PDF Publication Title:
Text from PDF Page: 005
Comparing Vacuum Drying and Conventional Drying Effects on the Coloration of Hard Maple Lumber Table 1—White maple drying schedule (T1-C5) Equilibrium Moisture moisture Relative Dry- content content humidity bulb Step (%) (%) (%) (°F)a Wet-bulb depression (°F)a 1 2 3 4 5 Above 30 25 to 30 20 to 25 15 to 20 11.8 68 100 10 9.8 58 105 14 7.6 44 105 20 4.1 22 115 35 <15 3.3 a°C = (°F – 32)/1.8. 17 120 45 Figure 4. Diagram showing best judgement sampling of clear areas on a tangential surface. Because dried wood appears brighter when surfaced, surface preparation of the sample boards for color analysis was performed with an industrial planer and drum sander to remove 3/16 in. (4.8 mm) from one surface of each board. The drum sander used 150-grit sandpaper to smooth the surfaces of the sample boards for easier interpretation with the spectrophotometer. A Color Master CM2 spectrometer (X-Rite, Inc., Grand Rapids, Michigan, USA) with a D65 light source illumination was used to measure sample color numerically as L*a*b* values, and the data were downloaded and analyzed by X-Rite Color Master software. The sampling protocol detailed by Rappold and Smith (2004) was followed. Four spectrometer readings of 13-mm-diameter spots were taken using best judgement from clear areas, between the growth rings, of both tangential board faces, for a total of eight readings per sample board (Fig. 4). Figure 5 shows the sample boards being measured using the spectrometer method described. Sample statistics and paired sample t-tests were run for each of the three variables measured with the spectrometer. The eight readings taken by the spectrometer for each variable were averaged for each sample board. The 40 paired sample averages were compared. Results and Discussion Samples in the vacuum kiln were dried in 58 h using a vacuum of 10 cmHg with a hold of 140 °F (60 °C) for 8 h, at which point the temperature was raised. The charge was completed when a wood core temperature of 160 °F (71 °C) was reached (Fig. 3). Samples in the conventional steam kiln were dried in 288 h using the T1-C5 schedule. The conventional steam kiln-dried the lumber using two 2-horsepower (1,492-watt) fans that averaged 500 ft (152.4 m) per minute during the kiln schedule, along with an electric steam boiler. This drying time difference is significant, with vacuum drying nearly five times faster than conventional steam drying. Kiln samples were used in both kilns to monitor moisture content during the drying process. Table 2 shows that the mean values for the 40 paired sample averages were very similar. No significant differences were shown for brightness (L*), a* (green–red), or b* (blue– yellow) scales. Figure 6 shows that both methods of drying produced an industry-accepted lightness value range of white hard maple Figure 5. Measurement of a sample board using the Color Master CM2 spectrometer (X-Rite, Inc., Grand Rapids, Michigan, USA) with a D65 light source illumination. Figure 3. Vacupress (Vacutherm, Inc., Barre, Vermont, USA) drying schedule, medium setting. 3PDF Image | Comparing Vacuum Drying and Conventional Drying
PDF Search Title:
Comparing Vacuum Drying and Conventional DryingOriginal File Name Searched:
fpl_rp708.pdfDIY PDF Search: Google It | Yahoo | Bing
5,000 BF Shipping Container Lumber Dry Kiln For Quality Lumber The 5,000 BF container kiln consists of one 40 foot high-cube aluminum shipping container... More Info
Shipping Container Lumber Dry Kilns by Global Energy Global Energy designed and developed the container kiln back in 1991. The purpose is to give access to portable sawmill owners, furniture makers, and small business the value added profit of dry kiln lumber and quality hardwoods... More Info
Vacuum Kiln Conversion Kit for Lumber and Wood Dry Kilns Convert your existing conventional dry kiln into a fast drying vacuum kiln. Similar to vacuum bagging in the boat building and aircraft industry, we have come up with a proprietary process which allows you to build a very simple vacuum kiln at a fraction of the price, and without the intensive conventional metal chamber structure... More Info
Vacuum Pump Cart System for Bagging Clamping Wood Drying and more Vacuum Cart with 2HP Pump and Dual Pistons with multiple multiplex vacuum ports and liquid reservoir... More Info
Vacuum Bagging Basics Vacuum bagging is a method of clamping, which has traditionally been used in the composites industry, but can also be used for vacuum drying materials, including wood products... More Info
CONTACT TEL: 608-238-6001 Email: greg@globalmicroturbine.com (Standard Web Page)