With our condition monitoring system, you are able to use the useful service life of our rubber-metal parts reliably and to the limit of what is possible, despite all tolerances and fluctuations in the operating conditions. It enables maintenance based on the actual condition of the components. On-demand maintenance and replacement extends the service life of your application, reducing costs and minimizing downtime.
What is condition monitoring?
Nothing lasts forever. Especially components wear out under large changing loads due to vibrations or components in which friction plays a role. Tyres and brake pads in vehicles of all kinds are examples of wear caused by friction. Our rubber-metal bearings are loaded by large vibrations and thus become softer and softer over time, usually designed for about 10 years, until they no longer fulfill their function. There are also other damage mechanisms of rubber, but they play a minor role in elastic joints, our main products.
There are measures that represent the degree of damage well. These must be identified, then measured and recorded. The state, condition, is monitored. The measurand itself or the change in the measurand is evaluated. In the simplest case, there is a fixed limit value, above which a warning is issued and an early replacement of the monitored component becomes necessary. Unfortunately, it’s usually not that simple. In most cases, a lot of data about the operating time is recorded and then processed by computational algorithms or AI, so that a timely indication
of a soon necessary exchange is generated. How long exactly the respective component will last can thus be “only estimated by qualified means”The supreme discipline for condition monitoring is predictive maintenance. The aim is to predict the time of the final end of service life as accurately as possible. A prediction accuracy of 10% would be very good at this point. This means that with a period of 10 months until the actual failure, the forecast would predict a period of 9 to 11 months until then, unless the loads increase or decrease.
CMS also avoids the unplanned failure of the component, which could potentially lead to major consequential damage to the machine in which the monitored component is used.
Is condition monitoring a
short trend or an innovative solution with a future for the digital age?
cost-effectively? Does that sound more like an advertising promise or like a
sensation? Today, a load is determined from measurements and calculations with
which the component is tested. Of course, almost all parts of this part group, which are installed in the various vehicles, e.g. elastic handlebar bearings of a truck, will last the planned 10 years. The loads vary greatly from vehicle to vehicle. The actual load capacity of the different parts of a series also differs. So you have to make sure that the weakest part with the greatest load is tested and lasts. This means that the most robust part could last much longer at the lowest load. If you do not see the part from the outside or only with great effort, whether it would have to be replaced, then it is replaced preventively. The more the loads differ from vehicle to vehicle – of one type, of course – and the more the load capacity differs from part to part – of one type, of course – the greater the waste due to too early replacement of the component.
We have seen examples where parts were replaced that were only one third of the individually possible operating time.
Our condition monitoring
system is able to reliably evaluate the usable remaining service life of
rubber-metal parts. It enables maintenance based on the actual condition of the
components. This reduces costs and minimizes downtimes.
What has condition monitoring to do with our rubber-metal parts?
In the case of our rubber-metal parts, slit bushings, dual bushings, etc., the physical measurand representing the progressive degradation is actually the component stiffness.
However, a decreasing stiffness of the component at the same force leads to a greater distance. As a result, more mechanical kinetic energy is converted into thermal energy, i.e. heat. The duo bushing as the bearing of an anti-roll bar in the truck chassis or as the bearing of the roll support in the bogie of a railway wagon will heat up more over time under the same load. Heat can be measured very well. It is necessary to measure the temperature difference of the bushing to the immediate environment in order to exclude influences of the ambient temperature. If one compares the course of this temperature difference, after the curve has been reduced by the downtimes, with the course of the increasing distances, a correlation can be clearly recognized. So you can use these temperature curves very well.
After a few mathematical operations, a point in time can be determined at which a soon necessary replacement of the component is indicated. You can set the parameters so that the warning occurs at about 70 to 90% of the actual possible runtime. Sometimes it is not optimal to plan the exchange only at almost 100% of the actually possible term. Often it is even cheaper to carry out the exchange even earlier.
This is the case if major maintenance has to be carried out on the vehicle or wind turbine anyway. Unless you can reach the next major maintenance with a very high probability.
So much for the theory of condition monitoring. How does it work with our components, with our rubber-metal parts? As I said, we measure temperatures or temperature differences. This is done with simple thermocouples or PT100 elements, which are installed as close as possible to the position where the highest temperatures are to be expected. Ideally, this would be in the rubber body itself. However, this is not possible because such a point would then be a mechanical notch and the connection between the rubber material and the sensor cannot be optimal, so that additional heat effects would occur here due to friction. However, it has been shown that even in the outer part of the rubber-metal part near the hotspot of temperature, the temperature difference is well measurable.
The change in temperature difference is then plotted and evaluated over time. From the course of this curve one can determine the time at which the rubber bearing should be replaced.
A charming advantage of the method of temperature measurement is its simplicity. The temperature sensors are among the most cost-effective sensors at all and because they output a voltage or a voltage change or a change in resistance as a measurement signal, the evaluation electronics are also extremely simple and cost-effective. The memory for the algorithm we need is very small, which means that we usually do not need our own controllers, but can simply connect to existing controllers, if we are allowed to. The result is a signal in the traffic light format of green, yellow and red, with yellow indicating that an imminent exchange is imminent. Red would mean that it must now be exchanged very urgently.
THE FUTURE’—this is
the surest way to
Where is this
monitoring is used in industries and in machines in which the devices to be
monitored are usually used commercially, i.e. with which money is earned,
capital goods, because capital goods naturally only earn money when they
operate undisturbed. Condition Monitoring for short CMS is just a contribution to the fact that these devices can run trouble-free or that maintenance can also be planned in the long term. Currently, a lot of CMS is used in the field of wind turbines. Most of these machines are to be operated autonomously, but currently service technicians have to climb the towers too often. For many years, wind turbine insurance companies in this industry have also been demanding appropriate remote maintenance via CMS to ensure damage prevention.
Here, mainly components such as ball bearings, rolling bearings and gearboxes are monitored.
Another industry in which the topic of CMS is just beginning to spread is that of rail vehicles. Here, too, we are talking about capital goods that simply earn money when they travel by rail, and not when they are in the depot and maintained.
applications are suitable?
Currently there is no application in series production with our parts. We are still in the area of pre-development, but have recently been in a field trial in real use.
Basically, our components, which are loaded with vibrations, are ideally suited for this concept and especially components that are installed relatively concealed, in which damage or damage progress cannot be determined by a simple optical inspection. In the field of rail vehicles, these are, for example, any type of handlebar bushings, stabilizer bearings or roll support bearings. In the field of wind turbines, these can be the generator and gearbox bearings.
Wherever an exchange of the parts is very time-consuming compared to the price of the parts, where it is not clear whether the parts are damaged or not, our system can be used sensibly.
It is certainly also conceivable to use this technology in truck chassis. Especially since that’s where we deliver our parts. We can also imagine applications in the field of construction machinery where monitoring of the components makes sense. Now, of course, you have to say that this technology is still new. The quantities still have to be developed in order to be able to realize economies of scale for the price.