Drying of wood and its features

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 the drying of wood consists of two processes: moisture transfer and moisture exchange. The first is the movement of water inside the tree, the second is the evaporation of water into the environment. In order to obtain the desired result, the same intensity of processes is necessary. Otherwise, there may be an internal stress, which eventually causes deformations and cracks.

The main problem that the technology of wood drying should solve is the acceleration of moisture transfer from the inner layers to the outer layers. For moisture removal, however, there are many different devices. The movement of water inside the tree is influenced by the following factors: humidity, temperature, pressure. To be more precise, their different values at different points of the material.

Drying of wood should be carried out using equipment that can solve the following tasks: minimize cracks and deformations, minimize energy consumption and time. One of the technologies used for this process is drying in special chambers. Vacuum drying of wood consists of preparing a stack of moist wood, its pre-heating, the main process of water removal, intermediate and final moisture treatment and conditioning.

Depending on the further purpose of the material, four categories of wood processing are provided: I, II, III, 0. The most qualitative is drying of wood of the 1st category of quality. It is produced for lumber, used in the future for the manufacture of things, which are subject to increased operational requirements. Category zero implies the removal of moisture to a level that allows transportation of the material for export as well as for domestic use.

The quality of drying is determined by several parameters. Among them are the main ones: the average moisture content of the tree in the stack and its deviation from a certain target value, the residual stress in the processed sawn timber, the comparison of the amount of moisture in the individual boards with the exponent as a whole, evenly folded. In addition, the percent change in the liquid content over the thickness is important.

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