The highly durable CalPanther calender roll cover works with all paper and board grades

Valmet’s (until December 2013 Metso Paper) new composite CalPanther calender roll cover, which was launched about this time last year, has been well received by the marketplace. More than fifty CalPanthers are already in use in Europe and North America. CalPanther covers are suited to a variety of paper and board grades, and are used on soft calenders, supercalenders and modern multi-nip calenders such as OptiLoad and Janus.

The CalPanther cover has been used on a coated fine paper line soft calender at M-real’s Kangas Mill in Finland for more than a year now. Surface roughness has remained good, which is obviously important for the manufacture of high-gloss smooth printing paper.

The majority of composite covers are found on supercalenders. CalPanther is used on many supercalenders for both LWC and SC calendering. One particular LWC line has used CalPanther at all nip locations. This machine's rolls are replaced at regular intervals, and CalPanther has not shown any indications of uneven wear or patterning. The cover has stayed very smooth, around Ra 0.2–0.3 µm.

Our second supercalender example is M-real’s Kirkniemi PM 3, where CalPanther has also been in service for more than a year. PM 3 produces high-gloss (68–74° Hunter) double-coated lightweight printing paper in the 65–90 g/m² grammage range. Calendering conditions at this 12-roll supercalender are challenging as the calendered sheet needs to be very smooth (PPS 0.8–1.0). This is why the linear load used is 300–350 kN/m and thermoroll temperature 135°C. The calenders are normally run at 850 m/min with polymer rolls.

Markus Muro, foreman of the M-real Kirkniemi day shift, is pleased with the performance of CalPanther, especially its durability.

Kirkniemi’s day shift foreman, Markus Muro, and the shift operators have found CalPanther more resistant to deformation than many other covers, which is why it is typically placed in the heaviest loaded bottom roll positions.

The calendering of release paper also needs to be very effective. One such release paper machine uses an average calendering load of 420 kN/m and a calendering temperature of 200°C. CalPanther has performed excellently under these challenging conditions, and the mill has been very satisfied with the durability of the cover. CalPanther has had no problem reaching the mill’s 45,000 km grinding interval target

CalPanther has provided many practical demonstrations of its durability and suitability for different calender types and paper grades. Experiences with the cover have been very positive, and no cover damage has been detected during normal production.