The drying process is the initial point in the entire preparation of the semi-finished product (wood) before processing.
Drying chamber for lumber and wood – perfect solution task, you can do it yourself. In order to avoid deformation of the logs, drying is carried out in specialized conditions, which are carried out exclusively in a drying apparatus.
Why is drying needed?
For a long time, when making any wood crafts, they used timber that had been cut down several years earlier. Products made from damp or under-dried boards will warp or develop numerous cracks.
When wood dries out, it shrinks, damp wood material Over time, it will “behave” and huge wide cracks will form in the log house. Under-dried semi-finished products are likely to develop fungus. But it is not advisable to overdry the tree, because it will begin to absorb water, which will lead to swelling.
What are the modes of drying chambers?
There is a whole list of drying modes for wood materials. In built with my own hands In machines, the mode from lowest to highest changes gradually, removing all excess water from the semi-finished product. The drying process is carried out based on the following material characteristics:
- wood species;
- overall dimensions of the semi-finished product;
- final and initial humidity levels;
- specifics of the unit;
- quality indicators of lumber.
The drying process can be characterized by high temperature or low temperature. The second case is notable in that primary drying is performed at a mode that does not reach 100ºC.
Low temperature conditions may be as follows:
- soft - after drying is completed, semi-finished products have their original properties without changing strength or color;
- moderate - the color changes slightly, the strength characteristics are slightly reduced;
- accelerated - during subsequent processing (breaking, sawing, cutting), increased fragility is possible, the color fades.
Change temperature regime Low-temperature processing is carried out in three stages.
High temperature processing is carried out in two stages. The second stage begins when the moisture level of the semi-finished product decreases to 15%. Such technological process used when further construction of secondary structures is necessary.
Main types of drying chambers
Drying of semi-finished wood products in industrial volumes is carried out in specialized drying apparatuses. Moisture is removed from the wood by heated air, which subsequently escapes into the atmosphere. The device ensures a full drying cycle for lumber. The machine body can be:
- solid/prefabricated metal;
- made using building materials.
The latter are mounted directly in carpentry workshops in the form of a structure, or as free-standing ones. The walls are made using reinforcement and concrete mortar. As an alternative, you can use brick. Large factories make a system of cameras, combining them into entire modules with centralized control and communications. Air moves inside the dryer in a horizontal plane or vertically transversely.
Heat sources in the dryer:
- radiant source from specialized units;
- hot shelves;
- electric current that passes through raw semi-finished products;
- high frequency electromagnetic field.
The chambers are equipped with main and auxiliary equipment. Basic systems:
- supply and exhaust equipment;
- heat sources;
- humidifiers.
Based on the principle of operation, drying machines are divided into:
- convective equipment;
- condensation equipment.
In convection machines, semi-finished products are “battered” with hot air waves, the heat is directed by the convection method. The time for completing a full cycle varies from 5 to 13 hours. Similar units are installed in large-scale sawmills.
Chamber-type dryers are more compact; a constant temperature and environment as a whole are maintained throughout the entire volume. This type of dryer will allow you to dry any type of wood material to the required condition, which is why many entrepreneurs who need to dry lumber choose chamber dryers.
Based on the technology of the drying process, the moisture that is released from the wood settles on the cooling elements, is directed into containers and then drained. The efficiency of such a unit is quite impressive, but it is time-consuming and leads to large heat losses. Price policy machines and the profitability of condensation drying is lower than convective drying.
Drawing
Drying chamber for lumber: step-by-step instructions
To build a drying apparatus with your own hands, you do not need to use technical documentation. You just need to provide:
- the area where the camera will be installed;
- insulation materials;
- source and communications for creating high temperature;
- blowing
The area of a car built personally is usually no more than 10 square meters. Room square section more suitable for ensuring the movement of warm air currents. It is preferable that at least one of the walls of the equipment be concrete, the others can be made of wood. The inside of the chamber must be insulated. Great insulation material- wood shavings. If you don’t have foil on hand, you can replace it with penofol.
A separate extension for the dryer can be constructed from aluminum sheets, this design will serve for a very long time. The base is made on the basis of profiles, it is covered with sheets of metal, which is then insulated. The thickness of the insulation must be at least 150 mm. The floor is covered with roofing felt material, a thick layer of shavings is poured on top, which will be excellent for heat conservation.
The heat source can be supplied as a heating pipe system. The liquid temperature in the pipes should be 60...90ºС. For an oversized chamber, having a two-burner stove would be quite acceptable. If the source is located directly in the room, it must be lined with bricks. Brick is capable of perfectly collecting heat and directing it to a machine for drying lumber.
Continuous circulation of liquid is important, which is provided by a compressor or an entire station. The room must be equipped with wet and dry thermometers.
For more convenient loading of semi-finished products into the chamber cavity, you can use a rail cart.
Video: DIY lumber drying chamber.
There is not a single woodworking enterprise that can do without the wood drying procedure. To prevent the occurrence of various defects, it is customary to use special technology drying wood in a drying chamber. If you want to produce wood products yourself, you will also need a drying chamber for drying wood. Today we will talk about how to do it correctly.
The need to dry wood
How to dry a board efficiently and quickly? This question has interested every carpenter since ancient times. People have long been engaged in storing wood for many years in order to have time to dry it evenly. The grandfather prepared wood for his grandson, using the very material that his grandfather left him.
The importance of properly dried wood is colossal! For example, if wooden furniture, which is in the room, is made of too wet wood that has just been cut down, then it will dry out over time, because wood can dry out and decrease in size, which means it will deteriorate!
If the door to the house is made of excessively dry wood, it will swell over time and will not be able to close! If the door panel is assembled from blanks that are unevenly dried in volume, then it may burst or warp! Therefore, it is recommended to dry all wood blanks. In addition, drying protects the material from damage by wood-destroying fungi, prevents the size and shape of wood, and improves the physical and mechanical properties of wood.
Drying wood is a lengthy, complex and expensive procedure. Tree by traditional technologies heated with superheated steam or hot air. Dried wood can be transported and stored longer. In addition, during operation it does not deform. The boards are dried in steam chambers, where the possibility of internal damage is excluded.
Wood moisture concept
To fully understand the essence of the drying process, it’s worth diving a little into the theory. The procedure for removing moisture from wood is not entirely simple, because there are two types of moisture in the material itself. Wood consists of elongated plant cells. Moisture can be found in the cell walls and in their cavities, filling the microcapillary system. The moisture that is present in the spaces between cells and in their cavities is called free intercellular, and moisture in the cell walls is called bound intracellular.
The content of bound moisture in wood is limited. The state when the cell walls are characterized by maximum humidity when in contact with liquid moisture is called their saturation limit. It is generally accepted that the moisture content of the saturation limit does not depend on the rock and is on average 30%. If the wood's humidity is above 30%, then it contains free intercellular moisture. The wood of a freshly cut or growing tree has a moisture content above the saturation limit, that is, it is raw.
Depending on the purpose of wood blanks, wood is usually dried in different ways. The wood is dried to a moisture content of 6 - 8%, when the material is needed for machining and assembly of products for high-precision critical connections that affect performance indicators(production of skis, parquet or musical instruments).
Transport humidity is 18 - 22%. It is with this water content that lumber is suitable for transportation over long distances in warm seasons. Wood dried to such a moisture content is used mainly in standard house construction, in the production of ordinary containers and when there is no need for interchangeability during assembly.
Carpentry dampness is divided into several subspecies. Molded products ( terrace board, sheathing, floor boards, casing) must have a humidity of 15 ± 2%. Wood products (windows, doors, stairs and interior elements) made from solid or laminated wood can withstand humidity fluctuations from 8 to 15%.
Furniture humidity, depending on the level of the product and the use of solid or laminated wood, is 8 ± 2%, because it is at this humidity that the wood exhibits the most optimal characteristics for processing, gluing and subsequent use. But it is usually customary to reduce the humidity to 7-10%, performing partial sterilization of the wood and taking into account the uniformity of humidity throughout the tree, preserving mechanical properties material, absence of surface and internal cracks.
Wood drying modes
Depending on the requirements for the quality of wood, lumber can be dried in different modes, which differ in temperature level. In a mini drying chamber for wood, during the drying process, the air temperature gradually increases in stages and the relative humidity of the agent decreases. Drying modes are selected taking into account the thickness of the lumber, wood species, final moisture content, quality category of the wood being dried and chamber design.
There are low- and high-temperature process modes. The first modes involve the use humid air as a drying agent, the temperature of which is initial stage is less than 100 degrees. There are three categories of these modes:
- The soft mode is capable of ensuring defect-free drying of the material while maintaining the natural physical and mechanical properties of the wood, including color and strength, which is important for drying wood to the transport moisture content of export lumber.
- The normal mode guarantees defect-free drying of wood with almost complete preservation of the strength of the material with minor color changes, which is suitable for drying lumber to its final moisture content.
- The forced mode maintains strength for static bending, compression and tension, but there may be a slight decrease in splitting or spalling strength with darkening of the wood, which is intended for drying wood to operational humidity.
For low-temperature modes, a three-stage change in the parameters of the drying agent is assumed, and from each stage to the next one the transition can be made only after the material reaches a certain level of humidity, which is provided for by the mode.
High-temperature modes provide for a two-stage change in the parameters of the drying agent, and you can move from the first stage to the second after the wood reaches a transitional moisture content of 20%. The high temperature regime is determined depending on the thickness and type of lumber. High-temperature conditions can be used to dry wood, which is used for the manufacture of non-load-bearing elements of buildings and structures in which darkening of the wood and a decrease in strength are allowed.
Drying chamber concept
Chamber drying is the main method of drying wood. Drying chambers are required to dry softwood and hardwood to different quality categories. One of the most popular and economical methods of artificial dehydration of lumber is drying, when bound and free moisture is removed from the tree using a water supply. wet wood heat by hot air and the removal of evaporated excess moisture by humidified and partially cooled air.
The drying chamber is completely ready installation, which is equipped with all the equipment necessary for drying wood. According to their design, wood drying chambers are divided into prefabricated metal ones and those made of building materials. The latter are constructed directly in workshops or as separate buildings from materials that are widely used in industry. The chamber can be made entirely of monolithic reinforced concrete. Its walls can be made of solid red brick, and the ceiling can be made of monolithic reinforced concrete.
If several dryers are used, they are often combined into a single block, constructing a common control corridor where the heat supply distribution and automatic control system for all chambers are located. Depending on the volume of wood loaded into the chamber, there may be horizontal or vertical transverse air circulation.
Loading of lumber into the chamber can be carried out in the following ways: on trolleys in the form of stacks along a rail track, like packages with a forklift. Heat transfer to wood can be carried out: by air, combustion products or superheated steam; radiant heat that comes from special emitters; solid body, if you organize contact with a heated surface; current that passes through wet wood; high-frequency electromagnetic field that penetrates wet wood.
Equipment for a wood drying chamber is divided into basic and additional. The main ones include the fan system, heating system, supply and exhaust ventilation and humidification, additional components include an insulated door and psychrometric unit, stacking trolleys, and a fan drive electric motor.
The process of controlling wood drying in a chamber can be automated. Automation is capable of maintaining the humidity and temperature of the environment in the dryer at a given level. The temperature is regulated by supplying coolant to heaters or by turning an electric heater on and off, and humidity by using supply and exhaust ventilation and a humidification system.
The wood drying control system may have the ability to remote control humidity and temperature in the chamber. When drying lumber in a drying chamber, it becomes necessary to control the moisture content of the wood, for which a remote moisture meter is used, which allows you to check the moisture content of the wood at several points without entering the chamber. With absence external sources Heat supply for the dryer can use autonomous heating modules and use gas, coal, wood waste, electricity and diesel fuel.
Types of drying chambers
IN real life It is common to use the following types drying chambers. The necessary energy in convective drying chambers is transported into the material using the air cycle, and heat transfer to the wood occurs through convection. There are two types of convection chambers - tunnel and chamber.
Tunnel convection dryers are deep chambers where stacks of stacks are pushed from the wet end to the drier end. These chambers must be filled at one end and emptied at the other. Pushing the stacks (the process of filling the chambers and emptying them) is done one stack at a time with an interval of 4 - 12 hours. These chambers are designed for large sawmills and allow exclusively transport drying of wood.
Chamber convection drying chambers are shorter than tunnel and vacuum drying chambers for wood; during operation, the same parameters are maintained throughout the chamber. When the blowing depth is more than 2 meters, the technique of reversing the direction of ventilation is used to equalize the drying conditions for the wood. The emptying and filling of the chamber occurs on one side if it has one door. Other loading systems are also known that are similar to the procedure for loading tunnel chambers. Any lumber can be dried to any final moisture content, which is why 90% of wood in Europe and Russia is dried in chamber dryers.
The condensation drying chamber differs from the previous ones in that the humidity that arises in the air condenses on special coolers and water comes out of the drying process. The efficiency of such a process is large, but the cycle is long, because the devices do not operate at high temperatures, and the total heat losses are also significant. The condensation chamber is primarily suitable for drying small volumes of wood, or for drying dense wood species - oak, beech or ash. The big advantage of such chambers is that a boiler room is not needed, the price of a wood drying chamber and the cost of drying are lower.
Drying chambers are also classified according to the method of circulation and the nature of the drying agent used, the type of enclosure and the principle of operation. Batch drying chambers are characterized by the fact that they can be fully loaded to simultaneously dry all the material, and the wood drying mode changes over time, currently remaining the same for the entire chamber.
According to the method of circulation, there are chambers with incentive and natural circulation. Dryers with natural circulation are outdated, low-performance, the drying mode in them is almost uncontrollable, and the uniformity of wood drying is unsatisfactory. For modern construction such devices are not recommended, and existing ones must be modernized. Depending on the nature of the drying agent, the chambers are divided into gas, air and high-temperature chambers that operate in a superheated steam environment.
Wood drying procedure
Before drying according to the selected mode, the wood is heated with steam, which is supplied through humidifying pipes, with fans running, heating devices turned on and exhaust ducts closed. First you need to calculate the drying chamber for wood. The temperature of the agent at the beginning of heating the wood should be 5 degrees higher than the first stage of the regime, but not more than 100 degrees Celsius. The level of saturation of the environment should be 0.98 - 1 for material with an initial humidity of more than 25%, and 0.9 - 0.92 for wood with a humidity of less than 25%.
The duration of the initial heating depends on the type of wood and for coniferous species (pine, spruce, fir and cedar) is 1 - 1.5 hours for each centimeter of thickness. The duration of heating of soft deciduous trees (aspen, birch, linden, poplar and alder) increases by 25%, and for hard deciduous species (maple, oak, ash, hornbeam, beech) - by 50% compared to the duration of heating of coniferous species.
After preheating, it is customary to bring the parameters of the drying agent to the first stage of the mode. Then you can begin drying the lumber, subject to the established regime. Humidity and temperature are regulated by valves on the steam lines and gates of the sugar-exhaust channels.
During the operation of an infrared drying chamber for wood, residual stresses arise in the wood, which can be eliminated by intermediate and final moisture-heat treatment in an environment of increased temperature and humidity. It is customary to subject lumber to processing, which is dried to operational humidity and subject to machining further.
Intermediate moisture-heat treatment is carried out during the transition from the second stage to the third or from the first to the second at high temperature conditions. Subjected to moisture and heat treatment conifers from 60 millimeters thick and deciduous from 30 millimeters thick. The temperature of the environment during the heat and moisture treatment process should be 8 degrees higher than the temperature of the second stage, but not higher than 100 degrees, with a saturation level of 0.95 - 0.97.
When the wood reaches its final average moisture content, final moisture-heat treatment can be carried out. In this process, the temperature of the medium is maintained 8 degrees above the last stage, but not higher than 100 degrees. At the end of the final moisture-heat treatment, the wood that has undergone drying must be kept in the chambers for 2 - 3 hours at the parameters provided for in the last stage of the regime. Then the drying chamber is stopped.
Making a drying chamber
If you decide to make wood products yourself, then you simply need a wood drying chamber. However, when constructing a dryer, comply with all required standards. You will need a camera, a fan, insulation and heating device.
Line up the dryer or highlight separate room, one wall and ceiling of which will be made of concrete, and the other walls will be made of wood that need to be insulated. To do this, it is customary to create several layers: the first of them is polystyrene foam, the second is wooden boards, which are usually wrapped in foil in advance.
After this you should install a heating element, which can be manufactured in the form of batteries. Water must be supplied to the batteries from the stove, in which it will be heated to 60-95 degrees Celsius. It is advisable to continuously circulate water using water pumps in the heating element. Also, a fan should be placed in a homemade wood drying chamber, which helps distribute warm air throughout the room.
Consider how the wood will be loaded into the drying chamber. One loading option could be a rail cart. To regulate the humidity and temperature in the drying chamber, you need to use work area corresponding thermometers - wet and dry. Provide shelves inside the dryer to increase work space.
During the drying process of lumber, sudden changes in temperature in the working room are not allowed, otherwise this will cause the wood to warp or cracks to appear in it. When constructing a drying chamber, it is extremely important to observe fire safety requirements. Therefore, be sure to install fire extinguishers in the immediate vicinity of the dryer.
And finally, remember that instead of a heating element at home, you can use a two-burner electric stove. You can insulate the walls of the drying chamber yourself using wood shavings. Instead of foil in the chamber, you can use penofol, which can provide good reflection of heat from the surface. In such a dryer, the wood is pre-dried 1-2 weeks in advance.
Maintenance problem optimal humidity in lumber is relevant both among builders and among those who like to make something in their own carpentry workshop. Drying wood at home allows you to save a lot on its purchase, because dry raw materials are always more expensive than wet ones.
By the way, if you don’t have time for construction works, then you can dry wood at home or in the country even under atmospheric conditions.
Some owners adapt ready-made haylofts, sheds or other suitable buildings for these purposes. This is the way out of the situation that one of our forum members found.
Timakval member FORUMHOUSE
I used the yard attic (former hayloft) size 10*5 m for drying. I laid it out, as it should, through spacers in each row. Total 3.5 cubes of boards of different categories. The advantages of this drying place are always shade, a finished roof and good ventilation. Took it last May different sizes boards, bars and beams - blanks for small construction. The boards were too heavy to lift due to moisture. During the time they were lying in the hayloft (1.5-2 months) they dried to fluff, they did not curl or bend.
Drying under atmospheric conditions is a rather lengthy process, and since we have decided to take a comprehensive approach to this issue, let’s look at the sequence of building a home dryer with our own hands, which allows us to more effectively achieve the required humidity levels. We suggest you choose a building as a suitable premises required size, and after that you can start working. The room can have dimensions of 2*3 m or 4*3 m (more is possible). It all depends on your needs and the scope of your activity. But when choosing a building, you should remember that there should not be much free space left in the dryer. After all, drafts and chaotic air movement negatively affect the quality of wood.
DIY wood dryer
The room chosen for arranging a homemade dryer must be heated by a stove or a specially installed fireplace. It is good if a heater is pre-installed in the room. If there is none, then be sure to leave room for it.
This is the project for making a home dryer suggested by a member of our forum.
Nikolay Valen member of FORUMHOUSE
There is a large garage with water heating; a potbelly stove using wood and waste is installed as a boiler. There is a pipe with a diameter of 800 mm and a length of 2.2 meters (former ventilation duct With industrial enterprise). The idea is as follows: install sealed covers on both ends of the pipe, leave fittings with a diameter of 150-200 mm for the supply and removal of hot air. The air is heated by a radiator (this can be a car heater). Air supply - table fan. 0.3-0.5 cubic meters of lumber are loaded into the pipe, the stove is heated (the coolant temperature reaches 90 degrees, I think that the supplied air can actually be heated to 50-60 degrees).
If you have chosen a room that is too large, then the space you plan to use homemade dryer, should be made insulated and sealed. For these purposes they are made wooden partitions, you can use insulation, brick and other materials that allow you to create your own microclimate in the dryer. Do not forget that it is necessary to leave a window in the chamber for ventilation and front door. After all, we shouldn’t end up with a hut without windows and doors.
Fans installed in the drying chamber will help create forced air flow and make the drying process more efficient.
mfcn FORUMHOUSE member,
Moscow.
It is advisable to place fans on the floor to the side of the stack so that the blowing is parallel to the spacers. Remember that when drying wood, you need to evaporate about several hundred liters of water from each cubic meter of wood.
To place lumber in the dryer, special shelves or flooring should be installed. These products can be made of metal so that the structure can withstand relatively large loads. Wood should be dried to levels corresponding to 8–12% humidity. Its measurements are carried out using a special moisture meter.
Drying wood is necessary following certain rules. Otherwise, the material will be hopelessly damaged and cannot be used in construction. To do this, the wood must be stacked. And between each new layer, spacers made of boards of the same thickness should be placed. Wood of any species, stacked in neat stacks, will never suffer from fungal infections and will retain its integrity and excellent consumer qualities.
Lao Czy member FORUMHOUSE
The spacers need to be made higher for better air ventilation between the boards. They will dry out better. You can place your cut 25*30 or 25*40 cubes on edge. The reason for limiting the height of the stack is to prevent the boards from being driven by a “helicopter blade”, secure the topmost layers of boards in the stack with self-tapping screws. I have been storing my boards using this method for the 3rd year at my dacha in the Moscow region. They are in excellent condition!
Gaps should also be left between boards located in the same row. This will ensure unhindered air movement inside the stack and improve drying quality.
Wood drying chamber project
Wood can be dried quickly and efficiently in well-equipped and free-standing drying chambers. Construction of such a chamber on the scale of a dacha or suburban area is not always advisable. After all, this type of construction will be very expensive, and its construction will take a lot of time.
The construction of such a premises can well be called the implementation of a full-scale construction project. You cannot avoid labor-intensive operations associated with pouring the foundation, erecting walls and installing complex equipment.
How to make drying for wood can be understood from the diagram.
DIY chamber drying
Such a mini-wood dryer requires the placement of not only basic equipment (heating and ventilation), but also additional automatic control systems.
Operating modes of the drying chamber
A chamber dryer does not require high heat during normal operation. A full cycle Work associated with drying one batch of wood can be divided into several stages.
The first stage lasts from 15 to 20 hours. During this period, the air in the chamber warms up to 45С. The ventilation does not turn on, and condensation forms on the walls of the room.
The second stage lasts about 48 hours. It involves connecting ventilation and heating the air in the chamber dryer to 50°C.
The third stage lasts until the required final moisture level is reached in the internal structure of the wood (8...12%). At this time, the air temperature rises to 55 C, the exhaust dampers open completely, and the fans operate at full power.
Once the humidity reaches the required levels, the heat supply should be stopped. The fans should remain on for another 24 hours. As a result of this heat treatment, you will receive dry wood, completely ready for use during carpentry or construction work.
Get acquainted with the practical developments of our forum members regarding correct construction stacks, you can in the "" section. Those who want to learn more about the technology of drying lumber can visit the “” section. For those who want to see a master class on wood aging technology, we recommend watching the corresponding video.
The construction industry today is experiencing an active stage of technological development, which is reflected in the tools used, the methodology for performing repair and installation operations, and, of course, the materials. At the same time, due to availability and low cost, traditional materials, including wood, still remain in demand. Another thing is to use it in pure form it is impossible, since even solid rocks no longer meet construction standards in terms of protective properties. This barrier can be overcome by special preparation operations, including drying wood in drying chambers - a technology that improves a whole range of technical and physical characteristics of the material.
Chamber drying technology
The principle of drying in vacuum chambers is based on the laws of evaporation and water circulation. That is, the main objectives of the method come down to ensuring optimally rapid removal of moisture from the wood structure, but without negative consequences for performance. The technology under consideration is aimed at performing this process. In practice, it is carried out using special installations that ensure water circulation through the wood structure in the direction from the core to the outer part. Next, water is removed from the surface through evaporation. But it is important to understand that getting rid of moisture is not the only task that drying wood in drying chambers accomplishes. The technology also allows you to eliminate physical defects, but for this it is used optional equipment like presses. As for the technical implementation of the process, it is usually performed by manually loading the material into the appropriate chamber. Then, due to the heating plates, the unit automatically warms up against the background of intense evaporation.
Features of the vacuum drying method
Compared with traditional drying chambers, new cylindrical vacuum drying technologies can achieve high speed process. This is connected not so much with the principle of influence on the material, but with the mechanics of loading and the location of the workpieces relative to the functional plates. But the thermal effect also has its own characteristics. Since the wood material is compressed between the plates under pressure, a high intensity of impact on the structure is ensured - accordingly, it evaporates large quantity moisture. In terms of energy consumption, vacuum drying of wood also has its differences. Features of the technology in this parameter are determined by increasing the temperature of the plates and optimizing the physical movement of the material inside the chamber. Therefore, to achieve the same alternative ways drying results, such chambers consume less energy.
Drying stages
Automated cameras allow you to implement a standard set of technological steps without user intervention, which looks like this:
- Warming up the material. Primary heat treatment, during which the wood structure is prepared for subsequent stages.
- Direct drying. At this stage, a combined moistening-drying operation is performed, which allows the material to be softened as much as possible for further drying.
- Cooling. In essence, this is the stage of crystallization of the structure, thanks to which the wood, which has become pliable due to heat treatment, regains its optimal hardness characteristics.
As noted above, all stages of the drying process are controlled automatically, and the operator monitors the safety indicators. But even before the start of the event, the user is required to set the optimal drying mode. In particular, it sets pressure and temperature based on the characteristics of the material. For example, for coniferous blanks with a thickness of 2.5 cm, a pressure of 500 kg/m2 is required. As for the temperature regime, it is in in this case can be 80 °C.
Drying chamber device
Modern cameras are made in the form of a parallelepiped or cylinder. The output side of the structure is equipped with a lid, through which material loading/unloading operations are carried out. Moreover, the structure of the lid includes a rubber sheet fixed on a metal frame - this solution allows you to create an almost perfect vacuum with increased sealing. Each layer of lumber is lined with heating plates, which are usually made of thermally conductive aluminum alloys. To carry out movements, the plates are equipped with roller mechanisms. The movement of the heaters ensures balanced drying of the wood in the drying chambers. The chamber manufacturing technology also provides for the connection of circuits with circulating water. Boilers with liquid are located separately and provide their own heating. To maintain a stable vacuum, a special pump is placed inside the chamber.
Application of hydraulic press
It has already been said above that during the drying stages, the structure of the wood softens and becomes pliable. This condition is a side effect and redundant within the drying process. Actually, to eliminate these consequences, the final cooling stage is provided. However, the softened structure of the material can be exposed to hydraulic press, which will relieve the workpiece from physical defects - at least ensure its straightening. Such presses are included in the general complex of capacities at which wood is dried in drying chambers. The pressing technology, in turn, eliminates possible defects that were acquired by the material in the chamber. The final workpiece will be “correctly” deformed with the parameters needed for working lumber.
Drying methods
At the moment of technology development, there are three main methods of vacuum drying. The first two methods have already been discussed - direct drying and press-vacuum preparation of the material. But there is also a steam treatment method in vacuum chamber. Its relevance is due to the possibility of eliminating heating plates from the chamber design, since hot steam covers the entire space, without requiring special direction of flows to individual sections of the workpiece. This approach provides many advantages that steam heating methods of wood drying provide. Drying chambers, for example, allow loading not only labor-intensive manually, but also with the help of forklifts.
What effect does drying provide?
Drying itself, as a process of optimizing the hygroscopic properties, gives the wood relatively high strength indicators. This is already enough for the material to correspond basic requirements building regulations. But large woodworking plants use the above-described technologies and methods of drying wood only as preparatory stage For further processing material. In particular, for impregnations, which will additionally give the workpieces the qualities of fire resistance, moisture resistance, frost resistance, etc.
Do-it-yourself drying
To make your own dryer available means First of all, you will need a separate room. In size it can correspond to a small utility room or utility room. The structure should preferably be made of brick or concrete, and internal surfaces insulate and insulate with layers of foil-coated foam. The result will be, although not a vacuum, a sealed dryer for boards. How to make elements thermal effects? To do this, several convectors or radiators should be provided - their number will be determined by the structural capabilities of the room and the requirements for the drying itself. Heating equipment will provide the evaporation effect. For greater efficiency, the thermal function can be supplemented with fans.
Conclusion
During construction and renovation operations, the question of choosing between different materials. Limited financial resources often exclude metal alloys and high-strength plastics, leaving wood as the only option. But this decision also justifies itself in many cases. technical specifications, if a lumber drying chamber is used. You won’t be able to make such a chamber yourself without spending money on expensive radiators, but in the long run, its use will be worth the investment. As the practice of using structures based on properly dried wood shows, the material can serve for years even in harsh conditions without losing its primary properties. Another thing is that a lot will depend on the type of wood that is planned to be used for such purposes.
The wood harvesting process includes a drying operation. It prevents future defects and damage to the material. The procedure takes place in a special chamber. Any logging enterprise cannot do without it. Vacuum drying of wood is most often used. It has a number of advantages over other methods. For example, short process times, uniform processing of all material and ease of installation and dismantling of the plant.
- Wood drying technology
- Vacuum drying
- We build a dryer with our own hands
A tree is a living organism. Like others organic compounds, it contains water. Freshly cut wood has a moisture content of more than 30%. To use it in the future for construction needs or making crafts, excess moisture needs to be removed. The excess water in the material may vary. Its standards depend on where the wood is planned to be used. For the manufacture of musical instruments, sports equipment and parquet, humidity is set at 6-8%. If the raw material will be subjected to further processing, then it is enough to leave 20% moisture in it. For the manufacture of building structures and finishing materials the parameter is controlled at the level of 8-15%.
Wood drying technology
Vacuum drying
The wood drying process consists of several stages. First, it is evaporated from the surface of the material, and then from its interior. Thin places dry out first, then moisture moves to them from thicker layers. If the process is disrupted, the thin layers begin to shift and the material is destroyed. To prevent this from happening, the workpieces are treated with a special mixture. It is made from drying oil and chalk. The end parts of the workpieces are treated with the resulting composition. They usually always have the shape of an equilateral geometric figure.
Accelerated drying mode is distinguishing feature vacuum drying chamber. It is known that water begins to evaporate when it boils. A very low pressure is created in the chamber. Due to this, water boils at more low temperatures, than usual. This way the process time is significantly reduced.
Another significant advantage is that vacuum drying significantly saves energy. Heating occurs by contact method. Temperature inside 
chambers and pressure are adjusted automatically. A vacuum is maintained in the chamber at 0.95 MPa. It ensures the heat and mass transfer process. Moisture is released from wood in the form of steam. After drying, raw materials are obtained with a given level of humidity. During the process, it completely retains its structure - it does not collapse.
This drying eliminates the use of fans. Humidification systems are also not needed. Neither dry nor wet bulb thermometers are used in the chambers. Humidity sensors are installed inside. They are controlled from outside. The entire control system is usually located in a separate vestibule.
Vacuum installations are often used for processing expensive types of raw materials: wenge, oak, rosewood, teak, angera. They use a convector type heating element. The maximum temperature in the chamber is +65 degrees. However, the process of moisture evaporation begins already at 45.5 degrees. The process completely eliminates the impact of high temperatures. Wood is practically not destroyed.
All the structural changes that accompany drying occur inside the tree. First, the moisture evaporates from the surface, then from the inside it approaches the surface again, and so on, up to 250 times over the entire time. Over the entire surface of the raw material, a humidity difference of 0.5-1.5% is allowed. Here are some indicators at which vacuum drying works:
We build a dryer with our own hands
It is not always possible for an entrepreneur to buy expensive equipment and use vacuum technology. For starters there are more simple methods.Do-it-yourself wood drying also occurs in drying chambers. To arrange it you will need the room itself, good insulation and a fan.
The design of the drying chamber with your own hands assumes that one wall and ceiling will be made of reinforced concrete. The remaining elements can be made of wood. The walls are insulated with polystyrene foam, lined with clapboard and covered with foil. Penofol can be used as a reflective material. It also reflects heat well and helps keep it inside the camera.
Mobile drying chamber.
Next, the heating device is installed. The most commonly used heating radiator. Its power should allow you to heat water to 65-90 degrees. The entire system is mounted separately from others heating circuits. It must work constantly, regardless of the time of year. Electric and gas appliances are often used. A fan is necessary to distribute air evenly in the chamber. Without this, it is impossible to dry the material evenly with your own hands.
It will also be necessary to build a system for loading lumber into the chamber. Usually they have big sizes and considerable weight. It is convenient to load boards on trolleys moving on rails or with a forklift. Inside the chamber, the material is placed on shelves or simply on the floor. It is also necessary to install control devices over the process, which will be carried out with your own hands. Without this, it is impossible to properly dry the wood so that it later has a marketable appearance and its inherent properties.
When building a drying chamber with your own hands, you need to adhere to the following rules:
When building a dryer with your own hands, the main thing is to ensure that the parameters required by the technology are maintained within it. The materials and equipment that will be used do not matter. Drying the wood in such a chamber, built with your own hands, will take from one to two weeks.
