The purpose of debarking

In the sawmill industry, logs are debarked before sawing. This way the timber and chips created as by-products of sawing can be kept free of bark.

The purpose of debarking is to break the vascular cambium layer between the bark and xylem and to remove the bark from the xylem.

Placing

At sawmills, debarkers are placed either by the infeed unit or at the beginning of the log sorting line before the timber is sorted according to diameter. In the Nordic countries, Russia and North America, the debarker is usually integrated into the sawline, whereas most sawmills in Central and Southern Europe position it in the log sorting line.

When the debarker is integrated in the sawline, the debarker must function reliably, as the entire line process is dependent on it.

When the debarker is integrated into the sawline:

1. The trunks can be fed into the sawline clean, which reduces blade maintenance costs.
2. Integration enables optimisation of the debarking speed according to size, as timber is often sorted by dimension.
3. Small log grades can be debarked faster than the bigger grades.
4. Myös puiden syöttäminen kuorimakoneeseen pää-päässä ilman tukkiväliä on toteutettavissa helpommin sahalinjassa, kun tukit tulevat pääsääntöisesti saman kokoisina. Tukkien pää-päässä -syöttämisellä on merkittävä vaikutus roottorikuorinnassa tukin päihin helposti syntyvien vaurioiden vähentämiselle, etenkin suurilla nopeuksilla kuorittaessa.
5. It is also easier to feed timber into the debarker log-to-log without spaces in a sawline where logs are usually the same size. Feeding logs log-to-log is significant for reducing damage to the ends of logs, which is typical for rotor debarking, especially when using high speeds.
6. The bark protects the timber for as long as possible prior to sawing. The bark slows down the drying process in warm weather and protects the surface of the timber from damage caused by loaders.
   

 Reasons for placing a debarker in the log sorting line:

1. The better yield that comes as a result of more accurate log measurement. In the log sorting line, the log is always debarked before measuring, so there is no need to estimate bark percentage. Instead, measurements are always correct.
2. The positioning of the debarker also depends on the pricing method used in the relevant market. For example, in Central Europe sawmills only pay for actual wood with the bark not included, which makes it sensible to debark the timber before the measurement that defines the payment.
3.  The sawmill’s capacity requirement. The operating time of the debarker can easily be adjusted at the log yard and so ensure a sufficient supply of debarked timber for the sawmill.