A field test of six millwork preservatives has been ongoing for 25 years, using a "Y-joint" as the test unit. Three preservatives provided excellent protection to white pine and white spruce: 5% pentachlorophenol in varsol, phenyl mercury oleate in varsol, and 0.75% oxine copper in varsol.
Pour une performance optimale, la couche d’usure d’une route (« surface de roulement ») devrait être constituée de granulats appropriés. FERIC a examiné les caractéristiques des matériaux de couche d’usure utilisés par plusieurs compagnies membres dans l’est du Canada et a comparé les résultats obtenus avec les spécifications des compagnies et celles des ministères des transports provinciaux. La plupart des granulats ne rencontraient aucun des deux types de spécifications. Le rapport décrit les caractéristiques des granulats convenables pour une couche d’usure et formule des recommandations de spécifications adéquates en vue d’améliorer la performance de la route.
This report analyses softwood-drying practices in Canada and identifies the R&D efforts required in this field. These issues need to be examined in order to address environmental concerns and implement solutions that will improve energy efficiency and reduce greenhouse gas emissions.
Developing advanced softwood-drying control systems would reduce energy use and enhance product quality. According to some researchers, the potential reduction in energy use by kilns in Canada would be 5.5 PJ per year, or 335 kT per year in carbon dioxide (CO2) emissions. Furthermore, it is estimated that CO2 emissions could be reduced by an additionnal 90 kT per year through a decrease in the amount of lumber that is downgraded.
This study aims to give an overview of the main trends in developing control systems and to identify barriers to their introduction. It will also serve as a starting point for launching and directing projects on control procedures for lumber-drying in cooperation with the industry, universities, private and public laboratories, manufacturers and users.
In keeping with this objective, researchers for this study surveyed members of the Quebec Lumber Manufacturers' Association and a few mills in British Columbia. The main findings are as follows:
- Industry opinion is that its facilities are sufficiently modern to meet current market needs.
- Industry opinion is that quality (grade reduction / rejection rate) is the most significant factor when evaluationg drying systems.
- Because it is not easy to measure the quality of the drying process, drying time is the most often used to evaluate drying performance.
- Although quality was identified as the main variable in the drying process, the proportion of under-dried and over-dried lumber units was 9 and 16 percent, respectively.
- Operators play a significant role in drying operations (they manage the process before, during and after drying), and their actions affect the results of the process considerably.
- The decision to purchase a drying-control system is driven more by the acquisition of a kiln than by requirements related to the process itself.
The researchers reviewed current technical knowledge of the main dry kiln control systems by considering two types of controls : air temperature control when drying ; and setting up drying programs. The figures in this report illustrate the use of these two approaches along with various other control methods employed in the industry.
There are five softwood kiln controller manufacturers in Canada, which together account for 75 percent of the Canadian market. Although they use similar controllers, there are differences in how drying programs are set up and how changes in moisture content are measured during drying. In spite of recent technological advances, proper drying operations still depend on operator expertise.
R&D on new measurements instruments and mathematical models has not resulted in advanced kiln controllers so far. Innovation in this area has not kept pace with the advances in other leadings sectors. One technical problem that has not been resolved is that of measuring moisture content. In spite of more than 20 years of effort, mathematical models are still being developed in the scientific community, and few applications resulting from this work have benefited the industry other than those supporting operator training.
The research community and the industry acknowledge that the development of an advanced controller represents a promising avenue for improving the lumber-drying process. Unfortunately, problems in modelling the drying process and measuring moisture content remain represent major obstacles to the development of high-efficiency controllers.
Another obstacle relates to the difficulty of evaluating the financial benefits that would accrue from potential advances with the necessary speed and accuracy. These, then, are the key factors hindering the introduction of new drying technologies. They also explain why length of drying time is still the most frequently used control variable, despite the fact that the industry considers finished product quality more important. Furthermore, it appears that operators' actions significantly affect what happens not only in the kiln but at all stages in the process, from sawmill to shipping.
In view of this, we believe that a system for monitoring the entire drying process is worth investigating. Such a system would :
- serve to collect all data generated by measuring instruments at all stages in the process, from the sawmill to the planing mill
- help to establish productivity and quality indicators for measuring the monetary value of process enhancements introduced by operators
- make it possible to provide a rationale for other promising research approaches such as multivariate analysis and experimental design
This approach would make it possible to enhance control of the drying process and process quality while also revealing potential energy savings.
With the pressures on our industry at this time, sawmills are using thinner saws to try and improve recovery without reducing current production levels. This has led to washboarding becoming a widespread problem in the industry. Washboarding is a wavy pattern that appears on the surface of lumber due to excessive vibration of the sawblade as it cuts through the lumber. In this study the washboarding behaviour of saws was studied at both the analytical and experimental levels to develop a much better understanding of the problem and lead to a set of guidelines for industry use.
This was a joint project between Forintek Canada Corp. and The University of British Columbia. Dr. S. G. Hutton led the analytical side of the work and Dr. J. Taylor the experimental portion of the work. This report is a portion of the overall research endeavour and presents the results of the experimental work that was conducted.
To compliment and validate the analytical portion of the work a series of cutting tests were conducted to examine the washboarding phenomenon and the factors that influence its occurrence. The effects of wheel rotation speed, strain, tooth bite, and depth of cut were examined and their effects recorded. As small changes in tooth design are known to influence a saws washboarding behaviour, but are not accurately predicted by the mathematical models, we also carried out cutting tests with saws of different thickness and tooth pitch, progressively increasing the length of the tooth face and the depth of the gullet until washboarding on the lumber surface was quite severe. In this manner we hoped to be able to develop some guidelines for the industry.
It was apparent from the initial tests that there were two types of washboarding. We have called the larger diagonal waves that often appear with industrial sized bandsaws, Type I. The narrow more vertical pattern or that on circular saws is called Type II. The results in this report are primarily associated with Type I and show the somewhat insensitive nature of the washboarding instability to changes in the operating parameters. The occurrence of washboarding is more sensitive to changes in the tooth geometry.
Industrial heat treatment technology for wood has been under development since the 1970s. The technology consists in heating wood to temperatures of from 150°C to 240°C while preventing it from burning. This is achieved by heating the wood in either an inert atmosphere or saturated vapour environment. Heating the wood over 200°C changes the chemical structure of the wood and results in a reduction in its hydrophilic behaviour. After heat treatment when wood colour has changed to brown, an improvement in dimensional stability and biological durability should be observed. However, some mechanical properties of the wood may have decreased. This enhanced dimensional stability and biological durability make heat treatment an interesting option for the protection of wood used in exterior applications. The objectives of this study are to assess the performance of heat treatment technologies and to determine the properties of jack pine and balsam fir after heat treatment, as regards to exterior applications. Owing to difficulties in the start-up period that significantly delayed the project, no experimental work had been conducted by the end of March 2003. The lumber has however been sent to two companies for treatment and the physical and mechanical tests will be conducted under a new project entitled “Quality Control and Certification of Thermally Modified Wood.” A final report will be issued at the end of March 2004.
Engineered wood flooring (EWF) is gaining in popularity since it appeared in Europe in the 70’s. 40% of the wood flooring installed in the USA is EWF and 75% are EWF in Europe. In layered wood composites such as engineered wood flooring, dimensional stability is of primary importance. The non-homogeneous adsorption or desorption of moisture by the composite may induce cupping, thus decreasing product value. These products were developed by the industry with the result that knowledge on the product and its behaviour is very limited. The objective of this study is to develop a finite element model of the hygromechanical cupping induced by moisture desorption in layered wood composites. The model is based on two sets of equations, 1) the three-dimensional equation of unsteady state moisture diffusion, and 2) the three-dimensional equations of elasticity including an orthotropic Hooke’s law, which takes into account the shrinkage, and swelling of each layer. The model was used to assess 34 different constructions. Results may be used as guideline in the design of new engineered wood flooring construction.