Wood drying common defects and prevention method

There many ways to dry wood,wood dry kiln is one of them .Many defects that occur during drying result. From the shrinkage of wood as it dries. In particular, the defects result from uneven shrinkage in the different directions of a board (radial, tangential, or longitudinal) or between different parts of a board, such as the shell and core. Rupture of wood tissue is one category of drying defects associated with shrinkage. Today we will talk about the wood drying common defects and solutions.

Wood drying common defects ：

Surface rupture are failures that usually occur in the wood rays on the flat sawn faces of boards They occur because drying stresses exceed the tensile strength of the wood perpendicular to the grain, and they are caused by tension stresses that develop in the outer part, or shell, of boards as they dry. Surface checks can also occur in resin ducts and mineral streaks. They rarely appear on the edges of flat sawn boards 6/4 or lees in thickness but do appear on the edges of thicker flat sawn or quarter sawn boards. Surface checks usually occur early in drying,but in some softwoods the danger persists beyond the initial stages of drying. They develop because the lumber surfaces get too dry too quickly as .a result of relative humidity that is too low. Surface checks can also develop during air drying. Thick, wide, flat sawn lumber is more susceptible to surface checking than thin,narrow lumber.

End rupture like surface rupture, usually occur in the wood rays, but on end-grain surfaces.They also occur in the early stages of drying and can be minimized by using high relative humidity or by end coating. End checks occur because moisture moves much faster in the longitudinal direction than in either trans verse direction. Therefore, the ends of boards dry faster than the middle and stresses develop at the ends. End checked lumber should not be wetted or exposed to high relative humidity before any further drying, or the checks may be driven further into the board.

Prevention method:

When loading pile, press timber pile tip gutter as close to the upper and lower ends of the alignment; When loading kiln, wood pile and the wood pile should close to the ends as possible to prevent the air from between the wood piles neutral short circui. in order to avoid excessive drying ends; plank ends in paraffin oil or thick paint brush, it can impede water evaporation from the end; prone to end crack for hardwood timber or thick, it often use soft drying process as far as possible and pay attention to timely humidity treatment.