All photos from the article
A do-it-yourself dryer for boards is made if it becomes necessary to process a large amount of unprepared wood. Of course, you can immediately purchase blanks with optimal moisture content, but in this case, the cost 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. How is the drying of the tree, and we give recommendations for self-arrangement drying chamber.
Theoretical aspects
Moisture in wood
Before proceeding with the design of the dryer, we need to understand why it is needed. As the name suggests, similar devices designed to remove excess liquid from wood, and here it is worth paying attention to theory.
All moisture in wood is divided into two groups:
- free - is located in the cavities of cells and in intercellular spaces. The content of free moisture is primarily determined by the conditions in which the tree grew, as well as the storage conditions of the sawn blanks. When drying, free moisture leaves the wood rather quickly;
- bound (structural) - a liquid that is part of the cell walls. Each tree species normally has its own level of moisture content in the structure. At the same time, the removal of the bound liquid occurs very slowly, therefore, under natural conditions, drying can take from several months to several years.
As a rule, the limit of saturation of wood with moisture is at the level of 30%. A tree with a higher moisture content is considered damp and is almost never used for work.
Humidity readings for different material differ:
Why drying is necessary
So, we figured out the moisture itself, now let's analyze why we need to reduce it.
- When moisture is removed in a natural way, the configuration of wood fibers changes, due to which the size of the board decreases - it “dries out”.
- In this case, the workpiece loses moisture unevenly, because the deformation can also occur in different planes at different speeds.
- Due to this, stress lines are formed inside the wood, which later give rise to cracks.
Note!
As a rule, the board cracks along the fibers, starting from the end.
This is due to the least strong bonds between the longitudinal fibers.
- In addition to cracking, it is also possible transverse deformation boards: the part is either arched, or the so-called “propeller” is formed due to uneven raising of the edges. This behavior is explained simply: not all fibers dry out at the same time, which means that their length also decreases in different ways.
As you can see, if you use wood with high content moisture, over time, individual parts may become unusable. This can be avoided in one way - before starting work, prepare the raw materials by drying it 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 mode, we can control operational properties received material.
To date, 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 somewhat reduced. |
| Standard | It is used to bring the material to the final moisture content with almost complete preservation of strength. In this case, a slight change in shade is possible. |
| Forced | Forced drying is used for the fastest preparation of lumber for work. After high-temperature processing, bending, compressive and tensile strengths are retained, but the splitting strength may be slightly reduced. Darkening of the wood and the appearance of a characteristic odor are also possible. |
Creation of a drying chamber
Finished premises
- We lay a strip or column foundation under the structure. Since the mass of the structure will be small, then we make the base shallow.
- After the foundation concrete has dried, we assemble the frame from an aluminum or galvanized steel profile. We connect the frame parts with the help of bolts and special brackets.
Note!
Price aluminum structures much higher, but at the same time they are significantly more resistant to corrosion in a warm and humid environment.
So use more expensive load-bearing elements quite justified.
- We sheathe the walls and roof with steel sheets, which we fix to the frame with metal screws (with a drill). For maximum efficiency we carry out double cladding, laying a layer of mineral wool insulation with a capacity of 100 - 150 mm between the metal sheets.
- We lay a dense waterproofing membrane on the floor, which we fill with a layer of sawdust.
- We install doors that should close as tightly as possible. For additional sealing, you can reinforce the door frame with bars with attached rubber sheets.
- As in the case of using an already finished room, we must equip ventilation products for air circulation.
After completion of work, we check the tightness of the room, if necessary, eliminating defects in the skin. Now it remains for us to equip our drying chamber.
Note!
In a closed dryer, there should be no gaps that allow uncontrolled air currents to enter.
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.
Nevertheless, it is quite realistic to formulate a general scheme:
- To begin with, we make supports on which a stack of boards will be installed. We fix on the floor, allowing you to raise the material to be dried by about 10-15 cm above the floor level, the proportion of circulation in the lower layer of air.
- Instead of supports, you can use wall racks. At the same time, we fix metal brackets on the bearing surfaces, designed for laying stacks along the walls of the drying chamber.
Note!
This option is most often used when temporarily converting a part of an outbuilding to a dryer.
- Next, install the heater. It can be a stove, a fireplace, heat gun, fan heater, etc. - it all depends on your preferences. Key parameter there will be the power of the device, which is calculated based on the volume of loaded wood: for drying 1 m3 of boards, at least 3 kW of thermal energy is needed, respectively, the more raw materials we need, the more powerful the device we need.
- Together with heating devices, we install fans that will provide air movement. Of course, you can save on the purchase of a ventilation system and get by with natural exhaust, but in this case, the time for preparing the boards for work will increase significantly, which means that the cost of heating the chamber will also increase.
- We position fans and heating devices in such a way that warm air flows across the air flow. This installation allows you to significantly reduce the aerodynamic drag of the system, so that the dryer will work more efficiently.
Since our camera will require a large number of electricity, it is desirable to bring a separate power cable to it. At the same time, we connect all used units to the switchboard through the RCD with the corresponding power partners. Such a precaution would not be superfluous, since a tree, even if not completely dried, can catch fire from the slightest spark that appeared during a short circuit.
Advice!
It is also desirable to become automatic system temperature and ventilation control.
It is quite expensive, but its use allows you to control the parameters of the internal environment of the dryer, thereby ensuring the maximum quality of wood processing.
Dryer use
If the drying chamber was assembled in accordance with all the rules, then it will be quite simple to use it. To do this, we lay the boards in a pile, laying bars up to 20 mm thick between the rows, and load the pile into the dryer.
After that, we begin to change the temperature, gradually increasing the heat.
There are many drying schemes, but beginners should use low temperature regime, as providing maximum quality with minimal risk of marriage:
- Heating - raise the temperature to 45 - 50 0C at a speed of 5 - 70 C per hour.
- Exposure - we keep 50 0C for 5 hours.
- Drying - we reduce the moisture content of the wood from 30 to 8%, gradually increasing the temperature to 60 0C. This step takes about 48 hours. Supply and exhaust ventilation is switched on at half power.
- Conditioning - we maintain the temperature at 600C for another 12 hours. Ventilation must be active.
- Cooling down to ambient temperature with heating and ventilation off.
As a result, we should get boards suitable for most types of carpentry and joinery.
Conclusion
As you can see, a do-it-yourself dryer for a board is quite simple (but, admittedly, with certain financial costs). At the same time, the use of this device makes it possible to obtain a large amount of building materials, which, if purchased from the manufacturer, would cost much more.
For a more detailed acquaintance with the technology of chamber drying of wood, we advise everyone who is interested in this topic to study the video in this article.
And the physical and mechanical properties are improved. If you use unprepared wood, defects in the product cannot be avoided: moisture evaporates unevenly, which causes cracks, deformations, and fractures.
Wood drying methods
Previously, lumber drying was carried out by evaporation and waxing, which made the wood very durable and wear-resistant. Nowadays, these methods are practically not used, since modern technologies allow us to achieve excellent results at much lower costs.
Atmospheric, natural drying does not require special equipment, which is an undoubted advantage of the method, but the drying period itself is quite long, from several months to two years. With this method, the wood is placed on outdoors, under a canopy or in a room with good ventilation. The blanks are stacked on special stands in such a way that there are gaps for the penetration of air flows.
As a rule, the edge boards dry faster and are more likely to deform, cracks may appear on the ends - all this should be taken into account when harvesting wood.
Chamber drying is considered the most effective: different types cameras and process automation allow you to choose best option drying for a specific type tree species, but this method is used only in large or small industries.
The wood drying chamber produces lumber with a certain degree of moisture at the output, which cannot be achieved by other methods, but the process itself requires considerable energy and financial costs in general.
How to make a dryer with your own hands?
If there is no opportunity to use industrial drying, you should try to build a drying chamber with your own hands.
DIY wood dryer- opportunity to achieve good results with minimal cash outlay.
For the construction of the dryer you will need: aluminum profile, metal sheets, thermal insulation, waterproofing, sawdust, heat gun.
Stages of construction and use
Frame sheathing aluminum sheets, door installation.
Laying thermal insulation up to 15 cm thick.
Covered the floor with waterproofing material and sawdust.
Checking the tightness of the structure and eliminating air leaks.
Construction of stack supports. In order to raise the bottom row of boards above the floor surface, it is necessary to install supports made of bars or other material.
Laying boards indoors. The lumber is laid out in rows using spacers from the bars so that air can freely penetrate between the boards anywhere in the stack. You can lay out the boards up to the ceiling.
Installation of a fan heater or other heating equipment. forced circulation air contributes to a faster drying process. The direction of flow must be perpendicular to the location of the boards.
Do-it-yourself dryer for boards is ready!
There is another way to create a dryer with your own hands - inside the house or cottage. It is suitable for small volumes of lumber.
First of all, you will need a room with a fireplace, a stove or an electric oven, where the dryer will be located.
Then partitions, doors and vents are installed. The tightness of the room must be perfect, otherwise drafts and air currents can affect the quality of drying. All cracks, crevices, holes are sealed with sealant, and the walls are tightened with insulation.
To maintain heat from the stove, you can overlay the room with bricks.
In case of insufficient circulation warm air fan is installed.
For laying lumber are constructed metal shelves with reliable fasteners to avoid collapse of the structure. The boards themselves are arranged according to the same principle: in even rows with gaps and spacers from the bars.
A drying chamber for wood will improve the properties of wood, increase its strength and durability, that is, it will allow you to get the highest quality raw materials for construction.
Photo sources: sawwood.ru, yugmassiv.ru, zharbond.ru, makilplus.ru, dnepro.com.ua, house-lab.ru, hobbyblog.org, stroydrev.by, sushkadrevesiny.com, saw-wood.com, strport.ru
Buy materials for thermal insulation on DOM.BY
 |
 |
How to make a cheap vacuum wood dryer
Hello dear readers and subscribers of Andrey Noak's Blog! Do you know what is the most important thing in wood materials? This is a quality dryer.
Each enterprise uses a special drying technology. But if you want to dry the material yourself, then I will tell you how a do-it-yourself vacuum dryer is made. But first, some theory.
Wood is a hygroscopic material, this is due to the fact that wood absorbs water vapor from the air.
Each wood material has a different degree of humidity, depending on storage conditions and the environment.
Why dry wood?
Drying is the process of removing moisture from a material by evaporation.
When a tree grows, the metabolism in it is carried out with the help of moisture circulation through the trunk. When cutting, circulation stops and moisture begins to evaporate.
In order to build a house or make any wooden product, you need to dry the logs with high quality.
Purchased vacuum dryer
Well-dried material is protected from fungi, damage and cracks, and the service life will increase markedly.
If the drying was of high quality, then the product will serve you for many years.
Wood is divided into categories depending on the degree of moisture:
- wet is the one that was in the water and its humidity is one hundred percent;
- freshly cut, with humidity ranging from 50 to 100%;
- air-dry, in cases where the material has been exposed to air for a long time.
The moisture content of such wood is approximately 15-20%;
- room-dry, with humidity 8-12%
- absolutely dry, the humidity of which is equal to 0.
Wet material will be difficult to process, but is flexible and elastic.
Dry wood properties
Dry material has greater biological stability. After drying, the strength increases, it withstands the load better. It is easy to process, and the products do not crack after processing, unlike gray wood, in which the rotting process can even begin under suitable conditions.
Old ways of drying
A long time ago, people used only wood to build houses.
In the houses you can find wooden utensils. Therefore, it was necessary to come up with methods for high-quality drying of a log, as the main building material.
At that time, people used several methods of drying.
For this method, the necessary piece of wood, water and sawdust were taken. The water was heated to 70 degrees, the workpiece was placed in it, then covered with sawdust and left for a certain time so that the material was steamed.
After drying, the workpiece did not crack, and the structure became more dense and flexible.
Waxing is another method that has been widely used for a very long time.
Here, wooden blanks were lowered into paraffin heated to 40 degrees and left for several hours. It was important to maintain the same temperature of the substance.
After the procedure, the wood should dry for several days. The properties of the material change after drying. The workpiece does not crack, does not rot and acquires an original tinted shade.
Masters used this method of drying to make wooden utensils, then the finished product was skillfully painted.
Wood moisture, measurement methods
There are many ways to determine humidity.
Special devices are used to accurately determine the moisture content of wood. Electric moisture meters are able to determine humidity with an accuracy of 2-3%. The basic principle of such devices is based on the fact that wood different humidity has different electrical resistance.
There are many more "folk" ways to determine humidity, but only professionals use them:
- By weight, weighing the same pieces of wood of the same species in the hand or on the scales alternately.
- Experienced experts determine the moisture "by eye", by the presence of cracks and faults.
- By strand.
When processing lumber, small chips are compressed in a fist. If it wrinkles easily, then the material is wet. Dry wood is indicated by the fragility of the chips, but if the chips crumble, then most likely the tree has dried out.
- By cutting. If during the processing of wood with a chisel a wet trace is noted, and the material is easily, smoothly cut, then it is not dried. It is better not to carve on such a surface, as cracks and flaws will appear when it dries.
We assemble a vacuum dryer at home
It is very profitable to dry the wood yourself, and if you do it with the help of vacuum dryer, then the drying time will be reduced significantly.
But to fly vacuum drying it’s a little expensive at the factories, and I’ll tell you how you can make it yourself, and also save on it.
Drying at home takes place in special chambers.
To equip it, you will need a large room, a heat source, as well as a fan to distribute heat inside the structure.
Be sure the floor, walls and ceiling of such drying must be very strong, reinforced concrete or an iron conveyor is best suited.
If you take a cheaply used iron conveyor, for example, with railway, then it will be even a very cheap option. Or, for example, to reduce the cost, you can weld the conveyor yourself from old iron.
To preserve heat inside the chamber, we strengthen the walls with foam plastic and trim with clapboard.
Instead of foam, you can use mineral wool or other insulation.
To reflect heat, you need to lay a special material. You can use foil, but penofol is also suitable, especially since its heat-reflecting and retaining qualities are much better.
We proceed to the installation of the heating device.
The entire heating system must be installed separately from others heating circuits and must always work. You can use a heating radiator, with which water is heated to 65-90 degrees.
In order for the heat to be equally distributed in the chamber, a fan is required, otherwise there will be uneven drying of the raw materials and, accordingly, poor quality.
Another point, the temperature in the chamber should change smoothly and gradually.
When building your own drying, you must follow all the rules fire safety.
An important point is the construction of a system for loading lumber into the chamber. You will be loading large and fairly heavy boards. For this, carts moving on rails or a forklift are well suited. The material inside is stacked on shelves or just on the floor. To control the drying process, you must install special sensors, and these are thermocouples and vacuum (pressure) sensors.
By doing everything right, you can get very quality wood with a good presentation.
The main point in the construction of drying is to achieve the necessary parameters inside the chamber, and the materials and equipment that were used do not matter.
In your chamber you can reduce the drying process of raw materials up to 2 weeks.
How Vacuum Drying Works
After you have put the material in the drying chamber, tightly closed the door, you can start drying. Air is extracted from the chamber to create a vacuum of about 9 - 10 bar. It is known that when the pressure is reduced, the water boils faster.
Thanks to this technology, bound and free moisture will move uniformly from the center to the periphery, thereby ensuring high-quality and uniform drying of the material, regardless of location.
Dry top wood cells will absorb moisture from those located in the core.
First, thin places dry out, then moisture from thicker layers moves to the dried ones, thereby moisturizing them. If this process is interrupted, then the material may be destroyed, since the displacement of thinner layers begins.
Covering the ends of thick lumber to prevent rapid release of moisture and the formation of cracks during drying.
To prevent displacement, lumber is treated with a special mixture, which is made from chalk, as well as drying oil.
Often it is necessary to process the end parts of the blanks.
Drying excludes the use of humidification systems, and thermometers should not be installed in the chambers. You can control the process using special sensors, which are controlled from the outside, often in a separate vestibule.
Often vacuum plants used for drying expensive species such as oak, merbau, padauk, wenge, zebrano.
It is very convenient, since the wood practically does not collapse during drying.
My help
I have the opportunity to provide advice on drying technology, the selection of new and used equipment.
You can contact me through SUPPORT.
My recently published A new book which gives recommendations on the operation of drying complexes in production. The information that is given in the book is simply unique, you will definitely not find it anywhere else.
More information about the book can be found in the "MY BOOKS" section.
Good luck and see you soon!
vacuum dryer
This blog is read by 3875 professionals in their field.
Read and you!
your comment
Appointment of modular wooden drying chambers.
Drying chambers Series SCM, students in the nomination "100 best products in Russia.", They are designed for drying hardwood and conifers in accordance with quality categories 0, 1, 2, 3, depending on the purpose of the wood. Drying chambers Our production certified and answer " General requirements to monitoring and control systems environment drying chambers" and "Quality Drying Requirements" according to Russian Technical Material (RTM) guidelines for kiln drying in wood.
Installation, design features of SCM wooden dryers.
Striving for maximum build speed and speed wooden drying chamber partly included in the SCM models. Modular design wooden drying chamber simplifies delivery and installation.
To meet the wishes of the company's customers, many standard sizes Drying chambers. Now "TERMOTECH" develops and manufactures wooden drying chambers and complexes with pneumatic load from 6 to 180 m³ operating on thermal energy generated by the combustion of wood waste or stationary boilers.
Drying chambers with a load capacity up to 20 cu. they have a body in the form of a complete container with a supporting frame, the dimensions of which can be shipped by road or rail.
High mobility and low cost installation work allow you to build a heated drying cabinet with heated floors. When renting production space wooden drying chambers with floor heating is more practical. With a low probability of frequent disassembly, for example. if we have our own space, we can offer a version of the drying chamber body without floor insulation. The cost of cameras without floor insulation is lower, we need more work to install.
Need to clamp cement cement regardless of the height of the already welded track in the place of our company, on the transverse stiffener. clam Drying chambers volume 20 cu. up to 180 m3. They are made in the form of modular blocks, easy to transport, easy to connect with screw connections. The time required to assemble a modular drying chamber is 4 to 8 hours in proportion to the number of modules.
The sealing of the joints when installing the modules of the drying modules is carried out with a special rubber profile and silicone sealant, which is delivered to the customer along with the drying chamber.
The roof of modular wooden drying chambers, depending on the volume of loading, is made one-sided or two-sided. All SCM drying chambers are equipped with a condensate collection and removal system, which increases the life of the fence. For better seal Wooden loading doors of the drying chamber are made with a floating hinge by closing the four-point door lock with the screws.
The door seal is a heat-resistant 3-strip profile. supplied drying chambers Control system, equipped with drying procedure, semi-automatic fully automatic (computer), S control of fuel supply, boiler operation, blinds, ventilation curtains, etc.
proposed wooden drying chambers manufactured both at rest and in a transitional version. The transition version allows the customer to organize the most efficient continuous process and increase the productivity of the drying chambers due to more rational use loading and unloading time compared to blindness.
Loading wood into wooden drying chamber produced by standard wheels. Depending on the load capacity of the chamber, the strings can be transported longitudinally or transversely. When drying wide raw wood, excluding the transverse tip of the tree, the pedestal is equipped with a block-type clamping mechanism.
In this case, the force pressing down on the upper types of beams is equal to the force on the lower types of lumber. When expressed numerically, this force is equal to the force of the weight of the fund.
Heating system.
Modular drying chambers and wooden complexes manufactured by "Termotech" operate on thermal energy obtained from the combustion of wood waste in the heat generators of our industrial or stationary gas boilers. Water heated to 95°C by a pump is provided through the supply pipeline to the side walls wooden drying chamber radiators, after passing through which it enters the boiler at a temperature of 75 ° C.
Useful water registers are single-sided double-sided bimetallic tube heaters (steel bolts with aluminum plates). It refers to the drying chamber of a specific boiler acting on a loaf (chips, leftovers, stove - 70 ... 100 vol.%) In a mixture of wood waste (30%).
When a large number of chips (100%) of solids are provided with a boiler funnel, - relying on sawdust feeding a screw mixer or a mechanical load carburetor, which allows each fraction (boards, chips, chips, bark) to be heated wood products. In case of insufficient amount of wood waste, we can fill the supplied heat source directly onto the burners, gas ovens or liquid fuel stoves.
For more efficient and stable operation of the boiler, a fan is installed in the turbine, and an ejector is installed in the chimney chimneys.
Air exchange system, fans, brackets.
For heat exchange between water registers and indoor air wooden drying chamber Installed centrifugal fan, Electrical engine which is installed outside Drying chamber for wood drying.
The use of rotary fans made it possible to reduce the consumption of electricity for ventilation in wooden drying chambers manufactured by TERMOTECH by 1.7 times compared to similar manufacturers. Drying chambers. Such effective results were achieved thanks to the rational redistribution of power when installing the fan. Wrong high pressure was reduced, resulting in an increase in fan efficiency.
In addition, pressure was reduced in cubic dependence, and increase power - squared. With aerodynamic calculation wooden drying chamber The greatest losses occur when the ventilation system is ventilated.
The fan motor power loss is directly proportional to the cubic velocity of the drying agent. Therefore, further optimization was carried out from the condition: The speed of the drying agent next to the sawdust storage should be between 1 and 1.5 m/s. Based on quality conditions, the same speed is regulated by CNIIMOD for drying wood in mild and normal conditions.
Because the domestic industry does not produce specialized fans for Drying chambers (high performance, low pressure) - all fan wheels of their own shape.
The fan wheels are static and dynamically balanced. In wooden kilns with a load of wood up to 12 m ³ Fan wheels are mounted directly on the motor shaft.
Fan for wooden kilns with wood volume over 12 m3 ³, is carried out through bearings and pulleys. The fan bearing bearing is the busiest device in the drying chamber.
For greater reliability, we use FAG, the company is the world's leading carrier (Germany) of the BND series with FAG spherical bearings. These bearings have a labyrinth seal, grease nipple during Maintenance and are centers that withstand heavy loads, as originally developed for crushing and grinding machines, roller drives for presses and wind turbines.
The most optimal cross extrusion of the chimney and the temperature regime inside drying dry baked lumber It comes with screens and external blinds. This design provides easy access to the inspection and maintenance of the rotating fan and registers. To exchange air with the atmosphere in Ljubljana wooden drying chamber installed aluminum inserts and exhaust valves.
Fences, wall insulation.
Corps of all Drying chambers have an optimal design for middle lane thermal insulation, a layer of solid mineral wool board that does not absorb moisture and has a high degree of fire resistance.
All steel members preventing corrosion in the drying chamber are protected by corrosion coating and waterproof coating. When shipping In regions with different climatic conditions, it is possible to build a thickness that provides the necessary thermal insulation.
How to make a wooden drying chamber
In accordance with the technical task of the customer, there are technological possibilities for the manufacture of monolithic insulation from polyurethane foam from closed cases wood dryingcams, or a combination of thermal insulation consisting of rigid hydrophobic, mineral wool (water absorption coefficient by volume - 1.5%), TIS mats - TIB TU 2123-299-89 and polyurethane.
Polyurethane foam has the best insulating properties, the lowest thermal conductivity coefficient (W 0.019-0.28 / Mº K), light weight (40-60 kg / m³), high adhesive strength and corrosion protection.
The warranty period for insulation of aluminum sandwich panels made of polyurethane foam is 30 years. ( Detailed description and comparative characteristics of rigid polyurethane foam and mineral wool, see here.) Internal walls wooden drying chamber from aluminum sheet or steel with a heat-resistant coating.
outer envelope drying chamber walls made of galvanized, corrugated film 0.8 mm thick. Places of probable offensive "dew" ( inner surface doors, inlet and outlet valves) are made of aluminium.
Thermal processing of wood.
At the request of the client for the production of dry wood from 0, 1, 2, 3 quality categories, wooden drying chambers they are made universal humidification, air conditioning and steam system - development and production of "TERMOTEH".
The diversity of the system is achieved by generating dry entropy steam and increasing the moisture content, i.e., creating the necessary and sufficient conditions for high-quality hardness and drying of wood, as well as thick softwoods.
The processing device of the technological operation must remove the internal tension in the wood when the wood is already dry in order to ensure the stability of the geometry of the workpiece after processing in woodworking machines. It's a concept, a tutorial. Very often, the conditions for storing joinery products after sawing wood are violated, for example: lack of sunscreen to protect against the sun, uneven air flow of a chimney with natural air circulation, loading one drying chamber into several packages with different sawing periods (sometimes important - months).
Therefore, there is an uneven distribution of moisture over the volume of one plate and the volume of the foundation. This leads to stress and improperly selected drying conditions. Avoid rejection with moisture compensation, which is achieved by conditioning the wood treatment at the beginning of drying. For the solid beech process, a steam process is necessary to create a homogeneous color palette for wood different ages. The intensity of the color is proportional to the duration of the steam.
In any case, during the heat treatment of wood, the temperature acts as a catalyst (fast) in the process of uniform redistribution of moisture with the help of the material (moisture transfer), and the high humidity of the desiccant slows down the drying process (stops the removal of moisture), moisturizes overdried wooden parts.
The duration of dampening depends on the thickness and type of wood. Woodworking recommendation for woodworking is "wood drying technology" which is equipped with our product drying kilns. CAM "Module C1", "C2-Module" includes the entire thermocouple drying program. In the absence of a water supply network, the humidification system, air conditioning system and water vapor can work in an unnecessary mode, an unnecessary tank with a consumer inside wooden drying chamber, whose volume is sufficient to complete the entire drying cycle.
In the event of an emergency in the event of a fire in a disaster, the same humidity should be used by the normal fire extinguishing system wooden drying chamber in accordance with PPB-01-93 "Fire Safety Rules in the Russian Federation".
If the client has vacant premises that are outdated Drying kilns for wood drying we are ready to provide technical solutions and equip necessary equipment for their transformation or modernization of drying chambers.
Drying kilns for wood convective type
The presence of drying equipment for drying wood and lumber, as a rule, is one of the main attributes of modern woodworking production.
Dryer for boards: creating and using a drying chamber
Drying chambers of convective type have found great application both in Russia and abroad. The convective wood drying technology makes it possible to obtain high-quality lumber with the required moisture coefficient. Modern drying chambers are equipped with automation that allows you to control and monitor the drying process remotely.
Company Negociant-engineering supplies kilns for wood Russian production.
The proximity of production, the introduction of the latest technologies and well-functioning service make it possible to provide our customers with inexpensive and high-quality drying equipment. We implement both small (with a small load volume) drying chambers, and large projects for various industries.
Features and benefits of drying chambers
Automatic control and monitoring of the wood drying process
Minimum terms of delivery, installation and launch of drying chambers
The design of the drying chambers is made of aluminum and stainless steel elements.
The ventilation and heating system is equipped with German-made reversible fans
The walls of the drying chamber building are insulated with Finnish mineral wool with basalt fiber
Inspection door as standard
Sale and service of drying chambers
We carry out delivery, installation and launch of drying chambers.
We provide warranty service and maintenance.
Drying chambers are made to order at the request of the Customer
Loading volume from 45m
We offer complex solutions organization of a wood drying site with the use of boiler equipment and wood waste disposal equipment.
The cost of drying chambers is lower than competitive ones.
Technical characteristics of drying chambers
Optional
Installation supervision and commissioning
A specialist arrives to carry out the installation supervision work, who measures the foundations in accordance with the documentation provided in advance, then proceeds to assemble the drying chamber with the customer's team.
Upon completion of the assembly, the specialist launches the drying chamber into operation and trains the customer's personnel.
Catalog kilns for wood
A detailed description of the design of the drying chamber for convective type wood can be downloaded here
Photos of completed projects for the installation of drying complexes
The drying mode depends on the type of wood and the thickness of the lumber. To prevent the boards from cracking and warping during drying, they are pre-steamed, for which wet steam is supplied to the chamber.
First, they are heated for 1-2 hours at a temperature of 50 ° C.
Do-it-yourself drying chamber for lumber
After steaming, increase the temperature to 60°C, then repeat steaming and, if necessary, steam up to three times. At correct mode drying wood does not undergo much deformation.
Rice.
6. Scheme of drying methods:
a - air-steam intermittent action, b - electric dryer operating at high frequency currents; 1 - heaters, 2 - supply channels, 3 - pipes for starting steam, 4 - exhaust pipes, 5 - special trolley (track), 6 - damper, 7 - movable electrode, 8 - fixed electrode
Soft wood species are dried at a temperature of 40-75 ° C, hard - at 35-55 ° C.
The drying temperature of lumber should not exceed 80 ° C, as the structure changes at a higher temperature surface layers wood, i.e. there is a kind of hardening of the material. Such material is difficult to process with cutting tools.
At the beginning of drying, the air should have a relatively high humidity and a low temperature.
The higher the moisture content of the wood, the more moisture the air introduced into the chamber must contain in order to avoid cracking the wood. Then, as the material dries, the air temperature is increased, and the humidity is reduced to a minimum.
For drying lumber of softwood and hardwood different sizes in most factories in model shops, steam-air chambers of periodic action with stimulating reverse circulation are used.
Unloaded lumber from drying (dried at a temperature of 60-70 ° C to a moisture content of 10-12%) before putting it into production is kept in the conditions of the production workshop for 2-3 days to release wood from internal and surface stresses (normalization) obtained in drying result.
In addition to steam-air drying chambers, there are gas chambers.
In the drying gas chamber of intermittent action, smokeless gas is used to evaporate moisture, obtained in the furnace during the combustion of raw wood waste, which is forced through the axial high-pressure fan through the gas ducts onto the stacks of sawn timber. The design of the chamber provides for a steam humidifier.
In the woodworking industry, intermittent gas dryers operating on natural gas are used, with a furnace in which the gas temperature reaches 1000-1300 ° C, but after circulation in the chamber, the mixture is fed at a temperature of about 100 ° C.
The working gas mixture is smokeless. Lumber dried in properly working gas chambers does not darken. Each of the drying chambers holds 4 stacks of boards with a volume of 1.8X2.6X6.5 mm each. gas chambers used for ordinary drying of sawn softwood.
Lumber can be dried by the high-speed method in electric dryers with high-frequency currents. Drying with the use of high-frequency currents lasts only a few hours, while the material dries evenly, without cracking or warping.
The waste of wood during such drying is much less than in steam and gas dryers, and is no more than 5%.
Features of heating semiconductors and dielectrics, which include wood, in high-frequency electric field are that heat is released directly in the heated material and the temperature of the material can rise for a short time.
For example, a wet board can be heated to 100°C in 3 minutes. The wood is simultaneously heated throughout its thickness. The current power absorbed by the material can be controlled by selecting and changing the parameters of the electric field.
The following is not to be taken as a DIY guide. Homemade chambers for drying wood exist and there are quite a few of them. But at the same time, the vast majority of them are far from perfect.
Drying chambers are calculated and designed, which means that specialists should deal with this.
Even if you decide to make a drying chamber "with your own hands", then at least, before building it, order a project from specialists or find and study literature on the construction of drying chambers.
Woodworking, its cost, product quality, depend on the quality of lumber drying. In turn, high-quality chamber drying of wood depends not only on compliance with the technology (correct lumber stacking, compliance with the regimes), but also on the design of the drying chamber.
I hope that the information given here will allow you to avoid mistakes when purchasing or help you improve the convective wood drying kilns available in your production.
Next, we consider the device of a drying chamber for wood with an upper arrangement of fans (vertical-transverse circulation of the drying agent), since this is the most common aerodynamic scheme in modern convective chambers for drying wood.
All calculations are given for easy-drying wood species: pine, spruce, cedar, and so on.
Lumber with a thickness of 50 millimeters is taken as conditional.
Drying chamber device for convective type wood
For uniform drying of wood along the height of the stack, the distance from the wall of the drying chamber to the stack of lumber must be at least a quarter of the height of the stack (see.
figure), otherwise it is necessary to ensure the narrowing of the air channel from top to bottom.
Scheme of a convective drying chamber (in section)
With two or more stacks, the distance between them (in Figure A) should be at least 15 - 20 centimeters.
For uniform drying of lumber along the length of the stack (with a board length of 6 meters), drying chambers, as a rule, must have at least three fans.
Drying kilns for timber should be designed to allow air to pass only through the stack of lumber.
Free passages reduce the airflow through the stack (hence the drying of the wood is slower) and make it uneven, which increases the moisture unevenness of the dried lumber.
The free passage of air on the sides, top, bottom of the stack must be blocked by curtains, thresholds and other things.
Side curtains are recommended to be installed in such a way that they overlap the stack by 10 - 15 centimeters from the ends, this will reduce the cracking of the ends. It is desirable to make the top curtains movable, since the drying of the wood leads to a decrease in the height of the lumber stack.
Air circulation during chamber drying of wood
Circulation is carried out with the help of fans, the air passes across the stack. The fan compartment is fenced off from the stacks of lumber with a false ceiling and has a baffle designed to prevent "short circuits" of the air flow. It is very important!
In some home-made drying chambers, this partition is absent, as a result, a significant part of the air is chasing uselessly over the false ceiling without getting into the stack.
Single-stack kilns for lumber allow the use of non-reversible fans, with two or more stacks, the fans must be reversible.
Requirements for fans for drying chambers
If the fan motor is located inside the drying chamber, it must be made in a moisture-proof design and have a heat resistance class "H" (up to 100 degrees), an electric motor that does not meet these requirements must be moved outside the chamber.
In self-made drying chambers, class F electric motors are often used. As a result, they fail at intervals of 3 to 6 months.
With insufficient fan performance, the chamber drying of wood is slower, and the unevenness of humidity across the width of the stack increases.
Heating of convective drying chambers.
The supply of heat necessary for the evaporation of moisture from wood is carried out by heaters, their power is determined at the rate of 3-4 kW per cubic meter of conventional lumber.
To ensure this, the heat removal surface of the heaters should be about 3.5 square meters per cube of lumber. It is not recommended to use electric heaters: the drying of wood in this case will have a high cost. Probably, for many, the best option would be to use a boiler that runs on wood waste.
It is desirable that the air entering the convective drying chambers during ventilation, before entering the stack, passes through the heaters.
Therefore, if the fans are reversed, the heaters are usually arranged in two rows, as shown in the figure. If the heaters are located in one row, and the fans are reversible, then the heaters must be located between the ventilation ducts of the pressure side and the vacuum side.
Such a scheme of the drying chamber is characterized by slightly higher heat losses, but lower manufacturing costs.
Chamber drying of wood requires less heat energy if convective drying chambers are equipped with recuperators (heat exchangers). In the heat exchanger, heat exchange occurs between the incoming and outgoing air during ventilation. The use of a heat exchanger, in addition to saving thermal energy, reduces temperature fluctuations during ventilation, therefore, drying lumber will be of better quality.
Unfortunately, in Russia, convective drying chambers for wood with recuperators are practically not produced.
Thermal insulation of drying chambers for wood.
Total temperature difference is 115 degrees. Consequently, with poor thermal insulation, part of the money that you pay for heat energy will go to heat the street.
In addition, with poor thermal insulation, moisture will condense on the walls, floor and ceiling of the drying chamber, which will not allow it to withstand the air humidity set according to the regime at the initial stages of wood drying.
If possible, drying chambers should be installed indoors, this will reduce the possibility of cracking of lumber during unloading due to a sharp temperature drop. But even when installing indoors, good thermal insulation is needed.
Tightness of drying chambers for wood.
At the initial stages, chamber drying of wood is carried out at high humidity, so moist air should be removed when and only when it is required by the regime.
With poor tightness, it is impossible to withstand the specified air humidity. Using a humidification system does not help: even if steam is supplied, a significant part of it falls out as condensate due to contact with cold air.
Therefore: wood drying chambers must be airtight, not have gaps, sealing gaskets must be installed on the gates. Especially often home-made drying chambers have poor tightness.
In industrial chambers, the deterioration of tightness usually occurs due to loose closing of the gate due to careless adjustment during installation.
Supply and exhaust ventilation during chamber drying
Typically, the arrangement of drying chambers provides supply and exhaust ventilation due to overpressure on the pressure side and underpressure on the vacuum side, additional fans are not used.
The required total cross-sectional area of air ducts for such ventilation is approximately determined at the rate of 40 square meters. centimeters per cube of conditional lumber from the pressure side and the same amount from the vacuum side. Air ducts are equipped with curtains that open and close as needed.
To reduce the formation of condensate in the air ducts, their thermal insulation is desirable.
Humidification system for chamber drying of wood
There is an opinion that drying of easy-drying wood species can be carried out without moisture treatment.
Indeed, when drying freshly sawn wood, the required air humidity according to the regime is gained in 6-12 hours. However, if chamber drying of wood is carried out, which has lain for 2-3 days after sawing, then this time can stretch for a day or more, which is already undesirable.
Drying kilns for lumber - a choice of equipment for drying wood
Thus, a humidification system for chamber drying of lumber is still needed. For humidification use steam or finely atomized (drops hang in the air) with the help of nozzles water. A very common mistake in homemade drying chambers is that when spraying, water hits the thermometer and air humidity sensor. As a result, automation receives false information about climate parameters.
It is unacceptable.
About the requirements for gaskets.
Gaskets are not a design element of the drying chamber and, of course, are not supplied with it, but without complying with the requirements for them quality drying wood is not possible, therefore, briefly about gaskets.
Gaskets must be made of dry lumber and have exactly the same thickness. The thickness of the spacers with a total width of stacks up to 4.5 meters should be at least 25 millimeters; with a larger number of stacks, it is recommended to increase the thickness to 30-35 millimeters.
With insufficient thickness of the spacers, the chamber drying of wood is slower, and the unevenness of moisture across the width of the stack increases.
The width of the gaskets is 40 - 50 millimeters.
The surfaces of the gaskets in contact with the lumber must be planed.
Quality drying of wood largely depends on proper styling lumber, so be sure to study this issue.
For various wood products (furniture, musical instruments, parquet, etc.), their own drying temperature is used and a certain humidity is maintained.
Wood, despite the development of modern technologies, is still an indispensable material in many sectors of the economy. It surrounds us everywhere, it is used in the manufacture of furniture, in the construction industry, even in aviation, it still finds its application. Of course, various polymers, synthetic resins, steels and alloys of various metals actively replace wood even in its traditional niches. But a complete rejection is not possible. Therefore, there will always be a need to prepare wood for use in various branches of human activity, in its drying. We will try to give answers to questions related to such necessary equipment as a lumber dryer, made and debugged with our own hands.
Why dry wood?
Drying for lumber is extremely required process, without which wood simply cannot be used.
The quality of wood depends on proper drying.
If you have your own business related to the production of wood products, then you can not do without your own drying chamber. But first, let's try to understand why this dryer is needed, why lumber needs to be dried. It's all about the natural moisture of any tree. If you make a product from undried wood, then it will dry out over time, crack, and all that remains is to throw it away. In addition, a properly dried wood improves its working qualities, becomes stronger, more resistant to environmental influences and less susceptible to destructive mold. In the old days, to prepare the forest for use, it was dried not even for years, but for decades. Often, logs prepared for grandchildren were laid under a special canopy. Imagine, not even for children, but for grandchildren.
Fortunately, modern technology allows us to significantly speed up this process. And although this process is still quite long and complicated, it still cannot be compared with traditional technologies, and the result is even better.
Back to index
Moisture content of lumber
It is important to understand that a tree is a living organism and its cells contain moisture while it is alive. In general, freshly cut wood has a moisture content of 30 percent or more. If we want to use wood, then we need to get rid of excess moisture. What kind of moisture is superfluous? It depends on what we are going to use the board or log prepared for production for. If the tree is used for the manufacture of products where the highest assembly accuracy is required (for example, for the production musical instruments, sports equipment, parquet and some types of furniture), then its humidity should be reduced to 6-8 percent. If you are just preparing lumber for long-distance transportation, for example, for export, then it is enough to reduce the humidity to 20 percent.
The same wood is also suitable for some types of buildings, for the production of containers and other goods. Other products require wood moisture between these two extremes. Floor boards, cashing, sheathing boards can have a moisture content in the range of 15 percent. And window frames, doors, stair elements or decorative items will require wood from 8 to 15 percent moisture.
Back to index
Making a dryer with your own hands
Consider, finally, the construction of the drying chamber itself. To begin with, in addition to the basic building materials for the manufacture of the camera room, you need to purchase a heating device, a fan and a good insulation.
The scheme of the drying chamber.
You can use a ready-made room for the construction of drying, or you can build it specially. It is desirable that the ceiling and one wall be made of reinforced concrete, while the rest of the walls are made of wood, which later need to be covered with thermal insulation materials: first we cover them with foam boards, sheathe them with clapboard and then cover everything with sheets of foil. The next step is to install some kind of heating device, for example, a heating radiator, in which the water should be heated to 65-90 degrees. Since continuous heating is necessary, it is better to immediately make the heating system autonomous, with its own furnace and pump for constant circulation of the coolant. A fan is absolutely necessary in the drying chamber, which, dispersing the air around the room, should ensure uniform heating of the entire drying space and the laid wood.
You need to think about the issue of styling in advance wood material for drying, how the wood will be brought into it, whether it will lie in the middle of the chamber or on special shelves, etc. good options for loading wood is a trolley on rails or a forklift. Take care of the availability of devices for recording humidity and temperature in the drying chamber, without which effective control over its operation is impossible.
Scheme of air temperature and wood humidity in the drying chamber.
When building, consider some more nuances. The temperature in the drying chamber should not fluctuate sharply, make sure that it changes smoothly. Otherwise, you run the risk of destroying all the stocks of wood laid in the drying. It can crack and warp. It is worth remembering about fire safety, because you are dealing with heating appliances and large stocks of dry wood. To do this, keep a fire extinguisher nearby. Of course, some of the above can be replaced with analogues available in the house, in particular, a water heating radiator can be replaced with electric heaters, up to an electric stove with a pair of burners on. Only again we remind you of fire safety, be careful. The walls of the dryer can be insulated not only with polystyrene, but also with others. suitable materials, up to the same wood shavings, and penofol can replace the foil, which is well able to reflect thermal radiation back into the camera.
The main thing during construction is to achieve the creation of suitable conditions inside the chamber, and what material or technology you used is not critical. In such home drying, lumber will dry for about 1-2 weeks.
Friends!
Those who deal with wood, process it and use it in any way, are forced to face the problem of drying it. Drying wood is always relevant and pays off, because a “wet” tree is much cheaper, and a dry finished one is very expensive. It is required to remove excess moisture from the wood so that the process of uneven evaporation of water and juices does not occur, which is associated with the heterogeneity of the wood structure along the longitudinal and transverse fibers. And wet wood is unsuitable for serious processing, and even more so for construction, otherwise it deforms, cracks, warps, and “leads” it. How can you make a dryer for wood with your own hands?
How to make a dryer for wood with your own hands at home or in the country
If space permits, then something like this:
- First, we free up space in the kitchen near the stove or electric stove, fireplace, etc. You need to carefully calculate and measure how everything will function and look.
- Partitions are installed from old doors and window frames, other available materials, for tightness everything needs to be adjusted and sealed. The size can be, for example, 2x2 or 3x3, depending on the possibilities and needs.
- It is necessary to leave, of course, the entrance doors and vents, and keep them tightly closed during drying so that there are no excessive drafts or simply excess air movement. Otherwise, this can lead to a less predictable drying process, loss of control over the process and the quality of the wood at the end.
- The fenced-off place must be tightened with a heater, all the cracks should be sealed, plugged, covered over, etc. That is, to seal the space of the future dryer as much as possible to close the space and improve the quality of drying.
- Since near the stove or heating appliance heat, then, if necessary, it is better to overlay with bricks, which will accumulate heat and give it to an enclosed space. In the case when the air does not circulate actively enough, then a fan should be installed.
- If you plan to dry a lot of wood or finished products from it, then you need to build strong metal shelves. It is better to fasten with anchors so that you can load with serious weight.
- To prevent the blanks from bending, you need to fasten the edges of the material with studs. If the length of the wood is large, then several pairs of studs (3-4) are used. Of course, it is better to use wood of the same species, thickness, size and weight, otherwise the drying will be very uneven. Be sure to transfer the material for drying with thin strips, bars, gaskets for better ventilation. It is necessary to carefully monitor the uniformity of temperature and air flow, then the drying will be smoother and the quality of the material at the exit will be higher. Moreover, it is more profitable to build several dryers of a not very large size than one large one.
Do-it-yourself wood dryer, as a separate design
- First, a frame is built aluminum profile, it will not rust, light and durable.
- Then it must also be sheathed with aluminum sheets, and thermal insulation 10-15 cm thick must be fixed on top. This insulation must be fire-resistant, strong and flexible. Roofing material should be laid on the floor, and sawdust should be poured on top.
- Next, you need to ensure the tightness of the building and close up all possible ways for the exit of heated air. The tightness of the structure is of great importance for high-quality drying.
- The boards intended for drying should be laid out in narrow (1-1.5 m) stacks and placed between the rows and boards of strips from the bars. And the height of the stack can correspond to the height of the room.
- Drying can be done using, for example, fan heaters, which must be installed across the air movement. Or choose another drying tool that suits your individual needs and possibilities.
A simple and effective way of tubeless infrared drying of wood from 1 board
If you do not want to build a dryer yourself or you do not have the opportunity for this, then you can use a ready-made solution. 
There is a relatively recently used method for drying wood using infrared radiation. The process itself is as follows: the wood is heated with infrared rays using a tubeless cassette dryer. What is the design of such a dryer? It consists of several thermoactive cassettes 1.5 mm thick. Cassettes are stacked in a stack of wood prepared for drying, alternating with gasket bars. That is, the coolant is already among the lumber intended for drying. Therefore, there is no need for a separate heat source, ventilation, maintaining accurate parameters, complex electronics and automation. Drying is controlled by a thermostat, which sets the required temperature for the individual layers of the stack. For more optimal performance drying structure, the stack is covered with a material with a reflective layer so that the condensate drains outside the stack. It is important that the process can take place both outdoors (preferably under a canopy to avoid possible precipitation) and indoors.
The advantages of this type of drying are
- ease of maintenance
- equipment mobility,
- high performance (8% humidity can be achieved).
- high quality of the final material (no warping and internal stress),
- speed (from 3 to 7 days),
- variability, i.e. you can dry both individual boards or even just one, or whole large stacks.
You can watch a video about this technology here:
Wood dryer from improvised materials. FlexiHIT.
Drying lumber in a tubeless cassette dryer
So, if you have a constant need for dry wood, then you can build a dryer, it's not so difficult. Or buy ready-made and enjoy ready-made dry lumber that can be used to make various necessary and interesting products.
