Bin Sort vs. Kiln Capacity

[TimothyD]

I am interested in any methods being used to provide "pseudo-sorting."  We know it can many times be very beneficial to provide pre-sorting of packages that go to make up a particular charge¹.  However, many times, even though there is available kiln capacity, there may not be sorting bin capacity to match.  For instance, some mills use a wet density measurement system^2,3 to provide green bin sorting into 2 or 3 different wet density ranges, maximizing charge driability across the spectrum.  For those mills who do not have actual bin sort capacity or the inline equipment to do so, are any other methods of "pseudo-sorting" being employed?

1. http://www.thefreelibrary.com/A+method+for+optimizing+lumber+sorting+before+kiln-drying.-a0212326862
2. http://www.wagnermeters.com/lds200.php
3. http://www.timberlinemag.com/articledatabase/view.asp?articleID=1999

[fbushaw]

We do sort our WF at the sawmill into 2 sorts, Heart & Sap. We have an NMI setup in the mill that sorts by moisture content. We still get alot of under dry in our WF. Does anyone think adding another sort or 2 would help with this problem? For example have a super heart, heart, sap, and super sap??

[TimothyD]

Hi fbushaw,
I would like to point you to a short paper written by Roseburg Lumber on a sawmill sort they did.  In the paper, you will see that the claim is that "dryability" is a better method of sorting than just by moisture content.  The concept is that denser wood with less moisture will dry typically the same as less dense wood with more moisture, so a better metric is the overall green density of wood that takes into account the density of the fiber and the water combined.

here is a link to the paper and an excerpt:

http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/6341/Reader%20and%20Wallace.pdf?sequence=1

"Green density is the combination of wood fibre and water, and gamma ray absorption cannot be used to distinguish between these constituents, so it is not possible to measure moisture contents. However, it is more difficult to extract water from higher density wood in the drying process, and green density has been proven to be a good indicator of the ‘dryability’ of green timber."

I think the main point I take from this is that if you have dense wood with high MC in a batch with much lesser dense wood and high MC, by the time the less dense wood is dried, the higher dense wood may very well still be wet.  However, if you put the high dense low moisture with the low dense high moisture in same sort, they should dry more uniformly.  i.e. the ideal sorting should be based on this "dryability" factor and not just on moisture content alone.

I know this doesn't answer your original question, but it might help shed more light on the topic in general and help in refining your sort strategy.

Tim

[fbushaw]

I will definately do some research, and check into this Tim.

Thank you very much!!!!