chromated copper arsenate
Chromated copper arsenate is a water-borne preservative with a history of over 60 years of safe use.
Assured quality reduces long term costs
Wood utility poles, even those treated with earlier, less efficient CCA formulations, have been used successfully by telephone and power companies for over 45 years. CCA poles put in service in 1940 show no decay related failures in tests conducted thirty-five years later. Poles properly treated with the newer oxide formulations of CCA are expected, based on on-going field and service tests, to last forty years and more. The proven ability of K-33 type CCA-C treated poles to provide decades of reliable service gives them a major economic advantage. Evaluation of initial costs versus an expected longevity of 40 plus years gives a decided advantage to CCA treated poles.
Environmental Safety and Yarding Practices
Another important benefit of CCA treated poles is their safety. CCA type preservatives undergo a chemical reaction during treatment and become permanently fixed in the cell wall virtually eliminating leaching or migration of preservative to the surface of the pole. K-33 type CCA-C treated poles, tested after 35 years in service, still retained over 98% of their preservative which assures a long service life while minimizing environmental concerns. K-33 type CCA-C treated wood is extremely low in mammalian toxicity, it can be used around plants, animals and people in applications where other preservative types are not permitted. It is clean to handle, non-oily, has no offensive odour and will not contaminate soil in your storage yard or the soil surrounding a pole in service.
It has been established that CCA treated poles have an outer layer which is harder than untreated poles or poles treated with oilborne preservatives. This outer layer of increased hardness is directly related to species, for example, southern yellow pine is noted for this increase in hardness whereas red pine and lodgepole pine poles have not been found to be so hard as to render them unsafe for climbing. If a linesman's spurs are kept sharp, in accordance with normal safety practice, no undue problems are caused by this hardness with respect to most species. In many cases it has been found that the harder outer surface holds a properly sharpened spur just as well if not better giving a more secure platform from which to work. A CCA treated pole, by virtue of its water based carrier, leaves a pole that is clean to the touch thereby minimizing contact with the preservative itself.
The Role of Preservatives
A wood preservative must do three things: penetrate the wood rendering the wood unsuitable, as a food source, for decay causing fungi and wood destroying insects, and be present in sufficient quanities, in a nonleachable form so that the protection outlasts the expected service life of the pole. K-33 type CCA-C preservatives does all three. The preservative is carried into the wood cells in an aqueous solution where it undergoes a chemical reaction with wood sugars found in the cell wall. This reaction results in the preservative being chemically bonded to the cell wall which prevents any leaching of the chemical out into the environment.
Oxide superior to salt formulations
K-33 is made from high quality oxide based materials. The complex chemical reaction during pressure impregnation results in the formation of insoluble chromates of copper and arsenic in the wood. The wood becomes highly resistant to rot, decay and termite attack. Although wood preserved with salt formulations has the same wood preserving value, oxide formulation offers significant advantages, with respect to conductivity, combustibility and corrosion resistance.
Lower electrical conductivity
Since K-33 water-borne oxide preservative is bound to the wood fibre it does not migrate to the surface to create a residue that can cause increased electrical conductivity and corrosion of metal fasteners. The passage of electrical current through treated wood utility poles is largely a factor of the moisture content and the concentration of free ions available to transport current leakage. Unlike salt formulations such as copper sulfate, potassium bichromate and sodium arsenate, oxide type formulation generates no excessive sodium ions. Testing by utility corporations around the world has shown that poles treated with oxide type CCA preservatives show no significant difference in electrical conductivity when compared to untreated wood at similar moisture contents.
K-33 preservative is carried into the wood in an aqueous solution. As a result a pole treated with CCA will not catch fire easily nor will it cause the flame to spread more rapidly than untreated wood. A CCA pole will develop a slow glowing type of combustion which can easily be extinguished with a thorough dousing of water.
Greater corrosion resistance
With newer CCA oxide solutions like K-33, the number of free ions are drastically reduced, and the potential for creating a galvanic cell which causes corrosion is minimized. However, to further reduce the potential for corrosion:
The increased hardness associated with a pole treated with CCA has created some reluctance, on the part of a few utility companies, to approve its use. In order to overcome this reluctance an additive has been developed, called PEG, which is used to soften the exterior of the pole. When wood dries, moisture trapped between microfibrils within the wall of the wood cell is removed and the wood becomes increasingly dense. This increase in density makes it more difficult for a linemans gaff to penetrate the pole. PEG is used in conjunction with CCA wood preservatives and replaces the moisture as it is removed from between the microfibrils reducing the tendancy of wood to increase its density as it dries. The replacement of moisture with PEG has two important results:
In addition to the above, a pole treated with a CCA-PEG solution maintains all of the important characteristics associated with a plain CCA pole which include:
SpecificationsTo ensure top quality treatment of utility poles the following points should be included in your specifications.
Treatment with CCA-C type C oxide preservative.