Steam and Vacuum Treatment of Large Timber in Solid Wood ......1 Steam and Vacuum Treatment of Large...

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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

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90

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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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0 60 120 180 240 300 360

Tem

per

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1/2L at 2-inch deep

1/3L at 4-in deep

Geometric center of


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

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90

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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


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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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

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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

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0 60 120 180 240 300 360

Tem

per

ature

(C

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Treating time (Min)

1/2L at 2-inch deep

1/3L at 4-in deep

Geometric center of


Chamber

Timber surface

Deck timber center

25

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

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0 60 120 180 240 300 360 420

Tem

per

ature

(C

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Treating time (Min)

1/2L at 2-inch deep

1/3L at 4-in deep

Geometric center of


Chamber

Timber surface

Deck timber center

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0 60 120 180 240 300 360

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Treating time (Min)

1/2L at 2-inch deep

1/3L at 4-in deep

Geometric center of


Chamber

Timber surface

Deck timber center

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2.


2.

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per

ature

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Treating time (Min)

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deep1/3L at 4-in deep

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of large timber1/4L at 4-in deep

Chamber

Timber surface

Deck timber center

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1/3L at 4-in deep

Geometric center of


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.


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


Chamber

Timber surface

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Timber surface

28


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


Chamber

29


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


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


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


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


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


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


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


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


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


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


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.


1a

1b

2a

39


2b

3a

3b

4a

4b

40


5a

5b

6a

6b

7a

7b

41


11a

11b

12a

12b

42


13a

13b

14a

14b

43


15a

15b

16a

16b

44


17a

17b

21a

21b

22a

45


22b

23b

24a

46


24b

25a

25b

26a

26b

47


27a

27b

Steam and Vacuum Treatment of Large Timber in Solid Wood ......1 Steam and Vacuum Treatment of Large...

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