Moisture content control is critical in
the manufacturing of consistent high quality Oriented Strand
Board. The mat moisture content and its distribution influence
the consolidation of the OSB panel in the Press. If moisture
levels are too high, the resin will not bind sufficiently
to the wood and de-lamination will occur. At very low moisture
levels, uneconomic usage of expensive resins results. In addition,
over drying is undesirable due to increased fuel costs, increased
fines, greater wastage, and potential for flash fires.
Logs are slashed, soaked, then debarked, prior to being cut
into strands ranging from 3.5” to 6” in length,
and 1” in width then stored in wet bins. The strands
are then dried, screened, and blended with a binder and wax,
before entering the Former where the mats are laid down. OSB
consists of 3 or more layered mats, strands are aligned longitudinally
within the surface layers, and are crossed or randomly aligned
within the Inner Layers. The mats are converted to panels
under high pressure and temperatures within the Press.
Measurements are made at all or some of the following locations;
On the green wood before it enters
the dryer, for example through a viewing window in
the side of a storage bin. This provides information on the
dryer load and enables feed forward control of the dryer.
*Post dryer, on the weigh belt
prior to the Blender. The measurement at this location
is not easy owing to non-equilibration of the product. It
is often used as an indicator of moisture level rather than
an absolute moisture measurement, the aim being to narrow
the final strand moisture content through tighter dryer control.
At the exit of the Blender
On the Forming line
Processes vary. Correspondingly, there is a variety of options
available for mounting the gauge. The sensor can be mounted
8” from a continuous flow of product on a conveyor belt,
and can also be located looking into a gravity chute or bin,
through a viewing window, or insertion probe.