News: passes 100,000 total viewsFrench Language Discussion

Recent Posts

Pages: [1] 2 3 ... 10
Training / Events / NHLA Progressive lumber Inspector Program Dec. 1-13, 2014
« Last post by admin on October 17, 2014, 09:04:45 AM »
Progressive Lumber Inspector Program Announced!

In an attempt to further its educational reach, the NHLA Inspector Training School is embracing new technology and offering a distance learning ITS Program. Block 1 of the much anticipated "Progressive Program" will run December 1-13, 2014.

For more information contact:
Becky Miller

or download an application.
Training / Events / NHLA Progressive lumber Inspector Program Dec. 1-13, 2014
« Last post by admin on October 17, 2014, 08:54:53 AM »
Progressive Lumber Inspector Program Announced!

In an attempt to further its educational reach, the NHLA Inspector Training School is embracing new technology and offering a distance learning ITS Program. Block 1 of the much anticipated "Progressive Program" will run December 1-13, 2014.

For more information contact:
Becky Miller

or download an application.
Job Postings / Boiler Chief/Kiln Operator - Bemidji, MN
« Last post by admin on October 07, 2014, 09:36:07 AM »
Boiler Chief/Kiln Operator

Location: Bemidji, Minnesota
Potlatch is an EEO/AA/M/F/Veteran/Disabled Employer

Operate boiler system and kilns in a safe, environmentally and quality focused manner. Maintain environmental compliance through technical competence and operational leadership. Lead and coordinate operations and maintenance for the boiler/kiln and plant heating systems. Maximize lumber quality through drying innovation.

Boiler/Kiln Operations:
  • Assist quality control supervisor in achieving maximum lumber grade and meeting mill production needs.
  • Lead the boiler/kiln team to improve drying results and meet quality goals.
  • Operate boiler systems to achieve safe and environmentally sound steam production to meet plant heat and drying needs.
  • Operate kilns, applying lumber drying concepts, to maximize lumber grade quality, achieve ALS certification standards and meet mill production needs.
  • Coordinate maintenance of two wood-fired boilers and three dry kilns.
  • Maintain current chief boiler license for the state of Minnesota.
  • Provide ongoing training for new and current boiler/kiln personnel.

Heating System:
  • Responsible for operations and maintenance of the plant-wide heating system including reducing stations and heaters.

Environmental Compliance:
  • Assist in preparation and submission of environmental records to federal, state and local agencies.
  • Perform required monitoring, testing and inspections as required to maintain environmental compliance.
  • Maintain current training, certifications and licensing required by federal, state and local agencies. Train mill personnel on environmental topics and changes.
  • Stay current with changing policies and procedures.

Boiler Maintenance/Shutdowns:
  • Plan and participate in boiler shutdowns utilizing contractors and mill personnel to maximize effectiveness at minimal cost.

Working Conditions:
Boiler and sawmill environment.
Exposure to heat, noise, moving equipment, dust and various weather conditions (heat, humidity, snow and extreme cold).

Essential Physical Functions:
Climbing stairs and ladders, bending and lifting of approximately 60 pounds on a regular basis.
Some fatigue from computer use.

Basic Qualifications
  • High School Diploma or GED required.
  • Specialized/technical training or some college courses in manufacturing or boiler technology required.
  • Must possess Minnesota chief boiler license. Hazardous waste management certification preferred or must obtain certification shortly after hire.
  • Minimum of five (5) years of previous experience in a mill boiler/environmental role (lumber drying experience preferred).
  • Intermediate proficiency in Microsoft Excel and Word and boiler operations software required.
  • Proficiency in operation of mill-wide rolling stock (forklift, front-end loader) required.
  • Experience coordinating environmental programs required (e.g., pollution prevention, waste management, storm water, spill control, etc.).
  • Ability to interface and communicate effectively in both written and oral form required.
  • Ability to plan, organize and implement activities and projects required.

To Apply Click Here

NOTE: Job postings on are provided as a free service. We do our best to keep all postings current. However, if you discover a job listed on our forum is no longer available, please send us a message to that effect and we will remove from the board. Thank you.
Yes, possibly.  Having smaller kilns could help the operator control the species or dimension mix better and also help to keep the inventory rotated.
General Discussion / Re: lumber temperature / wet bulb temp / fiber saturation
« Last post by MichaelM on September 25, 2014, 03:31:12 PM »

People have tried that in the past and, yes, it can be done.  The Lignomat control system can tell you about the shell and core but a capacitance system could also tell when the wood reaches 30%.  These don't use lumber temperature, however, except maybe to correct the meter.

In your question, you ask "with normal kiln control."  I suppose one could calibrate the TDAL for that purpose (for a given schedule and product).  Often people just use it for end point determination, but it can (and is) correlated to MC in some control systems.  Again, this is not lumber temperature, it is the air temperature.

I would say the most effective way (of using wood temperature) is to place a thermocouple or other sensor at the center of the piece.  This involves drilling, putting in the sensor, sealing the hole, and placing the board(s) in a representative location.  The surface of the board will lose the free water first and the surface temperature rises first, then the mid layers, then the core.  The temperature rises at the core when the free water leaves the core.

To make the measurement easier, cameras can be used to detect the surface moisture content.  This might be done with visible, NIR, or IR, light but the surface MC.  Surface MC, however, can vary a lot with conditions and with the previous wood handling.

Not sure if that's the whole answer, but it's what I have.  And, no question is a stupid question except the one that does not get asked.

Mike M.
General Discussion / lumber temperature / wet bulb temp / fiber saturation
« Last post by Craig Jensen on September 24, 2014, 02:52:56 PM »
I have what may be a stupid question, but I'm gonna ask it anyway.  ;D
I know that before fiber saturation point, I can pretty much assume that my lumber temperature in a charge is about the same as my wet bulb temperature.

Is there a simple means with normal kiln control to tell when the lumber temperature starts to rise past the wet bulb temperature?  It would seem to me that we could then assume we were past fiber saturation point, and then once we were able to determine our typical drying rate in a specific species and schedule, we would be able to more accurately predict when we hit our moisture target.  I am thinking this would result in fewer interruptions in the schedule to check moisture, and improve quality.
Suggestions?  Am I missing something obvious?
Craig Jensen
Moisture Variability / Using Near-Infrared Detection to Determine Moisture Content
« Last post by StavrosA on September 16, 2014, 08:54:42 AM »
Near-infrared detection holds great promise for determining moisture content, species, and density of wood in mill operations. Not only that, it can be done fairly quickly, speeding production on the line.

Hi, I'm Stavros Avramidis, a Professor at the University of British Columbia, Canada's, Department of Wood Science, and a expert, and I've found that when it comes to such factors as Moisture Content (MC), species type, and wood density in mill operations, high variation 'in' leads to high variation 'out'.

So what exactly am I talking about? Without presorting prior to kiln drying, you introduce a high variation of species, density or MC, leading to a high variation in product output. This is really an issue throughout the whole industry.

As you probably already know, not all species are created equal. Different species have different drying characteristics. If you don't know the species difference, then the sort can be based on either density or MC.

But telling the difference when pre-sorting in the forest can be very expensive. If you are in the mill and can't tell the species difference, then you can use MC instead.

Tight export standards can pose a problem, however. Typically, exports can have a variance of +1.5%, so if you input wood with a high variance in MC, you will get wood out with an equally high variance of MC and the whole shipment will be returned because it doesn't meet the export quality standards.

What is the solution to this thorny problem? Near-infrared spectroscopy. After extensive study on this topic, we've found that near-infrared spectroscopy in the 1300-2100 nm range of the spectrum coupled with multivariate statistical models provides a way to rapidly and accurately predict the surface moisture content of wood at line speeds of from 100 mm/s up to 1,000 mm/s, and of determining entire surface moisture distribution rapidly, as well as detecting wet-pockets in lamina for industry applications. The speed of the process also avoids problems caused by debris flying around inside the mill. Near-infrared technology allows a mill to determine MC, density, and species immediately in the mill, a great time-saver that can translate into increased productivity as well as increased profits.

What are your thoughts on this technique? Let us know at


Watanabe, Mansfield, Avramidis (2012) Detection of wet-pockets on the surface of Tsuga heterophylla (Raf.) Sarg. by near infrared (NIR) spectroscopy

Watanabe, Mansfield, Avramidis (2011) Application of NIR spectroscopy for moisture-based sorting of green hem-fir timber

Watanabe et al (2010) Wet-pocket classification in Abies lasiocarpa using spectroscopy
in the visible and near infrared range
Dry Kiln Control / Re: Wet bulb control
« Last post by PhilM on September 12, 2014, 12:45:37 PM »
I agree with everything that Mike M. said so very well.  I have tried to add just a few additional thoughts.

The wet bulb temperature that your controller is reading needs to be verified using a hygrometer.  A low temperature hygrometer can be obtained from Conway Cleveland Corp. and other sources as well.  This first step will cost you far less than a new control system.
Another relatively inexpensive item would be to install a view flow control valve on the WB feed water infeed.  This has a glass or plastic sight tube that lets you see the drip rate to the WB.  Our supplier in North Carolina is no longer in business, however, and I have not located another supplier.  It may be that Mike’s suggestion is better since he gives a source!

Ideally the wet bulb pan should be supplied with exactly the amount of water that is evaporated.  The wet bulb pan can be equipped with a constant-level device that incorporates a float valve to maintain water level in the wet bulb pan.

Get a hygrometer (or two !) to check that wet bulb temperature (and dry bulb) before you rush out and buy a new controller.
Dry Kiln Maintenance / Re: lignomat
« Last post by cork46 on September 11, 2014, 10:22:02 AM »
I use the dry bulb, I have the pins and we use the wafers for MC but they really do not work. I was curious because this system is a big pain.  I am trying to figure out why my kilns just shut off by themselves after 30 minutes to 4 hours in.  I am not even showing any error codes other than plc halted process so hard to troubleshoot.  Was just wondering if anyone was having the same issue and what they may have done to fix the problem.
Dry Kiln Control / Re: Wet bulb control
« Last post by MichaelM on September 11, 2014, 09:15:27 AM »
Your red oak is probably a 28-day or longer cycle.  Change the sock, do not rinse and reuse.  In our workshop (How to Dry Lumber for Quality and Profit, Dec. 8-10, 2014) we recommend changing it every week to 10 days on longer kiln cycles or changing it every charge on shorter cycles.  We also recommend getting your socks from a kiln manufacturer or other reliable source so that they wick well.  Throw a dry sock into a bucket of water and is should sink.  If it floats, then it does not wick well enough.

The wet-bulb sock should be wet to the tough.  Put your fingers on it when you are getting the kiln samples and you should see liquid water on your fingers.  If it is just damp, then it is probably not wicking as well as you would like.

The needle valve is a good step, but I would suggest a flow meter (see Dwyer catalog) that is in the range of 0-100 cc/min.  Regulate the flow to 50 to 75 cc/min and keep it the same for every charge.  Most of the meters have a meter built into them.  Use one flow meter for each tray.

Yes, you should have an overflow.  In theory you could control the flow in and make it match the evaporation rate out, but the evaporation rate changes during the kiln cycle because the rh and T change.  Water should flow into the wet-bulb sock reservoir, there should be a weir to keep the level constant, and there should be an overflow tube that allows you to see the amount overflowing.  I usually tell people to have an overflow (drip, drip, drip) of about a drip every second or two at a minimum, and a slow steady flow at a maximum.  You are probably fine as long as there is overflow.  Being able to see it allows you to ensure that there is water in the tray (the gage tells you there is water going in, but the tube could have failed).

Water temperature may have a little effect, but I would not worry about it unless you are putting in ice water or boiling water directly into the tray.  Wet-bulb theory says that the water supplied to the sock should be at the wet-bulb temperature.  Of course, in the simple way we use the wet-bulb in a kiln this is not possible nor am I aware that anyone does it.  You probably have a length of 1/4" od tubing that passes through the kiln wall and is exposed to the kiln's dry-bulb temperature between the wall and the tray.  If the tube was long enough, the water would reach the dry-bulb temperature (it would either warm or cool).  If you have room temperature water entering the tubing there is probably condensation on the outside of the tube which enhances the heating.  Most people use clean fresh water and the water is heated somewhat before it reached the tray and it seems to work.  Unless you are doing something strange, I wouldn't worry about this.  If you are using condensate (which I do not recommend) it probably cools enough.  Keep in mind that the water also has a chance to change temperature while it is sitting in the tray.

If you are not using computer controls, then you are one of the few.  However, people have successful dried red oak for 100 years without computers.  The circular chart should tell you if the wet-bulb sock dried out.  It might not tell you if the water flow is insufficient.  Example - suppose you want a 10F depression.  The 10 F depression is usually measured with a fully wetted sock.  If the sock is mostly wetted, but not fully wetted, the indicated Tw will rise and the vents will open to bring it back to 10F.  When this happens the real depression might be 12F or 15F.  The same thing would happen if you had a computer.  You as the operator would have to notice unusual vent operation to catch this early or see that there is no overflow from the tray.  As an operator  I would not use one bad charge to justify computer controls.  I would

Lastly - are you sure this was a wet-bulb problem?  Honeycomb can also be caused by raising Td too soon while the wood is still too high in MC - even if you have controlled the wet-bulb depression well.  You could also increase your chances for honeycomb (which will happen midway through the schedule) by pushing the dry-bulb up a little early.   Even worse - you control Tw, not Td-Tw.  If the dry-bulb temperature is not correct then the rh or wet-bulb depression will not be correct even with the best wet-bulb in the world.  Is it possible that the dry-bulb sensors are in need of calibration?

Mike Milota
Pages: [1] 2 3 ... 10

Forum experts

MichaelM lmod MichaelM
Michael Milota Ph.D.
Oregon State University
PhilM lmod PhilM
Phil Mitchell Ph.D.
Forum Expert
North Carolina State University
PierreA lmod PierreA
Pierre Asselin ing.f.
Forum Expert
StavrosA lmod StavrosA
Stavros Avramidis Ph.D.
University of British Columbia
TimothyD lmod TimothyD
Timothy Duncan MBA
Engineering Manager
Wagner Meters

* Events

* Job Opportunities