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Steaming of Logs for Veneer Production

Steaming of Logs for Veneer Production

Topics

  • Advantages of Steaming
  • Schedules

    Advantages of Steaming

    The degree of log preparation required depends on species, and frequently within a given species(Baldwin 1981). On the presence of knots, grain, and other irregularities. Generally, logs are stored in as great a length as possible to avoid losses from cracks at the ends, and stemming should be completed on whole logs where feasible. From the storage yard logs are debarked, usually by ring barkers, cross cut to length if necessary, and then heated in steam or hot water vats.

    Heating has the following beneficial effects on veneer production;

    1. The veneer log is temporally softened making it more plastic, pliable and more readily peeled.

    2. The quality and quantity of veneer recovered from heated logs is greater.

    3. Smoother veneer is produced from heated logs thereby decreasing adhesive consumption during gluing.

    4. Knife wear and power consumption during peeling are reduced.

    5. The severity of knife checks in the veneer are reduced.
    The temperatures and heating used with veneer logs depend on log size and species. Sorting logs into classes prior to heating can reduce variability of log temperature within batches of logs.

    Schedules

    Schedules both in terms of temperature and of time depends on species, size, density and figure variation. For conditioning prior to rotary peeling, Big River Timbers use the following treatment; water temperature of 35 degrees Celsius and heating times 15 to 16 hours for softwoods, and approximately 13 hours for Australian hardwoods which are heated at 100 degrees Celsius. The target temperature for the core of the log is usually around 35 degrees Celsius.

    Steaming is the preferred method for peeler logs from the standpoint of speed, safety of personnel and log buoyancy. Steaming of slicer flitches is carried out, with great care, with heating times of up to seven days.

    After the steaming period the log is removed whilst hot, and placed on a chain conveyor which leads to the lathe.

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