The amount of wood used in the world's construction industry is increasing every year: more and more people understand that wood is a natural, renewable material that has excellent physical properties for a wide range of uses. In addition, the use of wood meets the strictest environmental standards for energy efficiency. Deja, in Lithuania, although the country's wood production exceeds two billion euros, we use very little wood. Due to this, the knowledge of ordinary users and even many professionals in the construction industry about the medium is low because the quality criteria are low, and when choosing building materials you have to meet the honesty of the traders. The problem is that the big Lithuanian wood processing companies mainly produce their products for export, so buyers often have to settle for smaller bandsaw products, the quality of which is often very questionable.

Easy to assess parameters - the visual appearance of the surface and the accuracy of the geometric dimensions - initially still correspond to the specified product specification, but the moisture content in the medium is usually much higher than allowed, although it is precisely this that mainly determines the product's durability and longevity. The main reason is that most wood product dealers try to present naturally dried media as dried, although there is a huge difference in quality between industrial huts that have been dried in the sun. When a tape installed in the floor with a wooden roof structure lasts longer, every user of wood products should understand this difference.

Kuo yra important giovinimas?

Any log obtained from the forest is the wood produced from it with a natural moisture content of 50 to 100%. The media that is digested first loses its professional language called laisvőj drėgmę, so visual packages are not noticeable. However, when the humidity level reaches about 30%, the wood cells begin to release water, and during this process, the wood changes its geometric dimensions. Because of this, if you install a wet tape with it, it shrinks irreparably when it dries, it cracks and dries, and moreover, bruises and other signs appear quite quickly, so the service life of the structure is shortened several times, it quickly becomes unstable and even dangerous.

In order to avoid this, it is necessary to use dried media whose humidity corresponds to the average ambient air humidity in the intended place of use. 

The most widely used wood products in the construction sector - in exterior finishing strips, as well as roofs for wall constructions - are standardly dried up to 18% moisture, which would be reached in the natural countryside environment over time. Such a medium will maintain constant physical properties of the mat throughout its service life. Wood products for interior work need to be dried up to 12%, otherwise they will naturally crack and the 10% used in furniture production is wood with a moisture content of even 8%.

However, it is important to understand when dry materials should not be used where they would not be used - otherwise, over time, the moisture level in the medium due to the influence of the surrounding environment will cause the material to swell. 

Kaips properly izjiovinta?

People have long understood that the mechanical properties of dry wood are better, and the geometrical stability is much higher, so the wood has been dried naturally for thousands of years. The process is extremely simple and does not require human intervention - the air, circulating through the layers of wood, draws moisture from the tree; The sun is the main influence on the growth. Theoretically, the required 18% humidity can also be achieved in the construction of such huts. However, it will likely take several years, as none of the entrepreneurs is ready to freeze their funds in wood storage for a longer period of time. Therefore, in practice, we usually set aside a couple of weeks for natural drying, during which, depending on the dimensions, as well as the intensity of the sun and the wind, the wood reaches a moisture level of 24-25% in the best case. Considering the fact that there are not many dry and sunny days in Lithuania, the humidity exceeds 30% in many places where wood products are sold.

In order to obtain the amount of moisture corresponding to the purpose of use, and there are self-evident requirements for this in foreign markets, exporting companies use artificial air conditioners, using industrial dryers, the performance of which is based on the same physical principles that act on natural air conditioners. Unlike the sun, which is the wind that cannot be controlled by a person, wood drying computer program controls the air flow, temperature and humidity, and it is also possible to maintain a very precise microclimate, thus achieving maximum drying speed. This, of course, depends on many factors, the most important of which is the size of the wood in the huts of the final use. For example, small roof tapes or thin daily tapes up to 18% humidity can be dried in three days, while beams of supporting structures will take five to six days to dry. If the medium is kept at 10% with 12% humidity, the jiovinimo time is doubled.

For conifer wood dried in the world, including in Lithuania, two types of wood are used in kilns. The oldest are the most widely used cyclical devices, which are based on a computerized control panel and a metal ventilation chamber for media in 50-300 m3 capacity. The chambers are placed in wooden racks separated by spacers, where they are dried and removed - such a process can be replicated in another batch. However, in recent years, the continuous operating dryers, which consist of a long tunnel through which the wood moves slowly on a conveyor, have microclimates of various regimes, and when leaving, the amount of humidity reached is reached.

In both cases, even air flow is ensured by fans, the temperature is regulated by heating elements, which in most bandsaws are controlled by heating boilers, fueled by wood processing residues, the humidity level is regulated by taking dry air from the outside, and humid air is created by water sprays. 

"The advantages of cyclic operation chambers are the flexibility of the company's production - material of various sizes can be processed during each drying cycle, using a different microclimate regime. However, the costs of this type of drying are higher, because the energy consumption efficiency is not so high, but there are gaps in the loading and unloading methods. ", Nilas Kazakas , director of the AB PATA manufacturing company , a professional with more than 20 years of experience in this field, said about the differences between both methods of harvesting.

"Kita vertus, the biggest advantage of continuous operation is precisely the uniform flow of wood, which reduces production costs and simplifies logistics. The biggest disadvantage is that there is no flexibility, because the microclimate of the long tunnels is adapted to the fact that it dries up to a certain moisture level at a specific speed. Pjautinė media of real dimensions. Perkelių procesas šiuju yra long is lossy."

Since the raw material is dried in an industrial hut, it is necessary to sort it before further lengthening, oblijuant, profiling and calibrating, because at the end of the drying process wood damage occurs, mainly cracks. Having examined each wood product separately, they can be divided according to quality class, thus providing the company with the most useful result, and the end user - the most suitable wood product for the specific purpose of use. 

The pine wood used in Lithuania is a visual classification of pine wood based on the Nordic system, where the material is divided into the main A, B, C and D classes, and the highest quality A class is divided into 4 subgroups. The main evaluation criteria are cracks, cracks, scratches, mechanical damage, cracks, tar pockets, pest damage, fiber loss, rotting, and various forms of defects. On the other hand, according to the Europos Sąjungos standartą, when performing the strength test, sawn timber is assigned one of six strength classes - C14, C16, C18, C22, C24 or C27. 

The strip is prepared in cooperation with the executive director of the journal "Baltijas Koks" Paula Bekeriu.