Methods of drying wood for transport boxes
Wood is unique for its strength, lightness, insulation and flexibility. It is widely used in construction, furniture making, paper making and many other areas. However, when a tree is felled, it usually has a high moisture content, which makes it unstable and unsuitable for many applications.
Drying is the process by which wood is gradually dehydrated to reduce its moisture content to an acceptable level for a particular application. As a result, it becomes more stable, less prone to shrinkage, cracking and deformation.
We distinguish between the three most popular drying methods – air, chamber and pressure-vacuum. In this article we will discuss each of them and focus on their advantages and disadvantages. Finally, we will describe the method used at Danpol to produce our products, which is stricter than the standard accepted standards in order to achieve the highest quality products.
Advantages of drying wood
Drying reduces the moisture content, which makes the wood more stable and less susceptible to deformations such as shrinking, cracking or twisting. It also allows its mechanical properties to be adjusted. It enables the hardness, strength and elasticity of the wood to be adapted in a controlled way to specific requirements, and also reduces its weight. This allows the wood to retain its dimensions and shape, which is crucial in the construction and manufacture of wooden products such as transport crates.
The high moisture content of wood encourages the growth of mould, fungi and bacteria, which can lead to wood decay and reduce its quality. Wood also contains nutrients such as carbohydrates, which are necessary for their growth and reproduction. Drying removes the moisture necessary for the growth of these micro-organisms and cuts them off from food.
The high moisture content and availability of nutrients attract not only micro-organisms, but also a wide range of insects that penetrate it through its surface by gnawing, digging tunnels, or creating entrance holes. Once the insects get inside the wood, they settle there and start feeding which leads to their reproduction and spread. They mainly feed on cellulose hemicellulose and lingnine, which leads to j degradation of the wood. Dried wood deprives them of this opportunity, making it unattractive to insects.
Wood drying process
Drying wood is a key step in transforming raw wood into a durable and useful material. It aims to reduce the moisture content of the wood to an acceptable level, which is usually below 20%. There are several different methods of seasoning, each with its own advantages and disadvantages, as we will discuss briefly below.
Air drying (seasoning)
This is the traditional method of drying, which involves leaving the wood outside, exposed to the weather. The time it takes depends on several factors such as the type of wood, its thickness and climatic conditions. The process usually takes from several months to several years. Although it is the oldest drying technique, it is still used in many parts of the world.
Chamber drying is a more advanced method of drying wood that is widely used in the timber industry. The wood is placed in a special drying chamber where parameters such as temperature, humidity and air circulation are controlled. The water in the wood is removed gradually by heating and air circulation. This method is effective and provides precise control over the drying process, making it widely used where precision and high quality wood are crucial.
Pressure-vacuum drying is an advanced wood drying technology that uses controlled changes in pressure and vacuum to remove moisture from wood. It is one of the fastest and most precise drying methods.
Wood drying at Danpol
Danpol is a company with a long tradition in the production of wooden packaging, transport boxes and pallets. We provide our customers with products of the highest quality, which is guaranteed by subjecting wood to thermal treatment in accordance with IPPC requirements.
Our main tool in the drying process is a chamber dryer, which allows us to achieve the appropriate moisture content of the raw material we use for timber production. At Danpol, we regularly improve the wood drying process in order to meet the strict phytosanitary standards in the ISPM-15 standard.
IPPC certificate and ISPM-15 standard
The ISPM-15 standard is a regulation developed by the International Plant Protection Organisation, which specifies the requirements for the treatment of wood for the creation of wood packaging to transport goods through various countries. Above all, the application of the ISPM-15 standard is intended to prevent the spread of diseases and wood-dwelling insects that are a potential threat to the biota of other environments.
The IPPC certificate is issued for timber that meets the ISPM-15 standard. All pallets and sawn timber that have undergone heat treatment are marked with the IPPC mark with additional symbols indicating the identification code of the operator responsible for the fumigation process, the name of the country, the certification number and, if the timber has undergone suitable heat treatment, it will be marked with the HT symbol.
The ISPM-15 standard assumes that proper drying of the wood in the drying chamber takes place when the wood reaches a temperature of 56°C and this is maintained for a minimum of 30min. This is a key part of the drying process, as this temperature allows potential pests and fungi that may be in the wood to be destroyed.
Longer drying time for perfect results
Although the temperatures in our drying chambers are equal to those required and the thermal treatment maintains the time specified in the ISPM-15 standard, at Danpol we leave the thermally treated timber in our chambers for a longer period of time in order to achieve a better drying effect, thereby eliminating the risk of damp areas forming inside the raw material.