Optimization of a double shoepress

Initial situation:
Since commissioning, the existing double shoe press on PM3 had been showing increased wear and associated dewatering problems, which led to increased breakages, increased downtime, and higher maintenance costs. The wear was evident on both the Nipco-P and the Nipco-Flex due to the frictional connection. While the initial results for the Nipco-P rolls showed polygonality, the Nipco-Flex rolls showed enormous wear on the load-bearing elements and the associated seals. The service life varied between 3 and 9 months, which was significantly below the target of 18 to 24 months.

Analyses & methodology:
Together with the OEM, various analyses (e.g., material analyses) and measurements (e.g., concentricity measurements, vibration analyses, drainage calculations) were carried out, and modifications and adjustments to operating modes were implemented to ensure improved operational safety. The sum of all actions and results contributed to the joint 8D analysis, which revealed that the polyurethane coating was unevenly worn away by the scraper blade, leading to local wear in the CD and in the circumference of the roll cover. This development was also reflected in the appearance of the dewatered paper web at the inlet of the pre-dryer section in the form of damp spots and impaired runnability.

Further steps:
The comprehensive analysis enabled a clear definition of the measures and their prioritization in terms of time, taking into account the implementation period. The focus of the immediate measures was on operational safety combined with protective measures during the planned maintenance shutdowns. This was followed by an interim solution in the form of a new composite cover to extend the running time in a scraped operating configuration and bridge the implementation period of a final upgrade stage with a G-Flex cover.