The moisture content of wood is great importance to understand the further behavior of wooden products during operation. Wood is a living material consisting of cells, and cells, as we know, cannot live without water. There are such concepts as free moisture , which is contained in the pores and capillaries of wood and bound moisture , which is contained mediocrely in tree cells. On the border of these concepts is fiber saturation point - this is the wood moisture content at which all free moisture has been removed from the wood, i.e. There is no water in the cavities of the wood, but all the bound moisture remains, i.e. cells are saturated with water. Wood moisture content at the saturation point ranges from 22 to 35% depending on the type of wood and for practical calculations is taken equal to 28%.
Wood moisture content at fiber saturation point - 28%
Important to know: wood changes its physical dimensions at humidity from 0% to saturation point. Further moistening does not lead to a significant increase in size. The moisture content at the fiber saturation point is higher than equilibrium humidity. Equilibrium moisture content is established in the wood naturally during operation, depending on temperature and relative humidity, so the wood dries out.
For Minsk, the relative average annual air humidity is 78% , in autumn-winter 80-90%, in spring-summer 65-75%. Thus, when drying wood naturally, its humidity is set at 12-15% in summer and 18-20% in winter. It follows from this that when wood products are used outdoors, they change their geometric dimensions throughout the year depending on temperature and humidity. Getting wet from rain can increase the wood's moisture content well above its saturation point. It is also worth noting that when humidity is above the saturation point and warm weather Ideal conditions are created in the wood for the development of tree-destroying fungi. The limit of biostability of wood is considered to be a moisture content of 22% . Therefore, when operating on the street in the conditions of the Republic of Belarus.
The main rule for using wood: Before installation, the wood must have the moisture content in which it will be used in the future. . This rule also applies to other materials - WPC, laminate, plywood, etc. Thus, before installation, the wood should be left for some time in the conditions of the environment in which it will be used.
The main types of wood used in construction in Belarus are pine and spruce. The volumetric shrinkage of these rocks from freshly cut to dry is up to 15%, the change in size across the grain is up to 10%. Knowing this rule is very important when installing lining, imitation timber, block house, floorboard, especially when using raw or very dry materials.
When drying wood in air, the time of year, wind direction, temperature regime, material cross-section and other factors. Therefore, the time period for reaching the equilibrium moisture content of wood during natural drying can only be predicted. According to these parameters, during the Soviet era, Belarus was classified as the 3rd conditional zone in accordance with GOST 3808.1-80 and determined next term drying lumber naturally: 
According to the table, in Belarus natural drying is possible only from April to September. This is not true, because drying occurs even at 100% relative air humidity and a temperature of 0 degrees. Thus, from October to March, being outside, the wood also dries.
Wood moisture content after autoclave impregnation
To understand what moisture content wood has after autoclave impregnation, we will present some numbers and calculations.
- Freshly cut wood has a moisture content of 60-80%
- At 100% humidity, the amount of water in the tree is 50% of the total mass
- The weight of 1 cubic meter of wood with 100% humidity is conventionally equal to 1 ton (including 500 kg of water)
- Wood with a moisture content of approximately 25% is supplied for impregnation.
- When autoclaving 1 cubic meter. wood, it absorbs about 200 liters of antiseptic solution (conventionally equal to 200 kg)
Calculation of wood moisture content after impregnation
- Weight of water (B1) in 1 cubic meter. dry wood with a moisture content of 25%. B1=25x500/100=125 kg
- Weight of water (B2) in 1 cubic meter. impregnated wood. B2=125+200=325 kg
- Humidity of wood after impregnation VP=325/500*100=65%
Thus, after autoclave impregnation, the wood moisture content is approximately 65%. This is the moisture content of freshly sawn wood. Hence natural drying time to operational humidity can be approximately determined from the second table at the top of the page.
In our opinion, the most controversial issue on the Internet. Let's answer this question in detail, based on GOST. Also, based on experience and practical examples, let’s try to figure it out and give logical answers to all the above questions.
Wood moisture content - This is the ratio of the mass of moisture contained in the volume of wood to the mass of absolutely dry wood.
The moisture content of lumber is measured with a moisture meter.
A tree is a living material that grows, sleeps, breathes. Because of this, most indicators in wood change from year to year. And such an indicator as the moisture content in wood, as well as the moisture content of dry lumber, changes EVEN throughout the year. This indicator depends on the time of year, the region, and the place of growth.
There are two main indicators on which the natural moisture content of wood depends.
The moisture content of wood is also affected by the region and place of growth.
When the wood arrives less wet, it dries faster, and the drying process is softer and tears it less.
Dry lumber
Transport humidity and furniture humidity obtained by drying.
Wood moisture content is:
- Natural humidity (40-60%)
- Transport humidity (18+/-2%)
- Furniture humidity (8+/-2%).
Wood moisture content depends on the use of lumber.
- Natural humidity of 40-60% is used for formwork, in rafter system, for lathing, etc.
- Furniture wood with a moisture content of 8 +/-2% is used, the name already gives a hint, first and foremost in furniture production, as well as for the production of laminated veneer lumber.
- In all other cases, wood with a transport humidity of 18 +/-2% is used and is used for any construction, for the production of lumber, for example, block house, sheet piling, etc.
Sometimes a client comes and says: “I want the moisture content of the timber to be 8%.”
You ask: “For what?”
Answer: “They told me (I read) it would be better.”
Based on GOST 8486-86 and experience, for construction transport humidity is the most optimal humidity. Because at a humidity of 18 +/-2%, lumber does not warp, does not twist, does not turn blue, and is not susceptible to fungal infection. Transport humidity lumber fully justifies its physical and mechanical characteristics in construction.
Also, the belief that timber can be dried to 8% is absolutely false, and no one has ever seen such timber.It is impossible to dry the timber to less than 20%, and no one argues that the top layers can be dried to a moisture content of less than 20%, but what about the core? The moisture content of the timber in the core reaches 20%, which corresponds to GOST and DIN. At this humidity, timber and boards do not warp, do not twist, do not turn blue, and are not susceptible to fungal infection.
There is also interesting data that is included in the table below.
Based on the data in the table, the equilibrium moisture content of wood is 17-18.5%, based on average statistical data (air humidity 80-85% and temperature +10 C). It is logical that to build a house from timber, a humidity level of less than 20% is simply not needed. The construction site will not “gain” anything from this.
You can, of course, hear the argument about laminated veneer lumber; it is dried to a moisture content of 8%.
- Firstly, it is not the timber that is dried, but the lamellas (board).
- Secondly, manufacturers of laminated veneer lumber need to glue the lamellas together in the future so that they fit together tightly and do not come apart or dry out over time.
In principle, this is where the poor quality laminated timber came from. They dried it poorly, because it’s not easy to dry a board, not to mention timber, to a moisture content of 8 +/-2%, they didn’t dry it completely, they cheated, and over time the timber can dry out and the lamellas fall off.
Clients also come who say that we demolished my grandmother’s house, and we were never able to disassemble it. The roof “moved off”, but the frame remained rooted in place.
And the client sums it up with an exclamation: “They built it!”
Of course, before no one was chasing to build as quickly and cheaply as possible, no one was chasing “new technologies”. And they cut down the tree, debarked it, gave the log time to mature, and then just collected it.
How is it working out now? Everything is done exactly the opposite. The client wants faster and cheaper, the manufacturer gives what the client is willing to pay for. Here is the overall result.
The desire to obviously save money spoils the opinion about the best natural construction material. Wood, we repeat, is a living material; it “survives” only in the hands of professionals.
Wood moisture content is a value that shows the level of moisture exchange between wood and air. Since humidity environment changeable, then in wood it is constantly changing. The level of this indicator affects the quality and use of lumber. Products with high humidity more susceptible to mold and mildew, rot and deformation. Therefore, dry raw materials are chosen for the construction and manufacture of wooden products.
Humidity can be absolute or relative. The first represents the ratio of the mass of moisture in wood to the mass of absolutely dry wood. A more commonly used, convenient and easy-to-calculate quantity is relative humidity. This is the ratio of the moisture content of wood to the total weight of wood, which actually reflects the water content in the product. This value is decisive, so it is used in practice.
Types of wood by moisture content
The initial figure is usually 50-60%. With natural drying, after 1.5-2 years it drops to 20-30%, after which it does not change much and remains at approximately 25%. There are wet wood with a moisture content above 35%, semi-dry wood with a moisture content of 25-35% and dry wood with a moisture content of less than 25%. To reduce the moisture level to room-dry 7-18%, lumber is dried in special drying chambers.
The following types are distinguished:
- Floating wood that has been in water for a long time or a well-damp and wet log - over 60%;
- The initial rate of a freshly cut tree is 45-60%;
- Air-dry reaches 20-30%. This result is typical for logs and beams that have been in storage for a long period of time. outdoors or located in a dry, well-ventilated area;
- Room-dry is dried in rooms with heating and good ventilation or in special chambers. Amounts to 7-18%;
- Absolutely dry wood with a moisture content of 0% is dried to constant weight at a temperature of 100-105 degrees above zero.
To build a house or bathhouse, dry lumber with a moisture content of up to 20% is used. Today the safest and effective method, which allows you to achieve such indicators, is condensation drying. Drying uses both hot and cold air. This prevents the appearance of defects and defects on the log or timber, reduces the number of cracks and allows you to obtain high-quality, durable and dry lumber. Read more about condensation drying.
Logs and beams for building a house
In “MariSrub” you can order construction wooden houses only from high-quality and carefully selected dried materials. We independently produce logs and beams for the design of a wooden house, bathhouse, gazebo or garage. Choose custom design or customization already ready-made version which you will see in .
During production we use condensation drying, we comply with GOST requirements, storage and transportation standards. We carry out antiseptic treatment and control every stage of production, which allows us to obtain durable and quality lumber. Due to this treatment, the wood retains its original color for a long time and natural properties. It does not rot or darken or become moldy. The materials are resistant to moisture and cold, wind and insects, and temperature changes.
We are building wooden houses from timber and logs from the manufacturer. Own production- quality assurance and low prices for lumber! We offer turnkey construction, which includes the creation of a project and installation of timber or log house, construction of the foundation and roof, finishing inside and outside the house, installation and commissioning utility networks. We guarantee quality construction on time!
Wood is a rather porous material containing a large number of capillaries filled with moisture. In practice, wood moisture content is defined as the ratio of the weight of water contained in the tree to the weight of absolutely dry wood. There is a concept of “free” and “bound” moisture. “Free” moisture is contained in the pores and capillaries of the tree. “Bound” moisture is that contained directly in the cells of the tree.
When drying, the tree shrinks - it decreases in size (volume). In this case, there is practically no decrease in size along the fibers (along the length of the board), but in the direction transverse to the grain, there is a significant change in size (along the thickness and width of the board). The magnitude of this change depends on the type of wood and the specific value of the change in wood moisture content. In life, the most unpleasant surprises are associated with changes in the width of the board.
For example, if you lay a floor with a board that has natural moisture, then the decrease in its width over time can be so significant that two adjacent boards will lose their grip on each other. In this case, to remove the cracks, you will have to tear off all the boards from the joists and lay them again, fitting them end to end.
“What humidity should the board have?” you ask. It’s simple - any wooden product, during its operation, tends to the so-called “equilibrium humidity”. “Equilibrium humidity” is determined by the temperature and humidity of the air in the environment where the board will be located. You can see the values of this humidity in the table. For a residential premises it averages 8-10%, for a street it averages 12-14%. It logically follows from this that a damp board will dry out indoors, losing its width, on the other hand, a dry board will be moistened outdoors, expanding.
Natural moisture content, final wood moisture content
Natural humidity- this is the moisture inherent in wood in a growing or freshly cut (sawn) state, without additional drying. Natural humidity is not standardized and can range from 30% to 80%. The natural moisture content of wood varies depending on growing conditions and time of year. Thus, the natural humidity of freshly cut trees in a “winter” forest is traditionally less than the humidity of freshly cut trees in a “summer” forest.
Initial humidity- the same as natural humidity. A freshly felled tree has maximum moisture content, which various breeds may even exceed 100%. Balsa wood can have a freshly cut moisture content of up to 600%. In practice, we deal with smaller values (30-70%), because After cutting, some time passes before the tree is sawed and placed in the dryer, and it, of course, loses a certain amount of water. We take the initial moisture content to be the moisture content of the wood that it has before being sent to the drying chamber.
Final humidity- this is the humidity we want to get after full cycle drying. In this case, the purpose of the product made from dried wood is taken into account.
First of all, wood drying is the process of removing moisture from wood by evaporation.
Wood drying is one of the critical operations during wood processing. The wood is dried after sawing, but before wood processing. Wood is dried in order to protect it from damage by wood-staining and wood-decaying fungi during further storage and transportation. Drying prevents wood from changing shape and size during the manufacturing and use of products made from it, improves the quality of wood finishing and gluing. The humidity to which wood is dried depends on the scope of its further use. The whole point is to bring the moisture content of the board to the same value that a product made from this board would reach over time during operation under these conditions. This humidity value is called “equilibrium humidity”; it depends on the humidity and temperature of the surrounding air. For example, the board from which parquet and other products used indoors will be made should have a humidity of 6-8%, since this is the humidity that will be equilibrium. For products that will be used in contact with the atmosphere (for example: wooden windows, outer skin at home) the equilibrium humidity will be 11-12%.
You ask: “What will happen otherwise?” We answer: Otherwise, what happens all the time in Russia will happen, namely, the consumer will face problems. Imagine that you bought lining in order to sheathe the walls inside your country house or dachas. If you buy clapboard made from raw boards from a careless manufacturer and cover the walls of your house with it, it will begin to slowly dry out naturally in an already installed state. Let us turn to the table of equilibrium humidity and experience. If you heat a room in winter to 25 degrees Celsius, then with a typical indoor air humidity of 35% for winter, the equilibrium humidity value for a board in such a room will be 6.6%. At bases and markets, lining can very often have a humidity of 14% or higher (we have encountered 30%). Next, imagine that your lining begins to dry out, losing water from its pores. When drying, a process called “shrinkage” occurs and is expressed in a decrease in size. wooden product. The amount of shrinkage depends on the type of wood, the direction of the fibers in the product, etc. The main shrinkage occurs across the fibers (according to the thickness and width of your lining). When your lining dries in the installed state to equilibrium moisture, you, in the worst case, risk not only seeing that the lining has come apart in places, but getting gaps between the boards, almost the width of a finger.
The industry uses various technologies for drying wood, differing both in the equipment used and in the characteristics of heat transfer to the dried material.
The classification of types and methods of drying is usually based on heat transfer methods, according to which four wood drying technologies can be distinguished:
- convective drying technology;
- conductive drying technology;
- radiation drying technology;
- electric drying technology;
Each type of drying can also have several varieties depending on the type of drying agent and the characteristics of the equipment used for drying wood. There are also combined technologies for drying wood, in which they simultaneously use different kinds heat transfer (for example, convective-dielectric) or other characteristics are combined various technologies drying wood.
Independent drying technologies
Chamber drying
Chamber drying. This is the main industrial technology drying of wood, carried out in wood drying chambers various designs, where lumber is loaded in stacks. Drying occurs in a gaseous medium (air, flue gases, superheated steam), which transfers heat to the wood by convection. To heat and circulate the drying agent, drying chambers are equipped with heating and circulation devices.
With chamber wood drying technology, the drying time for lumber is relatively short (from tens of hours to several days), the wood dries to any given final moisture content at the required quality, and the drying process can be reliably regulated.
Atmospheric drying
The second most important and widespread method at sawmills is the method of industrial drying of wood, carried out in stacks placed in a special open area (warehouses), washed atmospheric air without heating. The advantage of atmospheric wood drying technology is its relatively low cost. In addition, this method is the most gentle. Disadvantages: seasonality (drying practically stops in winter); long duration; high final humidity. Atmospheric wood drying technology is used mainly for drying lumber at sawmills to transport moisture and at some woodworking enterprises for drying and leveling the initial moisture content of lumber before drying in wood drying chambers.
Drying in liquids
Drying in liquids is carried out in baths filled with a hydrophobic liquid (petrolatum, oil) heated to 105-120 °C. Intensive heat transfer from liquid to wood allows the drying time to be reduced by 3-4 times compared to chamber drying, all other conditions being equal. This method is used in wood preservation technology to reduce its moisture content before impregnation. Attempts to dry lumber in petrolatum at woodworking enterprises have not yielded positive results due to the fact that lumber after such drying does not meet the requirements for wood for furniture and joinery and construction products.
Conductive drying technology
Conductive (contact) wood drying technology is carried out by transferring heat to the material through thermal conductivity upon contact with heated surfaces. It is used in small quantities for drying thin wood materials - veneer, plywood.
Radiation drying
Radiation drying of wood occurs when heat is transferred to the material by radiation from heated bodies. The effectiveness of radiation drying is determined by the flux density of infrared rays and their permeability in solid wet bodies. The intensity of the radiant energy flow weakens as it goes deeper into the material. Wood is a low-permeability material for infrared radiation (penetration depth 3-7 mm), therefore this method is not used for drying lumber. It can be used for drying thin-sheet materials (veneer, plywood), in addition, this method is widely used in the technology of finishing wood products for drying paint coatings. Electric stoves, electric heating elements, gas (flameless) burners, and incandescent lighting lamps with a power of 500 W and above are used as emitters.
Rotary drying
Rotational drying of wood is based on the use of the centrifugal effect, due to which free moisture is removed from the wood when it is rotated in centrifuges. Mechanical removal free moisture is achieved at a centripetal acceleration value of at least 100-500g (g - acceleration free fall). Such accelerations have not yet been achieved in practice due to the difficulty of accurately balancing a centrifuge with a stack; only experimental development of corresponding devices is underway. In well-known industrial rotary dryers centripetal acceleration does not exceed 12g. Under these conditions, mechanical dehydration occurs to a small extent. However, intensification of the drying process in the humidity range above the hygroscopic limit is observed.
When installing a carousel in a drying chamber, the technology for drying lumber is the same as in conventional batch chambers. The duration of drying at the first stage (from the initial moisture content to the hygroscopic limit) is reduced several times depending on the thickness, species and initial moisture content of the wood compared to conventional convective drying under the same conditions. Although rotary dryers are economical and provide high quality drying, industrial use I have not yet found a rotational method for drying lumber.
Vacuum drying
Vacuum drying at reduced pressure in special sealed drying chambers. Due to the complexity of the equipment and the impossibility of obtaining low final moisture content of wood vacuum drying has no independent meaning. It is used in combination with other drying methods and as an auxiliary operation in preparing wood for impregnation.
Dielectric drying
Dielectric drying is the drying of wood in an electromagnetic field of high frequency currents, in which the wood is heated due to dielectric losses. Due to the uniform heating of wood throughout its entire volume, the emergence of a positive temperature gradient and excess pressure inside it, the duration of dielectric drying is tens of times less than convective drying. Due to the complexity of the equipment, high power consumption and insufficient High Quality drying Dielectric drying itself is not widely used.
Combined wood drying technologies
It is more effective to use combined wood drying technologies, for example convective-dielectric and vacuum-dielectric. For mass drying, the use of these methods is uneconomical, but in some cases, especially when drying expensive, critical lumber and blanks made from hard-to-dry wood species, these methods can be used.
Convective-dielectric drying
With a combined convective-dielectric technology for drying wood, high-frequency energy from a special high-frequency generator is also supplied to a stack loaded into a chamber equipped with thermal and fan devices through electrodes located near the stack.
The heat consumption for drying in the drying chamber is mainly compensated by the thermal energy of steam supplied to the heaters, and high-frequency energy is supplied to create a positive temperature difference across the cross section of the material. This difference, depending on the characteristics of the material and the rigidity of the given mode, is 2-5°C. The quality of convective-dielectric drying of lumber is high, since drying is carried out with a small difference in humidity across the thickness of the material.
Vacuum dielectric drying
This is another way of drying wood using high-frequency energy. This technology uses the advantages of both vacuum and dielectric drying. By heating wood in a high-frequency field at reduced pressure, boiling of water in wood is achieved at low wood temperatures, which helps preserve its quality. The movement of moisture in wood during vacuum-dielectric drying of wood is ensured by all the main driving forces moisture transfer: moisture content gradient, temperature, overpressure, which reduces drying time.
During vacuum-dielectric drying, a stack of lumber is placed in an autoclave or a sealed chamber, where a vacuum pump creates a reduced pressure of the environment (1-20 kPa). The lower the environmental pressure, the lower the evaporation temperature of moisture and wood during drying. Heat consumption for drying is provided by the supply of high-frequency energy to the wood. When using this wood drying technology, operational difficulties also arise - the complexity of the equipment, especially the setup and operation of high-frequency generators, and the high energy consumption for drying. Therefore, when deciding on the use of vacuum-dielectric chambers, it is necessary to first develop a feasibility study based on the conditions of a particular enterprise.
Induction or electromagnetic drying of wood
The method is based on the transfer of heat to the material from ferromagnetic elements (steel mesh) stacked between rows of boards. The stack, together with these elements, is in an alternating electromagnetic field of industrial frequency (50 Hz), formed by a solenoid mounted inside drying chamber. Steel elements (mesh) are heated in an electromagnetic field, transferring heat to wood and air. In this case, a combined transfer of heat to the material occurs: by conduction from the contact of heated meshes with wood and convection from circulating air, which is also heated by the meshes.
Wood is a “living” material that changes its properties not only during growth, but for a long time after the log house. Humidity is one of the most important characteristics of wood for its application. This material very susceptible to environmental changes. One of its properties is “breathing” - the absorption and release of gases by the cell walls of the material. By the same principle, these cells absorb and release moisture.
What can influence the moisture content of wood tissues? There are 3 main factors:
Wood species
The time of year in which it was cut down;
Features of the climate.
Let's consider the most commonly used concepts of wood moisture content.
Natural moisture content of wood
This is the level of moisture contained in the tree while sleeping. It is also called "initial moisture". This value is used as a basis for further actions with a batch of material: for example, the drying time and conditions can be calculated. Moisture content may vary under different conditions from 25 to 80%. When determining the natural moisture content of a particular batch wood material we will always mean "humidity under specific conditions".
Equilibrium humidity
When wood is exposed to the same air environment for a long time, without significant changes in air humidity and temperature, the material reaches equilibrium moisture content. This is a state when the process of drying or saturation with moisture under given conditions has stopped, and the percentage of humidity has become constant. It is worth noting that different types of wood under the same conditions achieve almost equal internal moisture levels.
Depending on the different conditions of detention, they distinguish 5 levels of wood moisture content:
Wet– humidity is more than 100%, this state is achieved when long-term storage tree in water.
Freshly cut- moisture level from 50 to 100%.
Air dry– from 15 to 20%. Such indicators are achieved when stored in air; they vary depending on temperature and precipitation.
Room dry– from 8-10%. The moisture level is set during indoor storage.
Absolutely dry– wood with 0% moisture content.
Free and bound moisture
There are 2 types of liquid in wood tissue:
Associated moisture– located inside the cells of the tree.
Free moisture- that which fills the pores and channels of tissues, but has not yet been absorbed by cells.
Wood fiber saturation point
Associated with these two concepts is the so-called fiber saturation point: that percentage of wood moisture content when all free moisture has been removed from it, but bound liquid remains in it.
For different breeds tree this degree is determined from 23 to 31%.
Ash – 23%
Chestnut, Weymouth pine – 25%
Pine, Spruce, Linden – 29%
Beech, larch – 30%
Douglas fir, sequoia – 30.5 -31%
This value is important because the volumes and dimensions of wood change at moisture content from 0% to the saturation point. Once the cells are completely filled with water, the volume of the tree will not increase significantly.
Measuring wood moisture with a moisture meter
Absolute humidity of wood
Let's look at the concepts of absolute and relative humidity.Let's take a wooden block.
Absolute humidity is the ratio of the mass of the internal liquid to the mass of the completely dried bar.
The value is calculated using the formula:
W = (m – m 0) / m 0 x 100,
where, (m) and (m 0) are the mass of the wet and dried bar.
GOST 17231-78 interprets this value simply as “humidity”. But this concept is inconvenient to use in calculations, since the amount of water refers specifically to the dry mass, and not to full weight. As a result, discrepancies arise: for example, 1000 g of wood contains 200 g of moisture, but the absolute humidity is calculated as 25%.
Relative humidity of wood
This is a more convenient concept for calculations, since it reflects the ratio of the mass of the internal liquid to the total mass of the block. The calculation formula is the simplest:
W rel. = m water / m sample x 100.
This formula is used in heating engineering calculations to determine the volume of water evaporated from firewood. According to it, at a humidity of 20%, a 1000-gram bar contains 200 grams of moisture and 800 grams of dry fibers—a completely logical result.
Moisture content of wood species
One of the factors affecting humidity is the type of wood. Due to different fiber structures, some breeds respond instantly to changes external environment, absorb and release water. Others are more stable and very slowly saturated with moisture.
The most actively absorbing moisture species include beech, pear, and kempas.
Oak and merbau are considered stable and resistant to change.
Drier rocks tend to crack when dried. Moderately humid ones, such as oak, are more resistant to such phenomena and change their properties less when conditions change.
When cutting under normal conditions, the moisture content of different types of wood has the following average values:
Wood moisture content for pellet granulation
Pellets and fuel briquettes are valued due to the low level of moisture in the fuel. Its moisture content is 8-12%. With such characteristics, a minimal amount of smoke is produced when burned.
The optimal level of wood moisture for pellet production is 12-14%. Hammer crushers They also work with wood chips up to 65% humidity, but at such humidity it is impossible to grind the material to the required fraction, so grinding occurs in several stages. To bring crushed sawdust to the desired condition, complexes with drying drums are used.
