PDF Publication Title:
Text from PDF Page: 004
MATEC Web of Conferences 108, 10001 (2017) ICMAA 2017 below 10% MC and above 14% is given in Table 4. RFV had more boards between 10% and 14% MC than KD. The variation of MC in RFV drying was reduced by placing the wettest lumbers at the centre of the stack, near to the positive electrode plate before and during drying. In the case of kiln drying, more even MC could be achieved by conditioning treatment at the final stage of drying. Table 4. Percentage of boards at difference MC range. Final MC KD30 KD55 RF30 RF55 range <10% 61 0 0 9 10% to 34 15 86 66 14% 14% 5 85 14 25 3.4 Moisture content variation within samples The MC difference between the outer and inner parts for 30 mm boards were comparatively low compared to 55 mm boards for both drying methods. RFV dried samples had relatively lower average inner-outer MC difference than KD with the variation below than 2%. MC difference of up to 7% were observed in some 55 mm boards dried using KD. It was also found that a number of 30 mm boards dried using RFV had a drier inner MC compared to the outer part. This could be due to the fact that RF wave selectively heats the wetter areas in a lumber, which most of the time are in the inner. 3.5 Shrinkage The shrinkage values for 30 and 55 thick boards dried using the same methods were essentially the same. Shrinkage in width (tangential) and thickness (radial) were substantially less for RFV. The shrinkage values for 30 mm thick boards dried using RFV were reduced to 27% tangentially and 15% radially compared to KD while for 55 mm thick boards, the reduction were about 33% and 14%. Both reductions in tangential shrinkage and in radial shrinkage resulted in approximately 30% less in T/R ratio and 22% less in volumetric shrinkage in the RFV dried boards. The reduction of T/R ratio for RFV dried timber could be primarily contributed by reduction of tangential shrinkage compared to radial shrinkage. [6] reported that, the low T/R ratio of RFV dried wood might be desirable to help prevent warping and checking during drying and improvement in dimensional stability might be expected. 3.6 Surface checks and end checks RFV had substantially less surface and end checks than KD. Thinner boards also had lower checks than thicker boards. In KD30, RF30 and RF55, none of the surface checks were deep enough (over 4 mm deep) to cause manufacturing problems. It was observed that some surface checks developed in the initial stage of RFV drying stage were closed towards the end of drying DOI: 10.1051/matecconf/201710810001 (Figure 3). These surface checks can be easily removed by planing the boards 3 mm from the surface. However, deep checks were found on about 5% of the boards in KD55. In all drying run, the end checks were less than 50 mm long which were not observed after cross cutting 100 mm from both ends. The lower checks in RF was contributed by the lower drying stress developed due to differential MC in outer and inner surface. This may also be contributed by reduction in T+R and T/R values in RFV drying compared to kiln drying method. There were no internal checks (honeycomb) and collapse in both drying methods. KD. RFV . Figure 3. Surface checks and end checks in 55 mm thick sample 3.7 Cupping, bowing, spring and twisting The amount of cupping, bowing and spring were very low and negligible in all drying run. There was no twisting detected in all drying methods. In this study, distortion due to the differential shrinkage in radial and tangential grain orientations was restrained mechanically by hydraulic pressing during RFV drying and placing a concrete block on top of the timber stack during KD. 3.8 Drying stress The percentage of boards with drying stress were lower in RFV compared with KD (Table 3). This was contributed by a lower moisture gradient across the timber thickness in RFV. Excessive residual drying stresses causes machining problems especially during ripping. 4PDF Image | Characteristics of Timbers Dried Using Kiln Drying
PDF Search Title:
Characteristics of Timbers Dried Using Kiln DryingOriginal File Name Searched:
Characteristics_of_Timbers_Dried_Using_Kiln_Drying.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)