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quarter sawn white oak won't dry in Nyle kiln, help

Started by Kelvin, May 30, 2008, 05:32:49 PM

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Kelvin

Howdy all,
I've recently had my Nyle kiln (200 series) compressor recharged and a leak fixed.  It started up fine and dired a load of cherry very well.  I went to a full load of about 1500 bd ft fairly wet quarter sawn white oak.  I read the Nyle manual pretty carefully and know not to overly dry white oak, max of about 2.5% MC per day.  So i was doing fine until i reached 10% MC it has run 3 days without budging.  Have any of you had this experience?  The first day i turned up the compressor from 40% they recommended to 50% next day to 70% and last 12 hrs to 100% and its not producing much water, but i did open a little vent for over temp problems.  I've opened the main doors and checked the main stack all over and its pretty much consistant at 10%-11% and not moving.  Either the over temp switch tripped on my compressor, which i don't think so as i hear it kick on, or its very hard to dry white oak down far enough?  I"ve been telling my customer who has been waiting for a couple of days now with me saying, "should be tomorrow"  Any experience with white oak being troublesome?  Do you turn up compressor?  Higher temps?  What can you do to speed up drying in the end?  I'm worried something is up with my compressor and its not working right, though it seemed fine up till now and did cherry/maple load very quickly and well right to the end.  I have to pull my load to check overtemp switch that is a manual reset on the compressor (didn't know about this till i built a rack infront of my access to backside of dryer unit)
Any ideas, suggestions?  Quarter sawn just very tuff to dry at the end?  I seem to have had similar trouble in the past, hard to get past 10%MC it acts like its dry, and won't give up anymore water.  Big sale riding on this load so i'm worried.
Thanks
kelvin

DR_Buck

Kelvin,

I'm sure Don from Nyle or any number of Nyle owners will also chime in here also.  But, my 2¢ worth is  that I dry a lot of QS white oak without any problems.  My kiln is the DH-4000 version from Wood-Mizer.   The big difference is the controller.   I set my final range when the load is <25% MC.  I set temp to about 120° and RH to 40%.  My compressor cycle time is preset so I don't do anything with it.    I just check the MC everyday and adjust temp and MC up or down to keep to about 2.5% loss per day.   

Last year I added the automatic over temp exhaust vents because inside kiln temp was hard to keep down in the hot summer days.   This threw me off a little and I'm still working on how to adjust when the kiln is venting.  The vents open 5° above desired kiln temp and close when back at desired kiln temp.
Been there, done that.   Never got caught [/b]
Retired and not doing much anymore and still not getting caught

beenthere

Kelvin
What do the moisture samples read?  You do take them out and weigh them, I presume.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

scsmith42

Kelvin, I second DR_Buck's comments - I have the same setup and dry oak all of the time w/o problems.

Once your load is below 25% MC, you should not need to worry about the max 2.5% daily drying rate.  I've found that extra heating coils added to my unit made a significant difference in how quickly and consistently that it dries.

Sometimes if I hit a plateau I'll set my MC% lower than 40 - say around 30%, to help accelerate the final drying, and then I'll increase it back up as the load gets close to the targeted % (usually 6 - 8%).  I've also found that if I start equalizing and sterilizing (135F) once the load gets below 10% then it ends up around 8 or thereabouts.

Scott
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

oakiemac

I've had that problem with oak before as well. I called Nyle and they told me to turn off compressors and heat up to about 145 for a day or so then cool down and turn on compressors again and then you should be able to suck out the final few points.

This worked well for me.
Mobile Demension sawmill, Bobcat 873 loader, 3 dry kilns and a long "to do" list.

Ironwood

That sounds to me like you have to "drive" out that fiinal bit. I think in some bigger kilns cycling the heat and reintroduction of humidity is used keep that moisture moving from the core. Moisture gradient issue type thing, so Okiemac's comment's make sense to me.

Ironwood
There is no scarcity of opportunity to make a living at what you love to do, there is only scarcity of resolve to make it happen.- Wayne Dyer

Kelvin

Yeah, oakiemac, it seems like the air is dry in the kiln, but the lumber isn't drying.  I'll try increase to 145.  Was the chamber closed, or vents open?  When vents are open on mine it looses a lot of moisture so i might be worried i'd over do it.  I hear the compressor come on, so i don't think the over temp switch is tripped inside.  This is annoying, but i'm glad i've got some ideas from you guys.  I sample with a couple of pieces of lumber that i carefully monitor with my wagner L606 meter and adjust for species.  I've always had good sucess with my samples matching the load, and i have been opening up and testing the stacks by pulling the carts out.  Seems like i can't get the H2O out of the core.  I'll try the temp tonight.
Thanks
guys,
Kelvin

Ironwood

If it is in the core, and the outside is dry (down to your target) then it is an issue of driving it out (gradient variation), like Scott said, if the your down this far you can get much more aggressive w/ no concern for honeycombing as the surface is already bottomed. Do you relax the load after you finish? Let it open to the air for a few days to equalize? Conditioning I bellieve they call it?



              Ironwood
There is no scarcity of opportunity to make a living at what you love to do, there is only scarcity of resolve to make it happen.- Wayne Dyer

Sawyerfortyish

There's one thing you might want to check if the water is slowly dripping or not at all. I have 2 Nyle L200 kilns running and both have had the drain hose plug up with crud.  Just pull it off the unit and blow through it. I thought one load was almost dry once and checked the MC it was high then I seen the wet floor around the compressor unit and realized the drain hose was plugged. Nyle told me not to run the compressor when you turn up the temp above a certain point I turn the compressor off above 125 degrees

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