Veneer Drying, Grading, and Handling

Dryer Theory SOP Overview

• This document explains drying, grading, and handling of veneer from raw material to finished product.

Green Veneer Production

• Green veneer is a thin wood sheet peeled from a log.
• The process includes storing, debarking, cutting the peeler log into a block.
• Blocks are conditioned with water or steam to achieve the right internal temperature, depending on species and block diameter.
• Conditioned blocks get loaded onto a lathe for peeling into thin veneer ribbons.
• Automated equipment grades moving ribbons of veneer to optimize 54" veneer output while recovering 27" and smaller pieces.
• NV4g uses deep learning to grade and recover veneer, while GEM measures green end moisture.
• Rotary clippers cut the veneer ribbon based on grade scanner results.
• Moisture content sorts include heart (least moisture), light sap, sap, and super sap (most moisture).
• Widths include 54", 27", random width (strip), and fishtails (8’ piece cut in half).
• Veneer gets stacked, marked with paint (red 1/10, green 1/8, black 1/6, blue 3/16 inch thickness), banded, and sent to the plywood mill.
• Douglas Fir does not get marked with species on the green end.

Veneer Storage

• Green veneer is stored in a yard, separated by length, width, thickness, species, moisture content, and date peeled.
• Use First In, First Out (FIFO) for storing any type of veneer
• Follow FIFO inventory and dry the oldest veneer first

Veneer Drying Science

• Drying veneer for plywood/LVL production is a pre-defined process combining temperature, time, humidity, and air flow.
• Drying balances water removal for lamination, without ruining structural integrity or causing case hardening.
• Free water is located within the wood cell cavity and dries first.
• Bound water is in the cell walls and dries second.
• Water of constitution is part of the wood's molecular structure, less than 2% of water weight and shouldn't be dried out.
• Drying starts on the veneer surface and works inward, converting wood water into superheated gas containing extractives, debris, and creosote.
• Each dryer sends it's exhaust to a RCO, Regenerative Catalytic Oxidizer, for air cleaning
• Creosote is a flammable residue requiring scraping or chemical cleaning to avoid fires and failures.
• Heat transfers twice as fast longitudinally, which is why veneer gets lapped, where it increases productivity, lessens surface area, and reduces splitting.
• Targeted moisture content is 3-8% after drying but Pacific Wood Laminates targets under 7% peak moisture.

Veneer Dryer Basics

• A longitudinal veneer dryer has: infeed, heating via conveyor rolls, quick cooling and grading/stacking.
• At Pacific Wood Laminates, longitudinal dryers get heated via steam from a boiler.
• Airflow is generated by main dryer fans through steam coil exchangers.
• Air enters the dryer near the infeed through the supply manifold (door 1), goes lengthways towards the exhaust manifold (door 16 on D, door 18 on A), then back through the superheater.
• Deck coils heat the rolls are help distribute heat.
• Wet End Seal (A and D dryers only) creates negative pressure using air mixing and reheating before recirculation.
• ADEC (automatic dryer emissions control) (A and D dryers only) controls exhaust flow to the RCO, preventing "smoking out the front".
• Humidity is maintained for even drying.

Control Factors

• Dryer Temperature is controlled by steam coils (superheater) and deck coils.
• Dryer Speed is controlled by Sequoia Moisture Meter after sampling.
• Air Flow is controlled by main fans, positive/negative pressures, and leaks.
• Humidity is generated by wet veneer drying and ADEC dampers.
• Dryer Tenders maintain settings and adjust all variables, plus all variables must be monitored, adjusted and repaired when required
• The ideal is to dry the wood to a well conditioned state but not too much.
• Redrying might be necessary if drying is imbalanced.

Dryer Infeed Layout

• The purpose is to present veneer so that it can be efficiently conditioned for gluing.
• Storage chains store the next charge of veneer (3 loads side-by-side) and the hoist conveys the wood to the hoist.
• Hoist and hoist chains feed wood into the dryer.
• Accumulators suspend charges when bringing the next charge in.
• Vacuum cups lift top sheets and feed them to the feed gate.
• Feed rolls drive wood into the dryer feeder once the feed gate is open.
• Pinch wheels apply downward pressure to wood as the feed gate opens.
• Feed gates hold wood back from feeder until tipple is in position.
• Tipples position the feed roll to feed onto a specific deck
• Chain Tensioners are pneumatic cylinders that hold tension on the dryer drive chain.

Dryer Infeed Operation

• 90% of plug ups trace back to how the wood was presented to the dryer at the infeed
• Dryers are unique requiring safety training to operate different infeed setups.
• Storage chains should get loaded with the oldest dated veneer first to stay ahead of the product mix
• Forklifts load the chain (3 bundles of veneer = charge) against the backboard leveled before being transferred to the hoist.
• Some storage chains swing to save space and pedestrians require audible alerts when chains are moving
• Storage chain operations may be at an infeed control console or via a remote button.
• Hoist chains convey the veneer to the infeed, which works manually or automatically depending on the dryer
• Automatic feeder dryers use photo eyes, whereas manual ones are controlled manually by toggle switch
• Top sheets are kept even with the top of the roll for their path into the infeed section.
• Use of accumulators improves productivity by continuing the feed cycle as the next charge is loaded.
• Accumulators are sets of arms running photo eyes and limit switches
• To troubleshoot look at the electric sensors
• Operators can manually operate accumulators from the control panel

Vacuum Cups

• Automatic infeed dryers use vacuum cups to pick up the top sheets of a charge and run fast and consistent
• This eases the ergonomic burden of an operator
• Automatic dryer feed cycles aren't perfect
• Cups tend to cause doubles with old veneer, but FIFO lowers that problem
• Fix or prevent doubles by “fluffing” the sheets
• Doubles require redrying
• Constant moisture messes with and slows down the moisture detection system
• Most of the time doubles end up in the trash
• The handling of veneer downgrades its value and can cause stacker plug ups

Feed Roll and Pinch Wheels

• The dryer feed roll is always on and the veneer rests on it until the gate and rolls descend
• Veneer should be level for even feed
• Pinch wheels prevent sheets from turning or not feeding at all
• If there are any issues, call the Dryer Tender/Millwright

Feed Gate and Tipple

• Feed gate is a set stop for veneer resting on a specific deck
• It is critical in timing the load of the infeed section
• Misaligned gates will cause sheets to turn if mechanical/electrical issues are present
• If there are issues like this call a Dryer Tender/Millwright
• Tipples move the feed roll framework, gate and wheels so that the veneer is set at the angle needed for the deck
• To start a cycle, veneer is placed against a feed gate, the tipple will moe into position, and the gate will open and the feed rolls will push the veneer
• On automatic dryers a lapper is in the infeed section for stopping sheets

Chain Tensioner

• The section and rolls that convey the veneer get driven by a drive chain
• Each deck has an air cylinder that has a chain tensioner
• Tension on the drive chain turns sensor which will disable a dryer should there be an issue

Dryer Layout

• The dryer is where veneer gets superheated before being cooled and is suitable for gluing
• We use a heating source combining air and deck coils using steam
• High-level components include:
  • A superheater, located at the top with circulating fans that exchange heat and goes into the heated section
  • A wet end seal section for dryers A and D which creates negative pressure using air that is re-heated
  • The heated section uses air and deck coils in tandem and creates superheated gas
  • An ADEC exhaust section (only on A and D) that is in between the
  • A cooling section is in between the ADEC and outfeed, creating positive pressure

Dryer Operation

• Every dryer is unique due to the purchase year and manufacturer
• The Delta ("D") dryer mimics the older Alpha
• There are two fewer doors (12 ft less range) with HMIs, human machine interface" panels
  • Dryer volume runs at 360 F with air moving counterclockwise and air heated with steam coils
  • There is positive pressure facing the front with negative pressure at the rear
  • There are three HMI locations that control dryer/stacker
  • The only push button console is at the corner
  • Users can shut down the re-feed line at that console
  • NEVER open any doors during operation because of its internal pressure
  • Do not enter until fans are off and the temperature reaches 120 F
  • Serious burns are possible of touching the outside of the dryer
  • Deck coils are at the west side and retain high heat even through the rest of operation
  • Do not open the dryer duct without authorization when its above 120 F.

Dryer Startup/Shutdown

• Air and breakers must be turned on
• Start the Dryer Drive when open Validate position and motion with stacker belts running or HMI
• Validate air pressure MCC
• In the HMI load 1/10 DF LS in both the infeed and the stacker which sets setpoints for the super heater and deck coils, stacker has species and measurements set
• HMI: click Start to place dryer at 215 then allow the feeder to continue
• Feed product through the GS2000 and Sequioa
• Allow 5 minutes before setting torque values.

Dryer Shutdown Procedures

• Do Not use deluge to cool the dryer
• Stop all feeding
• HMI: temperature to zero along with setting the control valve at zero
• Operate the dryer until empty in stacker
• Bleed valve lines to residual air the upper MCC deck if three psi or more are set
• Stop the "dryer drives"
• Open doors at both sides
• Stop the Stacker HMI
• Follow safety and lockout protocol

ADEC/WES

• ADEC, Automatic Dryer Exhaust Control System are used to manage exhaust volume under all conditions
• WES wet end seal sections use small exhaust fans for meter exhaust flow
• the ADEC system has entry and discharge end stop offs.
• Exhaust air runs through the round down stream duct

Controlling Dryer Settings

• Sensors, thermocouples and dampers control operation by setting ADEC and adjusting them for any conditions.
• The system PLC is controlled by whether or not there is air flowing as it should.
• The system needs adjustment when scaling gets too low or high.

Cooler Pressure Balance (CPB)

• The purpose of CPB systems are to balance pressure to minimize hot and cold air from entering
• Reduced pitch buildup can be gained, as can VOCs while the dryer increases thermal efficiency
• Stopoffs and a Beck actuator is placed between two adjacent sections with separate sections.
• This then reads 0 w.c. with negative readings that signify cool air and hot temperature that must be compensated for.
• Cooler pressure remains constant only with fans running at 100%

Veneer Surface Temperature Control

• This system maintains the Veneer temp. during exiting.
• Each fan is driven by the speed command.
• If at low temperature there is the option to stop

Method of operation

• Damper remains active, it can control the fans
• 1st stage: #2 and #3 fans.
• Adjust fan speed based on Veneer
• 2nd stage: same process but for after
• Damper works for temperature
• Low temps close with a low control

Torque Monitoring System

• The safety system manages the veneer
• The motors accurately monitor torque
• Dryers must monitor and report on it.
• Check values and sort at the same time
• Individual decks enable the operator.

Managing Warnings

• Alarms sound for potential plug
• Operators use right/left buttons to resolve issues
• Set levels below the yellow indicator
• The device has alerts to prevent dangerous errors.
• Always stop and investigate before anything.

Setting Conditions

• If control does not support a set amount of degrees a list of criteria must be investigated
• If control can't uphold it then investigate holes or components in the system.

Dryer Outfeed Layout

• Dryer outfeed is placed outside of the last cooling phase.
• Has an unloader transfer which is operated through the MCC.
• Once the Dryer exits passes the drop gate
• PLC pauses the veneer briefly
• Radius conveyor to the incline
• Operators verify sheet square

Outfeed Features

• As the Veneer travels beneath the brushes of the GS2000.
• If trash is flagged then gates turn on to separate it.
• If nothing is found it travels to the bin.

Unloader/Transer

• The unloader is synched with production
• If there is an issue perform checks.

RadiusBelts

• The belts must work so that they will turn to face the stacker at a 90° degree angle

Table

• The Even Ender is designed to ensure square sheets
• If its working well then the stacker handles things well with no bounce

Dryer Operation

• The GS2000/Sequoia are required to run.
• The GS2000 with its deep learning is 99.9 percent accurate.
• It scans the defects
• Rules are set that flag too much damage based on a moisture amount
• Based on that it destinations it.
• Do not feed double sheets.
• The system uses high light

Sequoia

• Calculates temperature and moisture, It measures in multiple zones for this process.
• It reads steam and has a large range of species

Trash Gate

• Works alongside the GS2000
• The feed can be opened manually
• Foot control is also available
• It is needed that it not turn sideways
• If sideways correct it and do not run it over.
• Calibrate all lights to calibrate

Stacker Operation

• Bins can be ejected of product and it reads on different levels for differing product.
• The 10 bin dryer separates out redry and re-feed while stacking to high level of grading
• With a backup redundancy feature each bin with its HMI
• Electricity can set each amount for each, this is how the veneer works.
• System needs to adjust as new layers for the system's thickness

Grade Assignment

• The grade assignment is received form the GS2000
• If at all incosistent then check the machine

Bins

• The default bins are all open until otherwise manually changed.
• Here is what a destination looks like
• This is when things get set to 10 if all features fail.

Sheet Count

• For production tracking set max for it before load amount
• The exact amounts are 3/16 at 135, 160 at 1/6, 200 at 1/8 and 225 sheets for 1/10

Conveying

• The process has rolls as part of the unload.
• If short manually guide to make it to the end.

ChangeOver

• Each must enable all actions.
• Then set for 2 seconds and it will automatically change for you.