System delivers predictive maintenance without interrupting operations

A new system developed in Germany has the ability to monitor the condition of lubricating oils, hydraulic oils and other fluids in industrial installations without interrupting ongoing operations. According to its creators, it offers benefits such as predictive maintenance of hard-to-access plants, no unnecessary oil changes, no unnecessary laboratory costs and reduced environmental impact.

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

The team of engineers, led by Professor Andreas Schütze from Saarland University and ZeMA, the Centre for Mechatronics and Automation Technology in Saarbrücken, will be showcasing their work from 7-11 April at the Saarland Research and Innovation Stand at Hannover Messe (Hall 2, Stand C 48).

Professor Andreas Schütze (left) and graduate engineer Eliseo Pignanelli (right) will be exhibiting the portable version of their measurement system at Hannover Messe, with which they can perform local on-site testing to detect signs of oil ageing and degradation. Image credit: Oliver Dietze.

Failing to change the oil at the right time can cause serious damage to machinery and equipment - a fact that is just as true for cars as it is for large industrial installations. Over time, a lubricating oil used to minimise friction, reduce wear and prevent overheating will become contaminated with fine metal dust and particles from abrasive processes. The oil will also gradually oxidise and the additives that help to optimise 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.

According to Professor Schütze, the key problem is that it is not obvious exactly when the oil needs changing. 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 usable, which is costly for both the operator and the environment,” said Professor Schütze.

In collaboration with partners from other universities and industry, Schütze’s team at the Lab for Measurement Technology and ZeMA have developed a measurement system that can be integrated directly into industrial installations where it continuously measures and monitors oil ageing and degradation while the installation continues to operate. The data from the measurement system are currently transmitted by mobile radio communication so that analysis and assessment can be performed 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,” said Schütze. The method is also suitable for use with hydraulic systems. The measurement system can test not only oils, but can also be used to monitor the condition of other fluids.

The methods developed by the engineers involve shining light into the liquid being monitored. In one case, light from a laser diode is 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. The scattered light is then recorded by photodiodes and the signals analysed. The system allows us to distinguish between metal dust, other solid particles and air bubbles, and to determine the concentration of each,” said engineer Eliseo Pignanelli, who has been involved in refining the system. 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,” said Pignanelli. This spectroscopic analysis also enables the presence of water in the oil to be detected.

Working with ZeMA in Saarbrücken, the engineers are now aiming to develop the technology into a market-ready product