Operation
Conditioning Process
Operation
WMDKdoc020322
4-12
4
4.9
Conditioning Process
We refer to the conditioning process as the point where the exhaust valve is totally shut.
At that point, core moisture migrates to the exterior of the board and to the surrounding air
inside the chamber. This moist air is not allowed to be vented out of the chamber and now
acts as our conditioning agent, and therefore continues to be circulated throughout the
timber. Any stress due to casehardening is then relieved by this circulating moist air.
1.
When the 11° depression is achieved and the exhaust vent closed, the conditioning
process should be maintained for at least 24 hours. The following day, expect a drop in
the depression. By relieving the core moisture and not allowing venting to occur, the
relative humidity in the chamber will go up, which will reduce the depression reading. How
much will depend on the severity of the stress or casehardening.
2.
If the depression drops from 11° to 8° in 24 hours, the timber has equalized to
approximately 10%.
3.
It is important to maintain these conditions (exhaust closed and kiln running), for at least
another 4 hours to make sure the depression has bottomed out.
4.
If after 4 hours you still maintain an 8° depression or higher, your charge is fully
conditioned and dried to approximately 10% MC. If not, go to step 5.
5.
If after 24 hours of conditioning, the depression dropped below 8°, then that would
indicate that more moisture should be vented from the chamber. It also indicates that the
drying process has been too rapid at some time during the drying cycle and changes in
exhaust settings should be made for like material in future charges.
6.
Opening the exhaust to 5% will vent this extra moisture slowly. The depression will then
increase and must do so back up to 11°. Closing the exhaust again for 24 hours and
repeating the conditioning process (steps 1 to 4) is then required.
NOTE:
CONDITIONING - A good "rule of thumb" to follow is to condition at least one (1)
hour for every one (1) day the kiln has run, but never less than six (6) hours.
Always remember, longer conditioning cycles never hurt, but always help maintain stress
free timber.
