Chapter 4
I Management Of Native Forests
II Plantations-high Productivity Resources
III Protecting The Resource
IV Harvesting The Resource
V Solid Wood And Its Processing
i Sawmilling
ii Drying
iii Preservation
iv Quality and standards
VI Minor Forest Products
VII Reconstituted Wood Products
VIII Pulp And Paper
IX Export Woodchips
X Future Directions
XI Acknowledgements
References
Index
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Drying (continued)
Compared with the eucalypts the kiln-drying of sawn plantation pine is relatively simple. Problems do arise, however, with wood from young trees, as this often shows a tendency to spring, twist and bow. To prevent this behaviour high temperature drying with top weighting of the stacks was developed in the late 1960s by Christensen of CSIRO.[52] In the process sawn timber is stacked under heavy restraint, pre-steamed, then dried at 120-150°C to about 10 per cent moisture content and finally conditioned. The resultant product is free of the distortion that is generally observed when juvenile pine is dried in the conventional manner. The improved product is said to be due to the softening of the lignin in the wood which enables internal stress redistribution to take place during the drying. The process allows some plantation thinnings to be used to produce building timber instead of lower value products, as well as a much higher production rate than conventional drying. Following developmental work which also involved the wood technology groups of the Queensland and NSW forest services the technique was successfully introduced to the industry in the early 1970s by adapting existing kilns and in 1973 a specially designed high temperature kiln was commissioned at Australian Forest Industries, Myrtleford, Vic.. Since then the technology has become widely used. In 1985 its application was extended to eucalypt drying in some Tasmanian mills.[53]Finally mention should be made of the introduction of solar drying in Queensland, where since 1979 three relatively small kilns based on the glasshouse principle have been installed and are satisfactorily drying slash pine, first air dried to 20-25 per cent, down to moisture contents of around 12 per cent.[54]
Organisations in Australian Science at Work - Australian Forest Industries, Myrtleford; CSIRO Division of Forest Products; Forests Commission of Victoria
People in Bright Sparcs - Christensen, F. J.
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Australian Academy of Technological Sciences and Engineering |  |
© 1988 Print Edition page 221, Online Edition 2000
Published by Australian Science and Technology Heritage Centre, using the Web Academic Resource Publisher
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