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Key Considerations for Underground Duct Bank Runs

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June 1, 2024 in Features
By Champion Fiberglass

underground duct bank runs

Underground duct bank runs provide essential protection for electrical wiring from environmental elements such as weather and natural disasters. The below ground placement of duct banks enhances the safety and integrity of these systems, making them indispensable for locations where disruptions cannot be risked. Despite higher initial costs, the long-term reliability and reduced maintenance often justify the investment.

Diverse facilities including utilities, data centers, and manufacturing plants benefit significantly from underground duct banks. These installations are crucial for managing large power needs securely, safeguarded from environmental and natural interferences.

Key aspects to consider for these projects include:

1. Stands and spacers: These components, often made from plastic or HDPE, maintain duct alignment and facilitate the encasement process during installation. They can range from simple snap-in configurations to more complex frames.

2. Types of duct banks: Most commonly, duct banks are encased in concrete for stability and durability, although alternatives like direct burial or gravel fill are also used.

3. Installation methods: Installation can be traditional, involving open trenches, or utilize trenchless technology. Trenchless installations, which are gaining popularity, employ methods such as directional boring and high-pressure concrete slurry for effective conduit placement.

4. Size: Underground duct bank runs are typically 3×3 or 4×4 with 9 to 16 rungs, but some can go well over 20 and beyond, depending on the scope and scale of the project.

5. Material considerations: Choosing corrosion-resistant materials like fiberglass conduit (RTRC) is critical, especially since it pairs well with concrete and efficiently dissipates heat. Materials like PVC and aluminum are less suited for underground applications due to durability and degradation issues.

6. Installation techniques: Different materials require different joining techniques and some are more time-consuming. For example, fiberglass conduit (RTRC) uses a gasket joining system that simplifies and accelerates the installation process while PVC is typically joined together with glue and steel is threaded.

7. Support spacing: Extended support spans can help save cost and installation time. Champion Fiberglass offers UL-listed conduit for longer support spans than PVC conduit. Greater support spacing allows for fewer spacers or chairs in a duct run, which can lower the costs of materials and installation.

8. Weight: Lightweight conduit eases and speeds up the installation process compared to heavier alternatives. Fiberglass conduit (RTRC) is one-third of the weight of PVC and one-tenth of the weight of steel so lifting a bank of twelve 20-foot sections plus spacers made out of lightweight fiberglass is much easier than lifting the same sections made out of PVC or GRC. Lighter weight conduit makes installation safer and more economical, too.

9. Coefficient of friction: Selecting materials with a low coefficient of friction can decrease the need for multiple vaults, reducing the overall project costs and facilitating longer cable pulls. Vaults are pull points to pull cable from one run of duct bank to the next. The heavy weight of the cables limits the amount of force that can be exerted to pull them safely. A material with a low coefficient of friction allows for longer pulls and a reduction of cost from $10K to $100K per pull point or vault.

Incorporating these considerations can optimize the design and functionality of underground duct bank runs, ensuring both cost-efficiency and robust protection for critical power infrastructure.

Learn more about the solutions, listings, standards and engineering of Champion Fiberglass conduit use in underground duct bank runs.

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