Rolling bearings – the key to avoid production stoppages

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

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 and potentially cost a firm in the five-digit euro range.

Schaeffler was given the task of developing a monitoring concept that would improve the overall availability of the facilities. The 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 production plant in Worms 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 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’s condition monitoring team developed two concepts matched to the customer’s specific conditions. The first concept involved the installation of an online condition monitoring system for permanent monitoring of the facilities. The second concept consisted of conducting regular recurring vibration measurements (offline strategy).

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 monitored.

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

Using the new monitoring concept developed by Schaeffler, Renolit can now closely monitor 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.

Data obtained through vibration monitoring helps to optimise maintenance activities over the long term. Another advantage for the customer is that it has 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.

In addition, 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.