Calendering lines, used in the extruded film and sheet sector, are expensive pieces of equipment, with many highly polished rolls working precisely together.
So this month, Best Practices takes you to Worms, Germany, and the headquarters plant of Renolit Group. We learn about bearings, the mechanism that supports the heavy rolls. Specifically, what can go wrong with said bearings.
This story is about how sensors can monitor vibration. Sensors are a hot topic in machinery circles, and you can expect to see them proliferate even more at NPE2018. Rather than waiting until equipment fails, sensors give you a heads-up beforehand that something has changed.
At Renolit's Worms plant, repeated bearing failures on some calendaring lines were causing unplanned downtime and production stoppages. Each of the six sheet calenders in the plant have at least four rolls.
Renolit officials contacted the Schaeffler AG, the big global automotive parts maker and industrial supplier. On the industry side, Schaeffler, based in Herzogenaurach, Germany, makes rolling and bearing systems for a wide range of applications.
So the experts at Schaeffler got to work. The task: Develop a monitoring system that would improve the overall production time. Challenges included very slow roller speeds and high temperatures in the housings that could reach up to 300° F. And it was hard to access the measurement point during production.
At Renolit in Worms, the calender rolls are supported by special multirow cylindrical rolling bearing assembles on both sides. The axial bearings can either be double-row angular contact ball bearings or deep-groove ball bearings. Preload and roll bending forces are applied on the rolls by double-row cylindrical roller bearings.
Schaeffler's team developed two concepts matched to Renolit's specific conditions. The first: Install an online condition monitoring system for permanent monitoring. The second: Conduct regular vibration measurements, offline.
Renolit officials picked the second option. That included the fixed installation of vibration sensors and the use of sensor switch boxes. Technicians can measure data from a safe distance using a mobile vibration measuring system. A total of 88 measurement points on 178 individual bearings are monitored.
"Renolit can now closely monitor the condition of its calender rollers without interrupting production," Schaeffler said. In the last five years, six cases of rolling bearing damage have been detected at an early stage using this method, the company said. Renolit replaced the bearings during planned maintenance, so the work did not cause any production stoppages.
Information obtained through vibration monitoring helps to optimize maintenance activities over time, evening out the work and avoiding a catastrophic failure caused by bearing failure. That also helps improve worker safety.
So it made sense for Renolit leaders in Worms. And Schaeffler points out that the conditioning monitoring concept can easily be transferred to other calender stands or similar production facilities.
The technology also is flexible. Schaeffler officials said the concept can be expanded later to provide permanent online monitoring with multichannel monitoring systems from Schaeffler, using sensors that have already been installed. The industrial company has 89,400 employees in more than 50 countries.
So it can handle a lot of bearings.