Optimisation of an accelerated drying schedule for regrowth eucalyptus pilularis Sm

Measurements of strain gradients, sets, moisture gradients, and length, width and depth of checks were made during the kiln drying from green of 100×50 mm backsawn Eucalyptus pilularism Sm. Two conventional kiln runs established the likely limits for relative humidity and temperature necessary to produce timber complying with the requirements of “Appearance Structural Grade No. 1” in Australian Standard (AS) 2082–1979. These limits were then used to develop an accelerated schedule. In the first trial of an accelerated schedule, the timber dried in half the time of the control (conventional) run, but deep face checks and unacceptable internal checks developed. The second trial of an accelerated schedule dried timber in 63% of the time of the conventional schedule for the same level of degrade. Energy consumption and severity of collapse are likely to be reduced using the accelerated schedule. The initiation of very small internal checks in some boards just prior to reconditioning suggests that this schedule is the most severe that can be used to accelerate the drying of this timber without causing down-grading of the quality under AS 2082–1979. Using a similar methodology and sequence of kiln runs, it should be possible to optimise an accelerated drying schedule for any species and thickness, once the acceptable levels of surface and internal checking have been defined.