Drying wood and its features

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Drying of wood is done to remove a certain percentage of moisture from it. It is carried out in order to ensure stable linear dimensions of the material. This is very important in construction and some other areas. Note that wood drying consists of two processes: moisture transfer and moisture exchange. The first is the movement of water inside the tree, the second is its evaporation into the environment. In order to get the desired result, the same intensity of processes is necessary. Otherwise, internal stress may occur, which will eventually cause deformation and cracks.

The main problem that wood drying technology should solve is the acceleration of moisture transfer from the inner layers to the outer ones. For dehumidification, there are many different devices. The movement of water inside a tree is carried out under the influence of the following factors: humidity, temperature, pressure. To be more precise, they have different values at different points in the material.

Wood drying should be carried out using equipment that can provide the following tasks: minimize cracks and deformations, reduce energy consumption and time as much as possible. One of the technologies used for this process isdrying in special chambers. Vacuum drying of wood consists of preparation of a stack of wet wood, its preheating, the main process of removing water, intermediate and final moisture heat treatment and conditioning.

Depending on the further purpose of using the material, there are four categories of wood processing: I, II, III, 0. The highest quality is the drying of wood of the I quality category. It is produced for lumber used in the future for the manufacture of things that are subject to increased operational requirements. Category zero means removing moisture to a level that allows the material to be transported both for export and for domestic use.

Drying quality is determined by several parameters. Among them are the main ones: the average moisture content of a tree in a stack and its deviation from a certain target value, residual stress in processed lumber, comparison of the amount of moisture in individual boards with the indicator as a whole for a uniformly folded batch. In addition, differences in the percentage of liquid content across the thickness matter.

Not always the drying process can achieve the desired parameters, with any deviations, various defects can occur. The main ones are: mold, shells, underdrying of the stack of material as a whole, strong warping of the boards, uneven removal of moisture along the thickness of the assortment or the volume of a uniformly folded batch of wood, collapse,cracking. The reasons for the appearance of defects are often: non-compliance with the technology, poor control over the course of the process, uneven heating, distribution and stagnant air circulation, poor stacking of a batch of material in a pile, excessive forcing of drying, wood species (in this case, additional preparation is required).