Types of drying chambers for wood: vacuum, convector, aerodynamic and additional equipment for them. Drying chamber for lumber (diagrams, videos and do-it-yourself creation) Dryer for wood from a container

Types of drying chambers for wood: vacuum, convector, aerodynamic and additional equipment for them. Drying chamber for lumber (diagrams, videos and do-it-yourself creation) Dryer for wood from a container

15.06.2019 Heating systems

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 put up from old doors and window frames, other available materials, for tightness, everything must 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 already 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, building several dryers is not very big size better than one big 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 as 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.

If you have a large amount of unprepared wood that needs to be dried soon, you need to get a special dryer to perform the initial processing of the material. This is a mandatory procedure during the construction and finishing work, since if the material is raw, then there will be problems with its installation, and in the future other construction defects will appear. You will learn how to make a dryer for boards with your own hands from this article.

A bit of theory

Before proceeding with the manufacture of such a design, you need to find out why you need to dry the tree. From the name it is clear that the design is intended to get rid of excess moisture from wood, however, it is necessary to dwell on some theoretical points.

Wood moisture

Wood moisture is divided into two groups:

Free, that is, located in the cell cavities and intercellular space. The content of such a moisture group is determined by the conditions under which a particular tree grew, as well as by how the sawn blanks were stored. During drying, this moisture evaporates quite quickly.
Bound or structural moisture - this is the name of the liquid that is part of the cell walls of the tree. The amount of structural moisture depends on the type of wood - this means that the duration of drying can vary: trees, depending on the type, can get rid of bound liquid for several months or several years.

Important! Usually a tree is saturated with moisture no more than 30%. Rocks with a high moisture content are called "gray" and are not usually used in construction.

What is drying for?

Before you make a drying chamber for wood with your own hands, you need to decide what it is for. Let's do a little analysis and answer this question:

When moisture is removed naturally, the configuration of the wood fibers changes, which is why the dimensions of the board are reduced.
At the same time, the board loses excess moisture unevenly, which is why the deformation of completely different planes and at different speeds occurs.
Due to uneven “shrinkage” inside the workpiece, so-called stress lines are formed, giving rise to cracks.

Important! Usually the board gives a crack along the fibers, originating from the end. This happens due to the fact that in these places the connections between the longitudinal fibers are somewhat weaker.

Another problem is transverse deformation boards - the part takes on a completely unusual shape, arching in an arc or “propeller”. This is due to the fact that the fibers dry unevenly and non-simultaneously, therefore, their length decreases, also differing from each other.

Important! From the above facts it can be seen that wood with a high moisture content during poor-quality drying can become unusable. You can get away from such a problem by preparing the raw materials and drying them on a do-it-yourself wood dryer.

Three drying modes

When you use drying chambers, you significantly save the time required to prepare the material for work. Moreover, you can control the drying modes by controlling operational properties wood. On the this moment time, there are three modes of tree dehydration:

Soft. A feature of this mode is the gradual increase in temperature in the chamber - due to this property, not only the original quality of wood is preserved, but also its natural color. This drying method is the longest.
Standard. In this mode, the wood retains its original strength, while the shade of the material changes slightly.
Forced. This mode is used if it is necessary to dehydrate the raw material as quickly as possible, however, the quality of the lumber is significantly reduced. It is also worth noting that after applying this mode, the tree may darken and acquire a characteristic smell.

We make a drying chamber

So, we figured out what this building is for. Now you can start making a wood dryer with your own hands.

Premises selection

The first step is to correctly select the room where the drying of the lumber will take place. To do this, follow these tips:

The area of \u200b\u200bthe room should be based on the dimensions of the boards that require processing.
Ceiling height should be 2-2.5 meters.
The width of the room is selected by the user, however, it is worth considering that you need to leave room for the passage of a person.
The windows in the room must be bricked up.
Doors must be such that raw materials can be easily loaded into them without problems.
There should be a window or a small vent for ventilation.

Important! If selected large room, it is better to make a partition for thermal insulation.

Dryer construction

Usually, a garage or a barn is chosen as a room for a dryer, but sometimes it’s not even possible to use them. For this reason, it is important to know how to make a wood dryer with your own hands, using the drawings:

Lay the foundation for the entire structure. Since the mass of the structure will be low, the foundation does not have to be deep.
After the concrete has dried, you need to assemble the frame from a galvanized steel profile (you can replace it with an aluminum frame). Connect the frame parts using bolts, as well as special brackets.

Important! The aluminum frame differs in its high price from the steel frame, however, it has many advantages. For example, it is much more stable and is not afraid of corrosion.

Sheathe walls with a roof steel sheets fixed to the frame with the help of special self-tapping screws. For the effect to be as effective as possible, you need to double-skin, laying a layer between two sheets mineral wool insulation having a capacity of approximately 150 mm.
Lay the waterproofing membrane on the floor, then cover it with sawdust.
Install doors. They should close as tightly as possible.
Build ventilation vents or vents so that air can circulate freely.
When the work is completed, check the tightness of the room. If necessary, correct any errors.
Equip an infrared wood dryer with your own hands. This point should be given due attention.

Equipment

Equipment design instructions may differ from each other. This is due to the fact that the camera equipment and the material budget for each user are different.

Consider general scheme room equipment:

Make a support on which a stack of boards will be placed in the future. To do this, you need to fix on the floor wooden structures, which allow you to raise the material approximately 20 cm above the ground. This is necessary for the circulation of air flow from below.
It is possible to use wall racks as supports. To do this, it is necessary to fix metal brackets on the bearing surfaces, which are designed for laying stacks along the walls of the chamber.
Install heating device. Its role can be played by a stove, a heat fan, a fireplace, heat gun and other facilities - the choice depends on your desires and preferences. First of all, you need to pay attention to the power of the device - it is calculated from the volume of loaded lumber.
Install fans for drying boards with your own hands. Devices will provide movement thermal air. Of course, you can get by with a conventional hood, but then the drying time of the raw materials increases several times, which means that electricity costs will increase.
Arrange fans and air heaters so that the heated air flows across the air flow. In this way, you will reduce the aerodynamic system drag, and as a result, the dryer will work more efficiently.

Important! Since you will need a lot of electricity, it is recommended to install a separate power cable for the structure. In addition, all the materials that you use must be connected to the distribution panel through an RCD with the required power parameters. This is necessary in order to protect yourself from a possible fire.

If possible, install automatic system, which controls the temperature and ventilation of the dryer. This system provides high-quality wood drying, so its high cost is justified.

Construction use

It is only necessary to lay the boards in a stack, laying bars between the rows having a thickness of about 20 mm, then load the stack into the room.

After that, you can change the temperature, gradually raising it.

Important! Exists great multitude schemes, following which you can make competent drying, but for inexperienced users it is better to use the low temperature mode first. This is due to the fact that its use is accompanied by the minimum amount defective boards.

Consider the classic wood drying process:

The temperature must be raised to 50 degrees, with a rate of increase of 6 degrees per hour.
This temperature must be maintained for 5 hours.
During drying, the moisture content in the tree must be reduced from 30 to 7-8%, for this it is necessary to withstand a temperature of 60 degrees for about two days. At the same time, both supply and exhaust ventilation must be kept at half power.
In order to condition the room, it is necessary to withstand the boards at a 60-degree temperature using actively working ventilation.

From this article, you learned that making a wood dryer with your own hands is not so difficult, but for this you need to spend quite a lot of material resources and time. It is worth noting that all these costs justify their result, because in the end you get much more dried boards than if you bought finished lumber from the manufacturer.

The following is not to be regarded 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 calculated and designed, which means that this should be done by specialists.

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 exclude " short circuits"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. Approximately calculate the required total fan performance (cubic meters / hour) for a one-two-stack drying chamber by multiplying the length of the stack by the height (in meters) and multiplying by 3200.

Heating of convective drying chambers.

The supply of heat necessary to evaporate moisture from the wood, is carried out by heaters, their power is determined at the rate of 3 - 4 kW per cube of conditional 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 there will be the use of a woodworking waste boiler.

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.

According to the recommended (soft) for conifers modes, drying of lumber in the last stages can take place at temperatures up to 75 degrees Celsius, the external temperature can reach minus 40. 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, that's why wet air should be removed when and only when 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 at the expense 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, during the drying of 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. 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, they are not supplied with it, but without meeting the requirements for them, high-quality drying of wood is impossible, 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.

The problem of maintaining optimal moisture content in lumber is relevant both among builders and among those who like to make something in their own carpentry workshop. Drying wood at home allows you to save a lot on its purchase, because dry raw materials always cost more than wet ones.

By the way, if you don't have time for construction works, then you can dry the wood at home or in the country even under atmospheric conditions.

Some owners adapt ready-made haylofts, sheds or other suitable buildings for these purposes. Here is a way out of the situation found by one of our members of the forum.

Timakval member of FORUMHOUSE

I used for drying the attic of the yard (former hayloft) the size of 10 * 5 m. I laid it out, as it should, through the linings of each row. Total 3.5 board cubes different categories. The advantages of this drying place are always a shade, a ready roof and it is well ventilated. Picked up last May different size boards, bars and timber - blanks for small-scale construction. The boards were heavy from moisture. During the time of lying in the hayloft (1.5-2 months) they dried up to fluff, they were not twisted or arched.

Drying under atmospheric conditions is a rather lengthy process, and since we have decided to take a comprehensive approach to this issue, let's look at the sequence of building a home dryer with our own hands, which allows us to more effectively achieve the required moisture levels. As suitable premises we suggest you choose a building required size and then you can get to work. The room can have dimensions of 2 * 3 m or 4 * 3 m (more possible). It all depends on your needs and scope of activities. But, when choosing a building, you should remember that there should not be much free space left in the dryer. After all, drafts and chaotic air movement adversely affect the quality of wood.

DIY wood dryer

The room chosen for arranging a home-made dryer should be heated by a stove or a specially installed fireplace. It is good if a heater is pre-installed in the room. If there is none, then do not forget to leave a place for it.

Here is a project for making a home dryer offered by a member of our forum.

Nikolai Valen FORUMHOUSE member

Available capital garage with water heating, a potbelly stove on wood and mining is installed as a boiler. There is a pipe with a diameter of 800 mm and a length of 2.2 meters (a former ventilation duct with industrial enterprise). The idea is as follows: install sealed covers at both ends of the pipe, leave fittings with a diameter of 150-200 mm for supplying and discharging hot air. Air is heated by a radiator (it can be a car stove). Air supply - table fan. 0.3-0.5 cubic meters of lumber is loaded into the pipe, the furnace is melted (the temperature of the coolant reaches 90 degrees, I think that the supplied air can really be heated up to 50-60 degrees).

If you have chosen a room too large sizes, then the space planned to be used for a makeshift dryer should be made isolated and airtight. For these purposes, wooden partitions, you can use insulation, brick and other materials that allow you to create your own microclimate in the dryer. Do not forget that it is necessary to leave a window in the chamber for ventilation and front door. After all, we should not get a hut without windows and doors.

Fans installed in the drying room will help create a forced air flow and make the drying process more efficient.

mfcn FORUMHOUSE Member,
Moscow.

It is advisable to place the fans on the floor to the side of the stack so that the blow is parallel to the spacers. Remember that when drying wood, it is necessary to evaporate about several hundred liters of water from each cubic meter of wood.

To place lumber in the dryer, special shelves or flooring should be installed. These products can be made of metal - so that the structure can withstand relatively large loads. Dry wood should be up to indicators corresponding to 8-12% moisture. Its measurements are carried out using a special moisture meter.

It is necessary to dry the tree, observing certain rules. Otherwise, the material will be hopelessly damaged and cannot be used in construction. To do this, the wood must be stacked. And between each new layer, gaskets from boards of the same thickness should be placed. Wood of any species, stacked in neat piles, will never suffer from fungal infections, retain its integrity and excellent consumer qualities.

Lao Czy FORUMHOUSE Member

Gaskets need to be made higher so that air ventilation between the boards is better. They dry better. You can put your sliced \u200b\u200bsticks 25 * 30 or 25 * 40 on the edge. The reason for limiting the height of the stack is to prevent the boards from being led by a "helicopter blade", fix the uppermost layers of the boards in the stack with self-tapping screws. For the 3rd year I have been storing my boards using this method at a dacha in the Moscow region. They are in excellent condition!

Between the boards located in the same row, gaps should also be left. This will ensure unhindered air movement inside the stack and improve the drying quality.

Wood kiln project

Wood can be dried quickly and efficiently in well-equipped and free-standing kilns. The construction of such a chamber on the scale of a dacha or suburban area is not always appropriate. After all, this type of building will be very expensive, and its construction will take a lot of time.

The construction of such a room can be quite called the implementation of a full-scale construction project. You cannot avoid the laborious operations associated with pouring the foundation, with the erection of walls and the installation of complex equipment.

How to make drying for a tree can be understood from the diagram.

Do-it-yourself chamber drying

Such a mini wood dryer requires the placement of not only the main equipment (heating and ventilation), but also additional automatic control systems.

Drying chamber operating modes

The chamber dryer does not imply strong heating during normal operation. And the full cycle of work related to the drying of one batch of wood can be divided into several stages.

The first stage lasts from 15 to 20 hours. During this period, the air in the chamber warms up to 45Co. The ventilation does not turn on, and condensation forms on the walls of the room.

The second stage lasts about 48 hours. It involves connecting ventilation and heating the air in the chamber dryer up to 50 Co.

The third stage lasts until the required final moisture level in the internal structure of the wood (8...12%) is reached. At this time, the air temperature rises to 55 C, the exhaust dampers are fully opened, and the fans operate at full capacity.

After the humidity reaches the required values, the heat supply should be stopped. The fans must remain on for another 24 hours. As a result of this heat treatment, you will get dry wood, completely ready for use during carpentry or construction work.

You can get acquainted with the practical developments of our members of the forum regarding the correct construction of a stack in the "" section. Those who wish to learn more about the lumber drying technology can visit the "" section. For those who want to see a master class on wood aging technology, we recommend watching the corresponding video.

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 from optimal humidity, but in this case, the cost of purchasing the material will be very high. So the building special device can be quite effective from an economic point of view.

In our article we will tell. How wood is dried, and we will give recommendations for self-arrangement of the 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 implies, such devices are 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, transverse deformation of the board is also possible: the part either bends in an arc, 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 used to build structures or craft various designs wood with a high moisture content, 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 the operational properties of the resulting 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

Under the structure we lay a tape or columnar foundation. 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!
The price of aluminum structures is 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 perform double sheathing, laying between metal sheets a layer of mineral wool insulation with a capacity of 100 - 150 mm.

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 can be strengthened door frame 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, 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: for drying 1m3 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 ventilation system and get by with a natural hood, 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.

Fans and heating appliances arranged in such a way that warm air went across the airflow. 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 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 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 novice craftsmen should use the low-temperature mode, as it provides 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 turns on at half power.
Conditioning - we maintain the temperature at 600C for another 12 hours. Ventilation must be active.
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.

Conclusion

As you can see, a do-it-yourself dryer for a board is made quite simply (but I must admit - 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 more information about the technology chamber drying wood, we advise everyone who is interested in this topic to study the video in this article.