Estimating Water Content in Oils: Moisture in Solution, Emulsified Water, andFree Water

摘要

This paper discusses the detrimental effects of moisture in lubricants,hydraulics, and transformer oils. It describes a means for automatic estimation of moisture content in lubricating oils, hydraulic fluids, and transformer oils. This is a field test method, used as an alternative when it is not convenient to measure water content by the Karl Fisher test or another analytical method. The total moisture content is found to be the sum of three separate measurements: moisture in solution, emulsified water, and free water. A single capacitive sensor is used to make all three measurements. Moisture in solution is instantaneously measured from a well mixed contaminated oil sample as compared to a similar measurement for a clean reference oil sample. Emulsified water is measured by determining the median-average rate of change in sensor output over time. Free water is measured by determining the accumulation of step changes in sensor output over time. The capacitive sensor is also used to identify the general oil type based upon the nominal dielectric value and upon the change in dielectric as a function of temperature change.