Wet wood is practically not used in the manufacture of high-quality and durable wooden structures– pieces of furniture, external and interior decoration, as well as load-bearing elements of the building. The installation and operation of lumber is preceded by the removal of moisture from it. The long-known process of natural drying can last several years, which is unacceptable for large volumes and rates. modern construction.
In wood, there are two main types of moisture that affect the value of density and technical specifications erected structure:
- intracellular moisture- it is easily removed, but it is also quickly absorbed back into the wood in a humid environment;
- intercellular water- is contained outside the wood cells (also called hygroscopic). This type of moisture is the most difficult to remove and forms the basis of a constant moisture content (about 30%).
Drying occurs as a result of two processes - the evaporation of water and its movement from the middle of the material to the surface.
If the evaporation rate is greater than the internal moisture migration, then the surface dries faster. This causes uneven changes in linear dimensions and leads to the appearance of cracks and bends. The gradual course of the process ensures the preservation of the structure and shape of the wood.
The foundations of modern drying methods are based on several methods of exposure that accelerate the evaporation of moisture from the surface of the tree:
- temperature rise;
- increased air circulation;
- pressure reduction;
- reducing the humidity of the air circulating over the wood.
What happens to a tree during drying, in addition to removing moisture
The main processes observed in the wood structure during drying are shrinkage and shrinkage. Shrinkage refers to the inevitable companions of moisture removal and represents a decrease in the dimensions of the lumber in all directions after the beginning of the removal of hygroscopic moisture.
An increase in the size of wood with an increase in free moisture content is called swelling. Shrinkage observed with the rapid removal of moisture, when the outer part of the tree is much drier than the inside. This phenomenon often occurs when drying thick wooden beams and logs. The flow of shrinkage and shrinkage is taken into account when planning future structures, as well as swelling during operation in humid environments.
When wood is overheated, which sometimes occurs during (chamber drying), a process similar to dry distillation occurs. It is the decomposition of wood fibers without air access, resulting in the release of gaseous, liquid and solid ( charcoal) products. This process is irreversible, therefore, when heating, it is important to maintain the optimal temperature regime.
More about the drying process itself:
Technologies and methods of wood drying
Vacuum (chamber)
Drying wood in vacuum drying chambers - involves the creation of reduced pressure in a chamber loaded with stacks of lumber. Moisture, which is in the form of saturated steam above the surface of the wood, is removed together with the drying agent. The role of the latter is performed by air, which in not in large numbers fed into the camera.
Changing the degree of vacuum and air supply allows you to adjust the rate of water removal. For material various shapes and dimensions, strict dehydration conditions are applied to keep humidity constant throughout the volume.
Depending on the type and size of wood, the drying time lasts from several days to a month. Lungs are the easiest to dry out conifers(pine, spruce), and heavy oak boards have to be kept until deep moisture removal for 3-4 weeks.
Photo of chambers for drying wood
Example 1 Example 2 Example 3
Condensation
It is based on the constant blowing of the drying chamber with a stream of dry heated air. The exhausted wet air mixture is sent to a cooling heat exchanger, in which water condenses after the air reaches the dew point.
This method most fully imitates the natural drying of wood. If the temperature does not rise above 40-60 ° C, then it does not undergo significant shrinkage.
Condensation dehumidification is a development of the classic kiln drying, in which the wood is kept in a stream of hot air. Kiln drying conditions are adjustable regulatory documentation and include soft, normal, forced and high temperature modes. The process can take place continuously in chambers of large volume and length, which provides increased productivity.
Natural
It is produced until the air-dry state of the tree is reached (about 25-30%) and does not ensure the removal of hygroscopic moisture. The lumber obtained in this way is usually used for construction purposes in the construction of frame structures that have undergone special processing from and supporting structures.
Drying in natural conditions is carried out in rooms closed from precipitation with good ventilation. When laying, the material is arranged in piles, in which there are distances between the boards to ensure ventilation.
How to dry wood in an atmospheric (natural) way will tell the video:
Drying chambers and their device
Drying equipment (chambers) are cylindrical or box-shaped, sheathed on the outside metal sheets. Raw wood material can initially be stacked inside or stacked on special shelves.
Convection is provided by compressor units, and air is heated in radiator heat exchangers. The air supply is carried out from above, because after contact with the wood load and the evaporation of moisture, the temperature of the air mixture decreases. This causes an increase in its density and the descent of cold humidified air into lower part cameras.
Dryers are batch and continuous. In periodic systems, work is interrupted while the dried batch is unloaded and a new block of wood is loaded. Continuous dryers ensure the constant movement of stacks from the “wet” part of the chamber to the “dry”, and loading is carried out as it becomes free inside the free space.
This video describes in detail a device for vacuum drying wood with your own hands:
Timber harvesting rules
The procedure and conditions for harvesting lumber are regulated in accordance with the Forest Code of the Russian Federation.
The basic rules that must be observed during logging are as follows:
- felling of trees is carried out after the submission and approval of the declaration, which substantiates and describes the volume of felling, territory, type of wood, etc.;
- the first on the list for felling are trees affected by natural causes or as a result of human activity (fire, storm, flood, disease);
- only trees corresponding to age standards can be cut;
- during logging, it is necessary to take out sawn material in time, prevent clogging of the territory and demolish temporary buildings used in the work;
- it is forbidden to leave undercuts - individual trees in cut down areas.
Drying wood with your own hands
If you need to prepare wood at home, it is recommended to proceed in this order:
- choose a place for drying. It is best to provide not a canopy with a roof, but a building with dense walls that prevent the penetration of precipitation;
- equip the base for future laying, under which air will freely pass;
- lay the lumber crosswise in several rows, as shown in the figure;
- close the resulting stacks in the upper part from accidental drops of water, dust and debris;
- fasten wooden boards or beams together. Best use for this polymer materials– rubber puffs or nylon cords;
- withstand the stacking time recommended for a particular climate zone(usually several months).
Self-preparation of lumber can be done if there is time and the need to prepare a large amount of wood. The resulting material is suitable for use in construction purposes, but is poorly suited for the manufacture of furniture products. To obtain dry wood for finishing and decorative works, a set of wood preparation methods should be used, such as, .
DIY wood dryer:
Vacuum drying is a process that has long been an integral part of many types of industries. The key industry, which at the moment cannot exist without this process, is the furniture industry.
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In fact, this is a special wood processing, which plays a significant role in the furniture industry. In order for the furniture to be of the highest quality and to keep its shape for a long time, the wood must necessarily undergo a vacuum drying process, which will remove all unnecessary substances from the material, remove moisture and make the wood more durable and practical in terms of use.
But in fact, this is far from the only industry where vacuum drying plays such a big role. It is also worth highlighting the production of products, which also needs a similar process. In the case of other industries, vacuum drying works in a completely different way, since in other areas slightly different tasks are required.
The structure of the process itself is quite complex, and there are a huge number of reasons for this.
The first is the need for a large amount of equipment in order for the vacuum drying process to be of the highest quality.
The second is high level equipment performance, without which it is simply impossible to achieve high quality indicators.
And the third is the area, namely the presence of a specially designed room that will meet all the criteria for humidity and temperature, since without adhering to all these standards, the vacuum drying process will no longer be so effective.
As for the cost of such an operation, this is a somewhat two-digit question. The price of vacuum drying depends on what kind of material will be amenable to such processing, what kind of vacuum equipment will be used, the area in which this process will take place, the time that will be spent on this operation, and so on.
All these points are more than important and in any case they must be taken into account if your key task is to obtain high-quality processed material that can be actively used for further purposes.
Vacuum Drying Technology
Earlier we have already said that vacuum drying is a very complex process that requires a lot of effort. Now we will consider the technology of vacuum drying, and we will do it on the example of wood, since it is in this industry that vacuum drying has gained the greatest popularity.
Before making wood furniture, it must in any case go through a drying process, which is a key part of it. In the process of vacuum drying, wood significantly loses its mass and decreases in size.
Now we will consider the main processes included in vacuum drying:
- Removing water from wood by evaporation
- Water circulation through wood
The circulation process occurs first, which, by the way, takes much longer than evaporation. The speed of vacuum drying of wood directly depends on how the water circulation process will take place.
But in no case should we forget that the drying process involves the complete drying of wood and in some cases the percentage of water in its composition reaches 30 percent, at which the saturation point of the fibers decreases significantly.
But this is not so scary, since in any case, in vacuum drying there is a rule that says that absolutely all water must be removed from the surface of the wood. After going through this process, the moisture in the core of the tree will come out with the help of circulation.
The process of removing moisture from the surface of wood also has certain nuances that should not be forgotten. The main thing is to remove absolutely all the moisture that will come from the product by the diffusion process.
But this was just a clear example of drying technology, where the main material we had was wood.
Now we will consider other directions in vacuum drying:
- Vacuum drying of liquid-viscous products
- Vacuum drying of milk
- Vacuum drying of cheese
- Vacuum drying of powders
- Vacuum drying of meat
This is not the whole list of areas where vacuum drying is an integral part. At the moment, such technology has already managed to clearly gain a foothold in most industries, which simply cannot fully function without this process.
So it is possible that soon the vacuum drying process will be used in all industries that are somehow connected with the production of products.
Vacuum drying chambers
A vacuum drying chamber is the device without which such an operation is simply impossible. The role of vacuum chambers in this regard is as great as possible, and the level of performance of the vacuum drying chamber depends on how fast the drying process will take place, how high the quality of the vacuum drying result will be, and so on.
As for the pricing policy for such vacuum plants, at the moment the situation in this regard is far from being the simplest. Most of these installations are in the high price range, and not everyone can buy such an installation.
In total, there are a huge number of varieties of drying chambers, each of which is designed for use in a particular industry. The principle of operation of each of the chambers differs in many aspects, which is why it is very problematic to talk in detail about the principle of operation of the drying chamber.
Now we will consider several types of drying chambers:
- Drying chamber for drying foodstuffs
- Drying chamber for wood
- Vacuum oven
- Vacuum chamber for drying fruits
The principle of operation of each of the cameras is completely different, and the reason for this feature various materials before exposure to the vacuum chamber. That is why, before buying such equipment, it is worth carefully reading the operating instructions, so as not to be in an uncomfortable position later.
Vacuum freeze drying
Freeze drying is a process that occurs by sublimation of ice crystals from frozen products. Such a process immediately bypasses the liquid state of moisture, and allows you to dehydrate products as quickly as possible, and do it with the highest quality.
With this principle of dehydration, it is possible to preserve all the properties of the products, which is a great advantage of this drying method. But this is far from all that can be preserved during vacuum freeze-drying, since the anatomical structure, vitamin activity, and even chemical composition products.
The vacuum freeze drying process consists of three main steps:
- Freezing the product, which is a key step, without which the further drying process simply does not make sense.
- Sublimation of ice, without the aid of heat, as this is the only way to keep the product in the same state
- Final drying in a special heated chamber, which gives the product a marketable appearance.
From all this, we can conclude that vacuum freeze drying is a process that is more than effective, and if necessary, it can be used in almost all areas.
Vacuum drying of wood
We have previously considered this type of drying as an example of the technology itself. In this technology, there are a huge number of nuances that should be taken into account so as not to subsequently spoil the tree from which certain products will be made in the future.
The process of vacuum drying of such material is carried out only in an environment that will meet all the standards of humidity, temperature and similar aspects that play a role in the final result.
The cost of such a process at the moment varies within the middle price segment, depending on where exactly you will be vacuum drying the wood. If this process is done by older equipment, then it will cost quite inexpensively. If we are talking about modern drying chambers, then in this case it will be necessary to overpay in order to get the highest level of quality.
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 yourself want to engage in the production of wood products, you will also need a drying chamber for drying wood. Today we will talk about how to do it right.
The need to dry wood
How to dry a board efficiently and quickly? This question has been of interest to every carpenter since ancient times. Since ancient times, people have been storing forests for many years in order to have time to evenly dry it. The grandfather prepared a tree for his grandson, using the very material that his grandfather had left him.
The importance of properly dried wood is enormous! 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 the tree can dry out and shrink in size, which means it will deteriorate!
If the door to the house is made of overly dry wood, then it will swell over time, and will not be able to close! If a door panel is assembled from blanks that are unevenly dried in volume, then it can burst or warp it! Therefore, it is recommended to dry all wood blanks. In addition, drying protects the material from damage by a wood-destroying fungus, prevents the size and shape of wood, and improves the physical and mechanical properties of wood.
Drying wood is a long, complicated 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 is not deformed. Drying of boards is carried out in steam chambers, where the possibility of internal damage is excluded.
The concept of wood moisture
For a complete perception of the essence of the drying process, it is worth plunging into theory a little. The procedure for removing moisture from wood is not entirely simple, because there are two types of moisture in the material itself. Wood is made up of plant cells elongated shape. Moisture can be in the walls of cells and in their cavities, filling the microcapillary system. 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 moisture in contact with liquid moisture is called the saturation limit. It is generally accepted that the moisture content of the saturation limit does not depend on the rock and averages 30%. If the moisture content of a tree is above 30%, then it contains free intercellular moisture. The wood of a freshly cut or growing tree has a moisture content greater than the saturation limit, that is, it is raw.
Depending on the purpose of the wood blanks, it is customary to dry the wood in different ways. The wood is dried to a moisture content of 6 - 8% when the material is needed for mechanical processing and assembly of products for high-precision critical joints that affect performance (ski, 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 weather. Wood dried to such a moisture content is mainly used in standard housing construction, in the production of ordinary containers and when there is no need for interchangeability during assembly.
Carpentry moisture is divided into several subspecies. Molded products ( terrace board, sheathing, floor board, cashing) must have a moisture content of 15 ± 2%. Wood products (windows, doors, stairs and interior elements), made of solid or glued wood, withstand humidity fluctuations from 8 to 15%.
Furniture humidity, depending on the level of the product and the use of solid or glued wood, is 8 ± 2%, because it is at this humidity that wood shows the most optimal characteristics for processing, gluing and subsequent operation. But it is usually customary to lower the humidity to 7-10%, making partial sterilization of wood and taking into account the uniformity of moisture throughout the tree, the preservation of the mechanical properties of the material, the absence of surface and internal cracks.
Wood drying modes
Depending on the requirements that apply to the quality of the tree, lumber can be dried different regimes that differ in temperature. In the mini wood drying chamber, 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, the type of wood, the final moisture content, the quality category of the dried wood and the design of the chamber.
There are modes of low- and high-temperature process. The first modes involve the use of moist air as a drying agent, the temperature of which in the initial stage is less than 100 degrees. There are three categories of these modes:
- The soft mode is able to provide defect-free drying of the material while maintaining the natural physical and mechanical properties of wood, including color and strength, which is important for drying wood to transport humidity export lumber.
- Normal mode guarantees a defect-free drying of wood with almost complete preservation of the strength of the material with slight color changes, which is suitable for drying lumber to the final moisture content.
- Forced mode retains strength for static bending, compression and tension, but some reduction in splitting strength or chipping with darkening of the wood is possible, which is intended for drying wood to operating humidity.
According to low-temperature regimes, 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 carried out only after the material reaches a certain level of humidity, which is provided for by the regime.
High-temperature regimes provide for a two-stage change in the indicators of the drying agent, and it is possible to switch 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 regimes can be used for drying wood, which is used for the manufacture of non-load-bearing elements of buildings and structures in which darkening of wood and a decrease in strength are allowed.
The concept of a drying chamber
Chamber drying is the main method of wood drying. Drying chambers are required for drying conifers and hardwood wood 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 by supplying heat to the wet tree with hot air and carrying away the evaporated excess moisture 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 the device, drying chambers for wood are divided into prefabricated metal and made of building materials. The latter are built 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 laid out of solid red brick, and the ceiling - from monolithic reinforced concrete.
If several dryers are used, they are often combined into a single unit, constructing a common control corridor, where the heat supply wiring and the system are located. automatic control all cameras. Depending on the volume of wood loaded into the chamber, there can be horizontal or vertical transverse air circulation.
Loading 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 if you organize contact with a heated surface; current that passes through wet wood; high frequency electromagnetic field that permeates wet wood.
Equipment for the drying chamber for wood is divided into basic and additional. The main system includes a fan system, a heat supply system, supply and exhaust ventilation and humidification, and an additional one includes a door insulated and psychrometric unit, stacking carts, and an electric fan drive motor.
The process of controlling the drying of wood in the chamber can be automated. Automation is able to maintain the humidity and temperature of the environment in the dryer at a given level. The temperature is regulated by supplying the coolant to the heaters or by turning the electric heater on and off, and the humidity is controlled by using the supply and exhaust ventilation and humidification system.
The wood drying control system may have options 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 independent heating modules and use gas, coal, wood waste, electricity and diesel fuel.
Types of drying chambers
AT real life It is customary to use the following types of drying chambers. The necessary energy in convective kilns is transported to the material by means of the air cycle, and the heat transfer to the wood occurs through convection. Convection chambers are of two types - tunnel and chamber.
Tunnel convection kilns are deep kilns where stack stacks are pushed from the wet end to the dry end. These chambers must be filled from one end and emptied from the other. The pushing of the stacks (the process of filling the chambers and emptying) is done one by one with an interval of 4 - 12 hours. These chambers are designed for large sawmills and allow only transport drying of wood.
Chamber convection kilns are shorter than tunnel kilns and vacuum kilns for wood, the same parameters are maintained throughout the kiln during operation. With a blowing depth of more than 2 meters, the method of reversing the direction of ventilation is used to equalize the conditions for drying wood. Emptying and filling the chamber occurs on the one hand, if it has one door. Other loading systems are known, which are similar to the procedure for loading tunnel chambers. Any lumber can be dried to any final moisture content, so 90% of wood in Europe and Russia is dried in chamber dryers.
The condensation drying chamber differs from the previous ones in that the moisture that occurs 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 loss is also significant. The condensation chamber is mainly suitable for drying small volumes of wood, or for drying dense woods such as oak, beech or ash. The big advantage of such chambers is that there is no need for a boiler room, the price of a drying chamber for wood and the cost of drying is less.
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. Drying chambers of periodic action are characterized by the fact that they can be loaded completely for simultaneous drying of all material, and the drying mode of wood changes over time, at the moment remaining the same for the entire chamber.
According to the circulation method, there are chambers with incentive and natural circulation. Dryers with natural circulation are outdated, inefficient, the drying mode in them is almost uncontrollable, the uniformity of wood drying is unsatisfactory. For modern construction, such devices are not recommended, and the existing ones must be upgraded. According to the nature of the drying agent, gas, air and high-temperature chambers are distinguished, which operate in an environment of superheated steam.
wood drying process
Prior to drying according to the selected mode, the wood is heated with steam, which is supplied through the humidifying pipes, with the fans running, the heaters turned on and the exhaust ducts closed. First you need to calculate the drying chamber for wood. The temperature of the agent at the beginning of wood heating should be 5 degrees higher than the first stage of the regime, but not more than 100 degrees Celsius. The saturation level of the environment should be 0.98 - 1 for material with an initial moisture content of more than 25%, and 0.9 - 0.92 for wood with a moisture content of less than 25%.
The duration of the initial warm-up depends on the type of wood and for conifers (pine, spruce, fir and cedar) is 1 - 1.5 hours per centimeter of thickness. The duration of heating of soft hardwoods (aspen, birch, linden, poplar and alder) increases by 25%, and for hard hardwoods (maple, oak, ash, hornbeam, beech) - by 50% compared to the duration of heating of softwoods.
After preheat it is customary to bring the parameters of the drying agent to the first stage of the regime. Then you can start drying the lumber, subject to the established regime. Humidity and temperature are regulated by valves on steam pipelines and dampers of sugar-exhaust channels.
During the operation of the 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 process sawn timber, which is dried to operational humidity and subject to mechanical processing in the future.
Intermediate moisture heat treatment takes place during the transition from the second stage to the third or from the first to the second in high-temperature conditions. Coniferous species with a thickness of 60 millimeters or more and hardwoods with a thickness of 30 millimeters or more are subjected to moisture heat treatment. The temperature of the medium in the process of heat and moisture treatment should be 8 degrees higher than the temperature of the second stage, but not higher than 100 degrees, at a saturation level of 0.95 - 0.97.
When the wood reaches the final average moisture content, the final moisture heat treatment can be carried out. In this process, the temperature of the medium is maintained at 8 degrees above the last stage, but not higher than 100 degrees. At the end of the final moisture heat treatment, the dried wood must be kept in the chambers for 2-3 hours at the parameters that are provided for by the last stage of the regime. Then the drying chamber is stopped.
Drying chamber manufacturing
If you decide to make wood products with your own hands, then you simply need a drying chamber for wood. However, during the construction of the dryer, comply with all required standards. You will need a camera, a fan, a heater and a heater.
Build a dryer or allocate a 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 foam plastic, the second is wooden boards, which are usually wrapped in foil in advance.
After that, you should install a heating element, which can be made 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 desirable to continuously circulate water by means of water pumps in the heating element. Also, a fan should be placed in a homemade wood drying chamber, which contributes to the distribution throughout the room warm air.
Think about how the wood will be loaded into the drying chamber. One of the loading options can be a rail trolley. To regulate the humidity and temperature in the room of the drying chamber, you need to use working area the corresponding thermometers are wet and dry. Provide shelves inside the dryer to increase the working space.
In the process of drying lumber, a sharp change in temperature in the working room is not allowed, otherwise this will cause the wood to warp or cracks appear in it. When building a drying chamber, it is extremely important to observe fire safety requirements. Therefore, it is mandatory to install fire extinguishers in the immediate vicinity of the dryer.
And finally, remember that instead of heating element at home, you can use an electric stove with two burners. You can insulate the walls of the drying chamber with your own hands using wood shavings. It can be used instead of foil in the chamber with penofol, which is able to provide good reflection from the heat surface. In such a dryer, the wood is dried in advance for 1-2 weeks.
Maintenance problem optimal humidity 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 always cost more than wet ones.
By the way, if you don't have time for construction works, then you can dry the 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. Here is a way out of the situation found by one of our members of the forum.
Timakval member of FORUMHOUSE
I used for drying the attic of the yard (former hayloft) the size of 10 * 5 m. I laid it out, as it should, through the spacers, each row. Total 3.5 cube boards of different categories. The advantages of this drying place are always shade, finished roof and it ventilates well. Picked up last May different size boards, bars and timber - blanks for small-scale construction. The boards were heavy from moisture. During the time of lying in the hayloft (1.5-2 months) they dried up to fluff, they were not twisted or arched.
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. As a suitable room, we suggest you choose a building required size and then you can get to work. The room can have dimensions of 2 * 3 m or 4 * 3 m (more possible). It all depends on your needs and scope of activities. 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 adversely affect the quality of wood.
DIY wood dryer
The room chosen for arranging a home-made dryer should 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 do not forget to leave a place for it.
Here is a project for making a home dryer offered by a member of our forum.
Nikolai Valen FORUMHOUSE member
Available capital garage with water heating, a potbelly stove on wood and mining is installed as a boiler. There is a pipe with a diameter of 800 mm and a length of 2.2 meters (a former ventilation duct with industrial enterprise). The idea is as follows: install sealed covers at both ends of the pipe, leave fittings with a diameter of 150-200 mm for supplying and discharging hot air. Air is heated by a radiator (it can be a car stove). Air supply - table fan. 0.3-0.5 cubic meters of lumber is loaded into the pipe, the furnace is melted (the temperature of the coolant reaches 90 degrees, I think that the supplied air can really be heated up to 50-60 degrees).
If you have chosen a room that is too large, then the space planned to be used for a makeshift dryer should be made insulated and airtight. For these purposes, 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 should not get a hut without windows and doors.
Fans installed in the drying room will help create a forced air flow and make the drying process more efficient.
mfcn FORUMHOUSE Member,
Moscow.
It is advisable to place the fans on the floor to the side of the stack so that the blow is parallel to the spacers. Remember that when drying wood, it is necessary 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. Dry wood should be up to indicators corresponding to 8-12% moisture. Its measurements are carried out using a special moisture meter.
It is necessary to dry the tree, observing 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, gaskets from boards of the same thickness should be placed. Wood of any species, stacked in neat piles, will never suffer from fungal infections, retain its integrity and excellent consumer qualities.
Lao Czy FORUMHOUSE member
Gaskets need to be made higher so that air ventilation between the boards is better. They dry better. You can put your sliced \u200b\u200bsticks 25 * 30 or 25 * 40 on the edge. The reason for limiting the height of the stack is to prevent the boards from being led by a "helicopter blade", fix the uppermost layers of the boards in the stack with self-tapping screws. For the 3rd year I have been storing my boards using this method at a dacha in the Moscow region. They are in excellent condition!
Between the boards located in the same row, gaps should also be left. This will ensure unhindered air movement inside the stack and improve the drying quality.
Wood kiln project
Wood can be dried quickly and efficiently in well-equipped and free-standing kilns. The construction of such a chamber on the scale of a dacha or suburban area is not always appropriate. After all, this type of building will be very expensive, and its construction will take a lot of time.
The construction of such a room can be quite called the implementation of a full-scale construction project. You cannot avoid the laborious operations associated with pouring the foundation, with the erection of walls and the installation of complex equipment.
How to make drying for a tree can be understood from the diagram.
Do-it-yourself chamber drying
Such a mini wood dryer requires the placement of not only the main equipment (heating and ventilation), but also additional systems automatic control.
Drying chamber operating modes
The chamber dryer does not imply strong heating during normal operation. BUT full cycle works related to the drying of 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 45Co. 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 up to 50 Co.
The third stage lasts until the required final moisture level in the internal structure of the wood (8...12%) is reached. At this time, the air temperature rises to 55 C, the exhaust dampers are fully opened, and the fans operate at full capacity.
After the humidity reaches the required values, the heat supply should be stopped. The fans must remain on for another 24 hours. As a result of this heat treatment, you will get dry wood, completely ready for use during carpentry or construction work.
You can get acquainted with the practical developments of our members of the forum regarding the correct construction of a stack in the "" section. Those who wish to learn more about the lumber drying technology can visit the "" section. For those who want to see a master class on wood aging technology, we recommend watching the corresponding video.
Drying is an obligatory stage of wood preparation before processing. To prevent the logs from deforming, they are dried under certain conditions, which are created in the drying chambers. For a home workshop, you can make a wood dryer with your own hands.
The importance of drying
Since ancient times, in the manufacture of wood products, wood has been used, cut down several years ago. Furniture made from damp or improperly dried boards will warp or dry out and crack. Drying, the material shrinks, raw wooden beams will lead over time, and cracks with a palm width will appear in the walls of the log house. AT raw wood mold grows. But overdried boards are also bad - the material begins to absorb moisture, swells.
Drying is carried out with hot air or steam, the process is long and expensive, but it gives the wood additional strength, prevents changes in shape and size, and the lumber is stored longer.
Drying modes
There are several modes of drying lumber. In self-made chambers, the temperature rises in stages, removing moisture from the raw materials. Drying technology is selected taking into account:
- types of wood;
- lumber dimensions;
- final and starting humidity;
- features of the dryer;
- raw material quality categories.
The drying process can be high temperature or low temperature. In the second case, the primary processing is carried out at a temperature not reaching 100 degrees.
Low temperature modes are divided into categories:
- soft - during the drying process, lumber retains all its properties, strength and color do not change;
- normal - color changes slightly, strength decreases slightly;
- forced - when chipping and splitting, brittleness is possible, the color darkens.
The change in the temperature of the medium in the low-temperature regime occurs in three stages. Go to next stage possible when the wood reaches the specified moisture content.
High-temperature processing is carried out in two stages. The second stage occurs when the moisture content of the raw material decreases to 20%. This technology is used in the preparation of wood for the construction of secondary structures, allowing for a change in color and a decrease in strength.
Types of drying chambers
Drying wood in industrial scale produced in special chambers. Moisture is removed from the lumber by heated air and taken out into the street. In the device there is a full cycle of wood drying. The room can be:
- prefabricated metal;
- built from building materials.
The latter are installed directly in the carpentry shops or as separate buildings. The walls are made of reinforced concrete or brick. At large enterprises, several cameras are equipped, combined into a module with common system control and communications. The air circulates in the dryer horizontally or vertically transversely. Wood in industrial dryers can be transported on rails on trolleys, laid out by forklifts.
Heat sources in the dryer:
- hot steam;
- radiant heat from special devices;
- heated shelves of racks;
- electric current that passes well through wet logs;
- high frequency electromagnetic field.
The camera is equipped with a main and additional equipment. The main system consists of:
- ventilation of supply and exhaust type;
- heat supply;
- moisture.
Additional equipment is wall and door insulation, trolleys for laying material, psychometric equipment, electric drive.
Industrial dryers are controlled automatically, small home-made dryers are manually controlled. Humidity is controlled by supply and exhaust ventilation and humidifiers. To measure the humidity in the room, a moisture meter is installed that collects data simultaneously in several places.
As an energy carrier for air heating, you can use: electricity, wood processing waste, liquid, solid fuel.
Types of dryers
According to the method of air movement, the chambers are divided into:
- with natural;
- with forced air exchange.
Cameras with natural air exchange unproductive, the process in them cannot be controlled. Therefore, they are used less and less.
According to the principle of action are distinguished:
- convective;
- condenser dryers.
In convection chambers, the wood is blown with hot air currents, heat is transferred by convection. They can be deep tunnel or chamber. Logs are loaded into the tunnel chambers from one end and unloaded from the other, moving along the chamber, the material is gradually dried. The duration of the cycle is from 4 to 12 hours. Such cameras are installed at large sawmills. Chamber dryers are more compact, a single microclimate is maintained throughout the volume. Allow to prepare any types of wood to the required condition. Therefore, most industrial dryers are of the chamber type.
According to the technology of condensation drying, the moisture released from the material is deposited on the coolers, accumulates in containers and drains to the outside. The efficiency of such a device is very high, but the process is long, accompanied by high heat losses. The technology is good for preparing hard lumber in small batches. The price of equipment and the cost of condensation drying is lower than that of convective drying.
Arrangement of a homemade dryer
In order to make a dryer with your own hands, you can do without drawings. It is necessary to provide:
- camera room;
- insulation;
- heat source;
- fan.
The area of a do-it-yourself dryer usually does not exceed 9 square meters. meters. In room square shape it is easier to ensure optimal movement of warm air. It is desirable that one wall of the chamber be made of concrete slabs, others made of wood. All walls are insulated from the inside in two layers: polystyrene foam and a foil board. Excellent and free insulation - wood shavings. And the foil can be replaced with penofol, which perfectly reflects heat.
A separate do-it-yourself dryer room can be built from aluminum, such a structure will last a long time. The frame is made from a profile, it is sheathed sheet metal which is insulated from the outside. The thickness of the insulation is at least 15 cm. The floor is covered with roofing felt, a thick layer of shavings is poured on top as thermal insulation.
Care must be taken to carefully seal the front door!
The heat emitter can be made in the form of pipes or heating radiators. The water temperature should be 65-95 degrees. It is heated by an electric boiler, wood burning stove, gas boiler. For a small chamber, even a two-burner electric stove is enough. If the stove is located directly in the room, you need to overlay it with bricks. The brick will accumulate heat and gradually radiate it into the dryer. It is easy to equip a convection chamber with your own hands by installing a fan heater as a heat source.
When equipping a dryer for a home woodworking workshop with your own hands, it is important to observe fire safety measures. There should always be a fire extinguisher near the building.
Constant circulation is essential warm water provided by the pump. To distribute heat evenly throughout the room, a fan is installed. The working room is equipped with a wet and dry thermometer.
For the convenience of loading the board into the chamber, you can use a trolley on rails. And to increase usable area racks are built on the walls.
The step-by-step instruction looks like this:
- We are building a foundation.
- We raise the frame.
- Sheathe the frame with sheets of metal.
- Installation of thermal insulation.
- We cover the floor with foil and sawdust.
- Installation of supports from the bars.
- Installation of heaters and fans.
The design of a homemade chamber for drying lumber in the video:
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