November 21, 2024

STEEL POLES ARE STRONG, COST-EFFECTIVE OPTION FOR DISTRIBUTION SYSTEM

by By: Dan Snyder, American Iron & Steel Institute, Manager, Market Development
The Power of Zinc and Weathering Steel Extends Steel’s Service Life

The quality and inherent value of steel distribution poles is often enhanced by the process of hot-dip galvanizing, or the use of weathering-grade steel. Each of these methods provide corrosion resistance and extended service life for steel distribution poles.

The Power Of Galvanized Steel
In the hot-dip galvanizing process, steel poles are submersed in a bath of molten zinc, forming a permanent metallurgical bond between the zinc and the steel substrate. This creates a tough, uniform barrier coating both inside and out. Also, if the steel becomes exposed, zinc will corrode first, maintaining the strength and integrity of the steel pole. Zinc flows across the coating break, in much the same natural way that the human body heals a skin cut.

The Protection of Weathering Steel
Uncoated weathering steel is a solution for atmospheric corrosion control. When exposed to the environment, it forms a dense and tightly adherent oxide barrier, sealing out the atmosphere and retarding further corrosion. The embedded section of a weathering steel pole is usually coated for below-grade protection.

Below Ground Protection
A range of advanced coatings, including some for below-grade protection, further extend the life of steel poles. These coatings, which can be applied over both galvanizing and weathering steel, provide a non-leaching, sustainable corrosion barrier that can last as long as the poles – even in harsh soil conditions.

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Traditionally, utilities have used wood poles to carry electric wires and cables from point to point. But the changing market is beginning to openly embrace steel distribution poles as a viable and cost-effective alternative. The number of steel poles in North America has more than tripled in recent years. Among the estimated 185 million electric distribution poles that crisscross the United States and Canada, about 600 utilities use this pole alternative.

Case in point: John Hudson of People’s Electric Co-op in Ada, Oklahoma recently switched to steel poles. He said the co-op's decision was impacted when a review of their pole change-out program uncovered a high failure rate in pole tops, due primarily to two factors: woodpecker and lightning damage. The steel poles resolved both problems.

Hudson initially chose steel poles for their life cycle value. “Even today with higher steel prices,” he said, “steel poles are the right choice.”

Hudson said that crew adaptation to steel poles has been favorable. “The feedback I get is that the crews don’t ever want us to go back to wood poles,” he said.

Steel poles are pre-drilled to the utility’s specifications by the manufacturer so there is little drilling in the field, making the installations quicker and easier. Hudson said they use NEC (Numerical Electromagnetics Code) ground on the base of the poles, eliminating the need to drive ground rods. Fiberglass crossarms and other hardware typically used on wood poles can be used on steel poles as well. Steel poles can by guyed using the same hardware used for wood poles. Permanent attachments can be welded into the poles for attaching guys.

Charles Guerry, the utility director for the City of Newberry, South Carolina has been using steel poles for seven years, with 250 in service and another 150 forthcoming. He said that the city initially chose steel poles for their life expectancy.

“An 80-year steel pole, verses a 30-year wood pole is a good value,” Guerry said.

The city picked up on other useful benefits once in operation.

One example is that steel poles perform better during lightning storms.

“There have been very few outages during storms,” Guerry said. “System reliability has
significantly improved, the steel poles are better grounded and it’s easier to make a good ground.”

The use of steel poles also reduces the risk of catastrophic “domino effect” system failure, as can occur when just one utility pole fails. Utility poles can be dangerous if they snap or break. The poles have to carry the tension and weight of the wires, which means there needs to be enough flexibility to cope with the sudden release of a broken wire. The release of tension can cause a long line of consecutive poles to snap in a domino effect until one manages to break the chain.

Steel distribution poles have consistently proved to stand tall in the event of a pole failure. An engineered product, each steel pole is designed to meet specific strength and load requirements. The result is an extremely strong and reliable product, with uniform dimensions and strength, without twists, knots, splits, or bows – all of which can lead to failure in severe situations. Steel Poles Can Save Time – And Money Cost savings can be significant when the following factors are considered:

• Steel poles are at least 30% lighter than woods poles – lighter weight can reduce the cost of transportation, handling, and construction.
• Steel poles require little maintenance, greatly reducing the costs associated with upkeep – there is little need for tightening hardware to compensate for pole shrinking.
• Due to the strength of steel, in most circumstances, steel poles involved in vehicle impacts can be repaired or changed during normal working hours, reducing the high cost of overtime pay.
• At the end of its long service life, a steel pole can be sold to scrap dealers and
completely recycled – eliminating the costs of pole disposal.
• Steel poles can be taller and carry heavier loads, permitting longer spans and requiring fewer poles.

Farmers Electric Cooperative of Clovis, New Mexico realized a significant savings. In one of their installations, ease of installation became a significant factor when purchasing steel poles. The co-op’s Engineering Manager Jeff Hohn said steel poles took less time to install than wood. He added materials cost less because poles were strong enough to support longer spans. They can also be taller and carry heavier loads. The co-op saved more than $50,000 on a recent 225-pole line project.

Easy to Install, Handle
There is little difference between the installation methods used for steel and wood so additional crew training is minimal. Plus, there is no need for inspections to monitor pole shrinkage or labor and material costs to re-tighten hardware because steel retains its shape and strength.

Weight reduction is also a factor in ease of use. The average steel distribution pole (40 foot, Class 4) weighs approximately 450 pounds, and is at least 30 percent lighter than a wood pole. Weight differentials can be as much as 70 percent less for steel when compared against wood structures. The weight savings make the poles easier to maneuver, reducing labor costs for transportation, handling and installation.

In addition, steel distribution poles are gaining favor in rural areas because their lighter weight makes them easier to transport into rough and off-road terrain. Two-piece pole design allows transport to a job site without special permits and requires lighter hauling equipment, such as a tractor.

Steel Offers Aesthetic Appeal
Guerry adds that the aesthetics of steel distribution poles are definitely a factor. “Even the public likes them better,” he says. “They’re just sharp looking poles.”

Residential customers and local housing groups are becoming more involved in the construction process that takes place in their local communities. Some customers prefer the environmental benefits and general appearance of a uniform power line. Steel poles are available in several finishes, including zinc-coated steel, weathering steel, and pre-painted galvanized steel.

And Then Environmental Benefits
The benefit to preserving woodlands and forests is also at issue.

“It takes an entire tree to make a typical wood pole,” says Charles Schmidt, chairman of the American Iron and Steel Institute (AISI) Steel Utility Pole Task Force “Yet one scrapped auto can produce more than four steel distribution poles.” Schmidt — general manager of IPSCO, Inc, a steel producer in Houston, Texas — adds that a steel pole contains between 25 and 100 percent recycled content.

Steel is a unique material because scrap is an essential ingredient in the production of new steel. Each year, millions of tons of pre- and post-consumer steel products, including used steel cans, appliances, automobiles and construction materials, are recycled by steel mills to form new steel products.

A Changing Market
While steel distribution poles currently account for only a small percentage of the total distribution-pole replacement market, those who’ve switched to steel are staunch supporters.

“I’ve used wood, concrete, and composite poles,” says Guerry, “but steel is trouble-free and economic. That’s why we’re using it exclusively now.” Hudson concurs. “Longevity is the reason we’re using only steel poles today,” he says. “It just makes sense from a management perspective.”

Source: American Iron & Steel Institute

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10 Reasons That Steel Poles Make Sense According to AISI research, here are the primary reasons utilities are switching to steel:

• Easy to Handle
• Light Weight
• Long Life
• Cost Effective
• Low Maintenance
• Sustainable
• Durable
• Safe
• Aesthetics
• Engineered for Strength