Bearing Fluting: The Results of a Long-Term Investigation into Bearing Fluting on AC Motors, DC Motors, and Rolls on Paper Machines

WHEN UNEXPECTED BEARING LOSSES WERE QUESTIONED AT A PAPER MILL, work began at the mill that led to a long-term investigation to determine the causes and incidence of a type of bearing damage called “bearing fluting.” It was discovered that many paper machines have bearing fluting that has caused significant down time and increased maintenance costs. Additionally, bearing fluting was found to be associated with the use of ac or dc sectional variable-speed control. This problem is not new, but the understanding of its origin, magnitude, and treatment has improved over the past couple of years. A number of ways to control the problem were investigated. Our first encounter with bearing fluting, that we were aware of, occurred in 1988 on a kraft paper machine approximately one year after it was rebuilt. The rebuild included replacement of a line shaft with 26 dc drives and four ac drives. The first bearing problem appeared in a dryer-drive dc motor. Within three years, we had found and replaced fluted bearings in nearly all of the variable-speed ac motors and 24 of the 26 dc motors.