Five best practices for roll performance and cover life

For optimum performance and to maximize cover life, observe the following five rules:

Keep the cover clean

Contamination on the cover surface increases the local nip load at that point or cross directional position on the cover. This eventually will cause damage to the cover structural integrity and may also mark the paper.

Avoid high operational surface temperatures

For most rubber or polyurethane covers, the ideal maximum surface temperature should not exceed 158 °F (70 °C). Valmet does offer covers that can withstand significantly greater surface temperatures. For these applications, contact your Valmet representative.

Monitor cover temperature

Localized hot spots or hot bands may indicate operational changes or potential cover failure. Determining base line temperatures and recognizing significant changes from baseline can save money by improving reliability and quality. Monitoring may be manual or via automated systems.

Regularly check the cover geometry

The cover can look good visually, but may actually be wearing irregularly. Periodic checks of the crown can aid in optimizing the appropriate grind cycle for the cover. Once the benchmark has been established, it can be used to help troubleshoot operations.

Avoid web breaks and other causes of impact damage

In a situation that causes a felt to wreck or paper to wrap, it is dangerous to continue operations. Remove a damaged cover from service. It is very unlikely that a cover damaged from the outside does not sustain some sort of internal or bond line damage. Even if it appears fine to run, the internal damage could cause a major reliability incident later. It is dangerous to continue operations with a damaged cover. Remove damaged covers from service!

For assistance maximizing roll cover life and roll performance, contact your Valmet representative.