The basic requirement is to perform up to 160 roll movements per hour during peak periods. The most cost-effective solution for this challenge was for these handling volumes to be tackled with four automatic cranes, each of which will have two hoists that can operate independently of each other to ensure fast and flexible finished goods handling in a compact space, even when working through peak workloads.
“Many paper manufacturers are converting their plant production from printing paper to packaging paper and upgrading their storage systems in the process. With our process cranes and extensive engineering experience, we can design customised and highly efficient material flow solutions for these needs,” said Dr Thomas Bönker, senior VP, Process Cranes, Demag.
With around 2,100 employees and a total annual publication paper production capacity of 2.1 million tons at five paper mills, the Norske Skog group is one of the world’s leading paper manufacturers. At the Golbey plant, which is located in the French Vosges region, around 565,000 tons of newsprint can be made annually on two production lines, most of it from recycled paper.
One of the two lines, PM 1, is currently being converted from the production of newsprint to production of 550,000 tons of recycled, lightweight packaging paper. As part of this change, Norske Skog will also be setting up a new finished-goods automated store for this production line and awarded a contract to Demag to plan and build the cranes for the store.
Rolls with a diameter of 1.40m will be stored in stacks up to a height of 15m at approximately 2,470 locations. The store layout is flexible, meaning it can be adjusted to accommodate rolls with smaller and larger diameters.
The store will feature space for a total of almost 15,000 rolls with a total weight of 41,400 tons when 100% full. To cater for future product variants, experience shows that the store will be operated at a capacity of 75%, i.e. with approx. 31,000 tons.
Since PM1 will have an annual capacity of 550,000 tonnes recycled containerboard, this means the warehouse will be replenished almost 18 times a year. The handling volume per hour is accordingly large: The forecast is that a maximum of 80 rolls will have to be stored and up to 140 rolls will have to be retrieved or re-arranged.
On average, the actual numbers will be 32 and 104, respectively. This entails demanding requirements regarding the automatic cranes’ capacity and performance and will require a smooth and smart logistics process. Just like with all projects, this process will be developed together with the customer and the conveyor equipment supplier and adjusted in line with future needs. From a warehouse management system perspective, the corresponding analyses and developments will include the entire material flow management from the winder downstream of the paper machine to loading the finished products onto trucks.
For validation purposes, Demag recommended a material flow simulation that considered not just the storage area and the required crane performance, but also the inbound and outbound materials handling equipment and the weights and dimensions of the paper rolls. For PM 1 in Golbey, the ideal solution consisted of four process cranes, each equipped with two hoists that would be able to travel independently of each other (each with a load capacity of 4.5 tons), as this arrangement would make it possible to handle very high transfer volumes on short notice.
Norske Skog confirmed the proposed solution of two double-girder overhead travelling cranes on a common runway with a span of 29.2 metres and a maximum lifting height of 18.5 metres, installed in each bay. The characteristic of these cranes will be a configuration with two travelling hoists that can move independently of each other. This configuration, combined with smart management by the warehouse management system, will be the key to the system’s high performance and flexibility. The winch units will not only be able to work in tandem and pick up or deposit two rolls (from either the same height or different heights), but also handle only a single roll and even take two rolls from a stack of rolls. Vacuum lifting units will be used to pick up loads gently.
Ultimately, the process cranes will take care of combined storage and retrieval operations while working automatically 24/7. The difference in quantity between the two types of operations is the result of the system working around the clock, i.e. filling the store while retrieval operations are only performed during the day.
Demag’s offerings for the paper industry also include solutions for the complete in-house transport of paper rolls, including staging and loading; including; Material flow management to track the paper rolls from the rewinder to the store infeed point; Warehouse management for organisation of the paper roll store; Shipping management for precise staging of the right roll at the shipping location at the right time and yard management for organisation of truck traffic in the shipping area.
