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August 02, 2018
Vis™ Divide Conduit Installation Methods

Posted by: Erin Schwasnick

Because Vis™ Divide is a high-density polyethylene (HDPE) conduit, it is both flexible and stiff. Its flexibility provides for ease of installation in existing pathways, while its stiffness allows it to withstand crush forces within direct bury applications. Vis Divide can be installed using a variety of techniques.

When you install Vis Divide or any conduit, there are a few considerations you should always keep in mind.

Mechanical stress
No matter what installation method you choose to employ, mechanical stress should be a top consideration, as exceeding the maximum allowable pulling tension or the minimum allowable bending radii can damage the conduit.

Pulling tension
While you are pulling cable through the conduit, pay attention to the number of sweeps, bends or offsets and their distribution over the pull. Placing breakaway swivels will help ensure you do not exceed the maximum allowable tension.

Bending radii
Pulling tension will have to be increased when conduit routes around corners. Before increasing the tension, determine the minimum radius to which the conduit can be bent while still maintaining its mechanical performance.

With those considerations in mind, Vis Divide can be installed using the following installation methods: horizontal directional drilling (HDD), plowed and open trench.

Horizontal directional drilling (HDD)
HDD uses a surface-launched drilling rig to install the conduit in a shallow arc along a prescribed bore path. The HDD installation method is the most commonly used installation method for Vis Divide, as it minimizes the impact to the surrounding area, including less traffic interruptions. HDD is best for installing long lengths of conduit (up to 1,000-foot bores).

When installing Vis Divide using HDD, all installations should be performed in accordance with ASTM FI962 recommendations as provided by the Plastic Pipe Institute and the North American Society of Trenchless Technology or as specified by the project engineer. The contractor should observe all appropriate safety requirements in accordance with local, state and federal regulations and codes.

For a guide on installing Vis Divide via the HDD method, check out this video.

Plowed
Plowed installations use a plow blade to split the earth and place the cable through a feed tube. Plowing is ideal for long continuous runs that have plenty of space below ground, such as rural areas, and is a low-cost installation option.

Open trench
As its name suggests, open trench installations involve digging an open trench and laying the conduit directly into it. You may include embedment material to protect the conduit. Digging the trench requires specialized trenching machines that cut the trench and remove the soil in a single action. This technique can be used to place multiple conduits over long or short distances. Open trench installations are similar to plowing installations. However, open trench installations remove the dirt from the trench, while plowing merely displaces it.

Open trench Vis Divide installations should be performed in accordance with ASTM D2321 or as specified by the project engineer. In open trench installations, care should be taken to minimize undulation in the conduit to lower cable pulling tensions. At a minimum the conduit should be placed under tension before backfilling and only fine particle backfill material should be used — avoid large rocks with sharp edges.

Vis Divide may be a unique offering, but when it comes to installation, it is just like a standard HDPE conduit, requiring the same considerations and even employing the same techniques. If you have more questions on Vis Divide installation and which standards it meets, start with our FAQ sheet.


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