Edge Damage Example

In this example, the mill was experiencing runnability problems on a tissue machine. The sheet was picking on the blade near the front, and the reel had a very wet front edge. Line-scanned infrared thermography was used to determine the temperature distribution on the dryer, showing both the wet edge and several even wetter spots within the wet edge. The thermal map is shown at the right. It was postulated that the wet spots were caused by depressions in the dryer since they were fully synchronous with the dryer itself.

In order to map the dryer to asses the condition of the surface, provisions were made to take measurements on-the-run. The resulting map of the dryer is shown in the accompanying figure. Three low areas along the front edge were found which matched the infrared image results. Due to the depth of the flaws and their growth rate, the mill decided to grind the dryer to restore runnability. It was later determined that damage had been done to the dryer during a blade change operation, and the creation of small damaged areas, combined with poor coating due to the wet sheet in that area led to the eventual deep flaws.

© 2007 PROdry Technology, Inc. Site last updated 3/7/07