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Application Note: AN9071

4 BALL EP FOR OIL AND GREASE ANALYSIS

INTRODUCTION


The MFT5000 is a versatile multi-function mechanical property tester capable of simulating a vast number of tribology and wear tests on same platform. This application note shows how the MFT5000 can be used to study grease, oil for EP and wear tests using its 4 Ball Module. 4 Ball module can be used for several standard tests such as ASTM D2266, D4172, ASTM D2596, ASTM D2783, BS EN ISO 20623, BS ISO 26422, CEC L-45-A-99, DIN 51 350, IP 239. The module is used to characterize lubrication properties of oils and greases under nominal and extreme pressure conditions.

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MATERIAL & METHOD

Typical test balls are alloy steel (E52100), with diameter 12.7mm (0.5 inches), Grade 25 (Extra Polish) and HRC 62-54. Four such balls are used for each test. Approximately 5g of grease or 10ml of oil is used in the test. The module can be customized for other size balls and lubricant containers. 



A steel ball is rotated under load against three stationary balls in presence of a lubricant. The rotation speed (upto 5000 rpm), loading rate and applied load ( up to 10,000N) and temperature (up to 150 C) are set according to the standard being followed. The load can be applied in a linearly increasing manner or the test can be ran at a constant load. 




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 Wear Test – This test is used to evaluate lubrication performance of grease or oil. The test is carried out at relatively mild test conditions e.g. 392N at 75C at 1200 rpm for 1 hour. Tests with higher loads, and longer durations can also be designed. The performance of the lubricant is evaluated by measuring and comparing the wear diameter of the balls after the test. Diameter of wear scar on each of the three lower balls is measured at two locations 90° to each other. The average of six measurements is reported as wear diameter for the 4 ball test.

 


Extreme Pressure Wear (EP Wear) Test – This test is used to test lubrication properties of lubricants (oils and greases) under extreme pressure conditions. The top ball is rotated at high speeds and high loads for a short duration of time e.g. 1800 RPM, 3000N and 30s. Load is increased in steps or linearly until the lubricant fails. The maximum load that can be applied is up to 10,000 N. The failure is determined by welding of the four balls, visible smoke, instantaneous increase in friction or torque. The test is automatically stopped at the onset of failure. The lubricants are rated based on their ability to “pass” the test without failure at applied loads.    

ANALYSIS

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Figure shows the 3D Image of the wear track on one of the lower sample after running a 4 Ball wear test for 1 hour at 1200rpm and 392N.  

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Figure shows results of an increasing load test. The test was configured to automatically apply a linearly increasing load from 400N to 4000N at a rate of 600N/minute. The acoustic signal was also recorded. It shows that the sample started to fail around 2800N, while complete failure leading to welding was observed at around 3600N. The inset in the figure shows the welded lower balls after failure occurred in the extreme pressure tests. 
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CONCLUSION

MFT5000 Four Ball Module is an excellent option to run multiple 4 Ball standard and several customized tests on the same platform. High loads up to 10,000N can be applied to evaluate the lubrication and extreme pressure properties of modern lubricants and additives. The temperature can be controlled ando monitored in real time. The acoustic data is also recorded to determine the onset of failure before complete failure as indicated by welding or smoke. The anti-splash containers allows to run these tests without spills and splashes. 

REFERENCES & KEYWORDS

ASTM D2596, ASTM D2783, ASTM D2266, ASTM D4172

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