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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
Job Postings / Kiln Operator - McCormick, SC
« Last post by admin on September 11, 2014, 08:32:04 AM »

Georgia-Pacific (GP) is among the world's leading manufacturers of bath tissue, paper towels, napkins, tableware, paper-based packaging, office papers, cellulose, specialty fibers, nonwoven fabrics, building products and related chemicals. Our building products business makes DensGlass® gypsum board often seen in commercial construction, DryPly® plywood and RESI-MIX® wood adhesives, among others. Our containerboard and packaging business offers high-end graphic packaging to bulk bins as well as Golden Isles fluff pulp. You may also recognize consumer brands like Angel Soft®, Brawny®, and Dixie® on retail shelves and enMotion® towels, Compact® bath tissue and SmartStock® cutlery dispensers when you are away from home. Our GP Harmon business is one of the world's largest recyclers of paper, metal and plastics. As a Koch Company, we create long-term value using resources efficiently to provide innovative products and solutions that meet the needs of customers and society, while operating in a manner that is environmentally and socially responsible, and economically sound. Headquartered in Atlanta, GA., we employ approximately 35,000 people. For more information, visit Georgia-Pacific.
The qualified applicant that is awarded this job must be able to perform all the necessary job tasks related to this job in a safe and productive manner.  Follow all safety procedures, lockout procedures, as well as specific PPE requirements.  We are an Equal Opportunity Employer (Minority/Female/Disabled/Veteran).
Basic Qualifications:
  • Eligible to work in the United States for an employer
  • High school diploma or GED equivalent
  • Must be a Georgia-Pacific certified lift truck operator or must become a Georgia-Pacific certified lift truck operator within the trial period of up to 56 days.
  • Possess a working knowledge of OSHA safety requirements for forklift/pedestrian safety
  • Willing to work any shift for rotations including weekends and overtime
  • Must wear various types of personal protective equipment (i.e. hard hat, eye protection, gloves, safety vests, etc.)
  • Willing to perform repetitive and physically demanding tasks for extended periods of time
  • Willing to work in a hot or cold, humid, and noisy industrial environment

Preferred Qualifications:
  • Two years of industrial experience.

Key Responsibilities
(the following list is not all inclusive and other responsibilities will be assigned as needed):
  • Adhere to all plant safety/environmental guidelines, policies and procedures
  • Load and unload each dry kiln
  • Separate lumber size
  • Assist co-workers as needed
  • Help meet or exceed production waste and quality goals
  • Keep work area clean throughout shift
  • Must follow all procedures for drying lumber
  • Some maintenance may be required
  • Perform proper and efficient PM’s grease equipment and check gearboxes

Salary and benefits commensurate with experience.
We are an equal opportunity employer. Minority/Female/Disabled/Veteran
Except where prohibited by state law, all offers of employment are conditioned upon successfully passing a drug test.

This employer uses E-Verify. Please visit the following website for additional information:
To Apply Click Here

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Job Postings / Kiln Supervisor - Plymouth, NC
« Last post by admin on September 10, 2014, 03:05:57 PM »
Kiln Supervisor-01008569

We are currently seeking a candidate to lead our Dry Kiln Leadership Team at our Plymouth, NC location.  The Plymouth operation is a random length sawmill primarily producing lumber up to 20 feet in length with some specialty related capacity.  Plymouth is located in beautiful north eastern North Carolina which offers small town charm, outdoor recreational activities and proximity to colleges.  Shopping and arts/entertainment are available in neighboring cities.  This opportunity is the Supervisor of the Lumber Dry Kiln and is responsible for safely planning, coordination and maintaining operation schedules and maintenance to ensure continuous improvement in the Kiln drying area.
Key Functions:
This position will be responsible for developing and leading team meetings and trainings, meeting productivity and reliability goals, identifying safety, quality and production issues, and coordinating reliability work with maintenance teams.  Additionally, the Kiln Supervisor leads the team by proactively resolving employee issues, builds team work, and ensures adherence to all applicable site policies and procedures in a fair and consistent manner.  This position is responsible for the safe and effective operation of 2 continuous direct fired Kilns and 2 Steam Kilns.
About our Wood Products Business
We manufacture and sell an innovative collection of proven structural framing materials to the residential, multi-family and light commercial markets, and also provide seamless building solutions, from design to installation to support. This team moves fast, works smart and never stops pushing to be and stay number one in the industry. 
About Weyerhaeuser
For more than a century, Weyerhaeuser has grown and harvested trees to make innovative products that meet important human needs. We’re serious about safety, focused on performance and proud of what we do. In every corner of our company, you’ll find talented people who care about each other, the communities where we operate, and the planet we all share.
Qualifications Required
  • 3 years of experience in manufacturing, maintenance and/or wood products drying processes.
  • Work related experience in leading and ensuring compliance with safety initiative.
  • Knowledge of safe and efficient operation and maintenance of wood burners and steam kilns.
  • Working knowledge of NFPA regulations.
  • Data driving decision making using solid analytical skills.
  • Communication and interpersonal skills consistent with managing multiple priorities in a team environment.  Demonstrated ability to raise performance by building and maintaining positive relationships with all associates.
  • Willing and able to work all shifts, including weekends.
  • Strong work ethic, good judgment and decision making skills.

The following qualifications are preferred:
  • BS in Engineering (Civil, Mechanical, Electrical, Industrial) or equivalent work experience.
  • Hands on experience working with dry kilns and sawdust fired combustion systems.
  • Knowledge of Maintenance Planning software such as Maximo or SAP.

Weyerhaeuser is an equal opportunity employer.  We are committed to taking affirmative action to employ and advance in employment women, minorities, qualified individuals with disabilities and protected veterans.
To Apply Click Here

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Job Postings / Boiler/Kiln Operator Trainee - Plummer, ID
« Last post by admin on September 10, 2014, 02:43:18 PM »
Boiler Trainee

Tracking Code     394

Job Description
We are seeking a Boiler/Kiln Operator Trainee who has a commitment to safety and possess great problem solving skills. You will execute your role within a group that embraces innovation, continuous improvement and provides educational opportunities to continuously sharpen your professional skills.  Trainees have a great opportunity to learn boiler processes and maintenance while working alongside our operators in an environment that values team-work and accountability.
Your accountabilities…
  • Develop a strong understanding of boiler operation, process and maintenance by assisting boiler operators in boiler and kiln operations
  • Under direction of supervisors and boiler operators, assist with equipment maintenance, including washing, greasing and other minor maintenance functions
  • Proactively communicate across departments to understanding implications associated with boiler operations
  • Able to fill in for other positions (where qualified) when needed

Required Skills
  • Proven experience or expertise in the following technical areas:
                Operating 950 and 966 Cat loader
                Operating all sizes of forklifts for snow removal
  • Mechanically inclined with an interest to further develop technical skills
  • Excellent verbal and written communication skills
  • Team player and highly self-motivated individual
  • Desire to learn boiler processes and maintenance
  • Flexible as the schedule can vary from day-to-day, and maybe include overtime
  • Willing to work outside where you may be exposed to weather elements (rain, snow, wind) in the course of normal duties

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.
Dry Kiln Control / Wet bulb control
« Last post by apalmer on September 10, 2014, 08:28:57 AM »
     The last charge of 5/4 RO in one of our two older 120,000bfm kilns suffered extensive honeycomb. I am suspecting that the wet bulb performance may have been a contributing factor. (We use a wick over a RDT. Rinsed out before use so that is soaks properly.)

I have read that WB feed water temperature can influence readings. We have had issues with water flow control, using a basic ball valve tap to adjust flow. Since the last damaged charge, a needle valve was added to gain more flow control. I have also read however, that water being too cold or too hot can affect readings. What temperature is right? Should there be overflow from the reservoir or should it only fill at the rate that evaporation occurs?

As a secondary question, should I just say 'screw it' and put in a recommendation to upgrade our kilns to computer controls with wafers? Is it worth the cost of the upgrade?
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topic Kiln Operator - McCormick, SC
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September 11, 2014, 08:32:04 AM
topic Kiln Supervisor - Plymouth, NC
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September 10, 2014, 03:05:57 PM
topic Boiler/Kiln Operator Trainee - Plummer, ID
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September 10, 2014, 02:43:18 PM