Trystan Casey
Wooden electric poles have been a vital part of America's electrical and communication infrastructure for over a century. They are typically made from tall, straight trees, such as pine or fir. In the United States, Southern Yellow Pine is the most widely used species, while other species like Douglas Fir, Western Red Cedar, and Lodgepole Pine are also commonly used. These trees are carefully selected and treated with preservatives to ensure their durability and longevity. The Rural Electrification Act of 1936 played a significant role in promoting the use of wooden poles, bringing electricity to rural areas across America. Today, wooden electric poles continue to be essential, especially in rural regions, despite the emergence of alternative materials such as steel, concrete, and composites.
| Characteristics | Values |
|---|---|
| Material | Wood |
| Origin | United States |
| First use | 1843-1844 |
| Inventor | Samuel Morse |
| Use | Electrical and communication infrastructure |
| Number in use | 150 million |
| Longevity | 40-70+ years |
| Treatment | Preservatives |
| Durability | High |
| Cost-effectiveness | High |
| Recyclability | Yes |
| Maintenance | Requires treatment and maintenance |
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What You'll Learn
Wood type: Pine, fir, cedar, and other trees are used
Wood poles have been an essential part of America's electrical and communication infrastructure for over a century. With an estimated 150 million poles in place in North America, they have become ubiquitous and deeply ingrained in the culture. The first documented use of wood poles was in 1844 when Samuel Morse constructed a 40-mile telegraph line between Baltimore and Washington, D.C., using 700 wooden poles after his initial attempt to bury the cables underground proved ineffective.
The versatility, availability, and cost-effectiveness of wood have made it the top choice for utility poles. The most commonly used wood species for poles include pine, fir, and cedar. Pine is the most widely used variety for telephone poles in North America, with Southern Yellow Pine being prevalent in the United States. Lodgepole pine is also mentioned as a variety used in California.
Douglas Fir is another commonly used species, often treated with waterborne preservatives and subjected to the Boultonizing process, where the wood is heated to high temperatures in a pressurized cylinder. This process is also applied to Southern Pine poles. Western Red Cedar is also mentioned as one of the primary wood species used for utility poles.
The selection of trees for utility poles begins in the forest, where standing trees are evaluated for characteristics such as length, straightness, taper, and other factors influencing their load-carrying abilities. Once selected, the logs are seasoned or conditioned to maintain their strength. The treating process involves pressure-treating the wood with preservatives to protect against rot, fungi, and insects, extending the poles' lifespan to 50 years or more.
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Treatment: Preservatives are used to protect the poles
Wooden utility poles are treated with preservatives to protect them from harsh environmental conditions, such as rain, ice, wind, insects, and decay fungi. The preservatives are integrated into the poles through pressure, forcing the chemicals deep into the wooden fibres to create a long-lasting protective barrier. This treatment process extends the lifespan of wooden utility poles to 50, 70, or even 100 years.
There are several types of preservatives used to treat wooden utility poles, each with its own advantages and disadvantages. One of the most commonly used preservatives is pentachlorophenol, often referred to as "penta". Penta is an industrial-strength preservative that has been used in wood pole treating since the 1930s and is known for its long record of service performance and safe use. However, it has been identified as a possible carcinogen and is banned in most countries, leading to its phase-out as a utility pole preservative.
Another preservative that has gained popularity among environmentally conscious utilities is copper naphthenate. It is classified by the EPA as a general-use preservative and is known for its long-term performance, safety, and low total environmental impact. Copper naphthenate can be used as a standalone treatment or in combination with other preservatives to improve their performance.
Dichloro-octyl-isothiazolinone (DCOI) is a relatively new preservative for utility poles but has already demonstrated superior performance to penta in third-party testing. DCOI is a well-tested preservation system, offering high performance and durability. It is also used in a variety of other applications, including water treatment, paints and coatings, adhesives, and outdoor furniture.
Other preservatives used for utility poles include ammoniacal copper zinc arsenate (ACZA), creosote, and chromated copper arsenate (CCA). ACZA is particularly effective for hard-to-treat wood species like Douglas Fir, and it is often used in aquatic environments and applications where wood is exposed to water. Creosote has been a successful preservative for well over a century, but its use has declined due to concerns about its carcinogenic properties. CCA has been used to treat Southern Pine and Western Red Cedar poles for many decades and is known for its durable performance and protection against preservative migration into the soil or groundwater.
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History: Wooden poles date back to the 19th century
Wooden utility poles date back to the 19th century, with the first documented use of wood poles in 1843 or 1844 with the development of the telegraph. British telegraph pioneer William Fothergill Cooke used wooden poles on a line along the Great Western Railway. In 1844, Samuel Morse received a $30,000 grant from the U.S. Congress to construct a 40-mile telegraph line between Baltimore and Washington, D.C. After attempting to bury the line underground, Morse turned to placing the telegraph lines overhead, advertising to buy 700 "straight and sound" wooden poles.
The use of wooden poles continued with the development of electricity generation, as the need to move electricity to homes and factories increased the demand for wooden poles. By the turn of the century, there was a need for standards to create a consistent supply of wood utility poles with predictable structural capabilities. In 1908, standards for round timbers were developed, and soon after, the American National Standards Institute (ANSI) adopted standards specifically for wood utility poles, defining the sizes and characteristics of the poles.
Wooden poles became an essential part of North America's electrical infrastructure, with an estimated 150 million poles in service across the continent. The Rural Electrification Act of 1936 provided funding for cooperatives to build the infrastructure needed to bring power to rural areas, and wooden poles became the backbone of this effort due to their availability, durability, and cost-effectiveness. Early power poles were often crafted from locally sourced pine or cedar, and their simplicity highlighted their pivotal role in reshaping rural life.
Wooden poles are typically made from three species: Douglas Fir, Western Red Cedar, and Southern Pine. The logs are selected in the forest while the trees are still standing and are judged for length, straightness, taper, and other characteristics that will impact their load-carrying abilities. The poles are then treated with preservatives under extreme pressure, forcing the chemicals deep into the wooden fibres to extend their lifespan. Treated wooden poles can last 40 years or more, even in harsh conditions, and are less expensive to produce and install than alternatives like steel or concrete.
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Durability: They can last for decades, even in harsh conditions
Wooden utility poles are renowned for their durability. With an estimated 150 million wooden utility poles in North America, these poles have become an essential part of the continent's electrical infrastructure. Wooden utility poles have a long record of in-place performance, with a lifespan of around 45 years without remedial treatment. The service life of a wooden utility pole can be extended to 70 years or more with preservative treatment.
The durability of wooden utility poles is due to the careful selection of high-quality wood species, strict limits on imperfections, and precise physical specifications. The three most common wood species used for utility poles are Douglas Fir, Western Red Cedar, and Southern Pine. Each of these species has unique characteristics that make them well-suited for use in utility poles. For example, Douglas Fir is known for its high strength-to-weight ratio and dense wood fibers, making it excellent for heavy load support. Western Red Cedar is lightweight and durable, offering natural resistance to decay and insects. Southern Pine is valued for its strength and ease of treatment with preservatives, as well as its cost-effectiveness and availability.
The preservative treatment used on wooden utility poles creates a chemical barrier that protects the wood from threats such as mould, decay fungi, and insects. This treatment process utilizes pressure to force preservatives into the wood fibre, allowing the preservatives to be integrated deep into the wood to provide long-lasting protection. The preservatives used can extend the lifespan of wooden utility poles by decades, even in harsh conditions.
Additionally, the strength and resilience of wood as a material make it a great option for utility poles. Wood is a strong yet lightweight material that can typically withstand surface damage and handling. This makes wooden utility poles cheaper and easier to transport and install, as heavy machinery is not required. The durability of wooden utility poles reduces the need for frequent replacements and maintenance, further contributing to their cost-effectiveness.
Overall, the combination of durable wood species, stringent quality standards, and effective preservative treatment methods results in wooden utility poles that can last for decades, even in harsh outdoor conditions.
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Affordability: Wooden poles are cheaper than steel or concrete
Wooden poles have been an essential part of America's electrical infrastructure for over a century. They are also used in other developed countries such as Australia, England, Norway, and France. They are affordable, lightweight, and easy to transport, especially after major weather events and hurricanes.
Wooden utility poles are cheaper than steel or concrete poles. The affordability of wooden poles is due in part to their lightweight and versatile nature, which makes them easy to transport and install. In contrast, steel poles are energy-intensive to create, and concrete poles often require special equipment for loading, offloading, and handling, driving up costs.
Wooden poles are also adaptable to different line configurations and hardware fittings, as holes can be drilled into them in any customer-specified number and diameter before treatment. This adaptability contributes to their affordability, as it reduces the need for costly modifications during installation.
Additionally, wooden poles have a long service life, typically lasting 50 to 70 years or more with proper treatment. This longevity further enhances their affordability by reducing the need for frequent replacements. Wooden poles are treated with preservatives under extreme pressure, forcing the chemicals deep into the wooden fibers to protect them from decay and infestation, which are common issues with wooden poles.
While wooden poles may be more susceptible to damage from extreme weather conditions, birds, and insects compared to concrete or steel poles, their overall affordability, durability, and versatility have made them the top choice for utilities in many countries.
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Frequently asked questions
Electric wood poles are typically made from pine or fir. In the US, the most common species is Southern Yellow Pine. Other species used include Douglas Fir, Western Red Cedar, Lodgepole Pine, Jack Pine, and Pacific Silver Fir.
Once a suitable tree is selected, the bark is removed, and the pole is shaped to make it as straight as possible. The poles are then reviewed, graded, and assigned a class. Next, the poles may be incised, bored, or conditioned to prepare the wood to receive preservatives. The poles are then branded, tagged, and stacked for treating. The treating process involves applying pressure to force preservatives into the wood fiber.
Properly prepared and maintained electric wood poles can last up to 100 years. On average, treated wooden poles can last 40 to 70 years or more, depending on the environment and maintenance.
Wooden poles became popular due to their availability, durability, and cost-effectiveness. They are also light and easy to transport, making them ideal for use in rural areas. Additionally, wooden poles can store carbon, unlike steel, which is energy-intensive to create.
