Knowing When to Change Oil

Wednesday, April 2, 2014 @ 12:04 PM gHale

There is a new system that can monitor the condition of lubricating oils, hydraulic oils and other fluids in industrial installations without interrupting ongoing operations.

This new system allows for a stronger predictive maintenance of hard-to-access plants, no unnecessary oil changes, no unnecessary laboratory costs and less environmental impact.

The method, developed by engineers from Saarbrücken in collaboration with project partners, is a compact sensor system which is also available as a portable unit or they can build it into industrial plants, wind turbines and other machinery.

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The system, which uses optical methods to measure the oil’s chemical makeup and the degree of particle loading, can also predict the best time for an oil change, said Professor Andreas Schütze from Saarland University and ZeMA, the Centre for Mechatronics and Automation Technology in Saarbrücken, who led a team of engineers working on this project.

Failing to change the oil at the right time can cause serious damage to machinery and equipment, which is true for automobiles as well as large industrial installations.

Over time, a lubricating oil used to minimize friction, reduce wear and prevent overheating will become contaminated with fine metal dust and particles from abrasive processes. The oil will also gradually oxidize. And the additives that help to optimize the oil’s properties also have only a finite lifetime. At some point, the oil will no longer be able to act as an effective lubricant.

The key problem is that it is not obvious when exactly the oil needs changing, Schütze said. In the case of plants or installations that are difficult to reach – such as offshore wind turbines – the method adopted up to now has been either to take oil samples and have them examined in costly laboratory analyses or to simply change the oil at some regular interval.

“As a result, a great deal of effort is expended in changing oil that is still actually useable, which is costly for both the operator and the environment,” Schütze said.

In collaboration with partners from other universities and industry, Schütze’s team at the Lab for Measurement Technology and at ZeMA developed a measurement system that can integrate directly into industrial installations where it continuously measures and monitors oil aging and degradation while the installation continues to operate.

The data from the measurement system currently transmit via mobile radio communication so experts can perform analysis and assessment off-site. A portable version of the system also exists.

“Our system allows us to identify and avert potential damage early on. We can predict when maintenance work will be needed and plant operators can plan accordingly,” Schütze said. The method is also suitable for use with hydraulic systems. And the measurement system can test not only oils, but also monitor the condition of other fluids.

The methods developed by the engineers in Saarbrücken involve shining light into the monitored liquid. In one case, light from a laser diode ends up scattered by any particles present in the oil or fluid.

“Each different type of particle scatters the light in a particular way, causing more or less light to be measured in the various spatial directions,” said engineer Eliseo Pignanelli, who is working on refining the system. “The scattered light is then recorded by photodiodes and the signals analyzed. The system allows us to distinguish between metal dust, other solid particles and air bubbles and to determine the concentration of each.”

The second optical technique measures the absorption of infrared light by the fluid at specific wavelengths as it flows through the measurement system.

“This permits us to draw conclusions about the chemical state of the oil, because chemical changes to the oil will cause changes in the light spectrum that we record,” Pignanelli said. This spectroscopic analysis also enables the user to determine the presence of water in the oil.

The team of engineers at Saarbrücken have been developing the system in a number of research projects, including the “FluidSens” and “NaMiFlu” projects that are collaborative efforts involving partners from academic institutions and from industry. Industrial partners include HYDAC Electronic GmbH in Gersweiler and EADS Deutschland GmbH (Innovation Works). One of the main areas of research concerned optimizing the optical and mechanical properties of the nanostructured layers used in the microsensors and adapting them for use at high pressures.

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