The main function of the drying kiln － control the temperature, humidity, and ventilate.
The humidity control system prevent the timber of transforming and cracking.The fan system confirm the cycling of airflow and drying the timber uniformity. The humidity will keep same for the surface or inner of the timber after drying.
It is hard to control the circulation of airflow and the moisture when using the hot air heat the usual timber in stove.And it is complicated to gain the high quality drying products by this stove.
3.Which is important?Equipment or the Technology?
The superior equipment is the foundation of drying process, and the technology is the key of link during the drying. The working lasted for days to weeks, so it is important to regulate the temperature and the humidity. To use the technology in a correct way could keep the quality and confirm saving the energy and time of timber. Instead, the wrong way will distribute the moisture in timber unevenly, then lead to the poor quality or even damage. The equipment is closely bound up with the technology.
The humidity of timber is a part of the most important parameter of monitoring by instrument during the drying process. When the humidity is higher than the standard, it must set up the lower temperature and higher humidity, the process could be in balance as the humidity contain 30%.
The humidity must keep in balance when it was different of timber in the kiln.
4.How to measure the humidity?
There is a relation scale between the humidity and the absolute drying of timber.
Moisture content of timber = (Wet timber's weight－Absolute drying timber's weight)/Absolute drying timber's weight*100%
The moisture content using in the drying technology is called absolute humidity.
The absolute drying timber is the weight of timber without any moisture.
The way to measure the quality of absolute drying timber:
1.Cutting off 300mm after drying the samples.
2.Keep 10~12mm thickness of the samples.
3.The timber must be completely polished and with no knurr, rot or any other defects.
b.The weight distribution correct to 0.01g.
c.Method:Keep the temperature in 103±2℃ when drying the timber in kiln, measure the quality each 2 hours. If there's no qualitative change in 4 hours, then the timber is absolutely drying.
The initial water content: the moisture content before drying wood.
Final moisture content: Humidity level after drying wood, it is unchanged in any case.
The balance of calculating air humidity and relative humidity
a. The air relative humidity is 30-80% in a standard humidity. The follow calculating equation is for calculating Humidity about balance:
Moisture equilibrium=relative air humidity/5
b. the wood neither absorb nor release water in determining the relative humidity. In dry process reach moisture balance, depends on the Wood species、the initial water content and the height of the timber.