How Are Multiple Pipelines Installed in a Single Road Bore?
Installing a pipeline beneath a highway, railroad, river, or other obstruction can be one of the more expensive portions of a pipeline construction project.
Horizontal Directional Drilling (HDD) provides a method of installing pipelines without excavating a continuous open trench across the obstruction.
But what happens when a project requires two, three, five, or even more pipelines to cross the same location?
Rather than drilling a separate borehole for every pipeline, contractors can sometimes install multiple pipelines through a single borehole.
This approach is commonly referred to as a bundled bore, multi-pipe HDD installation, or multi-line pullback.
While bundled installations can provide substantial construction efficiencies, they introduce an important challenge:
How do you keep the pipelines from contacting and damaging each other during installation?
That is where Bundled Bore Solutions (BBS) pipeline bumpers come into the picture.
Why Install Multiple Pipelines Through One Borehole?
Consider a pipeline project requiring four separate pipelines to cross beneath a highway.
One approach would be to drill four individual boreholes.
Each bore could require its own drilling operations, equipment setup, and installation sequence.
An alternative is to design one larger borehole capable of accommodating all four pipelines.
The pipelines are assembled into a bundle and pulled through the borehole together.
Potential advantages include:
Fewer individual drilling operations
Reduced equipment mobilization and setup
Less disturbance at the crossing
Potential reductions in construction time
Potential savings in overall installation cost
However, these benefits depend on the project design, ground conditions, pipeline sizes, and available equipment.
A bundled bore is not automatically the most economical or technically appropriate option for every crossing.
What Is the Biggest Challenge With Multiple Pipelines in One Bore?
The challenge is maintaining separation between the individual pipelines.
During an HDD pullback, the pipelines are subjected to pulling forces, bending, movement, and contact with installation equipment.
When multiple pipes are pulled together, they can move relative to one another.
Without adequate separation, one pipeline can rub against another.
This is especially concerning when the pipelines have external corrosion protection coatings.
For example, a pipeline protected with fusion-bonded epoxy (FBE), a polyethylene coating, or another approved corrosion protection system can experience mechanical damage if it repeatedly contacts an adjacent pipe.
A coating may perform extremely well against corrosion but still be vulnerable to abrasion or concentrated mechanical loading during installation.
If the protective coating is damaged, the underlying steel may become more vulnerable to corrosion.
The objective is to install the pipelines while minimizing pipe-to-pipe contact and protecting their external coatings.
What Are Pipeline Bumpers?
Pipeline bumpers are specially designed spacing components installed on the exterior of a pipeline.
Their purpose is to maintain physical separation between adjacent pipes.
Instead of allowing two coated steel surfaces to rub directly against one another, the bumper provides a designated contact and spacing surface.
A properly selected bumper system must account for several factors.
It must provide adequate separation, remain attached to the pipeline, withstand anticipated installation loads, and pass through the installation equipment without creating unacceptable interference.
These requirements become especially important when the pipeline bundle passes over rollers and enters the borehole.
What Is Bundled Bore Solutions (BBS)?
Bundled Bore Solutions (BBS) is a pipeline spacing system developed by Joint Specialists Inc. to address the challenges associated with installing multiple pipelines in a common borehole.
JSI introduced the BBS system in 2014.
The system uses specially designed bumpers that are attached to the exterior of the pipeline with an epoxy bonding agent.
Unlike improvised spacing methods, BBS components are designed specifically for bundled pipeline installations.
The bumper material, geometry, spacing, and attachment method are selected to address the demands of the installation.
How Do BBS Bumpers Work?
The basic principle is straightforward.
BBS bumpers create a physical standoff between adjacent pipelines.
When the bundle is assembled and pulled through the borehole, the bumpers help prevent the coated surfaces of neighboring pipelines from contacting one another.
The system incorporates several important design considerations.
1. Physical Separation
Bumpers provide clearance between the individual pipelines.
A commonly used BBS configuration provides approximately 1 inch of radial standoff, although the required dimensions depend on the project.
The bumper size and arrangement must be selected for the pipe diameters and expected bundle geometry.
2. Epoxy Bonding
BBS bumpers are attached using a specified epoxy bonding agent.
The bond is an essential part of the system.
The bumpers must remain attached while the pipes move through rollers, encounter installation forces, and pass through the borehole.
3. Engineered Bumper Material
BBS bumpers are manufactured using materials selected for the application.
Material hardness, often expressed as durometer, is an important consideration.
The bumper must be capable of providing separation without being unsuitable for the expected contact loads.
A bumper that is too soft, too hard, or improperly designed may not perform as intended.
4. Geometry That Accommodates Movement
Bumper shape also matters.
A protruding component with an abrupt edge can encounter problems when passing over rollers or other installation equipment.
BBS bumper configurations are designed with these installation challenges in mind.
The objective is to provide separation while reducing the likelihood of the bumper catching on equipment during pullback.
How Are BBS Bumpers Installed?
The exact installation procedure depends on the specified BBS design and the pipeline coating.
A typical installation involves the following stages.
Step 1: Evaluate the Pipeline Surface
The contractor identifies the existing external coating and confirms that the proposed bonding procedure is compatible with it.
This is especially important for pipelines with specialized factory-applied coatings.
Step 2: Prepare the Bonding Area
The bonding area is prepared according to the applicable installation procedure.
Proper preparation is necessary to develop the intended adhesion between the bumper assembly and the coated pipeline.
Step 3: Apply the Epoxy Bonding Agent
The specified bonding material is applied as directed.
The adhesive must be compatible with the bumper and the prepared pipeline surface.
Step 4: Position the Bumpers
The bumpers are positioned at the required locations around the pipe.
Their orientation and spacing must match the planned bundle configuration.
Step 5: Secure the Assembly
The applicable BBS installation method uses temporary positioning or retention components to hold the bumpers in place while the adhesive develops its required properties.
Step 6: Allow the Required Cure
The epoxy must achieve the required cure before the bumper is subjected to installation loads.
The contractor should follow the specified cure schedule rather than assuming that the bumpers are ready for immediate pullback.
Step 7: Inspect Before Pullback
The completed assemblies should be checked for correct positioning, secure attachment, and compliance with the project requirements.
The exact installation instructions supplied for the selected BBS configuration should always take precedence over a general description.
Can BBS Bumpers Be Used on Polypropylene-Coated Pipelines?
Pipeline coating compatibility is an important consideration.
Different factory-applied coatings have different surface properties.
For example, polypropylene-based coatings can present bonding challenges because of their surface characteristics.
JSI has performed bonding evaluations involving polypropylene-coated pipelines.
However, contractors should not assume that an epoxy bonding method suitable for one coating will automatically be suitable for every other coating.
The existing coating, surface preparation, adhesive selection, and any required qualification testing should be evaluated before installation.
Why Not Use Rope, Rubber Strips, or Ordinary Tape?
Contractors sometimes look for inexpensive ways to keep pipelines apart during installation.
Rope, rubber strips, and ordinary tape may appear to provide a simple solution.
However, these materials are not necessarily engineered to withstand the forces involved in a bundled HDD pullback.
Potential problems include:
Loss of the spacing material during pullback
Movement of the material along the pipe
Insufficient resistance to compression
Damage to the underlying pipeline coating
Interference with rollers or handling equipment
Inconsistent separation between pipelines
The initial cost of an improvised spacer may be small compared with the potential consequences of losing separation during installation.
A purpose-designed bumper system addresses the problem through controlled geometry, material selection, and attachment procedures.
Does Pipe Separation Matter After Installation?
Yes.
The importance of pipeline separation does not necessarily end when the pullback is completed.
Once the pipelines are in service, their external coatings and corrosion control systems must continue to function.
For buried steel pipelines using cathodic protection, the final bundle configuration can affect the surrounding environment and the distribution of protective current.
Maintaining physical separation can help avoid direct pipe-to-pipe contact and provide space around individual pipes.
However, the presence of bumpers alone does not guarantee adequate cathodic protection.
The pipeline operator and corrosion engineer must evaluate the completed installation, including the surrounding soil or drilling-fluid conditions, electrical continuity, and the cathodic protection design.
How Many Pipelines Can Be Installed in One Borehole?
There is no universal maximum number of pipelines that can be installed in a single borehole.
The answer depends on the engineering requirements.
Important factors include:
Pipe diameter: Larger pipes require more room.
Number of pipelines: More pipes create a larger and potentially more complicated bundle.
Borehole diameter: The drilled and reamed bore must provide sufficient clearance for the complete assembly.
Bumper dimensions: The bumpers increase the effective outside dimensions of the bundle.
Bore length and curvature: Longer or more demanding crossings may impose additional installation loads.
Pulling capacity: The drilling equipment must be capable of handling the expected loads.
Pipe and coating specifications: The installation must remain within the allowable limits of the individual pipelines and coatings.
JSI has experience supplying BBS bumpers for projects involving as many as 11 pipelines in a single bundle.
The suitability of any proposed arrangement must be determined through project-specific engineering.
What Information Is Needed to Design a BBS Installation?
Before selecting bumpers for a bundled bore, contractors should gather several important details.
These include:
Number of pipelines in the bundle
Outside diameter of each pipeline
Type of external coating on each pipe
Planned bundle arrangement
Borehole diameter
Approximate bore length
Expected pulling conditions
Roller and pipe-handling arrangement
Required clearance between pipelines
Installation schedule
This information helps determine the appropriate bumper configuration, quantities, and installation requirements.
It can also help identify potential problems before the pipes are assembled for pullback.
Why BBS Matters for Pipeline Contractors
Bundled HDD installations can offer meaningful construction efficiencies.
But installing multiple pipelines in one borehole introduces mechanical challenges that are not present in the same way during a single-pipeline pullback.
Protecting the external corrosion coating is particularly important.
The coating must survive construction and continue providing protection after the pipeline enters service.
Bundled Bore Solutions helps address this challenge by providing an engineered method of maintaining separation between adjacent pipelines.
Instead of relying on improvised materials, contractors can use a bumper system designed around the demands of multi-pipeline installation.
Bundled Bore Solutions From Joint Specialists Inc.
Joint Specialists Inc. developed Bundled Bore Solutions to help pipeline contractors protect multiple pipelines during HDD installations.
Since introducing the system in 2014, JSI has supplied BBS bumpers for a wide variety of bundled pipeline projects.
Whether your project involves two pipelines or a more complex multi-line installation, JSI can assist with evaluating bumper requirements and material quantities.
For more information about Bundled Bore Solutions, visit:
Or contact:
Steve Simpson
Joint Specialists Inc.
Phone: 936-321-3333
Email: steve@jsicoatings.com
When requesting information or a quotation, please provide the number of pipelines, pipe diameters, coating types, and approximate bore length.
We welcome the opportunity to help protect your next bundled pipeline installation.
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