Historically, power and telecom poles used to support overhead power and telephone lines have been made from wood. Wood is readily available all over the world, lightweight, strong, non-conducting and durable when treated with preservative.
Recent changes in legislation affecting wood preservatives have shortened lifespan in tropical locations and have led many utilities to look at longer-lasting alternatives. Alternative pole materials include reinforced concrete, galvanised steel and composites.
So, do these materials give a longer lifespan than wooden poles? We take a look at each alternative to see how they compare.
We can see that all materials have different failure modes. This means a regular inspection is required after the first 10 to 15 years in service if pole failure is to be avoided with replacement.
For any utility company, lifetime cost is the key deciding factor when looking at alternative pole materials. This cost is generally calculated based on initial cost and projected lifespan for a given material.
The challenge is in knowing the lifespan for poles made from each of the different materials. This is where things become more challenging with a lack of published data offset by manufacturers claims for lifespan.
A study undertaken in Australia gives data on expected lifespan based on real-life experience over many years. The graph below shows the results:
Source: Pole Service Life – An Analysis of Country Energy Data (Australia)Nathan Spencer Koppers Wood Products Pty. Ltd., Sydney, Australia (Contact: firstname.lastname@example.org) Leith Elder Country Energy, Goulburn, Australia (Contact: email@example.com)
In concrete poles, the typical failure mode is corrosion of the reinforcing bars. For steel poles, ground line corrosion is common over time and for wood, ground-line decay and termite attack are the common failure modes.
As we can see, the results clearly show that standard treated wooden poles whilst generally outperforming concrete, lag behind steel poles. But when taking account of the initial cost, it is clear that wood is still a good all-round choice.
It is readily available, low in cost, lightweight, easy to handle and available in a wide range of sizes to suit all needs.
In the last 20 years there has been a growing adoption and use of technology to overcome woods greatest weakness; decay and termite attack. This happens at the vulnerable ground line section of the pole. It is at this part of the pole that conditions are perfect for wood decay and termite attack. In contrast, the section of pole deeper in the ground and above ground often have a service life 3 or 4 times longer than the ground line section.
So, to prevent degradation and failure at this point, composite, heat applied sleeve products such as Polesaver offer an excellent solution. They isolate the wood from all the factors necessary for ground rot and termite attack, including moisture and fungi. This results in dramatically extending the utility pole life at low unit cost. With a typical expected pole service life similar to that of steel poles, the use of ground line sleeves has given wood another lease of life as the material of choice for utility poles.
*Source Conclusions and Summary Report on an Environmental Life Cycle Assessment of Utility Poles Prepared by: AquAeTer, Inc
Richard is the founder and CEO of Polesaver.
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Polesaver manufacturers and supplies guaranteed products that are proven to extend the life of utility poles. With over 7 million sleeves supplied to date, our patented ground-line barrier sleeves have been proven in volume use since 1994.
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