Horizontal Directional Drilling Explained

Horizontal Directional Drilling Explained

Horizontal directional drilling, or HDD, performs feats that can awaken the imagination. It’s quite incredible how pipeline can be placed underneath rivers, railways, highways, environmentally sensitive areas, and urban environments without disturbing the environment nor hindering traffic or urban activities for construction. So what is horizontal directional drilling, and how does directional drilling work?

What is Directional Drilling?

Horizontal Directional Drilling Machine By FRAC [CC BY-SA 2.5 (https://creativecommons.org/licenses/by-sa/2.5)], from Wikimedia Commons

Horizontal directional drilling, also known as directional boring, is a trenchless technology for installing pipe underground without impacting the area above the borehole. It is typically a shallow arc or crescent borehole in which pipeline, conduit, or cables are pulled through after the borehole is completed. Although typically a shallow arc, directional boring can also navigate turns during the boring process. This is especially important in urban boring situations where existing buried infrastructure such as sewer, water and tunnels must be avoided.

The directional boring machine bores a pilot hole, and consecutively larger reemed holes, pulling out the dirt and rock cuttings with a drilling mud. Once the borehole is large enough, the pipeline is pulled through the hole and the pipeline installation process can continue along it’s path with standard trenching methods.

How does Directional Drilling Work?

Here is a great horizontal directional drilling video from Kinder Morgan illustrating the process.  Below the video is our explanation of how directional boring works.

Horizontal Direction Drilling is comprised of three stages:

  1. Pilot Bore
  2. Reeming
  3. Product Pipe Installation

Stage 1: Pilot Bore

The drill bit is connected to a rotating drill pipe and pushed into the location designated for the borehole. It is guided through the boring process until it emerges on the opposite side of the boring project. Drilling fluids, or drilling mud is a mixture of water and bentonite clay and is very important to the operation. This drilling fluid is used in guiding the drill bit as it bores the hole. It also stabilizes the borehole and acts as a lubricant and coolant for the drill bit. Additionally, the drilling fluid carries all the soil and bedrock cuttings out of the borehole back to the drill rig location. The drilling fluid is then separated from the cuttings and recycled back into the boring process. Finally, the drill bit will exit the borehole at the exit pit.

Stage 2: Reeming

A reeming tool is then attached to the drill pipe and pulled back through the borehole. Successively larger reeming tools are pulled back and forth through the borehole until the hole is about one and a half times the size of the pipe that will be installed. Finally, a swab pass reemer is pulled through the hole to verify all is clear and ready to pull the pipeline through. This swab pass reeming tool is sized bigger than the pipe to be installed but smaller than the largest reeming already accomplished.

Stage 3: Product Pipe Installation

Pipes are brought to the exit location and welded together, coated, x-rayed, and pressure-tested. The completed pipe string, a little longer than the bored hole, is placed on rollers in preparation to be pulled through the borehole. It is then positioned and angled to make the pull as easy as possible with minimum resistance.

Once totally fabricated, tested, and properly positioned the pullback process begins. When the pipeline emerges at the drill rig location, it is then checked, surveyed, and tested. Lastly the worksites are cleared of equipment and restored to preexisting conditions.

Horizontal Directional Drilling Services

When looking for horizontal directional drilling services, make sure to call Hanging H Companies.  We are among the best horizontal directional drilling companies in the pipeline construction industry.  As a pipeline construction and HDD company, we are proud of our track record. We have standardized horizontal directional drilling procedure to ensure safety at all times, error free pipe strings, as well as accurate boring results.

We look forward to continuing to serve the continental United States in installation of both cross-country liquid and gas pipelines, as well as civil infrastructure pipelines such as water and sewer. Take a look at our services to see what all Hanging H Companies has to offer.

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