Operation
Preconditioning For Well Air Dried Stock
4
4-11
WMDKdoc020322
Operation
4.8
Preconditioning For Well Air Dried Stock
For customers who are drying well air-dried stock, i.e. less than 25% MC a
preconditioning cycle is advised. This will help to de-stress the timber before the kiln
drying process begins.
There can be as much as an 8% to 10% moisture gradient in well air-dried stock. In the
schedules section of this manual, SCHEDULE #8 is the recommended step for this
preconditioning cycle.
Preconditioning will cause a high humidity condition inside the chamber. Condensation
may occur on the floor. This is natural and nothing to worry about. Once the process has
begun, and at least a 1.5 to 3 degree depression is reached, venting at a rate 1/2 of what
the normal schedule for the species calls for can begin.
EXAMPLE:
Schedule #3 for 8m
3
of 24mm Oak
Set vent only at a setting of 10% (1/2 of the normal 20). Run that entire schedule at 10%
instead of the 20% for green Oak.
See Table 4-1.
The preconditioning cycle for schedule #8 for well air dried timber with
less than 25% MC is shown below.
Thickness
Time
24mm
12 to 24 hours
0
44
32mm
24 to 36 hours
0
44
38mm
36 to 48 hours
0
44
50mm
48 to 72 hours
0
44
TABLE 4-1
