Download - Session 16 ic2011 schimleck
Measuring the moisture content of green hardwood logs using time domain reflectometry
H. Raybon1, L.R. Schimleck1, K. Love‐Myers1, J. Sanders1, R.F. Daniels1 and E. Schilling2
1University of Georgia2NCASI
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Many forest products companies store wood in
wet decks
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Maintain steady wood supply when logging
productivity may decrease
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Wood stored at high moisture content to
prevent degradation and maintain wood quality
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Directional sprinklers deliver a constant supply
of water
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In the SE USA the use of water has become an
important issue
Introduction: Wet decks
Introduction: Wet decks
Introduction: Wet decks
Pine Calibration
‐77.52 + 98.64 x apparent distance
Hardwood calibration
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Hardwood wetdecks store a wide range of species
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“Hard”
hardwoods: red/white oaks, hickory
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“Soft”
hardwoods: black gum, red maple, sweetgum, yellow
poplar
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Regional differences in the species stored
Goals:
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Determine whether TDR measurements can be used to
predict moisture contents of various hardwood species
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Create a model or models to predict moisture content from
inflection point of TDR waveform
Hardwood calibration
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Four hardwood species selected:
sweetgum, yellow poplar, red oak,
white oak
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Four logs of each species, three bolts
from each log (48 bolts involved)
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Bolts fitted with TDR probes and
hydrated in tank for 1 month, then
allowed to air‐dry over 16 days (9
sets of measurements)
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TDR readings taking at each weighing
interval
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Samples oven dried, MC determined
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Calibration curves developed
Yellow Poplar
Sweetgum
Red Oak
White Oak
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Based on the sigmoidal shape, logistic
“growth”
model was used
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The model is MC =
is the maximum moisture content
is the inflection point of the curve, located at the point where half the maximum moisture content is obtained
is related to the curvature of the model
and vary randomly with the log/bolt to help obtain better estimates
Hardwood Calibration
αγ
κα γ
)}(exp{1 γκα
−−+ x
Yellow Poplar Calibration Plot
Sweetgum Calibration Plot
White Oak Calibration Plot
Red Oak Calibration Plot
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Two manipulative study sites
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Offerman Woodyard near Blackshear, GA
Rayonier
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McBean Woodyard near Augusta, GA
International Paper
Manipulative Studies
Offerman Woodyard
Treatments:
• Two treatments – nominal and 30% reduction by
turning off the sprinklers two days per week
• Actual rates not known at this time
• Two replications of each treatment due to limited
space
Species:
• Due to availability in Flatwoods included:• Sweetgum ‐
24 trees
• Yellow poplar ‐
24 trees
Offerman Woodyard
Offerman Woodyard
Offerman Woodyard
Offerman Woodyard
Offerman Woodyard Design
•2 probes per tree•1 tree of each species in each position
Offerman woodyard
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First readings taken in August 2010 during
installation, sprinklers turned on within a
week
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Yellow poplar moisture unsteady, even falling
below the original levels
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Sweetgum moisture generally increasing
Offerman First Plots
• Unstable moisture content• Currently no treatment effect…treatments began as different avg moisture contents
Offerman First Plots
• More stable moisture content• Currently no treatment effect…treatments began as different avg moisture contents
McBean Woodyard
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Again, two treatments
Nominal rate
30% reduction by turning off water 2 days per week
Actual rates not known at this time
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Two replications
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Two Species
Sweetgum ‐ 24 trees
Red oak ‐ 24 trees
availability
Conclusions
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TDR monitoring can be used to measure moisture
content successfully in hardwoods
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Each species requires its own model
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The model is partially determined by the maximum
moisture content of the species being monitored
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TDR is applicable to measuring moisture content in
operational wetdecks
Acknowledgements
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NCASI for providing funding for this study
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International Paper and Rayonier for providing
study sites