PrimeCal Y belt calender for paper and board machines
Calendering without compromising bulk and surface properties: ANDRITZ has developed a new state-of-the-art calender — the PrimeCal Y — which achieves superior paper properties while preserving the maximum amount of bulk. Mission accomplished.
Calenders have been in use in the paper industry for decades. They improve the smoothness and gloss of a sheet and/or reduce the porosity of paper and board. While achieving these desired properties, the challenge has always been to minimize bulk loss so as not to adversely affect the stiffness or opacity of the product. ANDRITZ, with its extensive experience supplying hundreds of calenders and rolls, has developed a new state-of-the-art calender — the PrimeCal Y — which achieves superior paper properties while preserving the maximum amount of bulk.
In the PrimeCal Y belt calender, the surface of the sheet is moisturized prior to entering an adjustable pre-heating zone around the Peritherm roll. Since the dwell time in the pre-heating zone is more than 50 times longer than in a typical hard nip calender, the temperature of the heated roll needs to be only 20-30° C above the glass transition temperature of the sheet. This approach makes it possible to properly soften the paper using high moisture and temperature, but in a thin surface layer of the sheet. Lower line forces are needed in the subsequent roll nip and less heat is required to achieve the desired quality at a much lower compression rate. The result is bulk preservation.
Compared to conventional soft or hard nip calenders, lower roll temperatures and lower line loads in the PrimeCal Y achieve the same, or better, calendering effects. This contributes to the calender’s significant energy savings.
Hard or soft cover deflection-controlled rolls can be used to form the nip with the heated roll. The PrimeRoll MHV ensures exact CD caliper control.
All ANDRITZ calenders are easily installed in new lines or as part of a machine rebuild.
At a glance
- Bulk is preserved
- Surface properties are enhanced
- Better densification and improved calendering effects are achieved compared to conventional calenders
- Heated roll temperature only 20-30° C above glass transition point – lower roll temperature means lower energy consumption and reduced thermal loss.