Effects of Varying Ball Bearing Cleaning Processes on Lubricant Life.
AEROSPACE CORP EL SEGUNDO CA ENGINEERING AND TECHNOLOGY GROUP
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The processes used to clean ball bearings and other components in precision spacecraft mechanisms have undergone significant changes to eliminate the use of ozone depleting chemicals, such as Freon TF. This study was part of a larger NASA-funded program to assess the impact of the elimination of ozone-depleting chemicals on lubricant performance in space mechanisms previously qualified for 5 to 10 year lifetimes. The document reports the results of bearing life tests and surface analyses performed with components cleaned with three different methods ultrasonic cleaning with Freon Th, ultrasonic cleaning with Vertrel XF a hydrofluorocarbon, and cleaning with Brulin 815 GD an aqueous detergent. The bearings were lubricated with Brayco 815Z, a perfluoro- polyalkylether PFPE lubricant widely used in spacecraft applications that is susceptible to degradation under boundary lubrication conditions. The bearing tests were operated under boundary conditions, and the endurance of the lubricant was inversely correlated to the cleanliness of the bearing prior to lubrication. Specifically, parts cleaned with the Brulin detergent were shown to have less hydrocarbon residue prior to lubrication and experienced failure due to lubricant degradation in roughly half the time observed for parts cleaned with Freon TF. The Brulin process may also alter the steel-oxide layer structure, potentially impacting performance. Alternatively, parts cleaned with Vertrel XF retained a much greater amount of hydrocarbon contamination from the protective mineral oil than observed for the Freon parts, and subsequently ran approximately two times longer in our tests. The tests and analyses show that care must be taken to understand the impact of new cleaning processes on lubricant chemistry in mechanical systems.
- Lubricants and Hydraulic Fluids
- Solvents, Cleaners and Abrasives
- Machinery and Tools