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Common Knowledge of Wood Drying

Feb. 11, 2020

Today Hot Press Machine China Exporter will introduce the common knowledge of wood drying.

 

1. What is wood drying?

Wood contains a certain amount of water. The amount of water in the wood varies depending on the species, age, and harvesting season. In order to ensure the quality and extend the service life of wood and wood products, appropriate measures must be taken to reduce the moisture (water content) in the wood to a certain degree. To reduce the moisture content of wood, it is necessary to increase the temperature of the wood so that the water in the wood evaporates and moves outward. In the air at a certain flow rate, the water quickly leaves the wood for drying. In order to ensure the quality of the dried wood, the humidity of the drying medium (such as the currently used humid air) must be controlled to obtain the effect of drying the wood quickly and with high quality. This process is called wood drying. The above method is also called convection drying because it uses a convection heat transfer method to dry the wood from the outside. In general, wood drying is the process by which water is discharged from the wood by evaporation or vaporization.

 

2. What is the significance of wood drying?

Wood has lower density and greater strength (higher coefficient of quality), resistance to acid and alkali corrosion, good insulation properties, easy cutting, beautiful texture and color. In the construction, machinery, vehicles, ships, textiles, agricultural tools, furniture, musical instruments, aviation and other parts of the national economy need to use a large amount of wood. However, the quality of products made from undried wood cannot guarantee the quality, so the wood must be dried. For example, the common equipment for drying plywood is Veneer Dryer.


 Veneer Dryer


Veneer Dryer


After the wood is dried, the following effects can be achieved.

(1) Improve the stability of wood and wood products. The long-term exposure of wood to air will cause swelling and shrinkage, and uneven wood swelling and shrinkage will often cause the wood to crack and deform, affecting use and causing waste. If you use wet wood or not-dried wood to make products (such as doors and windows, flooring, furniture, etc.), it seems to be good when you have just finished it. Warping, loose joints or cracking of the board surface cause great losses. If the production unit dries the wood to the required moisture content before use, it can ensure the stability of the wood product structure, make the appearance beautiful and durable.

 

(2) Improve the strength of wood and wooden parts. When the moisture content of the wood is lower than the fiber and saturation point, the strength of the wood will increase as the moisture content of the wood decreases. The dried wood can improve the cutting conditions, the strength of wood structural parts, the bonding strength and the surface decoration quality of wood products. The thermal and electrical properties of wood change with its water content. To improve the thermal insulation and insulation of wood, it is also necessary to reduce the water content to reduce thermal and electrical conductivity.

 

(3) Prevent the degradation and decay of wood. If wet wood is stored in open air for a long time, it will often decay or be damaged by insects if proper measures are not taken. When the moisture content of the wood is reduced below 20%, the invasion and destruction of fungi and pests can be greatly reduced. Therefore, generally in the production unit, the wood is dried to a moisture content of about 8-15%. This not only ensures the inherent properties and strength of the wood, but also improves the corrosion resistance of the wood.

 

(4) Reduce the weight of wood. The water content of newly felled wood even exceeds its own weight. After short-term storage and natural drying, its water content is still very high. After the wood is dried in the room, its weight can be reduced by about 30-50%, which is conducive to improving the carrying capacity of the vehicle. In short, dried wood can ensure the quality of wood products, improve the performance of wood, and extend the service life, thereby saving wood. Practice over the years has proven that wood drying is an indispensable process in production and has become a specialized discipline in science.


The above is the common knowledge of wood drying introduced by Hot Press Machine Supplier.

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