Stora Enso’s Veitsiluoto mill is an integrated production facility manufacturing office papers, coated papers from mechanical pulp and sawn products. It is the fourth largest paper and board mill in Europe. At the same time, Veitsiluoto’s PM 5 has the honor of being the world’s northernmost paper production line. It has the capacity to produce more than 700 tonnes of high-quality NovaPress LWC every day.
At the end of 2011, Veitsiluoto made the decision to invest in improving PM 5's runnability and production efficiency. The previous major changes to the production line were made in the mid-1990s, but preliminary surveys into new development options for PM 5 had been made since 2000.
“We wanted to improve the paper machine's efficiency over time by decreasing the number of production breaks and shortening the break time. One objective was to also decrease the amount of broke created at the reel. At the same time, we had our own efficiency development project in progress: a new operating model was sought for the LWC paper machine to enable operating the production with fewer personnel,” says Markku Åman, Production Manager of the printing paper mill.
From the start of the project it was obvious that the improvements sought could not be accomplished with just a few tricks, but technological improvements were required throughout the production line. In April 2012, Valmet (until Dec. 31, 2013 Metso Paper) was chosen to carry out the upgrades.
From the point of view of the operators of PM 5, the most significant change implemented during the project concerned tail threading of the paper web, whereby two tail threading units were added to the press section. The upgrades made work easier at the press section.
“In this project, the scope of the implementation was exceptional in that it was a complete tail threading project from start to finish; from the press section to the reel. As soon as the tail threading starts, we reach the first upgraded component, Valmet Press Tail Threading Belt. The line now uses nearly every tail threading unit that Valmet offers for the paper grade. Usually, the upgrades concern smaller subsections,” says Pekka Matilainen, Global Technology Manager at Valmet, who participated in planning the project.
The dryer section's runnability package was also upgraded during the project. The runnability boxes located at its start were upgraded to use the latest technology.
“Before the upgrade, we suffered from a typical problem where a minor fault somewhere interrupted the process at the drying stage. We sought to improve the situation with new Valmet Dryer Vac Rolls and runnability boxes by decreasing paper web breaks. The solution proved successful. Certain changes were also made to eliminate an edge flutter problem in the double-fabric area (Valmet Dryer Pocket Ventilator TR), and with these changes, we also reached our targets,” Markku Åman says.
Some of the technologies were chosen only after the sales project had already been started. At Veitsiluoto, potential causes of breaks were considered and it was decided that the 3rd press doctoring should be upgraded during the modification work. It was included in the package because poor doctoring is one factor contributing to breaks caused by precipitation. According to Åman, the new Valmet Doctor Holder Compact 1 double doctor blade holder has been working superbly.
Several different technological improvements were implemented during the project, but which technical measure was the most significant?
“Reel area tail threading was the topic that we had to consider most carefully in advance. However, the technology chosen started to work from the first tail threading and has been reliable ever since,” says Åman.
|“We succeeded in reducing the amount of production stoppages in PM 5. I can honestly say that we have reached the main objectives set for the project, “ states Markku Åman.|
Throughout, well-tested technology was employed in the project. Pekka Matilainen thinks that the most typical solution used with PM 5 was the middle threading and spreading to both directions implemented in the reel-calender area: “This solution was employed to decrease the amount of broke created during a break. When threading takes place in the middle, roll bottom formation is fine after just a few rounds, and there is less broke.
Åman confirms the observation: “Earlier, when threading took place at the edge, there was approximately three kilometers of broke per parent roll during a break. Now the figure is 500–600 meters. This means that there is nearly 2.5 kilometers less broke per break.”
The amount of broke is also decreased by the fact that there are fewer breaks. And with fewer breaks, less energy is wasted as it is not used for producing the extra broke.
The tail threading warranty tests included precisely defined test values for tail threading run-throughs, which were reached. According to Åman, the values defined for the project are constantly being monitored. Performance and efficiency have remained within the target values.
Stora Enso and Valmet signed an agreement on the Veitsiluoto PM 5 upgrade work in April 2012. The major installation work was carried out during week 42 of the same year, with a scheduled maintenance shutdown of a week. Preparation work had already been started by then. The success of the project required careful planning and doing as much as possible in advance, before the actual shutdown. According to Åman, the work was completed within the schedule.
“The implementation from paper to paper during the shutdown took eight days. A highly competent, experienced team both from us and from Valmet participated in the installations. At that stage, it started to become obvious that we had made the right choice about the technology.”
The project's business benefits and payback period are based on the improved efficiency. When the line is operating it produces marketable LWC as efficiently as possible.
“I can honestly say that we have reached the main objectives set for the project. The efficiency objectives included the impact on personnel. We can now operate the machine with just two professionals. Of course, this requires extensive expertise from them, but at the same time, it brings more interest and variety to their work,” Åman says.
A third employee is located at the dry end of the production line with the job of operating the rereeler, as the PM 5 coater is not directly connected to the previous parts of the process. The focus of further development is currently on the final part of the production process, in improving the quality of the finished product.
“Thanks to the upgrades implemented at PM 5 in 2012, we can now get a web out of the machine that is approximately four centimeters wider than before. This is largely thanks to the dryer vac rolls and the new runnability boxes. If we could cut an equally wide web at the cutter, we could bring the material benefit all the way to the customer. This would require some additional investments on the coating machine. A proposition on this has already been made," says Markku Åman.
Key technologies of the Veitsiluoto PM 5 project
Valmet Press Tail Threading Belt 2:
Valmet Double Doctor 3:
Valmet Hirun Web Stabilizer 2 4 :
Valmet Dryer Uno Roll 5:
Valmet Dryer Vac Roll 6:
Valmet Dryer Pocket Ventilator TR 7:
Valmet Tail Jet Cutter D 8:
|Tail threading in the calender-reel area:
1 earlier known as LiteCompact
2 earlier known as PressForce
3 earlier known as DoubleDoc
4 earlier known as HiRun 2000
5 earlier known as UnoRoll
6 earlier known as VacRoll
7 earlier known as TwinRun
8 earlier known as DoubleJet
9 earlier known as BlowForce
10 earlier known as FoilForce