Method and apparatus for detecting abnormal metal-to-metal contact in a journal bearing

This invention provides a method and apparatus for early detection of wiping contact between a rotating shaft and bearing metal in a flow lubricated bearing. In one form of the invention, a temperature sensor is provided to monitor bearing temperature at a location on the bearing in proximity to the maximum loading position. The sensor signal is sampled periodically by a plurality of sample and hold circuits so that present and immediately past values of the bearing temperature are always on hand. The sampled values are applied to a set of subtracters, each one of which provides a signal representing the difference between two consecutively sampled temperature values. Selected ones of the temperature differences are applied to summers and the largest sum is selected by a high-value selector and compared with a preselected setpoint value representing an excessive temperature change for a given time period. Based on the comparison, a decision is automatically made as to whether the bearing temperature at the sensed location is increasing at an excessively rapid rate, found to be indicative of a temperature "spike" which in turn is evidence of metal-to-metal contact in the bearing.