In horizontal directional drilling (HDD), casing pipe is essential for maintaining borehole stability, preventing fluid loss, and protecting surface structures from collapse. It supports the hole during construction and helps mitigate fluid loss, hole collapse, and surface collapse. Through casing, the drilled hole is provided stability through the curved sections during the HDD process. The use of casing is most common in soft or loose soil where the drill path is shallow, and where gravel or cobbles are anticipated.
Among casing materials, steel stands out for its strength, durability, and ability to handle high loads, making it the preferred choice for many HDD projects. From stabilizing entry and exit points to shielding the product pipe during pullback, steel casing plays a pivotal role in achieving a safe and successful installation.
Types of Casing in HDD
Conductor casing stabilizes the entry point of the borehole, particularly in unconsolidated soil formations where caving and erosion is more common in the initial drilling stages. The casing pipes are laid at a shallow depth, often cemented in place, to provide stable support for the hole.
Pullback casing protects the product pipe. It helps minimize friction and wear on the product pipe during the pullback phase, especially in difficult soil conditions, extensive bores, or significant curvature. The casing can protect the product pipe from sharp objects, rocks, or other obstructions. By reducing friction and providing a clear path, pullback operations can operate more quickly and efficiently.
Material Selection
When choosing casing materials for HDD projects, operators must understand geotechnical reports and how the subsurface data impacts HDD design and construction. The soil conditions and load-bearing requirements determine the appropriate
- Diameter
- Wall-thickness
- Length of the casing
First, it is important to know the surrounding soil properties, such as:
Cohesive soils, such as clay, also support open-hole drilling conditions. On the other hand, coarse soils like gravel and cobbles, or hard bedrock, can be challenging to conduct horizontal directional drilling.
The path of the bore must also be taken into consideration. Obstacles should be defined, and future utility locations should be considered. This way, the borehole’s alignment is optimized to minimize drilling through challenging zones like bedrock.
Additionally, operators must consider the loads and service life when choosing between pipe materials like steel, HDPE, and PVC. The material must be able to withstand pullback loads during installation and external loads after installation.
High-quality steel is essential for road boring projects because it can withstand the stressors of boring operations. Several strength properties make steel pipe the preferred choice for road boring projects. First, the steel can withstand being pulled. Steel can also absorb extreme force without breaking. During horizontal directional drilling, the pipe is under constant strain in applications, so withstanding force is essential. Finally, steel pipe in road boring applications is capable of structurally protecting the bore.
Operational Benefits of Horizontal Directional Drilling
HDD significantly reduces installation time compared to open-cut trenching, as it eliminates the need for extensive digging. The elimination of extensive digging also minimizes surface and environmental disruption. HDD is safer, reducing the risk of accidents that may occur with open trenches, such as cave-ins. HDD can also be used in a variety of soil conditions and is capable to cross obstacles like rivers and highways, making it ideal for complex projects.
To properly prepare for an HDD project, there must be a complete understanding of subsurface conditions and existing utilities. This ensures damage can be prevented and the drilling will be successful. The drill path must be monitored through guidance systems. Regular maintenance and inspections of drilling equipment must be in place to guarantee safe operation. Additionally, it is necessary to strictly adhere to safety protocols, including
- Proper Training
- PPE
- Emergency Procedures
These protocols minimize risks for workers and the public. Adhering to all applicable regulations and industry standards is essential for safe and responsible HDD operations. Guidelines on the proper course of action can be found in industry materials such as ASTM F1962, ASCE MOP 108, and NASTT Guidelines.
Reliable Pipe Necessity in HDD
Casing plays a large role in improving HDD performance and pipeline reliability. It offers critical protection to the installed pipe, contributing to both improved drilling performance and long-term pipeline reliability. Casing allows for more complex and challenging designs, stabilizes the drilled borehole, and acts as a protective barrier against external loads and potential damage.
Road boring projects require high-quality, durable, and reliable casing pipes for underground installations. However, newly manufactured pipes can become expensive and have unpredictable lead times. Read more about this dilemma in our road boring case study at https://cpipipe.com/resources/.
When a road boring project requires durable steel casing pipe on a tight schedule, sourcing new surplus and used steel pipe can be a dependable solution. Quick delivery of this readily available pipe can help save up to weeks of lead time. This expedited sourcing method can also lead to significant cost savings compared to newly manufactured pipe.
Request a quote from our readily available inventory at cpipipe.com.
References:
https://www.vigordrilling.com/info/casing-and-tubing-95735792.html