steam and vacuum treatment of large timber in solid wood ......1 steam and vacuum treatment of large...
TRANSCRIPT
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Steam and Vacuum Treatment of Large Timber in Solid Wood Skids
Zhangjing Chen and Marshall S. White
Virginia Tech, 1650 Ramble Road, Blacksburg, VA 24060
Email: [email protected], [email protected]
Ron Mack
USDA APHIS, PPQ, Pest Survey, Detection and Exclusion Laboratory,
W. Truck Road, Otis ANGB, MA 02542
Email: [email protected]
This study was funded by USDA, APHIS, PPQ. Pest Survey, Detection and Exclusion
Laboratory,W. Truck Road, Otis ANGB, MA 02542
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Abstract:
Forest pests are commonly transported with wood packaging materials. Ports in US
continue to intercept invasive pests in large cross section timbers used to transport heavy
consignments. The large cross section timbers present a greater risk because the fumigation and
hot air treatment as currently used for treating wood packaging materials are not effective. The
objective of our study is to determine the effectiveness of steam and vacuum for heat treating large
cross section timbers in wood skids and crates, according to the heat treating requirements of ISPM
15. Three wood species of large dimension (8×8 and 4×4 inches) timbers were tested. These
represented a high density hardwood, a low density hardwood and a commonly used softwood.
These were mixed oak (Quercus spp), yellow-poplar (Liriodendron tulipifera) and mixed southern
yellow pine (Pinus spp.). The timbers were partially air dried and are typical of large timbers used
in heavy wood skids. Larvae of pinewood sawyer beetles (Monochamus spp.) were used as a
representative surrogate for invasive cerambycids.
During each test, three skids assembled from each wood species were treated. Separate
and untreated large timbers and a 4×4 inch deck timber were set aside as control specimens during
each test. Prior to each test, eight larvae were inoculated into two large timbers (four each), and
single larvae seeded in a deck timber. Four larvae were inserted in the large control timber and
one larva in the control deck timber. The initial vacuum pressure was 100mm Hg and the test
chamber temperature was 90°C. The treatment cycle continued until the core temperature of the
large timber reached the required 56°C for 30 minutes. To measure temperature profiles within the
timbers, thermocouples were placed at various locations. After each test, larvae were recovered
and assessed for mortality. Potential treatment effects on the quality of the timbers and the
structural integrity of the skid were examined. The ends of each large timber were photographed
before and after treatment to monitor end splitting.
In order to document the change in moisture content (MC), large timbers were weighed
before and after treatment. Overall heating time to achieve 56°C for 30 minutes to core was less
than 7 hours for all 3 wood species tested (100 mmHg and 90°C steam). This is at least 30% less
time than predicted treatment cycles using hot air at atmospheric pressure. Using hot air would
dry the ends of the timber and result in splitting and degradation of skids. There was complete
mortality (100%) of larvae as a result of treatment. The quality of 8x8 timbers was not affected
by the treatment. The average MC of the 8×8 inches timber increased 4.1% after each test.
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1. Background
Heat has been used to kill insects, fungi and nematodes living in wood for a long time.
Asians have used this method for thousands of years. There are early publications about the use
of heat treatment to kill insects and fungi (Craighead 1920, Snyder 1923). Heat sterilization of
wood, in various forms, is currently used for killing insects or pathogens to prevent their transfer
from one geographical region to another. One important concern is the amount of time required
to heat wood of various cross-sectional sizes to a required temperature.
Treatments for logs and other wood commodities were reviewed by the US Forest Service
in the early 1990s as the international movement of wood products were seen as a major risk to
the importation of exotic forest pests (USDA 1991). Heat treatment is an effective method for
killing pests that affect forest growth. This paper reviews the history of heat as a wood treatment,
the scientific basis for its effect on wood pests (including insects, fungi, nematodes and bacteria),
the industrial processes by which wood is heat treated and how heat treatment can be incorporated
into phytosanitary measures to control forest pests. Heat can be from steam, hot air, and water or
generated using the microwave energy.
Wood packaging has been recognized as a pathway for invasive forest pests (Allen and
Humble 2001). The Asian Longhorned Beetle, Anoplophora glabripennis Motschulsky, migrated
into North America in infested packaging materials (Liebhold et al. 1995). Preshipment treatment
to 56°C for 30 minutes was adopted by many countries as a method of controlling the migration.
The ports of Baltimore and Philadelphia continue to intercept invasive pests in heavy
timbers of SWPM used to ship steel or heavy consignments. The large size timbers (20 to 30 cm
thick) are common and used in heavy duty skids and crates. These large timbers present a greater
risk because fumigation and heat treatment as currently applied to SWPM are not effective or
practical on such size wood material.
It is likely that the current Asian long horned beetle infestation in Bethel, Ohio was
introduced through heavy skids used to ship tractor parts that were shipped to a local business in
the core area. Certain dunnage, because of its irregular and large shapes remains a suspected
carrier of invasive pests as well.
Chen et. al. (2012) have shown that pallets with wood parts of smaller dimensions can be
heat treated to ISPM 15 requirements of 56/30 with steam and vacuum in less than half the time
and using 30% less energy than conventional hot air oven systems. Chen and White (2011) have
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also shown that this process may be very effective for heat treating wood commodities with larger
cross sections such a hardwood firewood and hardwood veneer logs. This process, which
incorporates the latent heat of water phase transition, the exothermic reaction of condensation and
vacuum to distribute the heat may effectively treat, large timber SWPM in skids and crates without
adversely affecting the material quality and skid structural integrity.
MacLean (1930, 1932) showed some agreement between experimental and calculated
heating time-temperature curves for rectangular cross-sectional timbers. Simpson (2001) has
calculated the heating time as a functions of diameter and the ambient temperature in steam and
dry air for round wood cross sections. Simpson also conducted some tests on the steam heating of
wood. The heating time is a function of temperature of the timbers and it has been both
experimentally measured and predicted based on the heat conduction equation in his paper.
Simpson (2001) sprayed the steam to increase temperature of aspen and maple timbers using an
experimental dry kiln (3.5 m3). The predicted heating time for the larger timbers (approximately
6 by 6 in. (152 by 152 mm)) is about 172 minutes from 12°C to a core temperature of 54°C. The
equations are able to estimate heating times in steam to a degree of accuracy that is within about
5% to 15% of measured heating times. In his testing, he did not incorporate the vacuum to
effectively distribute the heat.
2. Research Objectives
To determine the effectiveness of steam and vacuum for phytosanitary heat treating large
cross section timbers (8×8 inches) in wood skids and crates, according to the heat treating
requirements of ISPM 15.
3. Test Materials and Specimens
3.1 Large timber
Three wood species groups were tested to represent a range of wood densities and species
currently used in skids. They are mixed oak (Quercus spp), yellow-poplar (Liriodendron
tulipifera) and southern yellow pine (Pinus spp.). These timbers were partially air dried as is
typical of large timbers used in heavy skids. Figure 1 is a photograph of the 8 inches by 8 inches
by 6 feet long timbers used in tested wood skids.
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Figure 1. The 8 by 8 inches large timber of southern pine, yellow-poplar and oak spp.
The 4 inches by 4 inches by 4 feet long deck timbers of the same wood species are shown
in Figure 2.
Figure 2. The 4 by 4 inches deck timbers of southern pine, yellow-poplar and oak spp.
3.2 Large skids
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Skids were manufactured according to the base design in ASTM D 6039 “Standard
specification for crates, wood, open and covered”, for type V, style B crates. Figure 3 shows this
basic design with the dimensions. The parts were connected with lag screws in accordance with
the specification.
Figure 3. Schematic diagram of the tested skids.
3.3 Pine sawyer beetles
Pine sawyer beetles were inoculated into to the large wood at the locations shown in figure
4. The sawyer beetles (Monochamus spp.) were selected because these long horned beetles of
family Cerambycidae, inhabit living trees and have life cycles similar to the Asian long horned
beetle. The larvae weighed between 500 mg to 1.2 g.
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Figure 4. The locations in the large timber of temperature probes and larvae.
4. Test equipment
Figure 5 shows the 5×5×8.5 feet long vacuum steam chamber. The chamber is equipped
with a 7 hp vacuum pump with a 56 CFM exhaust capacity and a 100KW electric steam boiler.
The conditions in the chamber are controlled semi-automatically. The system also includes a data
acquisition system for real time recording of temperatures from 8 separate sources.
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Figure 5. Photograph of vacuum steam chamber used in the tests
5. Experimental design
Three skids were treated at a time to simulate commercial treatment of such structures.
Each wood species skid was be replicated three times. Therefore nine skids of each species were
treated. Additionally there is one control large timbers of each species that was not treated.
6. Test procedures
Eight larvae were placed in two large timbers and one in a deckboard in each skid. Four
larvae were placed in the large control timber and one in the small timber. After the tests, the
larvae were retrieved and the mortality of larvae was checked.
6.1 Test conditions
The initial vacuum pressure was 100mm Hg and test chamber temperature was set to be
90°C. The treatment cycle continued until the core temperature of the largest timber reached the
required 56 °C for 30 minutes.
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6.2 Measuring temperatures
Thermocouples were placed in the large timbers as shown in Figure 4. One, randomly
selected, 4×4 pieces of the skid was probed at the geometric center to monitor the core
temperatures. This was done to determine the extent of the treating smaller wood pieces and
whether this would degrade these pieces.
The holes of diameter of 3/16 inch were plugged with plumber putty and sealed after
thermocouples were placed at the locations shown (Figure 6). Real time temperature profiles were
recorded. Cycle times were determined.
Figure 6. A thermocouple was inserted into wood and plugged with putty.
6.3 Inoculation with live pests
Larvae of the pinewood sawyer beetles (Monochamus spp.) were used as simulants of the
invasive longhorned beetle (Cerambycidae). The larvae were collected from the infested pine trees
(Figure 7). After they are removed from the trees, larvae were placed on a diet prior to the use
(Figure 8). The larvae were transported in the containers to Blacksburg, Virginia (Figure 9).
During the tests, the larvae were be placed at the same locations as the temperature probes shown
in Figure 4. There were three large timbers during each test. One is used for measuring
temperature and two for placing larvae. It was assured that the temperature to which the larvae
were exposed was the same as the temperature measured at the corresponding location in a
different skid.
Larvae were also placed in a control, non-treated timber such that the mortality can be
compared and efficacy of treatment verified. The holes in which the larvae were placed were
plugged with wood dowels (Figure 10).
Thermocouple
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Figure 7. Pine sawyer beetles used as simulant in the tests.
Figure 8. Pine sawyer beetles were raised on a diet.
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Figure 9. Larvae were transported in the treatment containers.
Figure 10. The 3/8 inches hole was drilled and tightly plugged with the dowels after larva
was inserted.
6.4 Inspection of skids and dunnage parts
To monitor any effect of the treatment on the quality of the timbers and the structural
integrity of the skid structures, all parts and connections were inspected before and after treatments.
Any observed degradation of the parts or connections was noted. The ends of the large timber in
each skid were photographed before and after treatment to determine any change in end splits.
Figure 11 shows typical test skids ready for treatment.
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Figure 11. Photograph showing typical test skid.
6.5 MC measurement
Large timbers were weighed before and after treatment. After the treatment, one-inch
moisture sections were cut, at least one foot from each end of timber. This is section “b” in Figure
12. The moisture sections were oven-dried to calculate the MCs of timber. From these MCs and
the weight change of the timber, the change in MC can be determined.
The moisture gradient was determined within each large timber. A one inch thick by 8 by
8 inches section was cut from within each timber. The moisture gradient sections were cut by
sawing this one inch thick section into 7 pieces as shown in Figure 13 as section “C” in Figure 12.
Figure 12. Locations of moisture sections “b” and moisture gradient section “c”, a=12
inches, discarded.
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Figure 13. Seven moisture gradient sections were cut from one inch thick by 8 by8
inches cross-section.
6.6 Larvae were weighted
Larvae were also weighed before and after treatment using a scale to determine if
desiccation occurs during treatment (Figure 14).
Figure 14. Larvae were weighed before and after treatment.
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6.7 Mortality of larvae was determined
Larvae were observed for two days. If no movement was evident that larvae were assumed
dead.
6.8 Densities of large timber
Wood density was measured using the water displacement method. Oven-dried wood
samples are pressed below the water surface in a beaker on a top loading balance. The volume of
the wood is read accurately on the balance as the mass of the displaced water.
7. Test result and discussion
7.1 Temperature profiles
Figures 14 to 16 are typical temperature profiles for each wood species. Temperature
profiles for all tests are in the appendix. The chamber and surface temperatures increased rapidly
as soon as steam entered the chamber. Next the temperature next to surface slowly rose. The
temperature at center of timber initially remain unchanged for a certain time and linearly increase
later to the final set point of 56°C. This profile is similar to those recorded when treating large
diameter logs (Chen et al. 2012). The center of the 4 by 4 inches deck timber reached 56ºC within
60 to 90 minutes and remains at 85ºC for about 4 hours for many tests. The concern is the potential
for degradation of small timber in an attempt to treat the large timber to 56/30. There is very little
temperature gradient along length. The rate of heating is similar at ¼, 1/3 and ½ of the timber
length. When wood cross sections are uniform along the length, probing the geometric center is
recommended, but depending on the ease of thermocouple placement, it is not necessary. Theory
implies any distance from the end greater than 2.5 times the distance to the center of timber.
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Figure 14. Typical temperature profile of the 8×8 timber in the yellow-poplar skid at the
initial vacuum pressure of 100 mmHg.
Figure 15. Typical temperature profile of the 8×8 timber in the pine skid at the initial
vacuum pressure of 100 mmHg.
0
10
20
30
40
50
60
70
80
90
100
0 60 120 180 240 300 360 420
Tem
per
ature
(C
)
Treating time (Min)
1/2L at 2-inch deep
1/3L at 4-in deep
Geometric center of
large timber1/4L at 4-in deep
Chamber
Timber surface
Deck timber center
0
10
20
30
40
50
60
70
80
90
100
0 60 120 180 240 300 360
Tem
per
ature
(C
)
Treating time (Min)
1/2L at 2-inch deep
1/3L at 4-in deep
Geometric center of
large timber1/4L at 4-in deep
Chamber
Timber surface
Deck timber center
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Figure 16. Typical temperature profile of the 8×8 timber in the oak skid at the initial
vacuum pressure of 100 mmHg.
7.2 Treating time
The total treating times (including vacuum time and 30 minutes holding time) for the tests
are presented in the following table 1.
Table 1. Treating time at the initial vacuum of 100 mmHg for 8’ by 8’ timbers.
Test Red Oak Southern Pine Yellow-Poplar
Initial
wood
T
Vacuum
time
Total
time
Initial
wood
T
Vacuum
time
Total
time
Initial
wood
T
Vacuum
time
Total
time
(°C) (min) (min) (°C) (min) (min) (°C) (min) (min)
1st 20 13 409 16 13 326 12 14 345
2nd 14 14 407 11 12 318 15 13 311
3rd 13 12 403 8 13 320 7 12 384
Average 16 13 406 12 13 321 11 13 347
0
10
20
30
40
50
60
70
80
90
100
0 60 120 180 240 300 360 420
Tem
per
ature
(C
)
Treating time (Min)
1/2L at 2-inch deep
1/3L at 4-in deep
Geometric center of
large timber1/4L at 4-in deep
Chamber
Timber surface
Deck timber center
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The treatment duration of each log during each test is in Table 1 which includes vacuum
time and a 30-minute hold time. From Table 1, the treating time for 8 by 8 inches varied from 311
(5.2 hours) to 409 minutes (6.8 hours) depending on the wood species. Methyl bromide log
fumigation schedules require at least 24. The result indicate that the large 8 by 8 timbers can be
heat treated with vacuum steam technology to 56°C for 30 minutes, faster than fumigating.
In vacuum steam treatment, several variables affect the time required to heat wood to a
given temperature. Heating time is influenced by wood density, wood MC, initial wood
temperature, and geometry of wood.
7.3 The effect of species on the treatment time.
From Table 1, it is clear that it takes the least time to treat southern pine. The hardwood
of less dense wood, yellow poplar, has been heated up faster than the heavier wood, oak spp.
Softwood, such as pine, has a straight, linear tracheid, which transport steam faster. The hardwood
have more types of cells and its cells have irregular shape and arrangement.
7.4 Effect of size on the treating time.
The larger the timber, the longer the treating time. This is shown in the temperature profile
(Figures 14-16). The average time for 4 by 4 inches oak deck timber of to reach 56°/30 minutes
is about 100 minutes compared to the 311 to 409 minutes required to heat treat the 8 by 8 inches
cross section. Larger cross sections require more time and energy to heat treat.
The vacuum steam process would be ideally suited for treating wood structures with
different size timber. The process will not degrade smaller timber that will heat more rapidly and
remain at higher temperature than the larger timber. A hot air system would likely degrade the
small timbers in the skid.
7.5 Effect of wood density and initial MC on the treating time.
In general, it took longer to treat the oak than yellow-poplar or southern pine. Southern
pine required the shortest duration. The oven-dry densities of the three wood species in Table 2.
Southern pine has the lowest density and oak the greatest. However, as shown in Table 3, at the
time of treatment, the oak timber contained about 57% more water. For this reason, it is not
possible to separate the wood MC and oven-density effect. Figure 17 shows the linear relationship
between the gross density (effect of both oven-dry density and MC) and the treating time with R-
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squared = 0.85 and p-value = 0.0004 for the slope. The higher the gross density, the longer time
to treat the timber. The oak with high MC has higher gross density than oak containing less
water. It took longer to treat high MC oak timber even it has the same oven-dry density as oak
timber containing less water.
Table 2. The average oven-dry densities of test samples.
Species Number of samples Average oven-dry
Density (g/cm3)
Standard deviation
Yellow-poplar 8 0.52 0.071
Southern pine 8 0.48 0.071
Oak spp. 8 0.71 0.077
Figure 17. The relationship between timber density and treating time.
7.6 Moisture gained during treatment.
y = 3.6379x + 184.52R² = 0.8497
0
50
100
150
200
250
300
350
400
450
30 35 40 45 50 55 60 65
Tre
atin
g t
ime
(min
)
Timber density (lb/ft3)
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Based on MCs from the moisture sections measured in oven-dry method, the MC content
before and after treatment for the large timber can be calculated. The moisture gained during the
treatment was also calculated and listed in Table 3.
Table 3. MC gained during treatment
Species Number of
samples
Average MC
before treatment
(%)
Average MC
after treatment
(%)
Average MC
difference
(%)
Yellow-poplar 5 39.1 41.9 2.8
Southern pine 7 38.3 45.1 6.8
Oak spp. 7 60.6 63.4 2.8
Average 4.1
From Table 3, the average MC increase from the large timber is about 4.1%. The average
MC of hardwood timber averaged by 2.8% and southern pine timber increased by 6.8%.
7.7 Larva weight change during the treatment
Average larva’s weigh change for each individual test and a statistical analysis is in Table
4. The statistical analysis indicated that there is no significant difference in larvae’ weight before
and after treatment. Therefore, desiccation is not a mechanism of mortality as previously shown
by Chen et al. (2008) where only vacuum is used for treatment.
7.8 Larva mortality
After each treatment, larvae were recovered from the treated and control large timbers.
They were checked for mortality. They were then placed in the new diet and observed for two
days. After the larvae were retrieved from the testing samples, they were soft and pale.
Apparently, they were in a lethal state. If they remained immobile after two days they were
assumed dead. 100% mortality was observed for those larvae in the treated timbers. All larvae
that were retrieved from the control samples were alive. They burrowed into the diet and remained
active.
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7.9 Quality evaluation, checking and color change of large timbers
The timber quality of both control and treated timbers was carefully monitored and
compared before and after treatment. The primary measure of the timber quality was any change
the size and number of end splits. Photo images of the ends of the treated timbers were taken
before and after treatment. Photos from three timbers of each species are in Tables 5 and all photos
are included in Appendix. There were no obvious checks occurring after treatment or any
measurable increase of the existing checks. The color of timbers did not change during the
treatment.
The structural integrity of the skid structures was not affected. All connections were
inspected and no difference was observed before and after treatment.
Table 4. Comparison of larvae weight change due to the treatment.
Test
Species
Number
of treated
larvae
Avg.
treated
larva wt.
change
Number
of control
larvae
Avg.
control
larva wt.
change
P-value
1 Yellow-
poplar
9 0.008 5 -0.074 0.09
2 9 -0.032 5 -0.018 0.14
3 9 0.033 9 -0.052 0.03
4 Southern
pine
7 -0.017 5 -0.024 0.55
5 9 -0.032 5 -0.040 0.86
6 9 0.001 5 -0.028 0.19
7
Oak spp.
9 -0.009 5 0.042 0.07
8 9 0.010 4 0.023 0.03
9 8 0.066 5 -0.004 0.02
Overall 0.0031 -0.0019 0.17
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Table 5. Typical end grain images of large timbers before and after treatment.
Sample Image before test Image after test
1a
1b
11a
11b
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Sample Image before test Image after test
21a
21b
8. Conclusion
8.1 Total treating time to achieve 56°C for 30 minutes at core was less than 7 hours for all three
wood species tested (100 mmHg and 90°C steam). Treating cycle are less than methyl bromide
fumigation specified in ISPM 15.
8.2 There was complete mortality (100%) of larval surrogates as a result of treatment.
8.3 Quality of 8x8, 4x4 timbers and skids was not affected by the treatment.
8.4 During treatment, the average timber MC increased by 4.1%.
8.5 Vacuum and steam can be used to efficiently pre-shipment heat treat and to heat treat
quarantined, large timber SWPM in compliance with ISPM 15.
9 References
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Chen, Z., M. S. White, M. A. Keena, T. M. Poland and E. L. Clark. 2008. Evaluation of vacuum
technology to kill larvae of the Asian longhorned beetle, Anoplophora glabripennis
(Coleoptera: Cerambycidae), and the emerald ash borer, Agrilus planipennis (Coleoptera:
Buprestidae), in wood. Forest Products Journal, 58(11):87-93.
Chen, Z., M.S. White, and Y, Wu. 2012. Vacuum-steam phytosanitation of hardwood pallets and
stringers. Forest Products Journal, 62(5): 378-382
Chen, Z., M.S. White, and R. Mack .2011. Using vacuum and steam to sanitize hardwood veneer
logs for export. Project final report to USDA, APHIS, PPQ, Raleigh, NC.
Craighead, F. C. 1921. Temperatures fatal to larvae of the red-headed ash borer as applicable to
commercial kiln drying. Journal of Forestry 19: 250-254.
Liebhold, A. M., W.L. MacDonald, D. Bergdahl, V.C. Mastro, (1995). Invasion by exotic forest
pests: a threat to forest ecosystems. Forest Science 41: 1-49.
MacLean, J.D. 1930. Studies of heat conduction in wood. Pt. I. Results of steaming green round
southern pine timbers. In: Proceedings of American Wood Preservers’ Association. 26:
197-217.
MacLean, J.D. 1932. Studies of heat conduction in wood. Pt. II. Results of steaming green sawed
southern pine timber. In: Proceedings of American Wood Preservers’ Association. 28: 303-
329.
Simpson, W. T. 2001. Heating times for round and rectangular cross sections of wood in steam.
Gen. Tech. Rep. FPL-GTR-130. Madison, WI: U.S. Department of Agriculture, Forest
Service, Forest Products Laboratory. 103 p.
Snyder, T.E. 1923. High temperatures as a remedy for Lyctus powder-post beetles. J. of For. 21:
810-814
USDA. 1991. Pest risk assessment of the importation of larch from Siberia and the Soviet far East.
USDA For. Serv. Misc. Pub. 1495.
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10 Appendix
Figure A-1. Temperature profile at the initial vacuum pressure of 100 mmHg for yellow-
poplar test 1.
Figure A-2. Temperature profile at the initial vacuum pressure of 100 mmHg for
yellow-poplar test 2.
0
10
20
30
40
50
60
70
80
90
100
0 60 120 180 240 300 360 420
Tem
per
ature
(C
)
Treating time (Min)
1/2L at 2-inch deep
1/3L at 4-in deep
Geometric center of
large timber
1/4L at 4-in deep
Chamber
Timber surface
Deck timber center
0
10
20
30
40
50
60
70
80
90
100
0 60 120 180 240 300 360
Tem
per
ature
(C
)
Treating time (Min)
1/2L at 2-inch deep
1/3L at 4-in deep
Geometric center of
large timber1/4L at 4-in deep
Chamber
Timber surface
Deck timber center
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Figure A-3. Temperature profile at the initial vacuum pressure of 100 mmHg for yellow-
poplar test 3.
Figure A-4. Temperature profile at the initial vacuum pressure of 100 mmHg for pine test
1.
0
10
20
30
40
50
60
70
80
90
100
0 60 120 180 240 300 360 420
Tem
per
ature
(C
)
Treating time (Min)
1/2L at 2-inch deep
1/3L at 4-in deep
Geometric center of
large timber1/4L at 4-in deep
Chamber
Timber surface
Deck timber center
0
10
20
30
40
50
60
70
80
90
100
0 60 120 180 240 300 360
Tem
per
ature
(C
)
Treating time (Min)
1/2L at 2-inch deep
1/3L at 4-in deep
Geometric center of
large timber1/4L at 4-in deep
Chamber
Timber surface
Deck timber center
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Figure A-5. Temperature profile at the initial vacuum pressure of 100 mmHg for pine test
2.
Figure A-6. Temperature profile at the initial vacuum pressure of 100 mmHg for pine test
2.
0
10
20
30
40
50
60
70
80
90
100
0 60 120 180 240 300 360
Tem
per
ature
(C
)
Treating time (Min)
1/2L at 2-inch
deep1/3L at 4-in deep
Geometric center
of large timber1/4L at 4-in deep
Chamber
Timber surface
Deck timber center
0
10
20
30
40
50
60
70
80
90
100
0 60 120 180 240 300 360 420
Tem
per
ature
(C
)
Treating time (Min)
1/2L at 2-inch deep
1/3L at 4-in deep
Geometric center of
large timber1/4L at 4-in deep
Chamber
Timber surface
Deck timber center
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Figure A-7. Temperature profile at the initial vacuum pressure of 100 mmHg for oak test
1.
Figure A-8. Temperature profile at the initial vacuum pressure of 100 mmHg for oak test
2.
0102030405060708090
100
0 60 120 180 240 300 360 420
Tem
per
ature
(C
)
Treating time (Min)
1/2L at 2-inch deep
1/3L at 4-in deep
Geometric center
of large timber1/4L at 4-in deep
Chamber
Timber surface
0
10
20
30
40
50
60
70
80
90
100
0 60 120 180 240 300 360 420
Tem
per
ature
(C
)
Treating time (Min)
1/2L at 2-inch deep
1/3L at 4-in deep
Geometric center of
large timber1/4L at 4-in deep
Chamber
Timber surface
-
28
Figure A-9. Temperature profile at the initial vacuum pressure of 100 mmHg for oak test
3.
Table A-1. MCs measured from moisture gradient sections
Timber Moisture section Initial wt Final wt MC
g g %
1 1 61 46.26 31.9
2 70 50.59 38.4
3 65.3 46.26 41.2
4 62.5 44.16 41.5
5 63.4 45.29 40.0
6 61.7 44.18 39.7
7 57.1 43.48 31.3
2 1 63.5 46.75 35.8
2 69.9 48 45.6
3 70 47.63 47.0
4 66.8 45.58 46.6
5 59.6 41.26 44.4
6 53.7 37.65 42.6
7 51.8 39.84 30.0
3 1 51.1 38.09 34.2
2 56 37.26 50.3
0102030405060708090
100
0 60 120 180 240 300 360
Tem
per
ature
(C
)
Treating time (Min)
1/2L at 2-inch
deep1/3L at 4-in deep
Geometric center
of large timber1/4L at 4-in deep
Chamber
-
29
Timber Moisture section Initial wt Final wt MC
3 55.7 35.48 57.0
4 59 34.77 69.7
5 52.1 33.74 54.4
6 49.9 33.81 47.6
7 45.4 33.09 37.2
4 2 55.1 41.82 31.8
3 58.6 39.88 46.9
4 56.1 37.72 48.7
5 59.4 39.93 48.8
6 59 40.29 46.4
7 54 37.95 42.3
5 1 36 27.51 30.9
2 39.9 28.97 37.7
3 38.2 27.06 41.2
4 38.6 25.86 49.3
5 44.4 29.69 49.5
6 42.1 29.62 42.1
7 42.4 30.99 36.8
6 1 35.8 27.4 30.7
2 34.3 25.78 33.0
3 35.5 24.88 42.7
4 35.8 25.34 41.3
5 36.7 25.91 41.6
6 36 25.1 43.4
7 36.7 26.38 39.1
7 1 48 35.1 36.8
2 54.7 35.26 55.1
3 53 34.5 53.6
4 52.5 35.11 49.5
5 52.2 36.92 41.4
6 46.4 34.97 32.7
7 46.7 35.34 32.1
8
control 1 45.1 36.53 23.5
2 46.4 35.21 31.8
3 45.1 33.03 36.5
4 44.3 32.1 38.0
-
30
Timber Moisture section Initial wt Final wt MC
5 44.2 31.57 40.0
6 44 32.15 36.9
7 41.8 31.5 32.7
11 1 29.4 21.12 39.2
2 33 21.98 50.1
3 32.2 21.67 48.6
4 32.4 22.1 46.6
5 34.4 25.3 36.0
6 34.9 25.7 35.8
12 1 50.6 35.8 41.3
2 55.3 39 41.8
3 57.6 40.4 42.6
4 55.8 40 39.5
5 56.1 41.2 36.2
6 54.3 40.3 34.7
7 48.7 36.7 32.7
13 1 48.1 29.6 62.5
2 49.1 30.6 60.5
3 50.3 34.14 47.3
4 52.5 35.62 47.4
5 58.1 39.3 47.8
6 56.3 32.3 74.3
7 54.8 33.5 63.6
14 1 41.5 31.8 30.5
2 49.8 33.9 46.9
3 77.9 56.62 37.6
4 77.7 58.89 31.9
5 65.4 46.68 40.1
6 43.1 29.89 44.2
7 50.7 33.8 50.0
15 1 35 25.83 35.5
2 36.5 25.81 41.4
3 41.9 28.53 46.9
4 50.2 35.9 39.8
5 60.7 47.91 26.7
6 54 43.21 25.0
-
31
Timber Moisture section Initial wt Final wt MC
7 43.4 34.5 25.8
16 1 33.1 25.04 32.2
2 29.1 19.4 50.0
3 32.1 24.43 31.4
4 30.8 21.74 41.7
5 33.3 20.96 58.9
6 29.6 20.03 47.8
7 26.8 18.61 44.0
17 1 59.7 36.38 64.1
2 76.9 52.16 47.4
3 86.3 52.16 65.5
4 95.4 60.38 58.0
5 76.9 52.16 47.4
18
control 1 43.3
2 43.1 33.59 28.3
3 42.1 32.62 29.1
4 35 26.84 30.4
5 23.1 17.34 33.2
6 55.2 40.7 35.6
7 55.2 43.08 28.1
21 1 57.3 41.1 39.4
2 68.4 41.8 63.6
3 73.6 47.3 55.6
4 75.4 45 67.6
5 76.6 45.9 66.9
6 75.3 45.2 66.6
22 1 57.2 41.74 37.0
2 72.5 44.77 61.9
3 74.1 46.67 58.8
5 72.3 45.88 57.6
6 69.3 44.31 56.4
7 62.3 46.38 34.3
23 1 39.1 31.53 24.0
2 80.9 53.8 50.4
3 79.1 49.9 58.5
4 75.1 42 78.8
-
32
Timber Moisture section Initial wt Final wt MC
5 74.3 44.2 68.1
6 79.3 51 55.5
7 73.2 54.07 35.4
24 1 76.8 50.38 52.4
2 81.2 52.39 55.0
3 77.6 53.18 45.9
5 85.4 55.23 54.6
6 86.1 56.44 52.6
7 74.9 56.99 31.4
25 1 61.8 36.41 69.7
2 65.2 37.62 73.3
3 76.3 46.55 63.9
4 75.6 44.04 71.7
5 76.6 45.97 66.6
6 73.9 43.5 69.9
7 66.4 44.7 48.5
26 1 59.2 42.6 39.0
2 72 46.12 56.1
3 75.3 45.98 63.8
4 71.9 40.82 76.1
5 69.4 43.06 61.2
6 69.1 41.68 65.8
7 61.4 43.64 40.7
27 1 64.5 37.59 71.6
2 78.7 48.65 61.8
3 83.5 47.65 75.2
4 82.4 52 58.5
5 83.7 50.65 65.3
6 77.3 47.61 62.4
7 63.7 45.78 39.1
28
control 1
51.5 38.47 33.9
2 65 43.51 49.4
3 73.1
39.06 87.1
4 70.2 39.48 77.8
5 65 43.5 49.4
-
33
Timber Moisture section Initial wt Final wt MC
6 68.4 42.23 62.0
7 52.7 30.3 73.9
Larva weight
Table A-2. Larva weight measured before and after treatment.
Test
Larva wt
before test
(g)
Larva wt
after test
(g)
Difference
(g)
1
Yellow-
poplar
large lumber 1 1 0.57 0.6 0.03
2 1 1.1 0.1
3 0.74 0.7 -0.04
4 0.8 0.8 0
large lumber
2 1 0.41 0.41 0
2 0.41 0.4 -0.01
3 0.56 0.56 0
4 0.71 0.7 -0.01
deckboard 1 0.67 0.67 0
control lumber 1 0.48 0.47 -0.01
2 1.08 1.07 -0.01
3 0.69 0.67 -0.02
4 0.81 0.78 -0.03
2 large lumber 1 1 0.76 0.74 -0.02
2 0.85 0.84 -0.01
3 1.11 1.07 -0.04
4 0.74 0.72 -0.02
large lumber
2 1 1.11 1.07 -0.04
2 0.77 0.73 -0.04
3 1.19 1.18 -0.01
4 0.91 0.87 -0.04
deckboard 1 1.08 1.01 -0.07
control lumber 1 0.51 0.49 -0.02
2 1.04 1.02 -0.02
3 0.69 0.68 -0.01
4 0.72 0.71 -0.01
5 0.59 0.56 -0.03
3 large lumber 1 1 0.55 0.56 0.01
2 0.69 0.78 0.09
3 0.82 0.83 0.01
-
34
Test
Larva wt
before test
(g)
Larva wt
after test
(g)
Difference
(g)
4 0.88 0.91 0.03
large lumber
2 1 0.66 0.69 0.03
2 0.6 0.6 0
3 0.74 0.76 0.02
4 0.52 0.55 0.03
deckboard 1 0.73 0.81 0.08
control lumber 1 0.72 0.5 -0.22
2 0.6 0.59 -0.01
3 0.53 0.5 -0.03
4 0.75 0.75 0
5 0.66 0.66 0
11
Southern
pine
large lumber 1 1 0.53 0.51 -0.02
2 0.45 0.4 -0.05
3 0.69 0.68 -0.01
4 0.54 0.51 -0.03
large lumber
2 1 0.54 0.54 0
2 0.89 0.91 0.02
3 0.53
4 0.59
deckboard 1 0.73 0.7 -0.03
control lumber 1 0.91 0.89 -0.02
2 0.7 0.68 -0.02
3 0.89 0.86 -0.03
4 0.7 0.66 -0.04
5 0.81 0.8 -0.01
12 large lumber 1 1 0.77 0.76 -0.01
2 0.54 0.33 -0.21
3 0.69 0.69 0
4 0.84 0.89 0.05
large lumber
2 1 1.09 0.94 -0.15
2 0.83 0.83 0
3 0.84 0.92 0.08
4 0.73 0.7 -0.03
deckboard 1 0.51 0.49 -0.02
control lumber 1 1.02 0.97 -0.05
2 0.98 0.97 -0.01
3 0.63 0.54 -0.09
-
35
Test
Larva wt
before test
(g)
Larva wt
after test
(g)
Difference
(g)
4 0.82 0.8 -0.02
5 0.88 0.85 -0.03
13 large lumber 1 1 0.96 0.94 -0.02
2 0.67 0.67 0
3 0.8
4 0.57 0.65 0.08
large lumber
2 1 0.88 0.95 0.07
2 0.73 0.76 0.03
3 0.76 0.76 0
4 0.87 0.72 -0.15
deckboard 1 0.47 0.47 0
control lumber 1 0.6 0.59 -0.01
2 0.57 0.5 -0.07
3 0.75 0.73 -0.02
4 0.61 0.58 -0.03
5 0.52 0.51 -0.01
21
oak spp
large lumber 1 1 0.72 0.72 0
2 0.68 0.68 0
3 0.79 0.77 -0.02
4 0.77 0.75 -0.02
large lumber
2 1 0.89 0.88 -0.01
2 0.67 0.71 0.04
3 0.92 0.9 -0.02
4 0.84 0.84 0
deckboard 1 0.92 0.87 -0.05
control lumber 1 0.59 0.57 -0.02
2 0.66 0.63 -0.03
3 0.72 0.7 -0.02
4 0.76 0.65 -0.11
5 0.9 0.87 -0.03
22 large lumber 1 1 0.52 0.52 0
2 0.44 0.5 0.06
3 0.83 0.83 0
4 0.56 0.56 0
large lumber
2 1 0.73 0.72 -0.01
2 0.52 0.52 0
3 0.59 0.61 0.02
-
36
Test
Larva wt
before test
(g)
Larva wt
after test
(g)
Difference
(g)
4 0.97 0.99 0.02
deckboard 1 0.46 0.46 0
control lumber 1 0.44 0.45 0.01
2 0.49 0.45 -0.04
3 0.54 0.51 -0.03
4 0.77
5 0.78 0.75 -0.03
23 large lumber 1 1 0.9 0.95 0.05
2 1.06 1.1 0.04
3 0.7 0.8 0.1
4 0.47 0.53 0.06
large lumber
2 1 0.73
2 0.6 0.67 0.07
3 0.83 0.84 0.01
4 0.67 0.68 0.01
deckboard 1 0.79 0.98 0.19
control lumber 1 0.59 0.6 0.01
2 0.46 0.46 0
3 0.71 0.71 0
4 0.75 0.73 -0.02
5 0.88 0.87 -0.01
Oven-dry density measured
Table A-3. Measured oven-dry densities of the large timbers
Timber Oven dry
weight
Wt. before
submerge
Wt. after
submerge Volume Density
g g g Cm3 g/cm3
1 44.16 1127.3 1206.2 78.9 0.56
43.48 1141.8 1221.1 79.3 0.55
2 47.63 1126.1 1199.1 73 0.65
41.26 1132.8 1204.5 71.7 0.58
3 38.09 807 868 61 0.62
-
37
33.09 1117.9 1172.8 54.9 0.60
4 41.82 1145 1219.1 74.1 0.56
37.95 1143 1211.2 68.2 0.56
5 27.51 1134 1196.6 62.6 0.44
27.06 1130.8 1195.1 64.3 0.42
6 25.91 1122.5 1181.4 58.9 0.44
25.1 1119 1176.3 57.3 0.44
7 35.26 1120 1191.6 71.6 0.49
35.34 1125.1 1204.1 79 0.45
8 33.03 1128.5 1198 69.5 0.48
32.1 1121.8 1188.4 66.6 0.48
Y-poplar average Std
0.071 0.52
11 21.98 1115.6 1164 48.4 0.45
22.1 1116.9 1170.3 53.4 0.41
12 35.8 1111 1182.5 71.5 0.50
40.3 1114.6 1197.9 83.3 0.48
13 30.6 1112.7 1197.7 85 0.36
34.14 1106.5 1189.9 83.4 0.41
14 31.8 1109.3 1181.9 72.6 0.44
56.62 802 890 88 0.64
15 35.9 1094.2 1160 65.8 0.55
34.5 1096.6 1168.3 71.7 0.48
16 19.4 1105.4 1160 54.6 0.36
20.03 1103 1153.3 50.3 0.40
17 36.38 1099.8 1191 91.2 0.40
60.38 1098.2 1184.4 86.2 0.70
18 40.7 1102.8 1177.2 74.4 0.55
43.08 1101.4 1177.7 76.3 0.56
Pine average Std
0.071 0.48
21 41.8 1089 1153.3 64.3 0.65
44.77 1076.3 1140.4 64.1 0.70
22 44.31 1075.2 1142.5 67.3 0.66
46.38 1077.3 1143.3 66 0.70
23 53.8 1079.6 1144.3 64.7 0.83
54.07 1056.7 1125.6 68.9 0.78
24 56.44 1072.4 1140 67.6 0.83
-
38
56.99 1074.3 1143.6 69.3 0.82
25 45.97 1084.2 1144.6 60.4 0.76
44.7 1083.2 1147 63.8 0.70
26 40.82 1086.6 1151.9 65.3 0.63
43.06 1090 1155.9 65.9 0.65
27 37.59 1093.1 1162.3 69.2 0.54
45.78 1091.7 1157.4 65.7 0.70
28 39.06 1081.3 1136.4 55.1 0.71
42.23 1080.6 1141.5 60.9 0.69
Oak spp. average Std
0.077 0.71
Table A-3. End grain photo images of 8 by 8 inches timbers before and after treatment.
Sample Image before test Image after test
1a
1b
2a
-
39
Sample Image before test Image after test
2b
3a
3b
4a
4b
-
40
Sample Image before test Image after test
5a
5b
6a
6b
7a
7b
-
41
Sample Image before test Image after test
11a
11b
12a
12b
-
42
Sample Image before test Image after test
13a
13b
14a
14b
-
43
Sample Image before test Image after test
15a
15b
16a
16b
-
44
Sample Image before test Image after test
17a
17b
21a
21b
22a
-
45
Sample Image before test Image after test
22b
23b
24a
-
46
Sample Image before test Image after test
24b
25a
25b
26a
26b
-
47
Sample Image before test Image after test
27a
27b