Types of drying chambers for wood: vacuum, convector, aerodynamic and additional equipment for them. Using a drying chamber for wood Equipment for drying chambers buy

The drying process is the initial moment in the entire preparation of the semi-finished product (wood) before processing.

A drying chamber for lumber and wood is an excellent solution to the task at hand, you can do it yourself. In order to avoid deformation of the logs, drying is carried out in specialized conditions, which are carried out exclusively in a drying apparatus.

What is drying for?

For a long time, when making any crafts from wood, timber was used, cut down several years earlier. Products made from wet or dry boards will warp or become covered with numerous cracks.

When the tree dries up, it shrinks, the raw wood material will "behave" over time, huge wide cracks will form in the frame. In underdried semi-finished products, fungus is likely to start. But it is also not advisable to dry out the tree, because it will begin to absorb water, which will lead to swelling.

What are the modes of drying chambers?

There is a whole list of drying modes for wood materials. In self-built machines, the regime from lowest to highest changes gradually, extracting all excess water from the semi-finished product. The drying process is carried out based on the following material characteristics:

• wood species;
• overall dimensions of the semi-finished product;
• finishing and starting humidity levels;
• unit specifics;
• quality indicators of lumber.

Drying can be performed at high temperature or low temperature. The second case is notable for the fact that primary drying is performed at a mode that does not reach 100 ° C.

Low temperature conditions can be as follows:

• soft - after completion of drying, semi-finished products have their original properties, without changing their strength and color;
• moderate - the color changes slightly, strength characteristics decrease slightly;
• accelerated - in the process of subsequent processing (breaking, sawing, cutting), increased fragility is possible, the color fades.

Changing the temperature regime during low-temperature processing is carried out in three stages.

High temperature processing is carried out in two stages. The second stage begins when the moisture level of the semi-finished product drops to 15%. Such a technological process is used when it is necessary to further design secondary structures.

The main types of drying chambers

Drying of semi-finished wood products in industrial volumes is carried out in specialized dryers. Moisture is removed from the wood due to heated air, which subsequently escapes into the atmosphere. The device provides the passage of a full cycle of drying sawn timber. The machine body can be:

• solid / prefabricated metal;
• executed with the use building materials.

The latter are mounted directly in carpentry workshops in the form of a structure, or as free-standing ones. The walls are made using reinforcement and concrete mortar. Alternatively, bricks can be used. Large factories make a system of cameras, combining them into whole modules with centralized control management and supply of communications. The air moves inside the dryer horizontally or vertically transversely.

Heat sources in the dryer:

• a radiant source from specialized units;
• red-hot shelves;
• electricity that goes through raw semi-finished products;
• high-frequency electromagnetic field.

Cameras are equipped with basic and auxiliary equipment. Basic systems:

• supply and exhaust equipment;
• heat sources;
• humidifiers.

According to the principle of operation, drying machines are divided into:

• convective equipment;
• condensing equipment.

In convective machines, semi-finished products are "doused" with hot air waves, heat is directed by the convection method. The complete cycle time varies from 5 to 13 hours. Such units are installed at large-scale sawmills.

Chamber dryers are more compact, the entire volume is kept constant temperature and the environment as a whole. This type of dryers will allow you to dry any type of wood material to the required condition, which is why many entrepreneurs who are associated with the need to dry lumber choose chamber dryers.

Based on the technology of the drying process, the moisture that is released from the wood settles on the cooling elements, is sent to containers and then drained. The efficiency of such a unit is quite impressive, but time-consuming, leads to large heat losses. The pricing policy of machines and the profitability of condensation drying are lower than convective drying.

Drawing

Drying chamber for lumber: step by step instructions

To build a drying apparatus with your own hands, you do not need to use technical documentation. You just need to provide:

• the area where the camera will be installed;
• insulation materials;
• source and communications for creating heat;
• blowing.

The area of ​​a personally built car is usually no more than 10 square meters. A room with a square cross-section is more suitable for ensuring the movement of warm air currents. It is preferable that at least one of the walls of the equipment is concrete, others are allowed to be made of wood. The inside of the chamber must be insulated without fail. An excellent insulation material is wood shavings. If there is no foil at hand, then it is allowed to replace it with penofol.

A separate extension for the dryer can be constructed from aluminum sheets, such a structure will serve for a very long time. The base is made on the basis of profiles, it is covered with sheets of metal, which is then insulated. The thickness of the insulation must be at least 150 mm. The floor is covered with roofing material, a thick layer of shavings is poured over it, which will be excellent in the quality of heat saving.

The heat source can be supplied as a heating pipe system. The temperature of the liquid in the pipes should be at the level of 60 ... 90 ° C. For an oversized camera, the presence of a stove for two burners will be quite acceptable. If the source is located directly in the room, it must be overlaid with bricks. The bricks are excellent at collecting heat and directing it to the lumber dryer.

Continuous circulation of the liquid is important, which is provided by a compressor or an entire station. The room must be equipped with wet and dry thermometers.

For more convenient loading of semi-finished products into the chamber cavity, you can use a rail cart.

Video: do-it-yourself lumber drying chamber.

Any woodworking company cannot do without such a procedure as wood drying. And so that no defects appear in the process, a special drying chamber for sawn timber should be used. Such a dryer will also be useful for those who are engaged in the production of wood products at home, in such cases it will be possible to make it yourself.

Drying value for wood

Wood for the manufacture of various products must be pre-dried so that it is suitable for subsequent use. So, if your furniture is made on the basis of too damp wood, then it will quickly dry out and become unusable. And if the tree is too dry, then, for example, the door will swell quickly and will not close.

Drying wood is also beneficial for the following reasons:

• the material is protected from fungal attack;
• changes in size and shape are prevented;
• improve mechanical and physical properties material.

Drying is a long process, the wood is heated with hot air or superheated steam. After drying, the tree can be stored and transported longer, it will not undergo deformation.

Drying chamber for lumber

Drying in the chamber is key way drying the tree. With the help of dryers, deciduous and coniferous species are dried up to different types quality. The most common and economical drying technique is as follows. Free and bound moisture is removed from the wood by supplying heat to the moist wood with the help of hot air. Further, excess evaporated moisture is removed using humidified and partially cooled air.

The drying chamber is a completely ready-made installation, equipped with all the necessary equipment for work. By their design, such cameras are prefabricated metal or assembled from building materials. The latter are manufactured directly in workshops or as free-standing buildings based on industrial materials.

The chamber can be entirely made on the basis of monolithic reinforced concrete, the walls can be lined with solid red bricks, and the ceiling can be reinforced concrete.

If several chambers are used in production, they can be combined into one unit, which has a corridor with heat supply distribution and an automatic control system. Depending on the volume of the loaded wood, air circulation can be horizontal-transverse or vertical-transverse.

The lumber can be loaded into the chamber on trolleys along a rail track, or as packages using a forklift. Heat is transferred to wood in the following ways:

• through the air;
• through combustion products;
• using superheated steam;
• radiant heat;
• solid body;
• through the current;
• by means of an electromagnetic field.

The equipment for this device can be basic and additional. The main ones include the following:

• fan system;
• heat supply system;
• humidification and supply and exhaust ventilation.

Additional equipment includes:

• blocks (door, psychrometric and insulated);
• fan drive electric motor;
• undercarts.

The drying control process can be automated, which helps to maintain the temperature and humidity inside the chamber at a certain level. The temperature is regulated by supplying the heating agent to the heaters or by turning on or off the electric heater.

Humidity can be adjusted using a remote moisture meter, with which you can check the condition of the material remotely at several points at once. If there are no external sources of heat supply, then autonomous heating facilities can be used that run on electricity, coal, gas, lumber or diesel fuel.

Classification of structures

In convection-type chambers, energy enters the wood through the air circulation, and heat transfer occurs through convection. Such structures are tunnel or chamber.

Tunnel dryers are deep, pushing stacks from one end (wetter) to the dry end. They are obligatory filled at one end, and emptied at the other. The stacks are pushed one at a time every 4-12 hours. These dryers are used for large sawmills and help to carry out transport drying.

Chamber dryers are shorter, during the drying process the same parameters are maintained throughout the chamber. If the depth of blowing is from 2 meters, then in order to equalize the drying conditions, the method of reversing the ventilation direction is used. The chamber is filled and emptied on one side if there is only one door. Lumber can be dried in them any to different moisture indicators. It is these designs that are most often used in our country.

The condensation type of dryer differs in that the moisture that has arisen in the air begins to condense on special coolers, and then the liquid is removed. The efficiency is high here, but the cycle is long, since devices with high temperatures do not work and large heat losses are observed. These types of equipment are more suitable for processing small volumes of materials or drying dense wood - ash, beech or oak. But condensation chambers also have a number of advantages:

• no need for a boiler room;
• the cost of the camera and the cost of work are low.

Drying chambers also differ in the way of circulation and the nature of the drying agent, the principle of operation and the type of enclosure.

For example, circulation can be natural or forced. The constructions of the first type are outdated and ineffective, it is almost impossible to control the modes, and the uniformity of material drying leaves much to be desired. It is better not to use such dryers with modern requirements.

By the nature of the drying agent, chambers are:

• air;
• gas;
• high temperature.

Drying modes

Depending on the quality requirements, the drying of sawn timber in a special apparatus is carried out in different modes, which differ from each other in temperature... If it is a mini camera, then in the process the temperature rises slowly and the relative humidity of the agent decreases.

One mode or another is selected taking into account the following factors:

There are high-temperature and low-temperature process modes. In low-temperature ones, humid air is used as an agent, the initial temperature is less than 100 degrees. There are three categories of these modes:

• soft - drying is performed without defects, the mechanical and physical properties of the tree are preserved, including its color and strength;
• normal - drying is also performed without defects, the strength is almost completely preserved, the color may change slightly;
• forced - the strength for static bending, tension and compression is preserved, but the strength for chipping and splitting with darkening may decrease.

In high temperature conditions there is a two-stage change in the agent's indicators, it is possible to go to the second stage from the first only when the wood reaches a transitional moisture content of 20 percent.

Such modes are assigned depending on the species and thickness of the wood, and are assigned for drying materials used in the production of supporting structures of buildings and those products where it is possible to use dark wood with reduced strength.

Before starting to work on a particular mode, the lumber must be heated with steam supplied through humidifying pipes with fans running, closed exhaust ducts and heating devices.

Be sure to calculate the lumber chamber. The temperature of the drying agent at the beginning of heating should be 5 degrees higher than the first stage of the regime, but not higher than 100 degrees. The saturation level of the environment for a material with an initial moisture content of 25% is 0.98−1, and if the moisture content is below this indicator, then 0.9−0.92, respectively.

The length of the start-up period depends on the wood species. For conifers, it is up to 1.5 hours per centimeter of thickness. For soft hardwoods it will be 25 percent more, and for hard deciduous trees it will be half that of conifers.

After preliminary heating, it is necessary to bring the parameters of the drying agent to the first stage of the operating mode. Then the drying is switched on directly in compliance with the selected mode. Humidity and temperature can be regulated using valves on steam lines or dampers of supply and exhaust ducts.

During operation of an infrared dryer, residual stresses appear in the materials, which can be removed by intermediate and final moisture and heat treatment in an environment of high humidity and temperature. It is necessary to process those lumber that is dried to performance indicators and then needs mechanical processing.

Intermediate moisture-heat treatment should be performed during the transition from the second stage to the third, or from 1 to 2 when using high temperature. Conifers 60 mm thick or deciduous trees with a thickness of 30 mm or more are subjected to such processing. The temperature of the medium should be 8 degrees higher compared to the second stage, but not more than 100 degrees, provided that the saturation is 0.95-0.97.

When the final average moisture content of the material is reached, the final moisture heat treatment can be performed. It is carried out at a temperature 8 degrees higher than the previous stage, but not higher than 100 degrees. Further, the tree needs to be kept in the cell for another 2-3 hours with the parameters of the last stage of the mode and only then stop the operation.

Drying chamber manufacturing

If you are engaged in the manufacture of wood products at home, then you will need to dry the material yourself. You can also make a dryer yourself, but all work norms must be observed. For manufacturing you will need:

• camera;
• heating device;
• fan;
• insulation.

One wall and ceiling of the chamber should be made on the basis of concrete, and the rest of the walls will be based on wood, they will need to be insulated. In this case, there will be several layers:

• Styrofoam;
• boards wrapped in foil.

Now you need to install a heating element, it can be in the form of batteries. Water can be supplied to them from the stove in a heated form at a temperature of 60 to 95 degrees. It is best to ensure a continuous process circulation of water by means of water pumps in the heating element. You will also need to install a fan in the chamber, with the help of which warm air will be distributed throughout the room.

It is imperative to provide for a method of loading wood into the chamber. For example, it can be a rail cart. To adjust the temperature and humidity in the work area, you need to install wet and dry thermometers. Also inside the dryer you need to put shelves to expand the work space.

During processing, a sharp change in temperature must not be allowed, otherwise the wood may crack or warp.

The work on the construction of the chamber must be carried out in compliance with fire safety requirements, therefore, be sure to install fire extinguishers.

And also instead of a heating element you can use a two-burner electric hotplate. The walls of the chamber can be insulated with wooden shavings, and instead of foil, you can take penofol, which can reflect heat well from the surface of the walls. Drying in such a chamber is carried out within 1-2 weeks.

So there is a large number of various modifications of drying chambers for wood. One or another option should be chosen depending on the material itself and the expected results. And if we are talking about making various wooden products at home, then the camera is easy to make with your own hands.

On the domestic market, there is a very wide selection of chambers for forced drying of wood, operating according to various technologies, both Russian-made and imported.

This presents the customer with a difficult choice problem.

In this article, I will talk about what I had to face over three decades of work associated with various drying chambers. Perhaps the information given here will help someone not to be mistaken in this matter.

Don't underestimate the importance of drying

My experience of working in several companies dealing with drying various types of wood suggests the importance of this technological stage in the chain of production of finished sawn timber.

This is explained by the fact that it is qualitatively organized process drying allows you to minimize the number of rejects, improve the quality of the final product and, accordingly, ensures its implementation at higher prices, and also contributes to the growth of the number of regular customers.

The approach to financing the forced drying technology based on the residual principle is categorically incorrect. The result of such a decision may be low profitability (up to bankruptcy) of a timber processing enterprise equipped with the most modern machine park.

And if this is superimposed on the head's erroneous ideas about how to dry the forest “correctly” and the priority of “saving” funds on the purchase of equipment, the result will be disastrous. The camera will be. But you can't wait for high-quality dry lumber at the exit.

I had to work under the direction of various bosses (owners). And it must be admitted that the personality of the leader plays a colossal role in the correct solution of this issue.

One seeks to "snatch the ruble" here and now by any means, not thinking about tomorrow at all. Another one purposefully invests in the development and equipment of production, content with minimal profit and, ultimately, gets a highly profitable company that occupies a stable place in the market for providing such services, demonstrating positive development dynamics even in the off-season and with a decline in consumer demand.

Buy or do it yourself

In order to get a quality product, you should use a high-quality tool, one of which is the drying chamber.

However, a number of novice wood processors strive, in order to save money, to make a drying chamber on their own.

I admit that this is possible. But only in the presence of specialists who are able to correctly and fully carry out preliminary calculations (and such, at woodworking enterprises, can be found infrequently). And when it is required to periodically carry out drying of small volumes of wood.

In all other cases, such decisions lead to unjustified financial losses, a significant volume of marriage and the loss of regular customers.

Industrial production of significant volumes requires the use of cameras made by professionals. Self-activity in this matter is tantamount to suicide.

To confirm this thesis, I would like to cite a case that I witnessed in 2002-2003 (I don’t remember exactly). Then I just got a job in the company, which before and today are called "sharashki". It has positioned itself as a diversified enterprise manufacturing garden furniture, gazebos, fences and lumber.

Having heard that the kiln drying material could be sold at a higher price, the owner appointed three "smart men" as developers and manufacturers of the convection-type chambers.

The "masterpiece" of design thought was sculpted in less than a month. Moreover, with a huge number of flaws and gross violations that were visible even with the naked eye (I already had a certain work experience then). I tried to bring this to the attention of the employer. But the opinion of the "smerd" was not taken into account, but to insist, creating problems for yourself out of the blue. I didn't.

Examples. The fans did not have the possibility of reversible rotation, many metal elements of the structure were "forgotten" to ground, the heaters were of different power. And a young Tajik, who had no idea about it, was appointed responsible for the operation. He also dealt with issues of loading and unloading.

The creation worked for a little more than a week and ingloriously completed its short production biography with a powerful fire, in which not only the property of our owner burned down, but also the raw materials supplied by the customer, which he had to dry.

But that didn't teach him anything. This citizen continued to build his business according to the principle: "There are only two points of view on the question, mine and the wrong one." After working for a while, I thought it best to change jobs.

At the end of the section, a few wishes to those who decide to make a drying chamber on their own.

Before proceeding with the manufacture of a structure in a material, it is required to obtain at least minimal theoretical knowledge. Fortunately, the Internet today provides enormous opportunities for this. There are many quite solid tutorials on this topic. Among them, I would like to mention the books of Krechetov and Tsarev (co-authored with Peych). It will not be superfluous to familiarize yourself with the provisions of the current regulations. For example, SP114.13330.2016, which sets fire regulations for storing timber.

When creating a project for your own dryer, it is imperative to calculate:

• optimal material for its walls;
• achieve the tightness of the gate closing;
• determine the optimal method of loading materials for drying;
• select the type and power of the fans, calculate the places of their installation and the required number;
• resolve the issue with the coolant and the implementation of the humidification system;
• it is imperative to install a psychrometer and humidity sensors in the chamber.

ideally, automation should be provided. As a last resort. Semi-automatic control of the drying process. But these are rather complex questions that require deep specialized knowledge.

Practice has shown that one of the most common mistakes made by manufacturers of home-made drying devices is the ingress of water, when it is sprayed, onto the humidity sensor. as a result, the automation receives distorted commands. The result is marriage.

The second, in terms of the frequency of occurrence, is the fact of "forgetting" that the fans are powered by electric drives, which constantly have to be in conditions of high temperature and humidity. therefore, it will not work here to take any that are suitable in power. Only special models are required.

Pros and cons of different types of drying chambers for wood

Small companies mainly use Russian-made cameras. In addition, Czech and Italian are often used, less often Finnish (mainly in the north-west of the European part of Russia). This preference is explained by the following factors:

• optimal balance of performance, performance, durability and cost;
• the ability to quickly purchase spare parts and the availability of service (the overwhelming majority of dryers manufacturers have a wide network of representative offices in the CIS countries, including Russia);
• minimum delivery times, relatively low customs and delivery costs, the possibility of installation supervision and personnel training.

Regardless of the principle implemented in the design underlying the drying technology (convective, condensation, vacuum, other), any design solves the same problem - it evaporates the moisture contained in it from the wood. That is why, considering the issue of the quality of forced drying, first of all, they pay attention to such indicators as:

• drying time to a given moisture content;
• the occurrence of internal stresses during the drying process and the possibility of its relief;
• the difference in moisture between the outer and inner layers of lumber after the drying process is completed.

I would like to say a few words about specific drying technologies that I had to deal with.

1. Convective drying chambers for wood

Cameras of this type are most common in Russia, and in all regions. Therefore, the experience of working with such cameras forms the basis of my experience in servicing products for the forced reduction of the percentage of moisture in lumber.

The technology behind this drying principle is very simple. Moisture. Contained in the tree, it is removed from it by blowing it with a jet of hot air. The latter is heated by electric heaters (in the vast majority of models). The flow of the required strength and direction is formed by blocks of powerful fans, the number of which can reach ten or more units.

An important advantage of this type of chambers is the structurally provided possibility of steaming wood. This allows you to minimize internal stresses (ideally, completely zero them).

In all chambers with which I had to work, the parameters of the internal environment created inside were measured by an installed psychrometer, and the drying process was controlled by built-in automation.

The process is divided into several stages, at each of which the moisture content of the material and the magnitude of internal stresses are different.

The upper layers of lumber, when blown with hot air, dry faster than the inner ones. And the layers at the core do not have time to release moisture with the same intensity. This imbalance results in internal stresses that can lead to cracking.

To compensate for this negative process, an additional stage of moisture treatment is implemented in almost all convection chambers, when moisture is sprayed onto the surface of the material undergoing drying. Further, the drying process by supplying hot air continues again.

If the alternation of these stages takes place in a timely manner, after the completion of processing, a material is obtained that has approximately the same moisture content throughout the volume.

However, this is in theory. In practice, a lot depends on who made the camera, its model and the notorious "human factor".

If the product is purchased from a reliable manufacturer, installation is carried out in the presence of a company representative, and operation is carried out strictly according to the manufacturer's recommendations, then in such devices it is possible to obtain finished lumber with negligible internal stresses, which eliminates its cracking, increases the yield finished products and as a result, the profit of the company.

To the advantages of the considered types of cameras, I would carried:

• availability of models with a significant one-time capacity (about 1000 m 3), which is essential for large companies;
• the possibility of fine-tuning the control process, which provides for changing the values ​​of essential parameters at any of the drying stages;
• process control in automatic or semi-automatic modes;
• minimization of production costs.

Among the shortcomings I cannot but mention:

• sufficiently long drying times;
• the need to train trained personnel to service the device.

1. Condensing dryers for wood

The main difference between this technology and the one discussed above is the following technical feature. Moisture from the wood passing through drying, released into the air of the chamber, condenses on the special coolers available in the structure, collects in special drainage channels and is removed from the chamber, and the dried air continues the closed cycle of blowing the wood.

Coolers are charged with freon. Operating temperatures in these dryers are ≤ 45 ° C. This significantly increases the drying time for one bookmark, even in comparison with convection chambers. Depending on the selected model of the device, it may provide for the possibility of humidification, or not have such an option.

If available, moistening is carried out after the completion of the first stage of drying, which minimizes the internal stress that has arisen in the upper layers of the sawn timber.

In models where humidification is not provided, this issue is solved by the presence of inverters on the fan motors, which allow you to change the speed of the supplied air flow (This is done in order to ensure more smoothness and uniformity of moisture release from the tree). In other cases, it will not be possible to exclude cracking of products undergoing drying.

Chambers of this type are the best choice if drying mainly thick sawn timber or products made of dense wood (for example, ash or oak) is to be dried.

If you plan to dry wood for subsequent use in the joinery industry, this solution can hardly be called the best.

The advantages of the method include:

• low power consumption;
• almost 100% exclusion of cases of warping of sawn timber.

There are many disadvantages. The main ones:

• very long drying times, which are several times higher than those of convection-type chambers;
• the appearance of additional costs due to the use of freon;
• the quality of the finished materials cannot be called ideal;
• wood treated in this way has low resistance to pathogenic microflora (low temperatures in the chamber do not allow sterilization of the workpieces).

1. Aerodynamic drying chambers for wood

Twice I had to work on similar cameras. They have the simplest design in comparison with other types of products. This is an ordinary metal box with fans installed in it.

Air heating is carried out due to the heat generated by the operating fans (the mechanical energy of the rotating rotor is transformed into thermal energy).

When the required humidity in the chamber is reached, the fans stop. This is the simplest DIY solution. However, this drying technology has many disadvantages. Therefore, I would not recommend purchasing such cameras.

The main disadvantage is the fact. That blowing hot air dries the wood unevenly. While the upper layers are almost dry, the inner ones still have a fairly high degree of moisture. The result of this imbalance is significant internal stress in the finished product.

It is strongly discouraged to use such lumber in joinery. When you try to "dry up" such a material, it is guaranteed to burst (crack).

Of course, you can refer to the fact that the problem of the occurrence of internal stresses is inherent in any drying technology. But in the considered variant, they are the most significant and expressed as clearly as possible.

Benefits can be found in any method.

The advantages of aerodynamic drying are:

• ease of installation and low cost of operation (it is enough to connect the unit to a 3-phase 380V network);
• drying is performed at a significant intensity;
• the cost of such drying chambers can be considered small (in comparison with other types of products), if the costs are not considered. Which entails subsequent exploitation.

The downsides are:

• unsatisfactory drying quality;
• long drying time;
• very significant costs for electricity.

1. Infrared wood drying chambers

The main difference between the drying technology under consideration is the absence of the requirement to create a closed volume room (the chamber itself). To remove moisture, special designs are used, called infrared cassettes. When laying the stacks for drying, they are placed between the layers of the laid wood. The infrared radiation they create evaporates moisture from the tree to its entire depth.

In summer, drying in this way is permissible under awnings in the open air, having previously protected the stack from direct rain.

I had to work with such devices privately, in my own workshop. I really like to test the new technologies available to me for drying and processing wood.

On the whole, I can call the results obtained satisfactory. But the technology "did not look". And for industrial use, this solution is absolutely unacceptable, due to the length and complexity of the preparatory stage of the laying and subsequent selection of finished sawn timber.

Of the advantages, it should be pointed out:

• autonomy and compactness of technology;
• simplicity of bringing into working condition;
• high efficiency.

As disadvantages, attention should be paid on:

• significant difficulties in organizing control over the drying parameters;
• the possibility of using on tabs with limited volumes, not exceeding 5 m 3.

1. Microwave drying chambers for wood

The wood in them is dried due to the implementation of a process similar to that in a household microwave oven. The difference is only in the size of the products.

High-frequency radiation does not damage the wood, contributing to a delicate and uniform removal of moisture practically throughout the entire depth of the workpiece. The timing of reaching a given degree of moisture content of the finished sawn timber is rather short.

For the sake of curiosity, I worked with friends on a similar installation (new knowledge is never superfluous). The results are pretty good. However, the complexity of the device, the rather high cost, the high cost of components (the price of the same magnetrons starts from 300,000 rubles, and the service life, unfortunately, is not great) and, most importantly, the small volumes of one-time loading make such a solution unprofitable either for large-scale production or for private traders.

The latter is especially important when you consider how much maintenance of such chambers costs, especially if you have to replace a broken magnetron generator.

But, as they say, "the taste and color ...". The choice is yours.

The advantages of such installations are:

• high drying speed and excellent quality of the material at the exit;
• economical consumption of electricity.

Of the shortcomings, I would, first of all, name:

• insignificant one-time loading capacity, not exceeding -7-10 cubic meters;
• very complex control over the course of the process;
• high cost of magnetron generators.

I "fell in love" with these cameras. The constructions are completely sealed (in the vast majority of models). During the drying process, a pressure is created inside them below atmospheric pressure. Therefore, drying can be carried out at relatively low temperatures (up to 65 ° C).

This is explained by the fact that a decrease in pressure leads to boiling of water at lower temperatures. Therefore, the desired drying effect can be achieved with "little blood", without using high temperatures.

This automatically reduces heat loss in this type of chamber and allows very little discoloration of the material being dried.

The design features of such products depend on who they are produced by. For example, the Italian WDE Maspell dryers, which are quite often used by Russian wood processors, and some domestic chambers, are equipped with water heaters. Other domestic manufacturers prefer electric heating elements.

The main distinguishing feature of drying using vacuum technology is a curious situation when the temperature to which the board undergoing drying is heated exceeds the boiling point of water vapor (another name, saturation temperature). As a result, all processes that take place inside the board are significantly accelerated, and the latter dries faster.

This technology makes it possible not to use aggressive effects on the material of high temperatures during the drying process.

But, praising this or that technology, I urge future users not to forget that the minimum number of defective workpieces after drying is determined not only by the selected technology and the type of drying chamber, but also by the correctly selected technological modes that are laid down by manufacturers in each model and properly functioning automation.

In addition, an important factor is the choice of a bona fide manufacturer with the necessary technological know-how and drying experience. The technology is complex and, unfortunately, I have come across more than once when the owner chose the manufacturer after superficially understanding the issue. As a result, I got equipment with which there is more torment than work. The declared characteristics did not correspond to reality. I had to either modify the camera myself and spend time and money on it, or having measured myself to work on this equipment.

Despite the fact that in such chambers the impact on the wood is softer, there remains the possibility of cracking of the material being dried. It is always available for any drying mode. Since wood is a living material in which various types of stresses can form simultaneously. These processes are influenced by the type of wood and the place of its harvesting, the technology of cutting the log and the age of the tree.

Well, in terms of drying time, I can say that we dry a pine board "fifty" in a vacuum-type chamber (at the last workplace) from 50 to 8 percent in just 2 days. I have not seen such a speed in any other technology, perhaps, only in microwave.

Advantages of vacuum chambers:

• excellent quality of dried materials;
• record fast drying speed;
• high performance;
• suitable for both small enterprises (models from 1-8 cubic meters), medium-sized enterprises (models from 8-18 cubic meters), large enterprises(models from 18-36 cubic meters)

Disadvantages (unfortunately, she also has them):

• manual loading and unloading;

The importance of reliable automation in drying chambers

I would like to tell you about this separately. Drying wood is a very complicated process. Therefore, manufacturers automate high-quality modern cameras to the maximum. But no machine or automation can completely replace a person.

Therefore, the operator is needed in any case. And better, a competent operator. Since a mistake made at any stage of drying can turn into an irreparable waste at the exit, or lead to an emergency.

As a rule, marriage manifests itself on final stage when it’s impossible to fix something.

Therefore, the approach to the choice of the purchased camera, as well as the training of personnel, is required thoroughly.

Automation allows you to get rid of a significant number of problems, so I consider this component to be very important in the design of the drying chamber. Especially if drying is planned to be carried out on an industrial scale.

When choosing a camera, be sure to pay attention to the following:

• is it possible to organize automatic control, providing for the setting of various drying modes and the ability to load new templates (user programs that you create for your production);
• is there a possibility for the operator to intervene in the operation of the automation, which makes it possible to promptly adjust the drying process at any time;
• it is highly desirable to have a digital display on the automation, on which the main characteristics of the process (humidity, temperature, etc.) are displayed in real time;
• whether the manufacturers provide for the possibility of recording the progress of the chamber drying process with the fixation of all parameters and its subsequent display in the form of a graph (this allows subsequent analysis, if necessary);
• built-in automation should be “smart”, that is, exclude the possibility of making “wrong” decisions. For example, do not give a command for humidification when the ventilation curtains are open;
• whether it is possible to control the camera remotely;
• the presence of light and sound indication and emerging malfunctions.

When the automation is set up and working correctly, the chamber forms and maintains an environment that is optimal for a particular drying stage.

V the right time, taking into account the readings of the control devices, the humidity, temperature, and the level of conditioning in the inner volume of the chamber should change. All this will have a positive effect on the quality of the finished product.

When choosing automation, the main thing is not to overdo it. You shouldn't make "butter oil". Installation of automation is needed. But only under certain conditions. On chambers, for example of a convective type, with a volume of less than 20 cubic meters of one-time loading, its installation is economically unprofitable, since it will pay off for a very long time. On such cameras, the best solution is to use semiautomatic devices.

14 points to pay attention to when buying a drying chamber

It is possible to distinguish a good camera from a bad one, in each specific situation, not only by its type, but also by the one who made it. Without naming any brands here, I will focus on the main issues of choosing this product using the example of a vacuum chamber. There are not so many of them:

• heating elements must be structurally calculated and have an optimal design for transferring heat to wood;
• also, heating plates must be made of stainless steel or aluminum, which has a hanging resistance to corrosion;
• registers connecting elements must be covered with anti-corrosion compounds;
• the gates in the chamber and its enclosing surfaces must ensure maximum tightness of the internal volume. Air contact external environment and atmospheric moisture must be guaranteed to be excluded;
• the available heat and vapor barrier must be of high quality and installed correctly;
• the removal of steam from the chamber should be carried out as efficiently as possible;
• work from a solid fuel or gas boiler.

Otherwise, an increase in heat loss is inevitable and, automatically, electricity consumption. And, most importantly, the drying technology is violated. And the smartest automation will not be able to cope with violations caused by the presence of such defects. As a result, a rise in scrap and a decline in profits.

• The installed ACS should allow minimizing the operator's participation in the process, and the existing SDUK should make the drying process easier and more predictable;
• The entire drying process should be displayed on a PC in the form of graphs for analysis in the event of a malfunction;
• There should be online monitoring 24/7 by the manufacturer.

An ideal camera, in my opinion, must necessarily meet the following fundamental criteria:

• ensure the highest possible quality of finished products (dried sawn timber);
• require insignificant expenses for its construction, equipment and commissioning;
• have a low cost of drying one cubic meter of timber (in terms of);
• the entire drying process should not adversely affect the environment;

Important: long service life (the body and accessories must be calculated and made with quality materials), in the case of vacuum chambers this is especially important, more than once I had to see how the chamber rusted after 2 years under the influence of aggressive media inside and the body began to "siphon", every month it was necessary to weld it up and make metal patches. After 5 years, such a body looked like a colander. In the Rostov region, there was a case when the chamber after 3 years in the process of creating a vacuum, under the influence of corrosion "collapsed like a tin can." The ribs of the camera's reinforcement could not stand. The manufacturer simply did the wrong calculations.;

The most correct decision for a person who decides to purchase a drying chamber is a preliminary stage of thorough preparation, during which:

• it is necessary to determine the required annual volume of drying (today and for the future);
• to study the issue of the presence and amount of wood waste in production, and the possibility of their use in order to heat the coolant for the chamber (installation of an autonomous solid fuel boiler);
• analyze the possibility of atmospheric drying (open);
• to develop a layout of chambers, storage areas for raw materials and finished products.

Remember. Not everything depends on equipment, even the highest quality and most expensive. At least half the success is due to the camera operators and repairmen (their qualifications directly affect the result). For example, how they organize the storage of raw materials and finished lumber.

Rejection of lumber with incorrect drying modes

Some executives. Due to lack of awareness. Drying processes are considered to be quite simple and not worthy of special attention. He put the board down, turned on the airflow and heating for a certain time, took out the finished product.

In this case, I would like to quote my grandson's wise thought: "The taste and color ... all markers are different." If it were that simple, then the problem with choosing a camera would not exist in principle.

In fact, for "incomprehensible" reasons, there is almost no marriage in one cell, and in the second, its percentage goes off scale. To understand why this happens, sometimes it takes a lot of time (and the marriage goes on). And the quality can be affected by anything, from design defects to incorrect loading.

The main task that you have to solve when choosing a camera is not only and not so much saving money on the purchase and selection of the optimal cost / performance ratio, and not even possible prospects for its operation. The main thing is to understand whether the drying room is able to bring the moisture content in the lumber to the required indicators in short term uniformly throughout the depth of the wood, whether it is able to stabilize the geometry (in size and shape).

Any wooden product made from poorly dried material will fail very quickly. Moreover, hidden defects become noticeable only after a certain time. That they were. You will know by warping and cracking, paint peeling and other "delights".

On average it is considered. That a cubic meter of freshly harvested wood contains about 300 liters of liquid, which the chamber should evaporate. But in such a way as not to damage the material. Most of this volume is located in the capillaries, a smaller part in the cells of the wood tissue, which these capillaries form. Removing moisture at the cellular level is the most challenging task. It is the violation of technology at this stage that leads to cracking of lumber.

The hardest species to dry are the hardest (oak, ash, beech). Their top layer dries much faster and forms a crust that poorly permeates moisture from the inner layers. As a result, the likelihood of marriage is high.

That is why it is extremely important to comply with the standard technological modes of drying (for example, timely equalization of moisture content). This process is very complicated. Even the same board dries unevenly in length and volume with a spread of up to 2%.

If the stack is not stacked correctly, warpage can add to the cracks.

What are the most common problems of modern drying chambers?

During my long enough practice in various industries, I had to deal with various nuances of operation.

Problems can arise with any camera. Even produced famous brand and quite expensive. Most often, these are leaks in various pipes due to corrosion, downtime caused by a malfunction and lack of necessary spare parts (this problem is very relevant for imported cameras) or waiting for a specialist. Fan problems are common.

But the main problem, in my opinion, is the uniform heating of the stacked stack to the full depth and effective moisture extraction:

• Wood is heated in different chambers, different manufacturers by different agents (water, air, radiation waves, etc.), heating structures of various types, as a result, the sawn timber dries in different ways.
• The intake of moisture evaporated in the wood should be as efficient as possible at the right time.

These 2 problems had to be solved more often than others, since it is inherent in almost all types of cameras (to varying degrees).

The reasons can be listed for a long time. But, most often, these are:

• underdried material at the end of the stack and overdried at the beginning, or at the top of the stack and in the middle.
• the drying agent between the rows of the stack can practically not penetrate or differ significantly in temperature, which reduces the process to the level of natural drying in terms of time and quality.

To solve the problem, in the first case, the installation of fans with reversible rotation often helps. You can play with their placement and total number to determine the optimal solution. But this cannot be called a panacea. The desired result is not always achieved.

In vacuum chambers, everything is much more complicated, you will have to redo the design of the heating elements and the moisture removal system. Only a professionally performed calculation and competent design (reworking the camera) can help. This is in my experience a lot of time and money wasted.

The main thing should be understood -

NOBODY has been able to completely solve ALL problems of uniformity of drying and quality of finished products!

And, in the foreseeable future, a solution to this problem is not expected. Therefore, the main goal, which every manufacturer strives to achieve, is to minimize the percentage of rejects and the maximum approximation of the parameters to the ideal.

In the case of convection chambers, make sure that the fans inside are not external. They have a long shaft that breaks more often. These products are less efficient and require more thorough and frequent maintenance.

Moisture protection of fan motors must be class "H" (at internal temperatures in the chamber ≤ 130 ° C) or "F" (at temperatures below 85 degrees).

The presence of a reverse with an efficiency of about 90% is mandatory.

TOTAL

Towards the end of my story, I decided to break the obligation not to name specific models and manufacturers. With a clear conscience I can recommend vacuum chambers of the FALKON company (practically of any model) to small and medium and even large manufacturers. There were the least problems with these Russian products.

By performance characteristics. Performance and durability, they are comparable to the models of international giants in this market segment. Unlike them, they have a whole set of additional advantages:

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For the quality of any type of structure, it is important that the materials used are also of high quality and durable. And when it comes to wood, then it must be dry, strong and resistant to decay.

To endow the tree with such properties, it must be dried. But the purchase of equipment for the thermal processing of wood is very expensive, so many craftsmen are trying to assemble their own.

A do-it-yourself lumber drying chamber can be cost effective, but it is far from perfect. Indicators such as 6% humidity in a couple of days with less than 1% of rejects in it are clearly unattainable, since the assembly is usually carried out from improvised means without the use of sensors and various smart systems control of various parameters of the tree, and most importantly, practically without experience in creating drying chambers.

Features of do-it-yourself drying chambers

A homemade drying chamber is a room in which a heater is installed. And now it is worth considering if for drying 1 cubic meter. m will require at least 16 kW of energy, then how much will be required within 3-4 weeks (this is usually the standard drying time in such chambers. The costs can many times exceed the prices of the materials themselves. Plus, if temperature conditions are not observed, poor-quality heating length and without controlling the percentage of moisture, the boards are deformed in almost 100% of cases, which makes it very difficult to work with them.

The design of such cameras must be realized with the help of detailed miscalculations. Failure to follow the technology leads to various accidents. For example, the camera body under the influence of vacuum can shrink like an aluminum can and other moments are often life-threatening to workers.

It is also necessary to take into account the source of energy. Electricity is expensive. It is more efficient to implement the operation of a wood-fired drying chamber using a solid fuel boiler.

The indisputable advantages include the possibility of significant cost savings. Since it is a quality camera, it is often expensive to purchase. But the anticipated savings can actually translate into substantial losses.

pros

There are many reasons for this.

For example:

• the task of independent manufacture of the drying chamber is very difficult. To solve it, the purchase of raw materials and the necessary equipment will be required. And, most importantly, the presence of specialists in the staff who are able to perform all the necessary calculations and build this facility;
• the slightest inaccuracies in the calculations and technology for the construction of an object can lead to a significant increase in the volume of scrap. And these are direct losses, violation of delivery times, a drop in the business reputation and image of the enterprise. Moreover, these errors can lead to the destruction of the chamber itself (for example, the vacuum chamber "folds" like a tin can);
• significantly higher power consumption.

Example.

To dry a cubic meter of lumber in a homemade chamber, an average of at least 16 kW is required. Calculate your monthly expense (even with an 8 hour workday and 5 day work week).

• the parameters of finished lumber, which are provided by vacuum chambers manufactured by a specialized enterprise (for example, a moisture level of 6%, achieved in two days of work, or a scrap percentage not exceeding 1%), are practically unattainable in home-made devices.

Possible design options

If an objective analysis has shown that the company is able to solve all the upcoming difficulties associated with manufacturing, commissioning and subsequent operation, you can start working on this issue in detail.

To do this, you have to answer several questions:

• what kind of drying mode will be implemented in it (the required temperature in the chamber depends on this): low-temperature or high-temperature;
• its future device (prefabricated metal, or built from existing building materials (concrete, brick, blocks, etc.);
• installation site (detached building, site of the workshop). Since the miscalculation of subsequent work depends on such a decision (foundation, laying of engineering communications, delivery of raw materials, etc.);
• loading option (forklift, rail cart);
• heat supply option (hot air, radiant energy, superheated steam, electric current, other options);
• decide on the required equipment for the future furnace (main and auxiliary).

The first group must include a system of humidification and ventilation (supply and exhaust), heat supply. Secondly, psychrometric and insulated door blocks, electric motors for driving fans, pallet trucks, etc.

• process control organization option (manual mode, semiautomatic device, automatic mode). Ideally, you can provide for remote control of the processes.

All of the above issues are resolved in the context of the selected type of drying chamber. Today, there are chamber and tunnel options (they implement convective heat transfer).

The former are shorter than the latter and, most often, one door is used for loading raw materials and unloading finished products. As a rule, this option is chosen.

Tunnel ones provide for the movement of materials during operation along the entire length of the chamber. Loading, on the one hand. Unloading, from the opposite. These cameras are used in large enterprises.

There are drying chambers of the condensation type. They have significant efficiency, but the drying process is very long in time (the equipment is not capable of operating at high temperatures). This leads to significant heat loss and increases energy consumption.

There are many more criteria that must be taken into account when calculating:

• the method of circulation of the agent used for drying;
• its characteristics;
• the type of fencing to be performed;
• operating principle;
• way of circulation.

Each of these issues directly affects the drying rate, the possible volumes of lumber loaded at a time, the characteristics of the finished product.

In addition, it is necessary to take into account the species of wood, its initial moisture content, and the geometric dimensions of the sawn timber.

Careful analysis and detailed calculation, with a high degree of probability, will prove the economic feasibility of purchasing and installing a ready-made drying chamber. Although, in some cases, making it on your own can also be cost-effective.

How can we help

Falcon has been producing vacuum chambers for wood drying for nearly two decades. Cooperation with us is beneficial both for those who are going to make a drying chamber on their own, and for those who want to purchase a finished product in order to have guaranteed high-quality products in marketable volumes.

We are ready to offer our partners from the first group the equipment and units that are necessary for the functioning of the cameras in the range. Example, heating panels, in which the heat carrier is water.

They can be installed in structures of any volume, are designed for operation in a vacuum environment, and are capable of operating at high temperatures.

The panels can be selected according to a number of characteristics:

• by the volume of the chamber for which they are purchased (we offer 4 versions - for volumes up to 3 cubic meters, up to 8, up to 15, up to 21);
• they can be equipped with automatic equipment in standard, maximum or optimal, for the customer, execution;
• by size: 2000 * 3000 or 1500 * 3000.

In addition, we offer complete sets of heating units, pyrolysis boilers, liquid oil products, ready-to-install vacuum units and automation.

We manufacture automation for each type of chamber: Convective, aerodynamic, vacuum, etc.

Significant advantages of purchasing a ready-made solution are:

• significant time savings (it takes at least 14 months to develop a project independently and complete it);
• savings on unplanned expenses. Practice shows that it takes an amount comparable (or exceeding) the price of the finished camera to bring the performance of a home-made camera to the required parameters;
• guaranteed release of only high quality products;
• the company begins to receive net profits immediately after the completion of the NDP. Time for fine-tuning the equipment and characteristics of the finished product (downtime) is not required.

If you need to design a vacuum drying, it is better to seek professional help. We are engaged in the production of:

• mobile,
• stationary,
• high efficiency,
• low power consumption.

It is possible to design not only drying, but we can also supply new equipment at an acceptable cost. Powered by both electricity and production waste: slab, firewood, etc.

For those who know how to count money, save their own time and prioritize quality, a wide range of vacuum chambers of our production is available, the main characteristics of which can be found on the website, in the company's catalog or by contacting the nearest office in person.

We also implement more budget options from heating plates. More details can be obtained from the manager by phone or email on the main page.

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How to make a cheap DIY vacuum wood dryer

Hello dear readers and subscribers of Andrey Noak's Blog! Do you know what is most important in wood materials? This is a quality drying.

Each company uses a special drying technology. But if you want to dry the material yourself, then I will tell you how a vacuum dryer is made with your own hands. But first, a little 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 moisture, depending on the 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 by the circulation of moisture along the trunk. When cut, 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

A well-dried material is protected from fungi, damage and cracks, and the service life will be significantly increased.

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:

1. wet is the one that was in the water and its moisture content is one hundred percent;
2. freshly cut, with a moisture content ranging from 50 to 100%;
3. air-dry, if the material has been exposed to air for a long time.

   The moisture content of such wood is about 15-20%;

4. room-dry, with a humidity of 8-12%
5. absolutely dry, the humidity of which is exactly 0.

Wet material will be difficult to process, but it is flexible and elastic.

Dry wood properties

Dry material has a higher biological resistance. After drying, the strength increases, better withstands the load. It is easy to process, and the products do not crack after processing, in contrast to the sour wood, in which the process of decay can even begin under suitable conditions.

Old ways of drying

For a long time, people used only wood to build houses.

Wooden dishes can be found in houses. Therefore, it was necessary to come up with ways of high-quality drying of logs as the main building material.

At that time, people used several drying methods.

For this method, they took the necessary piece of wood, water and sawdust. The water was heated to 70 degrees, a 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 denser and more flexible.

Waxing is another method that has been widely used for a very long time.

Here, wooden blanks were dipped 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. Material properties change after drying. The workpiece does not crack, does not rot and takes on an original tinted shade.

Craftsmen used this drying method to make wooden dishes, then skillfully painted the finished product.

Wood moisture, measurement methods

There are many ways to determine moisture content.

To accurately determine the moisture content of wood, special devices are used. 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 of different moisture content has different electrical resistance.

There are many more "folk" methods for determining humidity, but they are used only by professionals:

• By weight, weighing the same pieces of wood of the same species in your hand or on a scale alternately.
• Experienced experts determine the moisture content "by eye", by the presence of cracks and faults.
• By shavings.

  When processing lumber, small chips are squeezed in a fist. If it wrinkles easily, then the material is wet. Dry wood is indicated by the brittleness of the shavings, but if the shavings crumble, then most likely the wood is overdried.

• Cutting. If, when processing 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 make a thread on such a surface, as cracks and flaws will appear when dry.

Putting together a vacuum dryer at home

It is very beneficial to dry the wood yourself, and if you do this with a vacuum dryer, the drying time will be reduced significantly.

But buying a vacuum dryer in factories is expensive, and I will tell you how you can do 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, and a fan to distribute heat inside the structure.

The floor, walls and ceiling of such a drying must be very strong, reinforced concrete or an iron conveyor is best.

If you take a cheap second-hand iron conveyor, for example, from the railway, then it will even be 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 reinforce the walls with foam plastic and cover 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 other heating circuits and must be in operation at all times. You can use a heating radiator, with which the water heats up to 65-90 degrees.

In order for the heat in the chamber to be equally distributed, a fan is required, otherwise there will be uneven drying of raw materials and, accordingly, low quality.

One more point, the temperature in the chamber should change smoothly and gradually.

When building your own drying facility, you must comply with all fire safety rules.

An important point is the construction of a system for loading lumber into the chamber. You will be immersing large and fairly heavy boards. For this, trolleys moving on rails or a forklift are well suited. The material is folded inside 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 high 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 to 2 weeks.

How vacuum drying works

After you have placed the material in the drying chamber and closed the door tightly, you can start drying. Air is extracted from the chamber to create a vacuum of about 9 - 10 bar. It is known that with a decrease in pressure, water boils faster.

Thanks to this technology, bound and free moisture will evenly move 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 areas dry out, then moisture from thicker layers moves to dry ones, thereby moisturizing them. If this process is interrupted, the material may collapse, as the displacement of thinner layers begins.

Coating the ends of thick lumber to avoid quick release of moisture and crack formation 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 workpieces.

Drying excludes the use of humidification systems, and no thermometers should be installed in the chambers. The process can be controlled using special sensors, which are controlled from the outside, often in a separate vestibule.

Very often vacuum installations are used for drying expensive species such as oak, merbau, paduk, wenge, zebrano.

It is very convenient, since the wood is practically not destroyed during drying.

My help

I have the opportunity to provide advice on drying technology, selection of new and used equipment.

You can contact me through SUPPORT.

Recently, my new book has been published, which gives recommendations for the operation of drying complexes in production. The information that is given in the book is simply unique, you will not find such information anywhere.

More information about the book can be found in the section "MY BOOKS".

Good luck and see you soon!

vacuum dryer

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Appointment of modular wooden drying chambers.

Drying chambers SCM series, students in the nomination "100 best goods in Russia. ", They are intended for drying hardwood and coniferous wood 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 for environmental monitoring and management systems drying chambers"and" Requirements for quality drying "in accordance with the guidelines of Russian technical material (RTM) for drying chamber in wood.

Installation, design features of SCM wooden dryers.

Striving for maximum build speed and speed wood drying chamber partly included in SCM models. Modular design wood drying chamber simplifies shipping and installation.

To meet the wishes of the company's customers, many standard sizes Drying chambers... Now "TERMOTECH" develops and produces wooden drying chambers and complexes with pneumatic load from 6 to 180 m³ operating on thermal energy generated by burning wood waste or stationary boiler houses.

Drying chambers with a lifting capacity of up to 20 cubic meters. 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 of installation work allow you to build a heated drying cabinet with a heated floor. When renting production space wooden drying chambers underfloor 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.

It is necessary to clamp the cement cement regardless of the height of the already welded track at the place of our company, on the transverse stiffener. clam Drying chambers volume 20 cubic meters 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.

Sealing of seams when installing modules of drying modules is carried out with a special rubber profile and silicone sealant, which is delivered to the customer together 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 service life of the intake. For a better seal Wooden loading doors of the drying chamber are made with a floating hinge by closing the door of the door of the door four points with the screws.

The door seal is a heat-resistant 3-strip profile. supplied drying chambers Control system equipped with a drying procedure, semi-automatic fully automated (computerized), S control of fuel supply, boiler operation, shutters, ventilation curtains, etc.

the proposed wooden drying chambers manufactured both at rest and in transitional version. The transitional version allows the customer to organize the most efficient continuous production process and increase the productivity of drying chambers through more rational use of loading and unloading time compared to blindness.

Loading wood into wood drying chamber produced by standard wheels. Depending on the carrying capacity of the chamber, the transportation of the strings can be longitudinal or transverse. When drying wide untreated wood, excluding the transverse tip of the wood, the pedestal is equipped with a block-type clamping mechanism.

In this case, the force on the upper beam types is equal to the force on the lower types of lumber. Numerically, this force is equal to the strength of the fund's weight.

Heating system.

Modular drying chambers and wooden complexes produced by Termotech operate on thermal energy obtained from burning wood waste in the heat generators of our production or stationary gas boilers. Water heated to 95 ° C by a pump is supplied through a supply line to the side walls wood 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 certain 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 solid matter is equipped with a boiler funnel, it is supported by sawdust, feeding a screw mixer or a mechanical load carburetor, which allows heating wood products of each fraction (boards, shavings, shavings, bark). In case of insufficient wood waste, we can fill the supplied heat source directly to burners, gas ovens or oil-fired ovens.

For more efficient and stable operation of the boiler, a fan is installed in the turbine, and an ejector is installed in the chimneys of the chimney.

Air exchange system, fans, brackets.

For heat exchange between water registers and indoor air wood drying chamber A centrifugal fan is installed, the electric motor of which is installed outside Drying chamber for drying wood.

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 in comparison with manufacturers of similar Drying chambers... Such effective results were achieved due to the rational redistribution of power when installing the fan. The abnormal high pressure has been reduced, resulting in increased fan efficiency.

In addition, the pressure was reduced cubic, and increase the power - squared... Aerodynamically calculated wood drying chamber The greatest losses occur when the ventilation system is ventilated.

The power loss of the fan motor is directly proportional to the cube speed of the drying agent. Therefore, further optimization was carried out from the condition: The speed of the drying agent near the sawdust storage should be between 1 and 1.5 m / s. Based on quality conditions, the same speed is adjusted by CNIIMOD for drying wood in soft and normal conditions.

Because the domestic industry does not produce specialized fans for Drying chambers(high performance, low pressure) - all fan wheels are of their own shape.

The fan wheels are static and dynamically balanced. In wooden drying chambers with wood load up to 12 m ³ The fan wheels are mounted directly on the motor shaft.

Fan for wooden drying chambers with a wood volume of more than 12 m ³, is carried out through bearings and pulleys. The fan 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, a grease nipple during maintenance and are centers that can withstand heavy loads, as originally developed for crushing and grinding machines, roller drives for presses and wind turbines.

The most optimal transverse extrusion of the chimney and temperature conditions inside drying dry baked lumber It comes with screens and external blinds. This design allows easy access to revision and maintenance of the rotating fan and registers. To exchange air with the atmosphere in Ljubljana wood drying chamber installed aluminum inserts and exhaust valves.

Fences, wall insulation.

Corps of all Drying chambers have optimal thermal insulation calculated for the middle strip, a layer of solid mineral wool board that does not absorb moisture and has a high degree of fire resistance.

All steel elements that prevent corrosion in the drying chamber are protected by a corrosion-resistant coating and a waterproof coating. When shipped In regions with other climatic conditions the thickness can be built to provide the required 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 enclosures 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 (W 0.019-0.28 / M º K), low weight (40-60 kg / m³), ​​high adhesive strength and corrosion protection.

The warranty period for the insulation of aluminum polyurethane foam sandwich panels is 30 years. ( Detailed description and comparative characteristics of rigid polyurethane foam and mineral wool see here.) Interior walls wood drying chamber made of 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 occurrence of "dew" (inner surface of the door, intake and exhaust valves) are made of aluminum.

Heat treatment 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 - developed and manufactured by TERMOTEH.

The variety of the system is achieved by generating dry entropic 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 conifers.

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. This is a concept, a tutorial. Very often the storage conditions for joinery products after sawing wood are violated, for example: lack of sunscreen to protect from the sun, uneven air flow of the chimney with natural air circulation, loading one drying chamber in 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 start of drying. For the solid beech process, a steam process is required to create a uniform color palette for the wood of 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 moisture redistribution with the help of the material (moisture transfer), and the high humidity of the dehumidifier 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 recommendations for woodworking - "wood drying technology", which is equipped with drying chambers of our products. CAM "Module C1", "C2-Module" includes the entire thermocouple drying program. In the absence of a plumbing network, the humidification system, air conditioning system and water vapor may operate in an unnecessary mode, an unnecessary reservoir with a consumer inside wood 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 moisture should be used by a conventional fire extinguishing system wood drying chamber in accordance with PPB-01-93 "Fire safety rules in the Russian Federation".

If the client has vacant premises that are out of date Drying chambers for drying wood we are ready to provide technical solutions and equip with the necessary equipment for their transformation or modernization of drying chambers.

Drying chambers for wood of convection type

The availability of drying equipment for drying wood and lumber is, as a rule, one of the main attributes of modern woodworking production.

Dryer for boards: creating and using a drying chamber

Drying chambers of convective type are widely used both in Russia and abroad. Convective wood drying technology allows to obtain high-quality sawn timber with the required moisture coefficient. Modern drying chambers are equipped with automatic equipment that allows you to control and monitor the drying process remotely.

Negociant-engineering company supplies drying chambers for wood Russian production.

The proximity of production, the introduction of the latest technologies and a streamlined service make it possible to provide our Customers with inexpensive and high-quality drying equipment... We implement both small (with a small volume of loading) 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 commissioning 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 reversible German-made fans

The walls of the drying chamber building are insulated with Finnish mineral wool with basalt fiber

Sightseeing door as standard

Sale and service of drying chambers

We provide delivery, installation and start-up of drying chambers.

We provide warranty service and service.

Drying chambers are made to order at the request of the Customer

Loading volume from 45m

We offer comprehensive solutions for organizing a wood drying site using boiler equipment and equipment for recycling wood waste.

The cost of drying chambers is lower than competitive ones.

Technical characteristics of drying chambers

Optional

Installation supervision and commissioning

A specialist leaves for the installation supervision, who takes measurements of the foundations according to 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 wood drying kilns

A detailed description of the design of the convection-type wood drying chamber 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 fed into the chamber.

First, they are heated for 1-2 hours at a temperature of 50 ° C.

Do-it-yourself lumber drying chamber

After steaming, the temperature is raised to 60 ° C, then steaming is repeated and, if necessary, steamed up to three times. At correct mode drying, the wood does not undergo much deformation.

Rice.

6. Scheme of drying methods:

a - air-steam periodic action, b - electric dryer operating at high frequency currents; 1 - heaters, 2 - supply channels, 3 - pipes for steam starting, 4 - exhaust pipes, 5 - special trolley (track), 6 - damper, 7 - movable electrode, 8 - fixed electrode

Soft woods are dried at a temperature of 40-75 ° С, hard ones - at 35-55 ° С.

The drying temperature of sawn timber should not exceed 80 ° C, since with more high temperature the structure of the surface layers of wood changes, that is, there is a kind of hardening of the material. Such material is difficult to handle with cutting tools.

At the beginning of drying, the air should have a relatively high humidity and low temperature.

The higher the moisture content of the wood, the more moisture must be contained in the air introduced into the chamber 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 coniferous and deciduous species of various sizes, at most factories in model shops, steam-air chambers of periodic action with incentive reversible circulation are used.

The unloaded sawn timber 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 a production workshop for 2-3 days to release the wood from internal and surface stresses (normalization) obtained in drying result.

In addition to steam-air drying chambers, there are gas chambers.

In a batch-type drying gas chamber, to evaporate moisture, smokeless gas obtained in the furnace when burning raw wood waste is used, which, by means of an axial high-pressure fan, is forced through the gas ducts onto the lumber stacks. The chamber is designed with a steam humidifier.

In the woodworking industry, batch-type gas dryers operating on natural gas are used, with the presence of 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 are used for ordinary drying of sawn softwood.

Lumber can be dried by high-speed method in electric dryers with high-frequency currents. Drying using high-frequency currents lasts only a few hours, while the material is dried evenly, without cracking or warping.

The waste of wood with such drying is much less than in steam and gas dryers, and is no more than 5%.

The peculiarities of heating semiconductors and dielectrics, which include wood, in a 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 entire thickness. The current power absorbed by the material can be regulated by selecting and changing the parameters of the electric field.

The following should not be construed as a DIY guide. Homemade cameras for drying wood, there are quite a few of them. But at the same time, the overwhelming majority of them are far from perfect.

Drying chambers are calculated and designed, which means that specialists should be engaged in this.

Even if you decide to make a drying chamber "with your own hands", then at least before you build, order a project for specialists or find and study the literature on the device of drying chambers.

Woodworking, its cost, product quality, depend on the quality of drying sawn timber. In turn, high-quality chamber drying of wood depends not only on adherence to technology (correct laying of lumber, compliance with regimes), but also on the design of the drying chamber.

I hope that the information provided here will allow you to avoid mistakes when buying or help you improve the convective wood drying chambers available in your production.

Further, the device of a drying chamber for wood with an upper arrangement of fans (vertical-transverse circulation of the drying agent) is considered, since in modern convection chambers for drying wood this is the most common aerodynamic scheme.

All calculations are given for light-drying wood species: pine, spruce, cedar, and so on.

Lumber with a thickness of 50 millimeters is taken as a conditional one.

Convection-type wood drying chamber device

For uniform drying of wood along the stack height, the distance from the wall of the drying chamber to the lumber stack must be at least a quarter of the stack height (see.

figure), otherwise it is necessary to ensure the narrowing of the air channel from top to bottom.

Diagram 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 sawn timber along the length of the stack (with a board length of 6 meters), drying chambers, as a rule, must have at least three fans.

Wood drying chambers should be designed to allow air to flow only through the lumber stack.

Free passages reduce the air flow through the stack (therefore, wood drying is slower) and makes it uneven, which increases the uneven moisture content of the dried lumber.

The free passage of air on the sides, top, bottom of the stack should be blocked by curtains, thresholds and other things.

It is recommended to install the side curtains 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 advisable to make the upper curtains movable, since drying the wood leads to a decrease in the height of the lumber pile.

Air circulation during chamber drying of wood

The circulation is carried out by fans, the air flows across the stack. The fan compartment is fenced off from the lumber piles by a false ceiling and has a baffle designed to exclude "short circuits" of the air flow. It is very important!

In some homemade drying chambers, this baffle is absent, as a result, a significant part of the air is uselessly chasing over the false ceiling, without falling into the stack.

Single-stack drying chambers for lumber allow the use of non-reversible fans; with two or more stacks, the fans must be reversible.

Fan requirements for drying chambers

If the fan motor is inside the drying chamber, it must be made in a waterproof 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.

Class F electric motors are often used in homemade drying chambers. As a result, they fail every 3 to 6 months.

With insufficient performance of the fans, the chamber drying of wood is slower, the unevenness of moisture along the width of the pile increases.

Heating of convective drying chambers.

The supply of heat necessary for the evaporation of moisture from the wood is carried out by heaters, their power is determined at the rate of 3-4 kW per cubic meter of conventional sawn timber.

To ensure this, the heat removal surface of the heaters should be about 3.5 square meters per cubic meter of sawn timber. It is not recommended to use electric heaters: drying of wood will have a high cost. Probably for many, the best option there will be a boiler using woodworking waste.

It is desirable that the air entering the convection drying chambers during ventilation passes through the air heaters before entering the stack.

Therefore, when 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 discharge side.

This layout 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 recuperator, heat exchange takes place between the incoming and outgoing air during ventilation. The use of a recuperator, in addition to saving thermal energy, reduces temperature fluctuations during ventilation, therefore, drying of sawn timber 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 115 degrees. Therefore, with poor thermal insulation, part of the money you pay for heat energy will go to heating 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 to withstand the air humidity set for the mode 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 installed 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, therefore, moist air must be removed if and only when it is required by the regime.

With poor tightness, it is impossible to withstand the specified air humidity. The use of a humidification system does not help: even if steam is supplied, a significant part of it falls out in the form of condensation due to contact with cold air.

Therefore: wood drying chambers must be airtight, have no cracks, and gaskets must be installed on the doors. Homemade drying chambers often have poor tightness.

In industrial chambers, the deterioration of the tightness usually occurs due to the loose closing of the doors due to their 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 discharge side; additional fans are not used.

The required total cross-sectional area of ​​the air ducts with such ventilation is approximately determined at the rate of 40 sq. centimeters per cubic meter of conventional lumber from the pressure side and the same amount from the vacuum side. The air ducts are equipped with curtains that open and close as needed.

To reduce the formation of condensation in the air ducts, thermal insulation is desirable.

Humidification system for chamber drying of wood

There is an opinion that drying of light-drying wood species can be carried out without moisture treatment.

Indeed, when drying freshly sawn wood, the required air humidity is collected in 6 - 12 hours. However, if wood is dried in a chamber, which after sawing has lain for 2 - 3 days, then this time can stretch for a day or more, which is already undesirable.

Drying chambers for lumber - a choice of equipment for drying wood

Thus, a humidification system for chamber drying of sawn timber is still needed. For humidification, use steam or finely atomized water (droplets hang in the air) with the help of nozzles. A very common mistake in homemade drying chambers is that when spraying, water gets on the thermometer and air humidity sensor. As a result, the automation receives false information about the climate parameters.

It is unacceptable.

About the requirements for gaskets.

Gaskets are not a structural element of the drying chamber and, of course, are not supplied with it, but without observing the requirements for them, high-quality drying of wood is impossible, therefore, briefly about the gaskets.

The spacers must be made of dry lumber and have exactly the same thickness. The thickness of the gaskets with a total width of the 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.

If the thickness of the gaskets is insufficient, the chamber drying of wood takes place more slowly, the unevenness of moisture along the width of the pile increases.

The width of the spacers is 40-50 millimeters.

The surfaces of the gaskets in contact with the lumber must be planed.

High-quality drying of wood largely depends on the correct laying of lumber, so be sure to study this question.