Horizontal Directional Drilling (HDD) has become an increasingly popular installation method for projects requiring multiple pipelines or conduits to cross beneath highways, waterways, railroads, and other obstacles.
In many applications, installing multiple pipes together in a single bore can offer significant advantages compared to drilling separate boreholes for each individual line.
However, pulling several pipes through one borehole introduces challenges that do not exist with a conventional single-pipe installation.
One of the most important considerations is maintaining proper separation between individual pipes throughout the pullback operation.
Without adequate spacing, bundled pipelines can experience pipe-to-pipe contact, coating abrasion, and other mechanical problems that may compromise the integrity of the installation.
Joint Specialists Inc. developed its Bundled Bore Solutions (BBS) bumper system specifically to help address these challenges.
What Is a Bundled HDD Installation?
A bundled HDD installation involves pulling two or more pipelines or conduits through a single drilled borehole.
These installations may include combinations of steel pipelines, coated pipelines, and other compatible conduits, depending on the project requirements.
Bundled installations can be particularly attractive when the available right-of-way is limited or when multiple crossings would increase construction costs.
Potential advantages include reduced drilling requirements, fewer separate crossings, and more efficient use of available underground space.
However, the individual pipes within the bundle must be properly managed to prevent unwanted contact during installation.
Why Pipe-to-Pipe Contact Is a Concern
When several pipes are pulled together through a borehole, they do not necessarily remain in the same position relative to one another.
The bundle may experience bending, rotation, tension, and changes in contact pressure as it travels through the drilled path.
These forces can cause adjacent pipes to move against each other.
If the pipes are in direct contact, several problems may develop.
1. Damage to protective pipeline coatings
Steel pipelines are commonly protected by external corrosion prevention coatings such as Fusion Bonded Epoxy (FBE), polyethylene coating systems, or other specified materials.
These coatings are designed to protect the underlying steel from corrosive environments.
During HDD pullback, however, direct contact between adjacent pipes can create friction and abrasion.
Repeated rubbing or concentrated contact pressure may damage the protective coating, potentially exposing the steel substrate.
Because the pipelines are being installed underground, locating and repairing coating damage after pullback can be extremely difficult.
2. Concentrated contact pressure
When two pipes contact each other directly, forces may become concentrated along relatively small areas.
This can increase the risk of localized coating damage.
Properly designed spacing systems help establish separation between adjacent pipes and can reduce direct coating-to-coating contact.
3. Movement during pullback
A bundled pipeline assembly can experience changing forces as it moves through bends in the borehole.
Individual pipes may attempt to shift relative to one another.
Without a properly engineered separation system, these movements can create unwanted contact and additional mechanical stresses.
How BBS Bumpers Help Maintain Pipe Separation
Joint Specialists Inc. developed its Bundled Bore Solutions system in 2014 to address the need for reliable pipe separation during bundled HDD installations.
The BBS system uses specially designed bumpers that are attached to the pipe surface at predetermined locations.
These bumpers help maintain separation between adjacent pipes during pullback.
Rather than allowing the primary pipeline coatings to rub directly against each other, the bumpers provide designated contact points between the individual pipes.
This approach helps protect the underlying coating systems while maintaining the intended spacing within the bundle.
Why Bumper Design Matters
Not every material is suitable for use as a pipeline spacer during HDD installation.
A bumper system must be able to withstand the anticipated installation conditions while remaining securely attached to the pipe.
Several design considerations are important.
Bumper height
The required bumper height depends on the desired pipe separation, pipe diameters, coating systems, and project-specific geometry.
Joint Specialists commonly uses approximately 1-inch bumpers in suitable applications, although the appropriate dimensions should be determined for each project.
Material hardness
Bumper hardness, often expressed as durometer, influences how the material responds to contact pressure and deformation.
A bumper that is too soft may compress excessively under load.
A material that is too hard may not provide the desired contact characteristics.
Selecting the appropriate durometer is therefore an important part of the system design.
Attachment to the pipe
The bumpers must remain securely attached throughout handling and pullback.
The BBS system uses a specified epoxy bonding agent to attach bumpers to compatible pipe surfaces.
Proper surface preparation, bonding procedures, and adhesive curing are essential to achieving the intended performance.
Bumper placement
Bumper spacing and positioning along the pipeline should account for pipe diameter, bundle configuration, expected bending, and installation forces.
Proper placement helps maintain separation at the locations where pipe-to-pipe contact is most likely to occur.
Why Rope and Improvised Spacers Can Be Problematic
Some bundled installations have historically relied on improvised methods to separate pipes, including rope or various tape materials.
However, these approaches may not provide predictable spacing or reliable mechanical performance under HDD pullback conditions.
Rope can compress, shift, or become displaced, potentially allowing pipes to contact one another.
Similarly, materials not designed for the anticipated loads may not provide consistent separation.
An engineered bumper system offers a more controlled approach to spacing, attachment, and material selection.
For projects where coating integrity is critical, these considerations can be particularly important.
BBS Experience in Bundled Pipeline Installations
Since developing the Bundled Bore Solutions system in 2014, Joint Specialists Inc. has supplied BBS bumpers for numerous bundled pipeline installations.
The system has been used on projects involving multiple pipelines pulled together through a single bore.
More than 100,000 BBS bumpers have been installed, with projects involving bundles of as many as 11 individual lines.
This experience demonstrates the practical application of engineered pipe separation systems in complex HDD installations.
Joint Specialists has also successfully tested BBS bumper bonding on polypropylene-coated pipe surfaces, expanding the range of coating systems that may be considered for compatible applications.
As with any engineered installation, specific pipe coatings, bonding requirements, and project conditions should be evaluated before selecting the system.
Protecting Coatings Before the Pipeline Goes Underground
Once a bundled pipeline installation is complete, accessing individual pipe surfaces may be extremely difficult.
That makes coating protection during the installation process especially important.
An effective bundled HDD protection strategy should consider not only the external forces imposed by the borehole but also the interaction between the individual pipes within the bundle.
BBS bumpers are designed to help address the second challenge by maintaining controlled separation between adjacent pipes.
When properly designed and installed, a bumper system can help reduce the risk of direct pipe-to-pipe coating damage during pullback.
Bundled Bore Solutions from Joint Specialists Inc.
Joint Specialists Inc. developed the BBS bumper system to provide contractors with a practical solution for maintaining pipe separation during bundled HDD installations.
With more than a decade of experience supplying BBS products and decades of involvement in pipeline corrosion prevention, Joint Specialists understands the importance of protecting pipeline coatings throughout construction.
Whether your project involves two pipelines or a more complex multi-line bundle, our team can assist with evaluating BBS bumper requirements, material selection, and installation considerations.
Contact Joint Specialists Inc. to discuss your next bundled HDD project and learn how BBS bumpers can help protect your pipelines during installation.
Contact Joint Specialists Inc.
Steve Simpson
Joint Specialists Inc.
Phone: 936-321-3333
Email: steve@jsicoatings.com
Website: www.heatshrinksleeves.com
Joint Specialists Inc. — Providing pipeline corrosion prevention solutions since 1995.
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