Comparison Between Wood Drying Defect Scores: Specimen Testing X Analysis of Kiln-Dried Boards

Abstract

-It is important to develop drying technologies for Eucalyptus grandis lumber, which is one of the most planted species of this genus in Brazil and plays an important role as raw material for the wood industry. The general aim of this work was to assess the conventional kiln drying of juvenile wood of three clones of Eucalyptus grandis. The specific aims were to compare the behavior between: i) drying defects indicated by tests with wood specimens and conventional kiln-dried boards; and ii) physical properties and the drying quality. Five 11-year-old trees of each clone were felled, and only flatsawn boards of the first log were used. Basic density and total shrinkage were determined, and the drying test with wood specimens at 100 °C was carried out. Kiln drying of boards was performed, and initial and final moisture content, moisture gradient in thickness, drying stresses and drying defects were assessed. The defect scoring method was used to verify the behavior between the defects detected by specimen testing and the defects detected in kilndried boards. As main results, the drying schedule was too severe for the wood, resulting in a high level of boards with defects. The behavior between the defects in the drying test with specimens and the defects of kiln-dried boards was different, there was no correspondence, according to the defect scoring method.Keywords: Eucalyptus grandis; Artificial drying; Drying quality. COMPARAÇÃO ENTRE ESCORES DE DEFEITOS DE SECAGEM DA MADEIRA: TESTE DE AMOSTRAS DE PEQUENAS DIMENSÕES X SECAGEM CONVENCIONAL DE TÁBUAS RESUMO -É importante desenvolver tecnologias de secagem para a madeira de

Changing the calculated surface area of wood samples to define drying schedules for Eucalyptus clones

“…Table 5 shows the initial and final temperatures and the drying potential, which were estimated using Equation 4, Equation 5, Equation 6, and compares the UM and the SM in tests at 100 °C for clones 58 and GG100, respectively. IT and FT mean values in Table 5 are similar to those reported in the literature by Brandão et al (1989), Barbosa et al (2005), Eleotério et al (2015), Batista et al (2015), Kang et al (2015), Tari et al (2015), Phonetip et al (2018a) and Phonetip et al (2018b), in which IT ranged from 39 °C to 49 °C and FT ranged from 62 °C to 76 °C. However, the mean DP presented in Table 5 was lower to the related by these authors (ranged from 2,0 to 2,7), which may be a disadvantage regarding the drying time.…”

“…Those studies confirmed that developed drying schedules shortens times and reduces overall work. Some studies also confirmed the correlation between defects detected in wood samples during the drastic drying test and those detected in planks during kiln drying, while others did not (Batista et al 2015).…”

“…Drying schedules have been developed by various authors using this method (Barbosa et al 2005, Ofori and Brentuo 2010, Klitzke and Batista 2010, Batista and Klitzke 2012, Batista et al 2015, Jankowsky et al 2012, Effah and Cofi 2014, Eleotério et al 2015, Soares et al 2016, Soares et al 2019. Those studies confirmed that developed drying schedules shortens times and reduces overall work.…”

“…These methods are based on the correlation of the wood behavior during drying in a conventional oven with the physical and mechanical properties of the wood and with the behavior of samples under different drying conditions (Jankowsky and Luiz 2006). Batista et al (2015) report that some researchers have to develop equipment and solve practical problems and tools, validate and improve research on a laboratory scale. In this way, they can reproduce the behavior of conventional drying on an industrial scale.…”