. The test cylinders can be mounted horizontally on a guide and driving wheels that rotate the cylinder at the specified rpm. A closed-loop temperature controller controls the temperature precisely in the test area.
Standard Method to Test Roll Stability of Lubricating Grease as per ASTM D1831-21
1 This test method measures the changes in consistency of lubricating oils when they are used in the roll stability testing apparatus.
2 SI units should be considered as standard.
3 The standard does not address all safety concerns associated with its usage. The user of this standard is responsible for establishing appropriate safety, health and environmental practices, as well as determining the applicability regulatory limitations, prior to its use.
1 Measure the working penetration of the grease. This should be done in accordance to Test Methods D1403.
2 Transfer 63.0g ± 6 0.2g of unworked grease for testing cylinder. Use a spatula to evenly distribute the grease on the inside of the cylinder.
3 Place the weighed roll in the cylinder.
4 Add 7.0g ± 0.2g distilled water to a cylinder and close the cap. NOTE 1–The ratio of grease to water can be adjusted, but the total material must not exceed 70g. For example, 56g of grease and 14g of water would equal to 20% of water.
4 Place the cylinder in its correct position and start the machine. The temperature around the cylinder should be kept at 20 to 35 degrees Celsius if it is contained within a cabinet.
6 After rolling the cylindrical for 2 h ± 05 min, drain the grease immediately and follow the instructions in Test Methods D1403. Keep track of the work penetration. Transfer the grease to the worker and wipe the apparatus with a clean cloth or tissue. 8.7 Use the Test Methods D1403 to convert the fractional penetration values (before and after) into equivalent cone penetration values by using the appropriate equations.
Interpretation and calculation of results
The following steps can be used to calculate the change in consistency:
Penetration change = P2 – P1
Where P2 is the final full-scale equivalent penetration measurement, and P1 is the initial full-scale equivalent penetration measurement
NOTE 2 – The penetration reading is measured in tenths (mil) A negative penetration change is a sign of hardening grease, while a positive penetration reading indicates softening.
This article briefly describes the Lubricant Roll Stability Testing machine. Many modern improvements are going on in this modern era on the different tribometers, thus enabling the tribologists to simulate the real-time applications.
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