Underground duct bank runs protect electrical wiring from weather and natural disasters. Placing duct banks below ground enhances safety and integrity, making them essential for critical locations. Though initial costs are higher, long-term reliability and reduced maintenance often justify the investment.
Facilities such as utilities, data centers and manufacturing plants benefit significantly from underground duct banks. These installations manage large power needs securely, shielding them from environmental interferences.
Key aspects to consider for these projects include:
Stands and spacers
These components, also called frames or chairs and made from plastic or HDPE, maintain duct alignment and facilitate the encasement process during installation. They range from simple snap-in configurations to complex frames.
Types of duct banks
Most duct banks are encased in concrete for stability and durability, though direct burial or gravel fill are also used.
Installation methods
Traditional installation involves open trenches, but trenchless technology is gaining popularity. Methods like directional boring and high-pressure concrete slurry ensure effective conduit placement.
Size
Typical underground duct bank runs are 3×3 or 4×4 with 9 to 16 rungs, though some projects exceed 20 rungs, depending on the scale.
Material considerations
Choosing corrosion-resistant materials like fiberglass conduit (RTRC) is critical. Fiberglass pairs well with concrete and efficiently dissipates heat. Materials like PVC and aluminum are less suited for underground applications due to durability issues.
Installation techniques
Different materials require different joining techniques. Fiberglass conduit (RTRC) uses a gasket joining system that simplifies and accelerates installation. PVC is joined with glue and steel is threaded, which takes more installation time.
Support spacing
Extended support spans save costs and installation time. Champion FiberglassⓇ offers UL-listed conduit for longer support spans than PVC conduit, allowing for fewer spacers or chairs in a duct run, which can lower the costs of materials and installation.
Weight
Lightweight conduit eases and speeds up installation. Fiberglass conduit (RTRC) is one-third the weight of PVC and one-tenth the weight of steel, making it easier and safer to handle. Lighter weight conduit makes installation safer and more economical too.
Coefficient of friction
Selecting materials with a low coefficient of friction decreases the need for multiple vaults, reducing 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 $10,000 to $100,000 per pull point or vault.
Incorporating these considerations optimizes the design and functionality of underground duct bank runs, ensuring cost-efficiency and robust protection for critical power infrastructure.
Learn more about the solutions, listings, standards and engineering of Champion Fiberglass conduit that has led to successful outcomes in many projects with underground duct bank runs.
