What is the minimum cooling down time for lumber to equalize

[tanderson]

I dry SYP in high temp kilns with limited dry storage, What is the minimum time that I should I let the cool down before it ran at the Planermill? I dry with a target of 15% moisture with about a 3.4 diviation.

[fbushaw]

Our planer supervisor tells us 8-10 hours minimum. It kinda depends on the weather also. I know if we try to run hot wood through our planer, the moisture sytem we have will call alot of it wet. I have also noticed that when you try to plane hot wood it will tend to come out fuzzy. White fir is the worst for this.

[Gilman Blackshear,Ga]

In our SYP mills with conventional high temp kilns, we try to let wood cool for at least 24 hours before running at planer.

[Craig Jensen]

So is there any set standard for how cool (temperature wise) lumber should be exiting the planer before there is a problem?
Our mill only has dry storage for about 1.5 million bf of lumber, so we have pretty quick turnaround times.  Resulting in animated discussions from time to time. . . .

 

Would love to break the argument circle by coming up with an established standard.  We have discussed taking a temperature gun up to the planer feed table and check the wood any time it is deemed questionable and then stop and run something else if it is above a certain temperature, but we don't know what temperature that should be.

Suggestions?

[Gilman Blackshear,Ga]

We also have limited storage due to my dry sheds being taken to store finished packs of lumber. A great portion of my rough dry inventory is stacked outside. I know this is not the ideal thing to do but now days you do what you have to do. As i mentioned above our rule of thumb is 24 hours. There are occasions when the wood gets ran thru planer is less than 24 but very seldom does a pack get ran at 12 hours or less. The system we came up with is to paint on side of each pack the date (for example 4/18) when the packs are offloaded from kiln carts. That way our lift drivers know when they can run the packs.

[Craig Jensen]

We are a studmill, and our sawmill stackers actually stack on carts.  These carts run on tracks out of the mill, to a transfer system, through the kilns, to dry storage, and then the planer unstacker actually unstacks off of carts.  The first time a forklift touches our lumber is after the planer.  So our storage is absolutely limited, and stacking down outside of our covered dry storage is not an option at all. 

Handy design for eliminating forklift damage, and dirt, grit etc introduction - but not good for allowing long cooling times, and without tearing down the mill and starting over, we are kind of stuck with what we have. . . .

We have even considered large fans in our storage areas to circulate air through the lumber as it cools. . .

My understanding is that the main reason it is a problem to run warm wood is about the fact that as wood is cooling it continues to shrink, so finished dimensions can be off spec if the wood is too warm.  Also moisture is still being released quickly as the wood cools, which gets caught in the solid stacked finished product, resulting in mold, stains, etc.

This is why I was looking for an actual cooling temperature where these problems can be minimized.  Does anyone have any data from tracking this, or see any holes in what I am thinking?

[GeorgeCulp]

I hope nobody screams but I like 3-4 days. With less than that we definitely can see a higher than average MC.  Of course the time of the year has a lot to do with it.

[kilnguy]

From a hardwoods standpoint...our mill's biggest concern seems to be the planer itself and what high temps may do to our planer knives etc.  I rarely run 'out of a kiln'.  Try to give it a few hours minimum.