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Borer Issues in Vacuum Kiln Dried Wood

Started by Swernicus, May 10, 2021, 01:19:10 PM

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Swernicus

Hello everyone,

I have a customer claiming there are active insects in an unfinished slab top I sold to him about 2 months ago.  The product is a walnut slab bookmatch glue up.  There were obvious signs of borer activity after milling this log.  The insects were larger beetle type and seemed to have yellow lines on them.  

Some emerged after milling and air drying (6-8 months outdoors). The slabs were then kiln dried in a Vac-Dry VK2.0.  I found many dead ones that I pulled out of their holes.  I did not see any signs of activity.  The customer is claiming new sawdust is emerging from some of the borer holes.

I was under the impression that wood borne insects could not survive in the temperature and pressures that occur inside a kiln such as a Vac-Dry.  The pressure goes much lower than any other DH or iDry kiln which would lead to water in body of insects flashing off (DEATH!).  I do not have specific temperatures and pressures achieved during the walnut cycle.

The customer is not being belligerent but obviously I want to advise him what is best to do.  I have a Nyle L200M but i do not have a sterilization cycle coming up for more than a month.  Bora Care is just going to affect any insects that he can see from my understanding.  

Should I tell him to wait til my next sterilization cycle (150 for 25 hours for 8/4), or is this possibly an infestation from after kiln drying?

K-Guy


It is possible that it is a new infestation but I would contact the manufacturer to see if the cycle did sterilize the load.

Either way I would offer to include it with other wood in a sterilization cycle again as a sign of good will.
Nyle Service Dept.
A common mistake people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.
- D. Adams

Swernicus

Yeah.  I figured with a VacDry most operating points would be extremely fatal to most insect life solely based on the low pressure.  I was looking to understand this before I go pointing fingers at anyone (something I would like to avoid at "most" costs).  I use the VacDry vendor quite frequently and was told by them that their kiln destroys any and all insect life.

Definitely learning the business and my searches here show that having contracts explaining the moisture, bugs, and other factors is a good safety net for issues like this.

My plan is to do your suggest K-guy however the customer is not thrilled about waiting until my current kiln is ready for that stage.  Thanks for the input!

longtime lurker

Give it a good wipe over with white spirit, and get some down every borer hole with an eyedropper.

H3 clear = LOSP = white spirit.

Little blighters don't like the taste of it at all
The quickest way to make a million dollars with a sawmill is to start with two million.

YellowHammer

Hold on, more info is needed.  I will tell you what I would do.  

Taking a manufacturer's claim on whether their kiln reaches sterilization conditions without data will leave you guessing.  Especially if there was a possible malfunction of the kiln.  That needs to be addressed no matter what the outcome.  The data must be recorded, at least on paper, for every single load from every kiln being used.  This data is mandatory both for your peace of mind as well as the customer.  As well as for your business.

The slab is 8/4 walnut? What conditions does the manufacturer say the vac kiln gets to?

Sounds like your current solution would be to stick it in the Nyle and sterilize it there, which certainly would solve this immediate problem, but if this is true, you have several bigger ones.  

I would advise don't do anything until you personally inspect the piece of wood, and do some investigation.  Not that the person is lying, they most likely aren't, but many people don't know what they're looking at.

I've had people tell me nail holes were active bug holes, that ants were in my wood only to find out that they had laid the board in an ant nest in their yard, and also a person who was being played by their home exterminator wanting to land a big contact because their ambrosia maple boards had holes in them which they obviously did.  That was fixed with me walking them through a Wikipedia search.  I had one person who said my wood had termites which later infested the house, when in fact, after inspection, my wood was the only wood in the house not infested with termites.

So get the board back and look at it in detail.  Immediately. Have the customer show you exactly what they are seeing.  Treat it like a crime scene.  Get to the bottom of the situation.  Inspect it in front of the customer so they don't think you are tricking them.  See what they are seeing. For all you know their cat is leaving cat litter prints in the table, or are just bread crumbs and they think it is sawdust.  Or they have flipped the board over and seeing old sawdust.  Is the frass centralized around the holes, or scattered out.  Look for bugs on the floor, or in the vicinity.  If there seems to be a true infestation, then get the board back, and keep watching it, and see if there are really bugs in it.  See if the bugs are really your bugs, or are their bugs.  Then you'll know for sure.  This is crucial.  

If there is an active infestation, then that raises the bigger question of how many boards did you dry in that load?  How many other potentially infested boards were sold?  How many loads have been produced with that kiln?  Have any other boards shown signs of activity?  Have any other loads shown activity?  This is a big clue.  If not, why? Did the kiln possibly malfunction on this load? Could it possibly have malfunctioned on other loads?

Can you identify the insect?  This is very important to determine its species and life cycle.  This is important to determine if the board was infected before or after it was sold.  

As far as fixing the problem, you can do it any way you want, but if I found conclusively that I was selling bug infested wood, then I would address the problem immediately with vigor.

However, just putting it in the Nyle won't solve the bigger problem of finding out if your vac kiln is not sterilizing wood, either due to a mechanical malfunction or not.  No matter what the manufacturer says, if the vac kiln is supposed to reach sterilization conditions, I would test that.  I would record the data every single load, especially if the sterilization conditions depend on more than pure heat.  I would get a data recorder, put the piece of wood back in, along with the existing load already in to match situations, and finish the load as normal, letting this piece go along along for the ride.  If this piece comes out sterilized, and you record the data to prove it, then you'll know you for sure what happened.

Lots to address here.  First, see if the wood is really infested.  Lots of people see UFO's, Bigfoot, and such.  Don't believe it until you see it with your own eyes.  If it's true, then find out why.  Then make it right with the customer.  That's what I'd do.  
YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

customsawyer

How far is the customers storage/work place from you. If it isn't to crazy I like to drive over to their shop and see what they are seeing. I had one customer that was complaining about ants in my wood. Come to find out the ant bed was in the back of his tahoe where his younguns had food crumbs scattered all over. The ants got on the wood in the 15 miles from my place to his. Get more details and all the info you can. If the mistake is on your end then fix it. If it's the customers fault then educate the customer.
Two LT70s, Nyle L200 kiln, 4 head Pinheiro planer, 30" double surface Cantek planer, Lucas dedicated slabber, Slabmizer, and enough rolling stock and chainsaws to keep it all running.
www.thecustomsawyer.com

Swernicus

Thank you for the very detailed reply!

The slabs were 8/4 walnut.  The kiln drops to 1 PSI(a) or 1/14th of sea level atmospheric.  From what the operator says the finishing temp is 120 deg.  I know that in conventional and DH kilns you need 150 deg for 24 hrs but that is considering atmospheric pressure.  

The insects were some sort of locust borer or related.  They had yellow striping and were larger than any powder post beetle by a large margin.

I've had very badly infested wood (ambrosia beetles, other borers, etc) go to this kiln and they've all come back dead as a doornail, no prior complaints.  I'm starting to think that the frass is falling out of the hole from when the slabs are moved.  He has not seen a borer but says that sawdust has been appearing at the holes even after it is vacuumed clean.

I will likely put the slabs into the DH kiln for sterilization regardless as I don't want an adversarial situation.  But Yellowhammer makes a good point that maybe the VacDry conditions aren't completely adequate for sterilization despite seeming so.

For my Nyle L200, how do you suggest doing data tracking to prove sterilization?  Beyond taking a dated picture of the control box with temp readouts.

K-Guy

Depending on how old your L200 is, we have a software package that you can install and use to connect to the control by ethernet cable to record it. If you post a picture of you control box, I can tell if it will work.
Nyle Service Dept.
A common mistake people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.
- D. Adams

Swernicus

The L200M is very new.  Just got it earlier this year.

K-Guy


That's what I needed to know. It will work but it has to be a hard wired connection.
Nyle Service Dept.
A common mistake people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.
- D. Adams

Swernicus

Send me a message regarding what I'd need.  I am able to run an ethernet cable via conduit to the control box.

GeneWengert-WoodDoc

All good info.  The vacuum does not kill eggs.  Dry wood is too strong for most insects to be able to cut a new hole, especially borers.  Insects like the borer needs water, so dry wood is bad.  The pow der post beetle can survive the vacuum, especially eggs, but they would have tiny holes, compared to borers.  If borers are present when you saw, sometimes the holes will be cut at an angle, so you will see oval holes and even open cavities...such holes indicate a prior injection, not present.  It does take 133 F or hotter throughout the piece of wood, which usually means 150 F or hotter air temperature, to kill insects and eggs.  
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

YellowHammer

@Gene

I am doing a literature search on this topic, and as you indicate, have so far not found anything that lists low pressure (vacuum) or even high pressure as a means to sterilize wood as a recognized process or standard.  I was thinking that this would be a good alternative to heat for sterilizing already built projects and furniture, where heat would melt glue and distort joints. However, at this point, it seems to be a non starter.      

So it is a fair statement to say that the only commercially or federally recognized standards for lumber sterilization reference heat only?  

In your experience, is there an informal, peer reviewed document discussing pressure vs sterilization?  

Have there been studies on insect eggs vs vacuum or pressure?  I haven't found any peer reviewed papers on that also. 

Thanks


 

YellowHammerisms:

Take steps to save steps.

If it won't roll, its not a log; it's still a tree.  Sawmills cut logs, not trees.

Kiln drying wood: When the cookies are burned, they're burned, and you can't fix them.

Sawing is fun for the first couple million boards.

Be smarter than the sawdust

Swernicus

I wouldn't think solely pressure (low or high) would do the sterilization, but the vacuum kiln lowers the vapor pressure so much that any moisture flashes off at 100 deg or lower.  The VacDry at 120 deg is causing water inside an insects or egg to flash off.  That seems to be a deadly scenario, but I'm not an entomologist.  I know a mammal would not survive as I've seen a mouse that looked like it exploded inside the vacuum kiln chamber after a charge came out.

Stephen1

Great topic. BUGS.
I would not think the vacuum alone will kill the eggs. Just because the kiln has a low vacuum, that only allows water to boil at a lower temperature. My Idry is 8" of vacuum and as such water boils at 153F. 
My temperature in the kiln will hit  160F and stays for at least 24 hrs. 
IDRY Vacum Kiln, LT40HDWide, BMS250 sharpener/setter 742b Bobcat, TCM forklift, Sthil 026,038, 461. 1952 TEA Fergusan Tractor

Swernicus

The iDry standard is a much different process than a VacDry. the iDry turbo is closer to what VacDry does.  

The VacDry goes down to 2-4 in Hg which means water vaporizes at 100 deg F.

I view the iDry standard as an "accelerated" DH kiln almost since the method of drying is still evaporation from the surface of the wood via airflow.  The VacDry and other comparable models actually vaporize water all the way to the core of the wood and the vapor is drawn out via pressure gradient.  There is no need for airflow in a true vacuum kiln, and most have metal plates with heating water or a microwave system. 


samandothers

Great question YH.  

This would seem while iDry will dry the wood, heat is still needed to sterilize.  I am assuming the iDry chamber is not insulated or designed to allow a higher heat at the end of the drying cycle?

I was considering taking air dried wood to an iDry kiln but I need the wood sterilized too.  This is a bummer. 

Stephen1

Quote from: samandothers on May 26, 2021, 10:29:19 PM
Great question YH.  

This would seem while iDry will dry the wood, heat is still needed to sterilize.  I am assuming the iDry chamber is not insulated or designed to allow a higher heat at the end of the drying cycle?

I was considering taking air dried wood to an iDry kiln but I need the wood sterilized too.  This is a bummer.
The IDRY standard and Plus take your wood temp to 160F so sterilization is part of the drying process. I like to call it an accelerated airdrying system.  
IDRY Vacum Kiln, LT40HDWide, BMS250 sharpener/setter 742b Bobcat, TCM forklift, Sthil 026,038, 461. 1952 TEA Fergusan Tractor

samandothers

Thanks Stephen,
I misread some of the information concerning VacDry and iDry.  After rereading I got it now.

Swernicus

I confirmed today that the VacDry cycles finish anywhere from 120-140 at 50 torr (about 1 psi atmospheric).

The walnut that I had dried was finished at 140 for 24 hours.  At that temp and pressure for that length of time I'm confident no insect could survive. Any borer will be exposed to the vacuum since they are connected to the outside environment via the hole they bored through the wood.   

The customer indicated sawdust was coming from an existing borer hole, so I think moving the slab caused sawdust to become dislodged and fall out from time to time.  This doesn't appear to be a new infestation, nor is it powder post beetles.  

Just clearing this one up.  I still plan on taking the table top and putting it in my DH kiln during sterilization period with all the warnings to the customer that it may not be flat when it comes out.  He is absolutely sure there are still living insects in the wood... 

japarker4

iDRY Kilns are capable of exceeding the requirements for killing bugs. Here is the actual USDA rule: click here

To know the wood core temp we use a wireless probe like this: CLICK HERE

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