50 Years of Reliable Restoration

Osmo-C-Truss® 50th Anniversary

2015 marks the 50th anniversary of the Osmo-C-Truss wood pole restoration system. Installations of the CTruss® and C2-TrussTM have restored over 1 million poles nationwide. These restorations also represent over $2 billion in savings for utility companies when compared to pole replacement costs. Furthermore, the wood pole life extension provided by these systems has been shown to equate to the expected life of a pole replacement.

This paper explains the history of the C-truss steel restoration method and includes data on the re-inspection of 42,000 restored poles that validates successful life extension of over 40 years. Life extension of a utility asset qualifies for capital treatment and details of capital budget optimization are also explained in this document.

Wood Pole Restoration

The first wood utility poles were installed over 100 years ago and today an estimated 150 million wood poles provide the support system for much of the electric grid. As poles age while in service, the original preservative treatment may no longer be effective at preventing decay in the groundline zone. The most decay prone section of the pole is from groundline to 18 inches below ground.  Inspection of the groundline zone, especially when excavation is included, monitors the condition of a pole and is recommended and sometimes required on a cyclical basis. The excavation also provides the means to apply supplemental preservative treatment; a booster shot to the original treatment that helps prevent decay and extend the life of a pole.

Poles identified with a remaining bending strength at the groundline that is below the requirements of the National Electrical Safety Code (NESC) are often referred to as "rejected" poles or "rejects". The code requires these poles to be restored or replaced.  Pole restoration with the Osmo-C-Truss system has provided utility companies with a cost saving option to pole replacement for 50 years. The steel truss is positioned against the pole and is driven into the ground to a depth well below the groundline decay zone. This forms a union with the sound portion of the pole below the decay zone, and the above ground portion of the truss is banded to sound wood above. The steel truss bridges across the decay zone and restores the bending capacity so the pole can remain safely in service.  

The C-Truss systems have been the most widely used wood pole restoration systems for 50 years. The flexibility of the installation method makes it possible to restore poles that are installed in rear-lots and in concrete along with poles having various attachments and difficult access.

Due to the historical data validating significant life extension, the cost of the C-Truss system can be capitalized and used to help optimize capital budgets. Savings compared to pole replacement costs have exceeded $2 billion dollars.

The Origin of Pole Restoration

In 1965, the original C-Truss was a C-shaped channel that was driven alongside a pole and secured with steel banding. The first C-Truss systems incorporated lengths of pipes that were not acceptable for oil pipeline applications.  These "repurposed" oil pipes were cut in half longitudinally, thus creating a "C" shaped cross-section.  In the early years of use, it was perceived by utility companies as a temporary solution that may only extend the useful life of a pole for 5 to 10 years. Poles restored during this time can still be found in service today providing evidence of a much longer life extension. The photos below show a repurposed oil pipe truss, the original C-Truss, still in service more than 45 years after installation.

 

The repurposed oil pipe restoration was awarded a patent entitled "Reinforced Pole Structure and Method of Banding a Reinforcing Stub to a Pole" issued to The Kamphausen Company and purchased shortly thereafter by Osmose Utilities Services. The image below includes some of the original patent drawings with Figure 1 and Figure 10 therein showing the side and top profile of an installed truss; the very system shown in Figure 1.


In the 1960's, utility companies often conducted their own tests of new products that were brought to market.  Below is an example of full-scale testing of the early  C-Truss system conducted at a Midwestern utility company in 1966.


Manufacturing Improvements

The very first oil pipe restorations did not have any form of corrosion protection. Osmose quickly recognized that long term corrosion protection was needed to help provide reliable restoration solutions. Hot-dip galvanizing was immediately added to the manufacturing process.  All Osmose trusses are galvanized according to the ASTM A123 standard.

As demand increased for steel truss restorations, Osmose began manufacturing trusses out of steel plates.  The flat plates were formed to simulate the radial shape of the oil pipe trusses and tested to ensure the appropriate strength was achieved.

Soon Osmose moved away from repurposed oil pipes and exclusively formed the trusses. Another enhancement was incorporating high strength low alloy steel plate. This provided more bending strength without an increase in weight. All trusses were then standardized using 60,000 yield strength steel.

Optimized C-Truss Designs & Development

In the mid 1980's, the C-Truss had its first major design overhaul. The general C-shape was maintained but was optimized by creating truss sizes that efficiently coincided with NESC code requirements. Higher strength steel (80,000 psi) was incorporated to achieve greater bending strength in lighter weight trusses, resulting in lower cost, higher value solutions. 

As the capabilities of the steel truss improved, the banding system, used to secure the truss to the pole, was also enhanced. Industrial banding is only protected against corrosion by a thin zinc coating applied through the electroplating process. This thin corrosion barrier is not adequate for long-term outdoor installations, so Osmose manufactures banding protected with hot-dip galvanizing.  This banding provides industry-leading yield strength of 138,000 psi and is the only banding in the industry protected with hot-dip galvanizing, which provides 3 times the amount of corrosion protection over electroplating.

The redesigned C-Truss system was thoroughly tested and evaluated throughout the latter 1980's and early 1990's. Full-scale load tests were independently witnessed to validate results, and several utility companies conducted their own on-site validations across the country.  Utility companies in Florida, Ohio, Missouri, Texas and California all performed successful load tests which gave confidence to customers that the C-Truss was a reliable restoration solution. The photo below shows this improved system in service.


Birth of the C2-Truss

In the late 1990's, higher strength steel (100,000 psi) became more readily available and cost effective. Osmose set out to develop a new truss that could utilize this higher strength, lighter weight material. Higher yield strength steel trusses behave differently than trusses made with lower yield strength and should not be directly substituted without considering the impact on overall performance.  For this reason, a new cross-sectional shape was developed specially for the higher yield steel to have an improved margin of performance over the "C" shape trusses.

With the progression of more accurate and complex computer modeling, Osmose evaluated proposed truss shapes by employing finite element analysis (FEA). Multiple proposed cross-sectional forms could be evaluated using FEA before any physical prototypes were made.  This saved substantial development time needed to achieve the desired performance. An example of a three-dimensional FEA model showing truss stress under load can be seen below. Observing concentrated high stress areas and the behavior at failure in these models lead to improved iterations until an optimal design was determined.


After extensive research, development, and testing, the Osmo-C2-Truss® was introduced in the early 2000's. The patent-protected C2-Truss™ provides a lighter, stronger, and lower cost solution for restoration, giving an even greater incentive for the pole owner to restore rather than replace their rejected wood poles. The photo below shows an installed C2-Truss with a brown paint coating applied for both aesthetics and additional corrosion protection.


Ensuring Optimal Life Extension

In order to achieve long life of the restoration system, the truss itself must adequately resist corrosion, and the wood pole must be treated to arrest further decay. C-Truss and C2-Truss products are hot-dip galvanized to strict standards under the ASTM A123 specification, and banding strips are hot-dip galvanized in accordance with ASTM A653. Products galvanized to these standards have been shown to withstand outdoor environments for well over 50 years.

To further express truss longevity, when a restored pole is removed from service due to road construction or for other reasons, it is common practice for customers to reinstall the truss on another pole; thereby extending the life of a second pole for the cost of labor only since the customer already owns the truss.

Every truss, when installed, is paired with highly effective remedial treatments applied to the pole to arrest further pole decay. To gain the greatest life extension, pole owners should continue to include trussed poles on the same inspection and treatment cycle as the rest of the pole plant. This will provide a boost-er shot of preservative treatment to inhibit decay.

Observed Trussed Pole Life Extension

Osmose has compiled empirical evidence validating that the C-Truss and C2-Truss systems add decades of service life to wood poles originally rejected due to groundline decay or damage. The table below shows the data from representative customers' inspection results of trussed poles between 2005 and 2008. These customers had relatively large restoration programs paired with good inspection and treatment programs that facilitated the collection of this data.


Analysis of the data indicates very high serviceable rates for each 10 year age band of an installed truss. A serviceable rate is the percent of trussed poles re-inspected that are still serviceable. For trusses in service for up to 40+ years, the overall serviceable rate found during these inspections was 98%.

A majority of the 2% to 3% deemed no longer serviceable were caused by above ground defects. These conditions, which are outside the groundline area, no longer meet code even though the groundline portion of the pole still meets NESC requirements. 

As the age of the restoration increases, the population inspected decreases because of the lower rate of steel truss installations in the early years of the C-Truss. Although the population decreases, high serviceable rates are still maintained. Overall the data supports the claim that restoration is a long-term solution, and can provide additional years of service comparable to the expected life a new pole.

The Case for Capitalization of Pole Reinforcement

As previously outlined and qualified through empirical data analysis, steel truss reinforcement extends the useful life of a wood pole well beyond when it is deemed a reject. As such, it represents an addition or betterment to the pole plant and can be classified as a capital expense.

This concept is clearly supported in the Federal Energy Regulatory Commission's (FERC) 2008 ruling on Novinium, Inc.'s request for capital treatment of the costs involved in installing injection rehabilitation products for URD cable. The approval from FERC notes "a company may capitalize the cost of installing injection rehabilitation products provided that the product is used by the company to extend the useful life of its segments of URD cables beyond their original estimated useful lives."

In a subsequent 2011 ruling on a petition filed by Waverly Light and Power, the commission allowed utilities to capitalize all costs incurred to retro-fill a substation transformer with a new dielectric coolant. FERC affirmed the fluid qualified "as a minor item of property that did not previously exist provided that a substantial addition results from its use."

In the past, utilities were hesitant to adopt the steel truss as a capital expense due to the financial treatment of an inferior alternate restoration solution used by utility companies referred to as "pole stubbing." While rarely used today, pole stubbing involves the installation of a cut-off section of wood pole adjacent to an in-service pole and lashed to it by steel wire cable or other fasteners. This method is specifically referenced in FERC guidelines as an O & M expense, not capital.

Osmose trusses are substantially different from pole stubbing.  Stubbing is more accurately defined and treated as a temporary repair rather than a full-scale rehabilitation or restoration. Each stub can be considered a unique repair because of the variability of both the materials and the methods used. Further, pole stubs are not tested to confirm their strength and often utilize a section or sections of poles that were previously in-service.

In contrast, Osmose trusses are specifically engineered and sized through detailed engineering analysis to restore a pole's strength. Trussing achieves increased service life, capacity, and durability for older, in-service wood poles. It clearly meets the criteria established to be classified as a capital expense.

Capital Budget Optimization

While the availability of capital is typically less constrained than O & M, operating managers must still ensure budgets are spent in a way that maximizes the overall value and benefit to the organization. In most utility companies the total capital available is less than what's needed to fund all the potential projects that have a positive return to the enterprise. A process of internal "capital rationing" is generally used to balance these local work projects with the other needs of the organization. With this in mind, it is compelling to restore a pole for a fraction of the cost of replacing it in order to make capital available for additional projects.  In evaluating restoration versus replacement from a pure cost-savings perspective, a utility would ideally reinforce the maximum number of eligible poles to minimize the remaining population requiring replacement. Steel trusses are used unless there are mitigating engineering reasons, construction standard changes, new clearance requirements or other factors that indicate pole replacement is the more desirable approach. This strategy can allow the utility to fully address their reject pole backlog within the allowable capital budget spend.

The decision to restore rejected poles may also be evaluated outside of a purely financial assessment. Pole replacement can be a lengthy and complicated process.  Replacement prioritization, potential customer downtime, permitting, coordination with pole attachers, and back-office preparation all contribute to an overall project timeline that can take many months or even years to fully complete. With so many departments involved and so many steps taken during a pole replacement process, it is very common for a backlog to develop and increase to unsustainable levels. A pole restoration program can be implemented quickly and the backlog of rejected poles can be addressed in a timely manner, thus reducing the rejected pole backlog and the pole owner's overall risk and liability. Program Managers concerned about any long-term rate base impacts of the restore versus replace decision can be assured there are always a myriad of other project opportunities within the company. Funding additional projects with the money saved through restoration ensures a robust annual capital spend and eliminates the declining rate base concern that is often a decision making factor.

The Next 50 Years of Restoration

Over the first 50 years, Osmose has worked to ensure that customers received industry leading reliable restoration products and services through substantial product improvements, quality workmanship and best-in-class safety practices.

Re-inspection data supports that Osmose C-Trusses and C2-Trusses are long term solutions, and long-time customers can attest to the substantial life extension steel trusses have given to their pole plant as well as numerous other benefits. These benefits include safely and effectively restoring wood poles to NESC code mandated strength for a fraction of the cost of pole replacement, without service interruptions, and reducing overall risk and liability to the pole owner.

Osmose engineers continue to evaluate designs, materials, and processes as technology evolves to provide the best pole restoration solutions for their customers. With 50 years of restoration experience, work will continue toward providing new innovations that are reliable and cost-effective restoration solutions for pole owners.

PDF Document Click here for a print-friendly version of this article

 

For questions regarding pole restoration, please contact Chad Newton at [email protected] or 770-632-6777.