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The Evidence Of Our Success In Preventing Utility Pole Failure

Polesaver dual-layer barrier technology sleeves are a proven and independently tested product. With  25 years of volume use and over 20 years of independent field test data Polesaver is a proven and highly cost-effective means of extending pole life. In this article, we will be looking at the effects of moisture, fungi and termites on sleeved and un-sleeved test samples and poles. These independent test results demonstrate the clear benefits of Polesaver when used in conjunction with existing wood preservative products. The evidence of our success is straightforward. 

What Causes Utility Pole Failure, And Why Should We Protect Against It?

All of the factors necessary for wood decay are present in the upper 20cm (8″) of the ground. This section is the most common point of failure for utility poles and is also the most mechanically stressed. To prevent decay, we must keep moisture and wood-decaying organisms out and lock in wood preservative. The Polesaver total barrier sleeve creates an air and watertight seal, keeping rot out, and preservative locked in. This unique dual barrier technology not only has the potential to reduce remediation costs significantly but also improves grid hardening, reliability and safety. 

Polesaver Cross Section Image

Putting It To The Test!

The evidence of our success comes from independent test data and standards with zero reported failures to date. Our sleeves comply with the following criteria:

    • European Standard EN252: 1989, ‘Field test method for determining the relative protective effectiveness of a wood preservative in ground contact’. “20 years of test data
    • ENV807 Wood preservatives. ‘Determination of the effectiveness against soft rotting micro-fungi and other soil-inhabiting micro-organisms’.
    • AWPA E1-97, American Wood-Protection Association: 2005.’ The standard method for laboratory evaluation to determine resistance to subterranean termites’.
    • They meet the requirements of A.W.P.A. (American Wood Protection Association) standard ‘Barrier systems’ P20-13, BP-1.
    • Large scale field pole test by a utility at three pole test sites. 

The Evidence 

In previous articles, we have highlighted the importance of moisture content as a catalyst for decay. Over time wetting and drying cycles can result in leaching and the subsequent reduction in the concentration of wood preservatives leaving the wood vulnerable to decay. Suppose moisture levels of the timber become higher than 25%, the potential for decay arises becoming a precursor to pole failure. During an Accelerated decay test (ENV807), a Polesaver protected sample showed less than 25% moisture content at the critical ground line level after 48 weeks. In direct comparison, the unprotected sample showed levels of saturation higher than 150% in the same area. As decay set in, the respective samples experienced weight loss due to decay as a result. The Polesaver protected sample showed no deterioration in the sleeved zone and no weight loss.

In contrast, the unprotected timber showed between 30 and 40% weight loss at the critical ground line level. Furthermore, an independent 20-year field test (EN252) using Scots pine sapwood stakes showed that some unprotected samples failed after eight years. In contrast, all of the Polesaver protected stakes suffered from zero decay after 20 years. Thanks to its air and watertight seal, the Polesaver total barrier protection system excludes moisture, fungi and other wood-decaying organisms from the timber. 

Graph showing loss of pole strength over time due to decay

Large Utility – Field Test

In 2012 we were approached by a large U.K. based utility who were planning ahead in case of a future ban on the use of creosote wood preservative. The utility had put in place a plan to look at alternative options to find the best option to match the lifespan of Creosote protected poles. They had already experienced issues with ground line decay in poles treated with waterborne copper wood preservatives and viewed the use of barrier sleeves as a potential solution when used in conjunction with this type of wood preservative. Having examined the options in detail, they were aware of possible issues such as wet band decay at the top of partial barrier systems. To gain independent assurance that this would not happen when using total barrier sleeve, they started pole tests at three different U.K. test sites. The objective of the test was to monitor the moisture content at the ground line or top of the sleeve for four different pole options as follows; Creosote treated poles (benchmark) water-based copper treated poles, water-based copper treated poles fitted with a partial bag type barrier sleeve, and a water-based copper treated pole fitted with a Polesaver full barrier sleeve

The three locations across the U.K. incorporated a variety of conditions including Poles set in tarmac, wet and boggy soils with a water table around 20cm (8″)  and dryer ground. A time period of 4 years was allowed before taking measurements to allow moisture levels to reach equilibrium. Moisture content levels were taken using a calibrated pin type moisture meter across all samples with pins inserted to a depth of 6mm. The creosote-treated poles had an average moisture content of 26% just above the ground line. The poles treated with water-based copper-based wood preservative had an average moisture content of 32% (>50% at the start of the test) just above the ground line. The poles treated with water-based copper-based wood preservative and fitted with a partial bag type barrier sleeve had an average moisture content of 43% just above the top of the bag (>50% at the start of the test). The poles treated with water-based copper-based wood preservative fitted with a Polesaver full barrier sleeve had an average moisture content of 20% just above the top of the sleeve ( >50% at the start of the test). The test results show that a pole fitted with a Polesaver sleeve is effective at reducing moisture content in the sleeve over time.

British Telecom/Open reach Polesaver test site showing the installation of Polesaver protected samples and non protected samples

What About Termites?

As well as being an impenetrable barrier to decay, Polesaver sleeves also provide protection against termite attack. Let’s look at the termite test results carried out by the  Mississippi State University. This test was conducted using ten cubes of Polesaver coated and non-coated wood. The cubes underwent two tests. Firstly a two-choice test where termites had the option of coated and non coated timber. The results show that the termites did not eat Polesaver protected wood. A secondary analysis was then conducted where termites only had Polesaver covered wood as a single food source option. In the second test, the Polesaver coated blocks were not fed on at all by termites despite the absence of any alternative food source demonstrating that the non-toxic Polesaver barrier was repellent to termites. As shown in our earlier blog termites are generally attracted to decaying wood as this is easier for them to digest than non-decaying wood. By preventing ground line decay, Polesaver can also greatly reduce the likelihood of termite attack.

Termites which eat wooden utility poles

Test Data Information 

Our test data has provided the information we need to calculate the expected lifespan of a treated pole with a Polesaver sleeve. Based on our 20-year accelerated field test, stakes dip treated with wood preservative started to fail after eight years. The test samples protected by Polesaver showed zero failures after 20 years. From this, we can calculate a minimum pole life increase factor when using Polesaver. If we take the total test time frame of 20 years and divide it by the length of time it took an unprotected pole to fail (eight years), we achieve a minimum pole life extension factor of X 2.5. Assuming a pole lifespan of 20 years for a standard treated pole, we can by calculation conclude that a Polesaver protected preservative-treated pole should have a  minimum expected pole life of 20 x 2.5 = 50 years. If you are interested in seeing any of the test data, then please go to the downloads section or send us an email and we will send it to you.

If this life extension is to be achieved, it is critical that the sleeve also continues to provide a barrier to the causes of decay for 50 years or more. Polesaver sleeves are made from costly, high-quality materials which have a proven long term track record when used as in-ground barriers. For instance, the film material we use is highly U.V. stabilised and has been in use in critical in-ground barrier applications for over 60 years without problems. The thermoplastic meltable liner also has a proven long term track record for both in-ground and timber protection applications.

It is this data that allows us to offer a 50-year sleeve guarantee with confidence. 

In the next blog article, we will be looking at the financial case for using barrier sleeve products. In the meantime, for those of you in Europe who currently use Creosote treated poles, we will be posting a short blog giving an update on changes and a brief look at the alternative options.

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Richard George

Richard is the founder and CEO of Polesaver. With over 26 years of experience in developing and testing Polesaver products, Richard is an expert when it comes to wood preservation.

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