Figure 1.22. The LVL production process. 1. LVL AS A CONSTRUCTION MATERIAL 1.6 PRODUCTION OF LVL The LVL production process is subject to strict quality standards and audited by inspectors to ensure the final product is safe to use and meets the specified end use requirements. LVL is made by gluing and layering wood veneers to produce a homogenous wood panel. The process distributes any natural defects in the wood raw material evenly throughout the product, eliminating any individual points of weakness. The following simplified production diagram illustrates the LVL production process inside the mill. Veneer logs are delivered from the forest to the mill at a specified length. The logs are debarked, conditioned, and cut Figure 1.21. Composition of LVL, from veneer mat to cut-to-size panel. Figure1.23. Log use distribution by volume: LVL and by-products (incl. shrinkage and compression losses). Figure1.24. Harvesting of logs. to blocks. On the peeling line, the veneer block is turned to produce a veneer mat. The green veneer is clipped to size and then dried, graded and composed when necessary. Glue is then applied on the top side of each veneer and the veneers are staggered to form a LVL billet. In hot-pressing, the glue cures and binds the veneers together. Finally, the formed LVL panel is edge trimmed or cut to size (e.g. to a specific beam width) before stacking and packaging. For every cubic metre of LVL about 2,5 m3 of logs (measured over bark) are processed, which is a similar raw material yield to plywood production. The LVL production process thus delivers more by-products than final product. None of these by-products go to waste. They are sold and used in pulp, fibreboard and other wood-based products, for energy production, and for decorative purposes. Glue residues are reused inside the mill. 1.6.1 Logs to blocks To maintain high raw material quality, veneer logs are transported to the LVL mill immediately after harvesting. At the mill site, the log piles are sprayed with water to avoid drying and cracking and attack by pests. LVL 01, Figure 1.20 LVL Green chips Bark Drying shrinkage Veneer handling Sawing dust Core Compression 0% 5% 10% 15% 20% 25% 30% 35% 40% PRODUCT AND BY-PRODUCTS SHARE FROM LOG VOLUME 26 LVL Handbook Europe
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