A green chain is a type of lumber-sorting process used in sawmills and logging facilities. This process is used to sort and stack freshly cut lumber according to its size and grade. Generally, a green chain is incorporated into the lumber production process right after the logs have been cut to size, but before the wood undergoes any treatment or processing. The term green chain has had several meanings throughout history, and may be used in different ways today based on region or country.
The green chain process gets its name from green lumber, which is a term used to describe all untreated lumber products. Green wood generally includes logs that are freshly cut, and may be stripped of their bark. They are considered green through all stages of the sawmill production process, including cutting and debarking. Much of this lumber eventually goes through some form of treatment, including pressure-treating, spraying, or coating. Green lumber may still be used by some wood craftsmen and builders who rely on more traditional materials and techniques.
Throughout history, most green chain lumber processes relied on manual labor. Freshly-cut wood was pulled from a pile by human laborers and dropped into piles or stacks. Workers might sort wood in several different ways based on the needs of the project. For example, they may process lumber by length, diameter, species, or grade. This type of green chain was very labor intensive, and also subjected workers to a great deal of injury risk.
Modern green chain production is typically automated, or relies on a combination of human and machine labor. This type of operation includes some form of lumber-sorting machine, generally a belt or series of rollers. The belts are often lined with steel chains, which help to hold the lumber in place and control its movement. Workers may pull different pieces of lumber from a pile and drop them onto these belts for sorting. Other sawmills may use multiple green chain belts to direct different types of lumber to different areas of the plant.
This process serves as an easy and effective method of sorting green lumber for further processing or sale. It allows workers to sort materials based on a variety of different factors, including size, species, or wood quality. A green chain also helps to control and organize the piles of lumber found in most sawmills. Modern plants may even incorporate handheld tracking systems or special software into the green chain process to allow the workers to account for each unit of wood as it is sorted.