Transmission Tower Maintenance

Bottom Line Savings Through Active Maintenance

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Bottom Line Savings Through Active Maintenance

Transmission towers and poles are among an electric utility's largest and most important commercial assets. Unfortunately, as the need to generate profits and shareholder dividends has intensified, regular investment in tower and pole maintenance has often been reduced or eliminated to cut costs. Ironically, such cost-saving measures have the potential to double or triple long-term maintenance costs while increasing the risk for power outages and public safety problems.

Exponential Corrosion Principle

More than 3,200 electric utilities operate hundreds of thousands of transmission towers in the U.S. These poles and lattice works of galvanized steel typically range from 50 to 180 feet in height, but can reach 900 feet or more. In the U.S., most of these structures were built between 1960 and 1990, which means they have had or will soon need maintenance and repairs.

Depending on where they are situated, galvanized transmission towers and poles can function for 20 to 35 years before showing the first signs of corrosion. While galvanized steel in rural or desert settings may remain rust-free for up to 50 years, coatings in salty coastal air or heavy industrial environments may only do so for 15 years or less.

Once a galvanized transmission tower or pole begins to corrode, the corrosion advances exponentially. As the figure on this page indicates, a tower or pole with less than 5 percent rust at age 30 can oxidize to the point of failure within 10 years. More critically, as the tower or pole corrosioin accelerates, so can the repair time and labor and materials cost.

Four Corrosion Phases

Four phases of transmission tower corrosion exist:

Phase I

  • Coffee stain rust-cosmetic, not structural;
  • 5 percent rust;
  • Rust appears on edges and bolts; and
  • Approximately 1-2 mils of galvanization remains.

Phase II

  • Abrasive rust;
  • Rust appears on bolts, edges and horizontal flat areas; and
  • Rust falls off on touch.

Phase III

  • Extensive, abrasive rust.

Phase IV

  • The tower falls.

Managing and Budgeting for Repairs

When corrosion begins to consume a transmission tower or pole, the key to managing repair costs is to arrest its progress before the unit transitions from one phase of corrosion to the next. For electric utilities, the optimal solution is to repair the entire inventory of towers and poles as early as possible in Phase I, when it is less costly. Unfortunately, that is not possible for most utility companies because of budget constraints and the varied ages of the towers and poles in their inventory.

Table 1 details the repairs and costs for tower maintenance in Phases I, II and III. Once Phase IV is reached, reparis are impossible and replacement is necessary.

Prioritizing Repairs

As Table 1 illustrates, repairs for Phase III damages can be up to 70 percent more than Phase I repairs. For this reason, the most effective way to maximize maintenance expenditures is not to fix towers and poles needing the most or least extensive repairs, but to fix those closest to transitioning from one phase to the next.

According to this protocol, repairs to towers and poles early in Phases I, II or III are typically deferred to those later in each phase. This approach saves not only several thousand dollars per repair over the short term, but also allows utilities to systematically plan ongoing repairs.

Long-term Cost Savings

When electrical utilities were deregulated in the late 1980s, many immediately and dramatically dropped resources directed to transmission tower maintenance. Although utilities often owned or maintained thousands of transmission towers and poles, for many the goal shifted from delivering power to maximizing return on investment. As a consequence, many of today's transmission towers and poles need significant repair.

Table 2 shows how much money utilities can save by actively maintaining large transmission tower and pole inventories compared to allowing them to deteriorate before repair.

In addition to saving millions of dollars, an active maintenance program delivers the benefits of increased employee and public safety, a lower risk for power outages and the goodwill of the community for towers that are clean and attractive.

Transmission Tower Maintenance Plan

PPG Industries offers a comprehensive maintenance program designed to eliminate the movement of transmission towers and poles from one phase of corrosion to the next. Elements of the program include the following:

  • Application of Keeler and Long's KL4400 Series paint, an anodic, self-priming PPG paint engineered specifically for use on electrical transmission towers, bridges and substation structures;
  • Free structural grid evaluations, including on-site surveys by trained and experienced PPG personnel;
  • Recommendations of trusted and qualified repair contractors;
  • Development of maintenance plans, including prioritization of repairs;
  • Paint specification proposals;
  • Application consultation; and
  • Proposed budgets.

Below Ground Inspections, Too

PPG's Eliminate the Movement program includes thorough underground transmission tower and pole evaluations. Underground sections deteriorate faster than visible sections due to constant exposure to sub-surface moisture, alkalis and other hazards.

About KL4400 Series Paint

KL4400 paints are technically advanced coatings developed specifically for the power industry by Keeler & Long, a coatings manufacturer with experience in the power industry. Keeler and Long's anti-corrosive coatings provide year-round protection from severe weather as well as the contaminants and aggressive exposure associated with heavy industrial environments.

In addition to self-priming on weathered galvanized or previously painted steel surfaces, KL4400 Series paints offer the following benefits:

  • Lowest cost-per-square-foot, per-year protection;
  • Minimal surface preparation;
  • Excellent surface wetting ability;
  • Single-coat application;
  • Easy application by brush or mitt;
  • Low VOC formulation;
  • 90 percent solids by volume; and
  • Single-component.

To learn more about Keeler & Long's coatings for the power industry or PPG's Eliminate The Movement transmission tower maintenance program, visit www.keelerandlong.com.

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