Empirical Model To Correlate Press Drying Time of Lumber To Process And Material Variables

William T. Simpson, Yi-fu Tang


Loblolly pine lumber was press dried with thickness and platen temperature as variables. Drying times ranged from about 20 to 85 minutes, depending on thickness and platen temperature. The dried lumber was free of collapse and surface and internal checking, although some surface darkening was noted at the highest platen temperature. A heat-transfer-based empirical model that relates press drying time of lumber to certain process and material variables was developed and tested. The potential use of the model is for a segregation system that will group boards of similar drying times so that they can be dried together, thus reducing variability in final moisture content and taking fullest possible advantage of the warp suppression benefits of press drying. The model relates drying time to several board characteristics that can be measured at production line speed so that an immediate grouping decision can be made on each board just before drying. The model predicts the expected consequences of changing the process and material variables and has potential as the base for a segregation system.


Drying;press drying;southern pine;warp

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