There is not a single timber company that is able to dispense with the procedure of drying wood.To prevent the occurrence of various defects common to use special technology of drying wood in the drying chamber.If you yourself want to be engaged in manufacture of wood products, you also need a drying chamber for drying wood.Today we will discuss how to do it.
- necessity of drying wood
- concept wood moisture
- wood drying kiln concept
- Types dryers
- wood drying kiln Manufacturing
The need for wood drying
How efficiently and quickly dry the board?This question interests of every carpenter since ancient times.People have long been engaged in the storage of wood for many years, to have time to dry it evenly.Grandfather had stored wood for his grandson, using the material itself, which left him by his grandfather.
importance of properly dried wood - is enormous!For example, if wooden furniture, which is in th
If the door to the house is made of wood too overdried, it swells with time, and can not be closed!If the panels are recruited from the door blanks that are unevenly dried by volume, it may explode or her offended!Therefore, all the bars of wood drying is recommended.Also drying material protects against attack by wood fungus, warning and razmero- formoizmenyaemost wood improves the physical and mechanical properties of wood.
Wood drying is a long, complex and expensive procedure.Tree by traditional technologies heated with superheated steam or hot air.Dried wood can be transported and stored longer.Moreover, during the operation it does not deform.Drying boards produced in the steam chamber where is a possibility of an internal fault.
concept wood moisture
For a complete perception of the essence of the drying process is a bit of a dip in theory.Procedure for removing moisture from the wood is not quite simple, because in the material there are two types of moisture.Timber consists of plant cells elongated shape.Moisture may be present in the cell walls and cavities in their filling mikrokapilyarnuyu system.The moisture that is present in the spaces between the cells and their cavities, called free intercellular and moisture in the cell walls - related intracellular.
content of the wood bound moisture is limited.Condition, when the cell walls are different maximum humidity, in contact with liquid water, is called the limit of saturation.It is believed that the moisture saturation does not depend on the breed and the average is 30%.If the moisture content of wood above 30%, it contains free intercellular moisture.Wood or fresh, just growing tree has a moisture content greater saturation, ie it is raw.
depending on the destination of the pieces of wood, dry wood made in different ways.The wood is dried to a moisture content of 6 - 8%, when the material is required for the machining and assembly of high-precision products responsible for compounds that affect the operating characteristics (manufacture of skis, parquet or musical instruments).
transport humidity is 18 - 22%.It is with such a water content of timber is suitable for long distance transportation in the warm season.Dried to a moisture content of wood is mainly used in standard housing construction, the production of an ordinary container and when there is no need interchangeability during assembly.
Joiner humidity is divided into several subspecies.Moulded products (decking, siding, flooring, cashing) must have a moisture content of 15 ± 2%.Wood products (windows, doors, stairs and interior elements) made of solid or laminated wood, can withstand fluctuations in moisture from 8 to 15%.
Humidity furniture, regardless of how the product and the use of solid or laminated wood is 8 ± 2%, because it is at such humidity tree shows the most optimum characteristics for processing, bonding and subsequent operation.But usually taken to lower the moisture content of 7-10%, making partial sterilization timber and taking into account the uniformity of moisture around the tree, preserving the mechanical properties of the material, the lack of surface and internal cracks.
Modes wood drying
depending on the requirements that apply to the quality of wood, lumber can be dried in different modes, which are different temperature levels.The mini drying chamber for drying the wood during the steps of gradually increasing temperature and decreasing the relative humidity of the agent.Drying mode is selected based on the thickness of the timber, wood, final moisture, quality category being dried wood and chamber design.
There are modes of low- and high-temperature process.The first mode provides the use of moist air as a drying agent, the temperature is in the initial stage is less than 100 degrees.Established three categories of these modes:
- Soft mode is able to provide a defect-free drying of the material while maintaining the natural physical and mechanical properties of wood, including color and strength, which is important to dry the wood to transport humidity export lumber.
- Normal mode ensures defect-free drying of the wood with an almost complete preservation of strength material with a slight discoloration that resembles drying lumber to a final moisture content.
- Forced mode preserves the strength of a static bending, compression and tension, but there may be some reduction in strength at cracking or chipping with a darkening of the wood that is used for drying wood to operational humidity.
low-temperature mode provides a three-step change in the parameters of the drying agent, and with each step the subsequent transition can be carried out only after reaching a certain level of humidity of the material that is provided on the regime.
High regimes provide a two-stage change in the parameters of the drying agent, and move from the first stage to the second timber is possible after the transition moisture content of 20%.High temperature mode is determined depending on the thickness of lumber and rocks.High temperature regimes can be used for drying wood, which is used to make non-bearing elements of buildings and structures, which allowed reduction in the darkening wood and strength.
kiln drying chamber is the main method of drying wood.Drying chambers are required for drying of softwood and hardwood to the different categories of quality.One of the most popular and cost-effective methods of artificial drainage is drying lumber when the output of wood and connected via a free moisture supply to the wet wood heat hot air and ash vaporized excess moisture moisturize and partially cooled air.
drying chamber is a completely finished plant that is equipped with everything needed for a wood drying equipment.According to the device for wood drying chambers are divided into ready-made of metal and building materials.Last constructed directly on the shop floor or as individual building materials that are widely used in industry.The camera can be completely made of reinforced concrete.Its walls can be laid out corpulent red brick, and floors - reinforced concrete.
If multiple dryers, they are often combined into a single unit, building a common corridor management, which houses the wiring and heating system of automatic control of all cameras.Depending on the volume of timber loaded in the camera, can be vertical or horizontal-lateral air circulation.
Loading lumber in the camera can be carried out the following ways: on trolleys in the form of stacks of rail track, the packages forklift.The transfer of heat to the wood can be carried out: air, combustion products, or superheated steam;radiant heat, which comes from the special emitters;solid if arrange contact with a heated surface;current that passes through the wet wood;high-frequency electromagnetic field, which penetrates the damp wood.
equipment for wood drying chamber is divided into primary and secondary.To rank the main fan system, heating system, ventilation and humidification, further relates to a door insulated and psychrometric block podshtabelnye carts, electric fan drive.
wood drying process control in the chamber can be automated.Automation is able to maintain a predetermined level of humidity and temperature of the medium in the dryer.The temperature regulates the flow of coolant in the radiator or through the on-off electric heater and the humidity - through the use of ventilation and humidification system.
In wood drying system control may be capable of remote control humidity and temperature in the chamber.When drying lumber in the drying chamber is necessary to control humidity of wood, which is used for remote moisture meter, which allows you to check the moisture content of wood in several places, without going into the camera.In the absence of external sources of heat to the dryer can be used stand-alone heating module and use gas, coal, wood waste, electricity and diesel fuel.
In real life, made use of the following types of kilns.The necessary energy to convective drying chambers in the material is conveyed by means of air circulation and heat transfer occurs by convection wood.Convective cameras are of two types - the tunnel and chamber.
Tunnel convection drying chambers are deep chambers, where the pack pushed piles of wet end to the drier.These cameras have to fill out one end, and on the other - are emptied.Pushing the stacks (the process of filling and emptying chamber) is made of one stack with an interval of 4 - 12 hours.These cameras are designed for large sawmills and enables to perform exclusively the transport of wood drying.
Chamber convection drying chamber shorter tunnel and vacuum drying chambers for wood, in the process throughout the chamber supported the same parameters.With a depth of ventilation by more than 2 meters to equalize conditions of wood drying technique used reversatsii direction ventilation.Emptying and filling of the chamber occurs on the one hand, if it has one door.Known and other loading systems that are similar to the procedure for loading of tunnel chambers.Drying can be any timber before any final moisture content, so 90% of the wood in Europe and Russia is dried in a dryer chamber.
condensation drying chamber is different from previous ones in that humidity, which occurs in the air condenses on the special coolers and out of the drying process the water.The efficiency of this process, a large, but the cycle is long, because the devices do not work with high temperature, as well as significant total heat loss.The condensation chamber is suitable mainly for small amounts of drying wood, or drying of dense wood species - oak, beech or ash.The great advantage of these cameras that do not need a boiler, the price of the drying chamber for wood drying, and the cost of less.
Dryers are also classified by the method used and the nature of the circulation of the drying agent, the type of fence and the principle of action.Kilns batch are characterized in that they can be fully loaded to simultaneously dry all the material, and the mode changes in the wood drying time currently remaining the same for all chambers.
By way of circulation are cameras with incentive and natural circulation.Dryers with natural circulation - antiquated, inefficient, drying mode in which almost do not control, uniformity of drying wood is unsatisfactory.For a modern building such devices are not recommended, as the mandatory to be modernized.There are by the nature of the drying agent chamber gas, air and high temperature, which operate in an environment of superheated steam.
procedure for drying wood
Pre-drying prior to the chosen mode of wood is heated with steam, which is fed through a tube humidification, with fan included heaters and exhaust ducts closed.First you need to calculate the drying chamber for wood.The temperature of the agent at the beginning of heating wood to be 5 degrees above the first step mode, but not more than 100 degrees Celsius.The level of saturation of the medium has to be for the material with an initial moisture content greater than 25% 0.98 - 1, and the wood with a moisture content of less than 25% - 0.9 - 0.92.
duration of the initial warm-up depends on the wood and makes for softwood (pine, spruce, fir and cedar) 1 - 1.5 hours per centimeter of thickness.The duration of the warm soft hardwood (aspen, birch, linden, poplar, alder) increased by 25% and for hardwood (maple, oak, ash, hornbeam, beech) - by 50% over the duration of the warm softwood.
After preheating decided to bring the parameters of the drying agent, the drying up of the first stage of the regime.Then you can start drying lumber subject to the established regime.Humidity and temperature control valves in the steam lines and dampers sugary-suction channels.
In operation, infrared drying chambers for wood in the tree having residual stresses, which can eliminate the intermediate and final Moist environment of increased temperature and humidity.Processing received expose timber which is dried to humidity and operational be machined subsequently.
Interim Moist committed during the transition from the second to the third stage, or from first to second when the high temperature mode.Moist subjected coniferous thickness of 60 mm and a thickness of 30 deciduous millimeters.The temperature of the medium during teplovlagoobrabotki should be above 8 degrees temperature of the second stage but no higher than 100 degrees and the saturation level of 0.95 - 0.97.
When the timber reaches the final average moisture content can be carried out end Moist.This process maintains the ambient temperature at 8 degrees above the last stage but no higher than 100 degrees.Upon completion of the final wood Moist elapsed drying, to survive in the cells for 2 - 3 hours at parameters that provide the last stage of treatment.Then, the drying chamber is stopped.
If you decide to make his own wood products, the drying chamber for wood you just need.However, during the construction of dryers comply with all required standards.You will need a camera, fan, heater and heater.
Line up the dryer, or allocate a separate room, one wall and the ceiling which will be made of concrete and other wall - made of wood, you need to insulate.