Vacuum drying of lumber. Vacuum drying of wood

Wet wood is practically not used in the manufacture of high-quality and durable wooden structures - furniture, exterior and interior decoration, and also load-bearing elements buildings. Installation and operation of lumber is preceded by removing moisture from it. The long-known process of natural drying can last several years, which is unacceptable given the large volumes and pace of modern construction.

There are two main types of moisture in wood that affect the density and technical parameters constructed structure:

intracellular moisture– is easily removable, but is also quickly absorbed back into the wood in a humid environment;
intercellular water– found outside the cells of wood (also called hygroscopic). This type of moisture is the most difficult to remove and forms the basis of constant humidity (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 rate of evaporation is greater than the internal migration of moisture, then the surface dries faster. This causes uneven changes in linear dimensions and leads to the appearance of cracks and bends. The gradual occurrence of the process ensures the preservation of the structure and shape of the wood.

Basics modern methods drying is based on several methods of influence that accelerate the evaporation of moisture from the surface of the wood:

increase in temperature;
increasing the frequency of air circulation;
decreased blood pressure;
reducing the humidity of air circulating over the wood.

What happens to wood when drying, besides removing moisture

The main processes observed in the structure of wood during drying are shrinkage and shrinkage. Shrinkage refers to the inevitable companions of moisture removal and represents a reduction in the dimensions of lumber in all directions after the removal of hygroscopic moisture begins.

An increase in wood size with an increase in free moisture content is called swelling. Shrinkage observed with rapid removal of moisture, when the outer part of the tree is much drier than the inner. This phenomenon often occurs when drying thick wooden beams and logs. The occurrence of shrinkage and shrinkage is taken into account when planning future structures, as well as swelling during operation in humid environments.

When wood overheats, which sometimes occurs during (chamber drying), a process similar to dry distillation occurs. It represents a decomposition wood fibers without air access, resulting in the release of gaseous, liquid and solid (charcoal) products. This process is irreversible, so when heating it is important to maintain optimal temperature conditions.

More information about the drying process itself:

Technologies and methods for drying wood

Vacuum (chamber)

Drying wood in vacuum drying chambers involves creating 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 played by air, which is supplied in small quantities into the chamber.

Changing the degree of vacuum and air supply allows you to adjust the rate of water removal. For material of various shapes and sizes, strict dehydration conditions are applied to maintain constant moisture content throughout the volume.

Depending on the type and size of wood, drying time lasts from several days to a month. The lungs dry out most easily conifers(pine, spruce), and heavy oak boards have to withstand up to deep removal moisture 3-4 weeks.

Photos of wood drying chambers

Example 1 Example 2 Example 3

Condensation

It is based on 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 its 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 removal of moisture is a development of classical chamber drying, in which the wood is kept in a stream of hot air. Chamber drying conditions are adjustable regulatory documentation and include soft, normal, forced and high temperature modes. The process can occur continuously in chambers of large volume and length, which provides increased productivity.

Natural

It is carried out until the wood reaches an air-dry state (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 structural frames that have undergone special processing from and supporting structures.

Drying under natural conditions is carried out in rooms that are protected from precipitation and have good ventilation. When laying, the material is placed in stacks, in which distances are left between the boards to ensure ventilation.

The video will tell you how to properly dry wood in an atmospheric (natural) way:

Drying chambers and their structure

Drying equipment (chambers) are cylindrical or box-shaped, lined on the outside with metal sheets. Raw wood material can initially be stacked inside or placed on special shelves.

Convection is ensured compressor units, and the air is heated in radiator heat exchangers. The air is supplied from above, since after contact with the wood load and 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 the lower part of the chamber.

Drying devices are intermittent and continuous action. In batch systems, work is interrupted while the dried batch is unloaded and a new block of wood is loaded. Continuous dryers ensure constant movement of stacks from the “wet” part of the chamber to the “dry” one, and loading is carried out as free space becomes available inside.

This video describes in detail a device for vacuum drying wood with your own hands:

Wood harvesting rules

The procedure and conditions for lumber procurement are regulated in accordance with the Forestry Code of the Russian Federation.

The basic rules that must be followed during logging are as follows:

felling of trees is carried out after submission and approval of a declaration, which justifies and describes the volume of felling, territory, type of wood, etc.;
the first on the list for cutting down are trees that have suffered from natural causes or as a result of human activity (fire, storm, flood, disease);
Only trees that meet age standards can be felled;
during logging, it is necessary to remove the sawn material in a timely manner, prevent clogging of the territory and demolish temporary buildings used in the work;
It is forbidden to leave undercuts - individual trees in deforested areas.

Drying wood yourself

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 a base for future installation, under which air will flow freely;
lay the lumber crosswise in several rows, as shown in the figure;
close the resulting stacks in the upper part from random drops of water, dust and debris;
fasten wooden boards or bars between each other. It is best to use polymer materials for this - rubber puffs or nylon cords;
keep the stack for the time recommended for a specific climate zone(usually several months).

You can prepare lumber yourself if you have time and the need to prepare a large amount of wood. The resulting material is suitable for use for construction purposes, but is poorly suited for manufacturing 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:

All photos from the article

A do-it-yourself board dryer is made if there is a need to process a large volume of unprepared wood. Of course, you can immediately purchase blanks with optimal humidity, but in this case the costs of purchasing the material will be very high. So the construction of a special device can be quite effective from an economic point of view.

In our article we will tell you. How to dry wood, and we will give recommendations on how to independently arrange a drying chamber.

Theoretical aspects

Moisture in wood

Before we start designing a dryer, we need to understand why it is needed. As the name suggests, such devices are designed to remove excess liquid from wood, and here it is worth paying attention to the theory.

All moisture in wood is divided into two groups:

free - found in cell cavities and intercellular spaces. The free moisture content is primarily determined by the conditions in which the tree grew, as well as the storage conditions of the sawn pieces. When drying, free moisture leaves the wood quite quickly;
bound (structural) – a liquid that is part of the cell walls. Each type of wood normally has its own level of moisture content in the structure. In this case, the removal of bound liquid occurs very slowly, therefore, under natural conditions, drying can take from several months to several years.

As a rule, the limit of wood saturation with moisture is at the level of 30%. Wood with higher humidity is considered damp and is almost never used for work.

Humidity indicators for different materials differ:

Why is drying necessary?

So, we’ve dealt with moisture itself, now let’s analyze why we need to reduce it.

When removing moisture naturally the configuration of the wood fibers changes, due to which the size of the board decreases - it “dries out”.
In this case, the workpiece loses moisture unevenly, so deformation can also occur in different planes at different rates.
Due to this, stress lines are formed inside the wood, which subsequently give rise to cracks.

Pay attention!
As a rule, the board cracks along the grain, starting from the end.
This is due to the least strong bonds between the longitudinal fibers.

In addition to cracking, transverse deformation of the board is also possible: the part either bends in an arc, or due to uneven lifting of the edges, a so-called “propeller” is formed. This behavior is explained simply: not all fibers dry out at the same time, which means their length also decreases in different ways.

As you can see, if used to build structures or craft various designs wood with a high moisture content, over time individual parts may become unusable. There is one way to avoid this - before starting work, prepare the raw materials by drying them in one way or another.

Drying modes

The use of drying chambers can significantly reduce the time required to prepare lumber for work. At the same time, by controlling the dehydration regime, we can control operational properties the resulting material.
Today, experts distinguish three drying modes:

Mode	Peculiarities
Soft	The temperature in the chamber rises gradually, due to which not only the natural strength of the wood is preserved, but also its color. At the same time, the rate of dehydration of raw materials is slightly reduced.
Standard	It is used to bring the material to its final moisture content while maintaining almost complete strength. In this case, a slight change in shade is possible.
Forced	Forced drying is used to prepare lumber for work as quickly as possible. After high-temperature treatment, the flexural, compressive and tensile strength is maintained, but the splitting strength may be slightly reduced. It is also possible that the wood may darken and a characteristic odor may appear.

Creating a drying chamber

Ready premises

So, we have argued the thesis that lumber must be prepared for use by drying. Now let's figure out how to make a board dryer with your own hands.

First, we need to select the room in which the drying process will take place:

Since removing moisture from wood requires significant energy expenditure, the drying area must be selected based on the planned volumes of material.
The optimal room height is 2 – 2.5 m (so as not to bend over). The width should allow the placement of one or two stacks of boards of 1.8 - 2 m each with a passage between them.
The windows in the dryer must be covered with bricks.. We expand the doors so that we can easily load the processed material.

Pay attention!
For ventilation, either a small window or a vent is left, into which we will later lead the air duct.

If drying boards is planned in a fairly large room, then it is advisable to make a separate partition in it. We build partitions from brick or thick enough timber to provide thermal insulation.

Construction of a dryer

However, find suitable premises(most often a garage or barn plays this role) it doesn’t always work out.

This is why it will be useful to learn how to make a drying board for boards from scratch:

We lay a tape or columnar foundation. Since the mass of the structure will be small, we make the base shallow.
After the foundation concrete has dried, we assemble a frame from an aluminum or galvanized steel profile. We connect the frame parts using bolts and special brackets.

Pay attention!
Price aluminum structures significantly higher, but at the same time they are significantly more resistant to corrosion in warm and humid environments.
So the use of more expensive load-bearing elements is completely justified.

We cover the walls and roof with steel sheets, which we fix to the frame with metal screws (with a drill). For maximum efficiency We perform double cladding, laying a layer of mineral wool insulation with a thickness of 100 - 150 mm between the metal sheets.

We lay a dense layer on the floor waterproofing membrane, which we cover with a layer of sawdust.
We install doors that should close as tightly as possible. Can be reinforced for additional sealing door frame bars with rubber sheets attached.
As in the case of using an already finished room, we be sure to equip ventilation ducts for air circulation.

After completing the work, we check the tightness of the room, if necessary, eliminating defects in the cladding. Now we just need to equip our drying chamber.

Pay attention!
A closed dryer should not have any gaps that allow uncontrolled air flow.
This is due to the fact that the presence of the slightest draft can provoke uneven processing of the boards, causing them to crack or deform.

Equipment

Instructions for arranging a dryer can be very different, because the equipment of the chamber largely depends on both our requests and financial capabilities.

And yet general scheme It’s quite possible to formulate:

First, we make supports on which the stack of boards will be installed. We fix it on the floor, allowing the material to be dried to be raised approximately 10-15 cm above the floor level to ensure circulation in the lower layer of air.

Instead of supports you can use wall shelving. At the same time, we attach metal brackets to the load-bearing surfaces, intended for laying stacks along the walls of the drying chamber.

Pay attention!
This option is most often used when temporarily converting part of an outbuilding into a dryer.

Next, install the heating device. It could be a stove, fireplace, heat gun, fan heater, etc. – it all depends on your preferences. The key parameter will be the power of the device, which is calculated based on the volume of loaded wood: to dry 1 m3 of boards, at least 3 kW of thermal energy is required, respectively, the more raw materials we need, the more powerful the device we will need.
Together with heating devices, we install fans that will ensure air movement. Of course, you can save money on your purchase ventilation system and make do with natural exhaust, but in this case the time to prepare the boards for work will increase significantly, which means that the cost of heating the chamber will also increase.

We place fans and heating devices in such a way that warm air flows across air flow. This installation allows you to significantly reduce aerodynamic drag system so that the dryer will work more efficiently.

Since our camera will require a large amount of electricity to operate, it is advisable to connect a separate power cable to it. In this case, we connect all used units to the distribution panel through an RCD with the corresponding power partners. Such a precaution will not be superfluous, since wood, even if not completely dried, can catch fire from the slightest spark that appears during a short circuit.

Advice!
It is also advisable to install an automatic temperature and ventilation control system.
It is quite expensive, but its use allows you to control the parameters of the internal environment of the dryer, thereby ensuring maximum quality of wood processing.

Using the dryer

If the drying chamber was assembled according to all the rules, then using it will be quite simple. To do this, we stack the boards, placing bars up to 20 mm thick between the rows, and load the stack into the dryer.

After this, we begin to change the temperature, gradually increasing the heat.

There are many drying schemes, but novice craftsmen should use a low-temperature mode, as it ensures maximum quality with minimal risk of defects:

Heating - raise the temperature to 45 - 50 0C at a speed of 5 - 70 C per hour.
Exposure – keep at 50 0C for 5 hours.
Drying – reduce the humidity of the wood from 30 to 8%, gradually increasing the temperature to 60 0C. This stage takes about 48 hours. Supply and exhaust ventilation turns on at half power.
Air conditioning – maintain the temperature at 600C for another 12 hours. Ventilation must work actively.
Cooling down to temperature environment with heating and ventilation turned off.

As a result, we should get boards suitable for most types of carpentry and joinery work.

Conclusion

As you can see, making a board dryer with your own hands is quite simple (but I must admit, with certain financial costs). At the same time, the use of this device allows you to obtain a large amount of construction raw materials, which, if purchased from the manufacturer, would be much more expensive.

For a more detailed introduction to the technology of chamber drying of wood, we advise everyone who is interested in this topic to study the video in this article.

The need to make a mini vacuum dryer for wood arises when it is necessary to save both money and time. Since purchasing a vacuum dryer at a factory is a rather expensive undertaking, and high-quality wood processing, in particular drying, is absolutely necessary for the further use of wood and the preservation of its mechanical properties and proper appearance.

Done homemade dryer for wood in a large room where there is a heat source and where you can install a fan that will distribute the heat inside the structure itself. A railway conveyor is ideal as a dryer; a used one will be quite cheap. You can also weld the conveyor yourself.

Wood drying methods

There are various types drying wood, each of which has its own characteristics. Some of the types are obsolete and are currently practically not used.

The natural method of drying wood is the longest, and at the same time does not require financial costs. With this drying method, the bark is not removed from the tree; air access is ensured by cutting holes across the trunk. Drying using the natural method should be done in a dry, well-ventilated room, otherwise the wood inside will remain damp, which will subsequently lead to warping. Depending on the moisture content of the wood, it sometimes takes 2-3 years to dry naturally, which makes this method in modern realities completely unclaimed.
Paraffinization is also a type of drying that has been used for a long time. In this case, wooden blanks should be immersed in paraffin heated to 40 ° C. After several hours, the wood is removed and dried for 1-2 days. After this procedure, the wood acquires a pronounced texture pattern and an original tinted shade, and is not subject to cracking, warping or rotting.
Evaporation - here, in addition to wood, water and sawdust are needed. The workpiece is placed in water heated to 70 ° C and covered with sawdust so that the material is thoroughly steamed. Another known drying method is steaming in linseed oil. Here the technology is slightly different: the workpiece is placed in a special container, filled with linseed oil and steamed required quantity time. This method was often used in past times - dishes made from steamed wood did not crack or deform for a very long time.
The process of drying wood in a specialized drying chamber takes place at a temperature of 40 to 90 °C, in some cases the temperature in the dryer reaches 115 °C. A dryer is a stationary structure equipped with a fan, a device that directs air currents and controls the humidity in the container. The heat source in such a chamber is steam, hot water or electricity.

At the moment, we are considering with you how to create a vacuum drying chamber, which allows you to make the wood drying process not only economical, but also significantly reduce its time.

Drying wood at home

Drying wood at home, as noted earlier, can be done with a special conveyor. You will also need a fan, insulation and a heating device. To retain heat, your chamber must be insulated; for this, foam plastic or mineral wool can be used. You will also need to lay a special material to reflect heat - for this purpose, as a rule, foil or penofol is used.

The heating element can be installed in the form of a battery, into which water will be supplied from the stove, heated to 60-95 ° C. The system for loading wood into the chamber also deserves special attention. Rail carts or a forklift can be used for this. You will definitely need to monitor the drying process - for this you need to install specialized sensors.

When answering the question of how to dry a board at home, it is definitely worth mentioning that when building your own drying chamber, you must adhere to all the rules fire safety. If you do everything correctly, you will be able to subsequently obtain high-quality wood that has a good presentation.

Video of drying wood at home

Any lumber is obtained by longitudinal sawing of a log. The result is bars, slats, and boards of various thicknesses necessary for construction and repair. Only dry lumber is used in construction. They have higher quality indicators. To dry wood at home, you can equip a special do-it-yourself lumber dryer. The construction process of this structure will take a lot of time. But as a result home handyman will always be provided quality material to perform various jobs.

The quality of the timber depends on how dry the wood is. The moisture content of the timber should be 12%.

Construction of a dryer

Construction of a simple dryer for drying small volumes of wood with your own hands under natural conditions consists of several stages:

It is necessary to select and prepare an area to place the building. You can build a dryer on the adjacent building plot of land. Suitable for building a small dryer flat roof. The floor can be made from several layers of roofing felt, sprinkled with sawdust.
Wood to be dried is placed in a stack no more than 120 cm wide. Optimal size its width is 80 cm. The stacking height is 50-70 cm. Separate layers of boards or beams are laid with slats at least 2 cm thick. It is recommended to lay the stack across the air flow in this area.
Provides protection from rain and snow. Dry ones are placed on the top row of the stack. wooden beams cross section approximately 50x50 mm. Iron is placed on them, which is pressed against the same beams.

In such a dryer, the material is blown with air, the moisture gradually evaporates, and the humidity level decreases.

Drying chamber

The most effective way to dry wood is in a special drying chamber. It can be installed automatic systems, which control the entire process of drying wood of specific species. At the output, the lumber will have a predetermined moisture level. You can also build such a camera yourself. But this building will cost a lot of money. For construction you will need:

aluminum profile;
sheet metal;
thermal insulation material;
waterproofing film;
sawdust;
heat construction gun.

Construction is carried out in the following order:

You should start with the construction of a foundation of any type. It can be piled or strip. For its construction you can use brick, concrete, metal pipes and other materials. It all depends on the size of the camera.
A frame is built on the foundation. The best way to do this is to use aluminum profile. It is assembled using bolts and nuts. Other methods of connecting frame elements are possible.
The finished frame is sheathed with aluminum or steel sheets. They are fastened using self-tapping screws, bolts, and welding. The walls can be made of brick, concrete, or other materials.
Thermal insulation is installed from mineral wool 10-15 cm thick.
The floor is covered waterproofing film and sawdust.
To lay stacks of lumber, supports are prepared from bars in the form of a kind of well. This is done in order to raise the bottom row of the stack above the floor level.
Lumber prepared for drying is stacked through wooden spacers. Air should flow freely between the rows of boards. The height of the stack is limited only by the height of the ceiling.
For forced circulation fan heaters or other heating devices are installed to provide heated air. The air flow should be directed across the location of the boards in the stack. This promotes a more efficient drying process.

Dryer inside the house

A small number of boards can be dried inside the house or cottage. The dryer is arranged like this:

You need to choose a room that has a fireplace or stove. Electric fireplaces and stoves can be used.
The room is separated from the rest of the house by partitions. Tightly closing doors are installed. A window may be needed for ventilation. All cracks must be sealed, since extraneous air flows and drafts negatively affect the quality of the dried material. It is also recommended to insulate the walls. On top of the insulation, you can line them with brick, which well maintains heat from the stove and from electrical heating devices. For forced circulation warm air install fans.
Raw lumber is stacked on specially made durable metal shelves.

Before drying, you need to check the moisture level of the material. This is done using a moisture meter. High humidity causes early wear and tear of buildings, the appearance of mold and mildew. Overdried wood becomes deformed due to moisture absorption and swelling. Wood is usually dried to a moisture level of about 8-12%. To prevent it from cracking, experts recommend treating the ends of the boards with a mixture of drying oil and sifted chalk. The consistency of the mixture resembles thick sour cream.

Lumber can be dried either with or without bark. You just need to remember that birch, aspen, poplar and beech in the bark can be affected by rot. In general, the drying process can last up to 2 weeks. During this time, temperature changes in the dryer should not be allowed. There should be a fire extinguisher in the dryer room. This is required by safety regulations.

Operating modes of the drying chamber

The camera should not be immediately heated to high temperature. In normal mode it works like this:

Within 15-20 hours, the air in the chamber is heated to approximately 45°C. The ventilation system is not working yet. Moisture should appear on the walls of the chamber.
When the temperature reaches 45°C, the supply air should be opened by a third and exhaust system ventilation. In about 2 days the temperature rises to 50°C.
The dampers must be fully opened and the temperature must be brought to 55°C. This is usually sufficient for a normal drying process. As soon as the humidity reaches approximately 8%, all dampers must be completely closed and the heat supply must be turned off. The fans continue to run for another day. Once the temperature drops to 40°C, dry lumber should be obtained, ready for use.

Additional equipment

As additional equipment, you can install automation in the drying chamber. Its properties:

the system is capable of working with cameras different sizes and with different sources heat;
is relatively cheap;
does not require special knowledge for its maintenance;
is easy to install;
measures temperature and humidity in the chamber;
provides fully automatic or semi-automatic operation of the drying chamber;
automatically controls the operation of valves, dampers and fans.

To operate the system, it is enough to set the thickness and type of lumber and the desired final moisture content. The system helps dry various types of wood: pine, spruce, oak, birch, beech, linden, ash, maple, alder, hornbeam, poplar, aspen, sycamore. Every 2 hours, the automation takes readings of humidity and temperature and makes the necessary adjustments to the operation of all air heating and ventilation systems. The approximate cost of such a system ranges from $400-450.

Building a dryer with your own hands is quite troublesome and expensive.

But the result covers all costs. This is especially important for those who manufacture wooden products like furniture and wood carvings. Dry wood costs several times more than raw wood. In addition, in your own dryer you can achieve a certain moisture content of the workpieces. Everything can be done independently if you have a strong desire and the availability of a suitable place.

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 that it cannot be used in its pure form, since even solid rocks no longer meet construction standards in 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 additional 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 to traditional drying chambers, new cylindrical vacuum drying technologies allow for a high process speed. 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, more moisture is evaporated. 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 results as alternative drying methods, 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 event starts, the user is required to install optimal mode drying. 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. Regarding temperature regime, then he's 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 cover includes a rubber sheet fixed to 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 It is within the drying process that it is a by-product and redundant. Actually, to eliminate these consequences it is envisaged final stage cooling. 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 introduced into general complex 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 for drying wood 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 of the 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, but a sealed dryer for boards. How to make thermal elements? 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 and will provide an evaporation effect. For greater efficiency The thermal function can be supplemented with fans.

Conclusion

During construction and repair operations The question often arises 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 long term its use will be worth the investment. As practice shows in the operation of structures based on properly dried wood, 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.