Wrapping up the slope friction issue

Piping Up For Technology Series (Part 5)

Innovation never stands still – there’s always a new advancement coming down the pipe. Enbridge is constantly testing commercially available technologies, and looking for opportunities to enhance existing technologies, in the areas of design, prevention, monitoring and leak detection, to keep our pipelines safe.

Our Piping Up For Technology Series, on the @enbridge blog, offers a glimpse of various research projects we’re engaged in, and the efforts we’re making to adapt and harness technology for safety’s sake. These proactive investments in innovation are intended to add another layer of safety and security to our pipeline network – and, ultimately, to the energy transportation industry as a whole.

Gravity can do its thing, and we can do ours.

Pipelines are buried through all kinds of terrain as they crisscross North America. On rare occasions, that includes slopes that move incrementally over time – at a rate of a couple of millimeters per year.

“In this particular slope scenario, the soil wants to grip the pipe, because of the friction between the steel and the soil, and that can potentially cause strain on the pipeline,” says Millan Sen, an engineer with Enbridge’s Pipeline Integrity group. “That’s where geotextile coating comes in.”

While our pipelines are engineered to manage moving forces, where necessary, Sen in recent years led a specific Enbridge geohazard project to tackle the issue of incremental slope movement. The pragmatic solution? Wrapping the pipe with low-friction geotextile fabric, a robust weave of monofilament polypropylene yarns. And the key was using two layers, not one.

When our carbon-steel pipe is wrapped with two layers of geotextile fabric—an interior layer of lagging, and an exterior sheath—those two layers glide against together and reduce the friction factor from the soil’s contact with the pipe.

“The material is a lot like silt fence. It’s a plastic, like Teflon,” says Sen. “With two layers of fabric, you get three friction planes. And the layer where it’s fabric on fabric . . . that’s the most slippery layer of all.”

The solution came as a result of Enbridge’s ongoing involvement in Pipeline Research Council International, a collaborative global research organization. “The application of this geotextile material was Enbridge initiated, but it was originally studied by PRCI,” says Sen. “It just goes to show how valuable industry-led collaboration, and associations like PRCI, can be when it comes to advancing safety.”

Since 2012, we’ve used geotextile wrap on several Enbridge pipeline construction projects in our network where our engineers anticipate potential for slope movement. As an extra precaution, we use remote fiber optic strain-gauge monitoring on those pipeline segments to back up our design assumptions.

“The use of geotextile wrap is definitely considered for new construction projects where necessary,” says Sen. “It’s a small preventative investment, with a long-term benefit.”

Watch for upcoming posts from our Piping Up For Technology series on the @enbridge blog channel.