Successful tissue making with optimized fabrics
“Getting paper machine clothing and machine technology from one supplier is a benefit to our customers,” says Mikko Blom, General Sales Manager, Paper
Machine Clothing at Valmet.
Valmet offers tissue mills a full scope of forming fabrics, press felts and shoe press belts - all optimized for ideal performance.
Felts for best dryness
Valmet’s StarMaster FT family includes press felts for all kinds of tissue machines, from traditional ones where maximal dryness is typically achieved with one nip, to presses. The ideal kind of press felt depends on, for example, whether the machine produces premium or heavy grades, whether it is a fast or superfast machine, or if a short breaking-in time is needed.
“The base structure of the felt must be dense to create hydraulic pressure. On the other hand, it must be open to allow the water to flow onto the surface of the suction roll and to utilize the suction roll vacuum effect on the back side. Optimization presents a challenge,” Blom says. “One of our ‘secret weapons’ in R&D is a water flow simulator that measures water flow resistance through the felt in both the cross and machine directions. Our tissue felts are also tested on our pilot machine in Karlstad, Sweden.”
Introducing: A new coated seamed press felt for safe installation
Seamed felts greatly improve safety at mills. It is much safer to install a seamed felt than an endless one. Thanks to the seam, felt installation is much faster and it takes much less manpower to change the felt. In addition, tissue felts are typically very long, averaging some 40 meters. Installing a long felt can be challenging and time-consuming. That’s why Valmet has developed the coated SeamMaster FT felt.
“Coating, in turn, allows us to make a seam flap that not only protects the seam, but also eliminates potential problems caused by the seam on light tissue paper,” Blom explains. The treatment makes the felt structure dense, non-compacting and perfect for a fast start-up and immediate nip dewatering. It also gives the felt a much smoother surface.
Good dewatering and long lifetime with BlackBelt
Today, all ViscoNip presses are equipped with the BlackBelt FT shoe press belt. It features accurate dimensions and easy installation, as well as a unique matt treatment on the inside surface to ensure low friction between the ViscoNip beam and belt. A large open area and void volume ensure good dewatering with no risk of marking.
“High-density grooves have proven to be a good solution, especially for tissue machines. The narrow lands ensure fast dewatering without leaving any water flow marks on the sheet,” Blom adds.
So far, the record running time of a BlackBelt in a tissue machine has been over 200 million nip cycles. Another belt lasted for over 17 months in a shoe press.
Record-high energy savings
The combination of a Valmet felt and BlackBelt has resulted in an energy savings world record in tissue production. A modern tissue machine in Chile became the first in the world to lower its specific energy consumption to under 1,800 kWh per tonne produced. In July 2015, the same machine achieved record-high efficiency of 89.7%.
“The machine has run many Valmet felts, and the results have been very consistent. This proves that the repeatability of our products is high,” Blom points out.
Excellent runnability in the forming section
For high-speed tissue machines with the highest fabric stability requirements, Valmet’s solution is GapMaster Ultra FT. The benefits of this modern SSB fabric include a high dry content, high retention and cleanliness, as well as excellent trimming.
“Results from tissue machines have proven that GapMaster Ultra FT’s fiber and water carry is lower as compared with other corresponding products. Also trimming has worked very well. These benefits have resulted in improved runnability”, Mikko Blom concludes.