Dissolved Wear Metal Monitoring in Lubricating Fluids

Lubricating fluids play a critical role in the operation of many machines in commerce, industry, and the military. Failure of a lubricant often results in accelerated metal wear and the release of wear debris in the lubricant. Early detection of abnormal metal wear is important for fault detection and failure prevention. An electrochemical cell can be operated in a lubricating fluid in such a way that the operating characteristics of the cell can provide an indication of the chemistry of the fluid. For example, certain ions in the fluid, such as wear metal ions, will react to particular potential values applied to electrodes in the electrochemical cell. By applying a changing potential across the electrodes in an electrochemical cell and observing the resulting current it is possible to detect and identify the ionic species present in the lubricating fluid. The objective is to provide real-time monitoring of lubricating fluids using an in situ sensor to detect and diagnose conditions leading to machinery failure. A series of experiments have been conducted to confirm the ability of an electrochemical cell to detect wear metal ions in lubricating fluids extracted from machinery. Additional tests have been conducted to test the hypothesis that the presence and amount of wear metal ions corresponds to the type and amount of wear particles in the fluid. Initial laboratory tests have established a positive correlation with wear particles detected in used lubricating oil with ion presence determined using ion chromatography. The results reported indicate that a small, real-time multielement sensor with an electrochemical cell will be able to detect wear metal ions and provide an early indication of unusual material wear. This capability may provide an early warning of atypical wear patterns and provide a cue to an operator or service engineer indicating the type of fault occurring and the specific component experiencing wear or early failure.