By Andràƒ© Besner, Hydro-Quàƒ©bec
Paul Dandy, Arch Wood Protection
Hydro-Quàƒ©bec, in partnership with Arch Wood Protection, a U.S.-based firm which manufactures wood preservatives, has developed a polymer-based additive which, when injected into chromated copper arsenate (CCA)-treated poles, gives them a degree of climbability comparable to that of poles treated with oil-based wood preservatives such as pentachlorophenol (PCP). There are plans this year to treat 1,200 poles, which will be installed on Hydro-Quàƒ©bec’s and Bell Canada’s distribution systems.
Hydro-Quàƒ©bec and Bell use about 4 million wood poles through out the province of Quàƒ©bec. Each year, over 25,000 poles are added or replaced. The poles are treated with preservatives to protect them against rot and damage caused by insects. Poles in use on the distribution system con tain either PCP or CCA and are commonly referred to as “brown” and “green” poles, respectively.
Use of CCA as a wood preservative has been growing over the years but its benefits are accompanied by some disadvantages upon aging. For instance, the wood tends to harden, forcing line workers to use more force to dig in their spurs and making them feel more constrained in their movements, especially when having to move laterally while working higher up on the pole.
The polymer-based additive devel oped by the joint Arch-Hydro-Quàƒ©bec R&D team is water-soluble in its initial state. It is part of a patented mixture that is injected under pres sure into the wood being treated. The wood is then heated and the additive polymerized to form a three-dimen sional network that is water-insolu ble. This process takes place in large horizontal cylinders.
Two series of climbing tests were carried out at Hydro-Quàƒ©bec Research Institute (IREQ) pole testing site. Last February, twelve Hydro-Quàƒ©bec line workers conducted field tests on 18 red pine poles divided into three groups of six which were treated with PCP, CCA or polymer-based CCA (CCA-PA). The line workers were not aware which of the CCA-treated poles had the polymer additive in it. The tempera ture at the time was minus14 C and followed a few days of mild and wet weather, which were ideal conditions for the tests. Each worker would climb onto each pole in turn and assess the hardness of the wood, the level of com fort experienced and would assign a climbability rating. The line workers’ psychophysical assessment was com pared with objective data collected mechanically by a device on the ease of penetration of the spurs in each pole. In summer conditions, the CCA-PA poles were more accepted than the PCP-treated ones whereas in winter conditions, their acceptability was just slightly below that of PCP.
Andràƒ© Besner, an R&D chemist at the Research Institute of Hydro-Quàƒ©bec, can be reached at [email protected]. Paul Dandy, general manager of Arch Wood Protection Canada, can be reached at [email protected].
