This is Part 4 in our series on proper pipeline installation and tile repair with Mad Dog Foam Bridges. We previously examined the trenching process, or the way by which trench measurements are properly conducted and the hole dug. Today we’ll look at pipe stringing and bending in preparation for installation.

At this point, the pipeline itself has been created at mills, specifically for the project at hand. And, after reading our previous posts, you probably realize that things won’t be as simple as taking those segments of pipe and dropping them in the trench.


Pipeline stringing is the next step in the construction process, and it’s an activity that requires the utmost attention to detail. Pipelines are more like puzzle pieces than they are building blocks: Every segment is different, and misplacing them prevents the completion of the project.

“Stringing” is the method by which pipeline construction workers assemble the pieces prior to completing the “puzzle,” making sure everything is accounted for. Every length of pipe is marked to indicate where it belongs along the line, as the thickness of the pipeline and the coating used on it has been applied based on the location and soil conditions in the area.

Even the equipment used to transport and unload the pipeline parts is highly specialized. Truck trailers rarely carry more than eight segments at a time, and these trailers are designed with single-point suspensions to make traveling rough right-of-ways less hazardous. Many pipeline installation companies have opted for vacuum-based lifting technology to securely remove the pipeline from the trailers.

Now the pipeline is laid out in a line along the trench, in its proper order, to await welding (see our next blog post for more on that topic). Still, not every segment is ready to be attached.

Although a pipeline contractor would love for the channel to travel straight and flat for hundreds of miles, the truth is that elevation increases and decreases, and some topographical elements require it to change direction. This is where pipe bending machines come in.


A piece of pipeline is fed through a pipe-bending machine. (Photo courtesy CRC-Evans)


These large devices take segments of pipeline and do just what their name implies: bend them, so that they can rise and fall with elevation, or curve where necessary. The machine is equipped with a specific bending set and die—based on the diameter of the pipe—and the operator programs the machine to shape it to specifications. As with every other part of this process, using the wrong equipment or curving the pipeline wrong will cause major delays.

Bending a 36” pipeline takes plenty of effort, and steps are taken to make sure that exertion doesn’t negatively affect the body of the pipe. Another tool, a mandrel, is inserted inside the pipeline before it’s fed through the bending unit. This element exerts pressure from within the pipeline, ensuring that “wrinkles” don’t form on the body during the process.

After all this work, it’s almost time for the pipe to be installed, finally. There are still three more steps to go, and we’ll look at all of them in the next post.