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Holz als Roh- und Werkstoff

, Volume 49, Issue 4, pp 153–159 | Cite as

Optimisation of an accelerated drying schedule for regrowth eucalyptus pilularis Sm

  • P. N. Alexiou
Forschung und Praxis

Abstract

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.

Keywords

Moisture Content Equilibrium Moisture Content Moisture Gradient Fibre Saturation Point Average Moisture Content 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Zusammenfassung

Während der Trocknung von waldfrisch eingeschnittenem Eukalyptusholz wurden Spannungsgradienten, Verwerfung, Feuchteverlauf und die Dimensionen der Trocknungsrisse gemessen. Aus zwei konventionellen Trocknungsläufen ergaben sich die Randbedingungen, un den Anforderungen des Australischen Standard (AS) 2082–1979 zu entsprechen. Auf deren Grundlage wurde ein beschleunigtes Trocknungsprogramm entwickelt. Eine Halbierung der Trocknungszeit war nicht möglich, weil dies zu einer unvertretbaren Rißbildung an der Oberfläche und im Innern der Bretter führte. Dagegen gelang es, die Trocknungszeit auf 63% einer konventionellen Trocknung bei gleichem Schädigungsgrad zu verkürzen. Energieverbrauch und Ausmaß der Trocknungsschäden können wahrscheinlich noch weiter herabgesetzt werden. Die Ausbildung sehr kleiner innerer Spannungsrisse in cinigen Brettern kurz vor Beginn der Konditionierung deutet darauf hin, daß diese Trocknungsbedingungen die oberste Grenze darstellen, um die Qualitätsansprüche des AS 2082–1979 für diese Holzart nicht zu unterschreiten. Mit ähnlichen Methoden sollte es möglich sein, ein beschleunigtes Trocknungsprogramm für jede Holzart und beliebige Dimensionen des Schnittholzes für die zulässigen Qualitätsgrenzwerte zu optimieren.

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Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • P. N. Alexiou
    • 1
  1. 1.Forestry Commission of New South WalesBeecroftAustralia

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