Bearing fluting [motors]

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. Electrical bearing damage, including fluting and frosting, was controlled by using shaft grounding.