On-line Fluid Condition Monitoring Technology

Modernizing condition monitoring procedures and maintenance practices is often driven by the introduction of innovative technologies that facilitate the gathering of previously unavailable data, or data that required advanced instrumentation or complex analytical techniques. Because fluid life is contingent on various factors, proper assessment of fluid conditions requires simultaneous monitoring of several properties. Regular fluid sampling is important in enterprise operation because deteriorating fluid conditions adversely affect system components and manufacturing processes. Direct in-line measurements offer a good source of data because errors that arise in the course of fluid sampling and processing are reduced.


Figure 1. Top View of Sensor Showing Viscosity (QCM), Temperature (RTD) and Dielectric (DC) Sensing Elements

There is an additional need for analytical devices suitable for employment in industrial environments and direct installation in hydraulic and lubricating systems. A significant part of the development of industrial sensors has centered on discovering properties that correlate to results obtained from conventional evaluations. In this regard, the selected properties included those often associated with fluid condemnation guidelines, such as viscosity and acid number (AN), because both are indicative of irreversible physical or chemical changes in the fluid makeup.


Figure 2. Bottom View of the MEMS Sensor Showing the Relative Humidity Sensing Element

The HYDACLab sensor comprises four individual sensing elements for simultaneous measurement of temperature, relative humidity, relative viscosity and relative dielectric constant. In general, oil viscosity and polarity increase with age as a result of exposure to physical stress, thermal degradation or hydrolytic breakdown due to formation of acidic byproducts and polymerization. Although the measurements of viscosity and dielectric constant are not absolute and need to be referenced against those obtained for fresh oil, they provide a reliable indication of the overall oil condition. By tracking changes in these parameters, fluid replacement intervals can be optimized by linking them to fluid condition. The HYDACLab can also identify cross-contamination arising from top- offs with inappropriate fluids, as these will be reflected by changes in viscosity and the dielectric constant.


Figure 3. HydacLab Condition-monitoring Sensor

Proper interpretation and trending of the HYDACLab data can result in considerable savings in equipment maintenance and plant operation due to the elimination of unplanned shutdowns, unnecessary fluid replacements and preventing fluid-related problems.

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