Telephone poles have a look which is recognizable to everyone in the United States and across the globe. There’s a smoothness to them, a darker hue than natural bark. And they’re so hard that they will not be nice to your car if you run into one. In addition, they last for decades without replacement, even when the cables connected to them need to be switched out. Why is this? Because telephone poles are made with pressure treated wood for a strength that is hard to match.
And, yes, there are still hundreds of thousands, if not millions, of poles still in use for locations where power and phone lines can be placed underground. This is why companies like Brown Wood Preserving still exist — to make sure product is available due to wear and tear or severe weather, like that of Puerto Rico, where most poles have to be replaced from scratch.
The process to create pressurized wood starts with one of three preservatives — Penta, CCA, or CCA-ET. The one which is used depends on the geographic location of the pole and its application. For example, Penta, also known as Pentachlorophenol, has been used to preserve utility poles in North America since the 1930s.
To prepare the wood for the preservatives, the utility poles are exposed to a power vacuum process. This opens the cells of the wood and makes them more receptive to absorb the preservative. The chemicals are then pumped into the wood with a compressor at approximately 150 pounds per square inch (psi). This forces the preservatives into the wood and helps to avoid potential damage. What the wood retains depends on its species.
The utility pole is then put aside to continue the preservative process. Some are sprayed with water to allow the chemicals to further bond with the interior and exterior of the wood. Once this is completed, the utility poles go through a quality analysis to ensure their strength before they are shipped to the client.
The next time you while away by leaning on a telephone or power pole, think of the work which was done to preserve it. Who knows, your children or grandchildren may lean on the same pole in the future.