Fire Protection for Poles

Risk Reduction Category

Fire Protective Materials

Each year, wildfires passing through forested and grassy terrain damage or destroy large numbers of distribution poles. Wood poles are particularly vulnerable and are ubiquitous because wood often provides the most attractive combination of features such as cost, availability, strength, and durability. However, wood is a combustible material and furthermore, the chemical treatment manufactured into the pole to resist natural decay may exacerbate smoldering when exposed to fire, reducing its loadbearing strength or destroying the pole.

Damage to poles is a function of the temperature and duration of exposure to fire. According to RS Technologies [5], pole exposure can have the following characteristics. These are important because they are the basis for the RS/Ackerman Fire Test, which is a full scale fire exposure test designed to be a consistent and repeatable assessment of fire performance specifically for utility poles of various construction.

  • Peak heat flux, the rate of energy transfer through a surface per unit area, can be around 250 kW/m2
  • Max temperature around 800-1200°C (approximately 1500-2200°F)
  • Most fires around 1000°C (approximately 1800°F)
  • Exposure durations < 30 seconds for grassy fires, up to 90 seconds for conifer forest fires
  • Average dwell time is 45-60 seconds

Significant challenges for utilities in high-risk areas for wildfire include the costs of labor and materials to set new poles and to rebuild the lines, along with the intrinsic costs of extended customer outages. As a strategy to improve survivability of poles, utilities may opt to replace damaged poles with those made of fire resistant (FR) materials such as steel, concrete, hybrid steel-concrete, and ductile iron. Whenever a business case does not support installing poles of alternate construction, perhaps due to costs alone or due to performance trade-offs, an increasingly practical solution involves applying a protective external treatment to existing wood or composite poles. Most of these solutions are applied in the field, while others are available during manufacture of the pole. Either option is generally field-replaceable after being exposed to fire. Designing an external fire barrier for utility poles presents some unique technical challenges. Any protective solution applied to a pole’s surface must not promote decay in the pole and should not impact:

  • The ability to climb and service the pole
  • The pole’s dielectric properties
  • Environmental waste management

Technology Description

Aftermarket treatments for improving the fire resistance of existing poles are available in forms of coatings, fabric wraps, and solid layer materials. The effectiveness of any treatment is influenced by the intensity and duration of the fire. Therefore, performance is coupled to how well vegetation fuel is cleared in the vicinity of the pole.

Fabric Wraps

Fire wraps are typically made from fire-resistant materials such as fiberglass or wire mesh. They are often coated with an intumescent material that expands when exposed to heat, creating an insulating barrier that protects the pole from fire. When a fire occurs, the intumescent coating on the wrap swells and forms a char layer, which insulates the pole and prevents it from igniting. This protective barrier can withstand high temperatures and helps maintain the structural integrity of the pole during a fire. A field-applied fabric wrap is typically attached to wood poles with staple beginning at or just below the ground line and as high up the pole as needed for the anticipated fire threat (grassy fire versus brush fire, for example). The wrap inhibits fire damage by simply reflecting heat and restricting airflow, two essential elements that set up smoldering in wood. Wraps maintain their breathable and UV-protective fabric form until exposed to fire. The main ingredients in intumescent fire wraps are expandable graphite and ammonium phosphate. Under U.S. Resource Conservation and Recovery Act (RCRA) guidelines, these compounds are not deemed hazardous and are acceptable as construction waste at landfills.

Coatings

Fire-resistant (FR) coatings are intended to shield various materials from fire damage. They can be applied using a brush, roller, or sprayer. These intumescent coatings expand when exposed to fire, forming a char layer that insulates the wood, deprives the fire of oxygen, and thereby prevents the pole from burning. These intumescent coatings are typically non-toxic, water-based, and environmentally friendly.

Rigid Coverings

Rigid FR coverings are commonly used with composite poles. Fire resistant composite poles can burn when flame is present, but self-extinguish when the flame is removed. The rigid covering is made of the same type of polyurethane resin as the pole, but acts as a sacrificial outer layer that can be easily repaired with a proprietary polyurethane resin coating or quickly replaced, depending on the extent of the damage.

Technical Readiness (Commercial Availability)

Externally applied fire protection for utility poles is commercially available in forms of wraps, coatings, and rigid coverings. These technologies have been laboratory tested and field deployed. Scaled deployments by large west coast utilities have also seen poles exposed to recent wildfires with favorable results. This list of manufacturers was compiled through an Internet search using general descriptions of the technology. Multiple variations of the search terms were sometimes used. The goal is to find the most demonstration-ready products in the category. Manufacturer websites usually provide useful information, such as successful use cases, field demonstrations, deployment numbers, or other indicators of readiness. If online information is insufficient, further inquiries are made by phone. Typically, one to three leading candidates are identified as most prepared for field demonstrations. Preference is given to manufacturers that sell in the United States or, for emerging technologies, those that have participated in US-based field demonstrations.

Fabric wraps

Hexion – ArmorBuilt™
https://www.hexion.com/en-us/brand/armorbuilt

Genics – Fire Mesh™
https://genicsinc.com/fire-mesh/

Polesaver – Blaze-Guard
https://polesaver.com/products/polesaver-fire-fabric/

Adroit Fire – INCA WFS net®
https://adroitfire.com/inca-wfs-net-wildfires/

Coatings

PoleCare – FireSheath™
https://polecare.com/products/fire-retardant

FIRESHELL – Utility Guard
https://fireshellcoatings.com/products/thermal-and-ignition-barrier-coatings/utilityguard/

Osmose – Fire-Guard®
https://www.osmose.com/products-fire-protection

Rigid Coverings

RS Technologies FIRE SHIELD™
https://www.rspoles.com/solutions/products/fire-shield

Implementations / Deployments

Fabric Wraps

More than 10,000 wrapped poles were purchased in 2020 by the two largest utilities in CA., with planned purchases of more than 35,000 poles in 2021. [3] Large utilities in western US and Canada are field-wrapping existing poles. Wraps are also being used in Oregon, Washington, Colorado, Montana and western Canada since 2020. [3]

Stella-Jones, a North American manufacturer and distributer of treated wood products, reports having conducted fire exposure tests and post-fire destructive strength testing on fabric-wrapped wood poles, subjecting them to temperatures of 2100°F with a tip load. The wrapped poles exhibited no decomposition or charring and maintained their strength. A key takeaway from that study is that the remaining strength of a visibly un-charred pole, after the removal of the intumescent wrap, can be assessed through a simple circumference test for that pole classification.[3]

Hexion – ArmorBuilt™

  • Commercial launch of the ArmorBuilt product in 2020 [1].
  • Currently in use by BC hydro, SaskPower, PG&E, and others [1].
  • Participated in three prescribed canyon burns [1].
  • Multiple poles involved in California’s Mosquito Fire of 2022 [1].

Genics – Fire Mesh™

  • Tested to ASTM standards at Western Fire Center, Kelso, Washington [2].
  • Participated in several controlled burns in different climactic zones [2].
  • Installed by a west coast US utility and tested under wildfire conditions [2].

Polesaver – Blaze-Guard

  • Product launch of fire protection fabric in 2014.
  • Independently tested by a major African Utility company (Test report available from PoleSaver).
  • Effective for low-lying brush fires.

Coatings

After a loss of approximately 60 wood poles in 2011and more from previous fires, Idaho National Lab (INL) painted 3000 of its wood poles with Osmose Fire-Guard® latex based intumescent paint to a height of 5’ above grade. Every pole that was painted, even those not re-painted since 2012 and 2013, survived the Sheep Fire of 2019 in eastern Idaho, a grass and sagebrush fire. [6]

Sulphur Springs Valley Electric Cooperative (SSVEC) hired Osmose to apply Fire-Guard® to the poles in the path of the 2011Monument Fire in Arizona. From a safe distance ahead of the fire, Osmose cleared brush at the base of the poles and applied Fire-Guard to 1,100 poles. The Monument Fire covered 27,000 acres, claiming 60 homes, 14 buildings, and 4 businesses, but did not claim any of the 1,100 poles that were treated with Fire-Guard. [8]

FR Coverings

RS Technologies FIRE SHIELD™

  • Engagement with SCE since 2020, FR pole testing (full-scale burn test, strength tests) since 2020. [5]
  • Large scale deployment of FR composite poles at SCE. [4]
  • SCE covers their 50ft composite poles up to 23’7” above grade and 40” below grade [4]
  • A composite pole with RS FireShield was exposed to a controlled forest burn with approximately 38 seconds of peak exposure time. The physical damage inspection revealed no damage to the pole and no reduction in load bearing strength. [5]

Innovations as of Mid 2023

TBD

Potential Enrichment Work Opportunity

External barrier solutions can be highly effective, though they often only withstand a single fire event. Current research is exploring post-fire actions. For each of the three protective strategies mentioned earlier, consider the following aspects:

  • Ease of removal/replacement
  • Disposal
  • Effectiveness in protecting the pole
  • Methods to confidently assess the pole’s condition after a fire
  • Long-term impacts on the pole

References

[1] Scott McIntyre. “Hexion’s ArmorBuilt Wildfire Shield is a Proven Solution for Utility Pole Protection.” YouTube, uploaded by Electricity Today Magazine, 10 Apr. 2023, https://www.youtube.com/watch?v=-WXufa0srnQ

[2] The Energy Network. “Fire Hardening Wood Pole Assets.” 2021, https://www.tengroup.com.au/attachments/Product/20589/TEN%20Group_Genics%20Fire%20Mesh%20-%201221.pdf?ts=1638405637

[3] Jeremy Meyer, Stella-Jones. Presented at T&DWorld webinar, 2020.

[4] Brian O’Keefe, Southern California Edison. “SCE Fire Resistant (FR) Composite Pole Deployment.” Presented at T&DWorld webinar, 2020.

[5] Galen Fecht, RS Technologies. “Wildfire Mitigation Strategies – Fire Resilient Poles for Overhead Lines.” Presented at T&DWorld webinar, 2020.

[6] Bill Gabbert. “Power poles treated with fire resistant paint survived the Sheep Fire” Wildfire Today, 9/3/2019. https://wildfiretoday.com/2019/09/03/power-poles-treated-with-fire-resistant-paint-survived-the-sheep-fire/

[8] “Protecting Poles from Wildfire with Fire-Guard®” Osmose Utilities Services, Inc., 2016. https://f.hubspotusercontent30.net/hubfs/20067784/Osmose_Nov2021/pdf/Fire-Guard%20Profile.pdf