Condition monitoring of calender rolling bearings reduces downtime

Yet repeated rolling bearing failures on various calender units at the production plant in Worms, Germany were causing unplanned downtime and costly production stoppages.

Challenges included the very slow roller speeds, high housing temperatures (up to 150°C) and the difficulty of accessing the measurement points during production.

Each of the six plastic sheeting calenders in the plant consists of at least four calender rolls, which are supported by special multi-row cylindrical rolling bearing assemblies on both sides running under highest accuracy.

The team developed a two-fold approach: online, installation of a system for permanent monitoring of the facilities; offline, regular recurring vibration measurements

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 calender rolls by double-row cylindrical roller bearings.

Two-concept solution

Schaeffler was commissioned to develop a monitoring approach that would improve the overall availability of the facilities.

Its condition monitoring team developed a two-fold approach: online, installation of a system for permanent monitoring of the facilities; offline, the application of regular recurring vibration measurements.

Renolit initially chose the offline strategy, which included the fixed installation of vibration sensors and the use of sensor switch boxes for querying the measurement data from a safe distance using a mobile vibration measuring system. A total of 88 measurement points on 178 individual bearings are now monitored.

Customer benefits

Using the new monitoring concept developed by Schaeffler, Renolit can now closely check the condition of its calender rollers without interrupting production. Since 2013, six cases of rolling bearing damage have already been detected at an early stage using this concept. The affected bearings were replaced during planned maintenance intervals without causing any stoppages to production.

If rolling bearing damage suddenly occurs during operation of a machine, this may result in a shutdown of the entire facility that could last for several days. The costs for such a shutdown are in the five-digit euro range.

In addition, the data obtained through vibration monitoring helps to optimise maintenance activities over the long term. Another advantage for the customer is that it has found a partner who can supply high quality rolling bearing products and condition monitoring services from a single source.

The offline condition monitoring concept can easily be transferred to other calender stands or similar production facilities. Precise positioning of the permanently installed sensors ensures that repeated measurements can be conducted according to occupational safety requirements

The concept can easily be expanded at a later date to provide permanent online monitoring with multi-channel condition monitoring systems from Schaeffler using the sensors that have already been installed.