The Importance of Lateral Junction Repairs in Pipe Rehabilitation 

The Importance of Lateral Junction Repairs in Pipe Rehabilitation blog LP banner

The Importance of Lateral Junction Repairs in Pipe Rehabilitation

Introduction

Rehabilitating pipes is a critical aspect of infrastructure maintenance, and selecting the right technique is influenced by several factors, including pipe material, size, defects, depth, location, and existing conditions. One common approach is to use trenchless methods, such as Cured in Place Pipe (CIPP) lining and spiral wound lining, to restore the mainline integrity. However, even after these rehabilitation methods, a crucial step remains; lateral junction repairs (LJR). 

Lateral Junction Repair
Image Source: Advanced Pipeline Services Ltd L.L.C.

Advantages of Completing a Lateral Junction Repair

LJR plays a pivotal role in ensuring the success of mainline rehabilitation. It can be carried out either by excavation and installing a saddle or by using trenchless technology. The latter method is widely favoured due to its environmental and economic advantages. Various names, such as “Top Hat,” “LCR,” or “LJR,” are given to this repair method by different contractors, but their core purpose is the same: sealing the gap between the new liner and the host pipe. 

Equipment Required

Two primary pieces of equipment are used for LJR installation: a specially designed LJR packer and a CCTV camera. The LJR packer is typically constructed from steel tubes with an inflatable rubber interior, which expands like a balloon when filled with compressed air. The CCTV camera is essential for confirming the correct sealing of the junction. 

Methods of Installation

Once the initial lining technology (CIPP or Spiral wound) has been installed, connection / junction locations will be recut for hydraulic connection to the mainline using robotic cutting equipment. Followed by one of the two primary methods for LJR installation: 

  1. Pull and Inflate the Packer: In this method, the LJR packer, coated with resin-impregnated felt, is pushed into the mainline. Compressed air is then blown into the packer, causing it to expand and adhere to the inside surface of the host pipe. The resin cures over time, and once hardened, the packer is deflated and removed.
  2. Pull and Invert the Sealing Liner: With this method, the packer is pulled between maintenance holes, reaching the lateral’s point. Then, the sealing liner is inverted inside the lateral using compressed air. The liner adheres to the inner wall of the host pipe and cures.

Risks Involved

Several technical risks can be encountered during LJR installation: 

  1. Limited Time for Resin Placement: Epoxy resin used for LJR work has a limited curing time. If the crew fails to position the felt correctly within this time, the process must start anew with new felt.
  2. Bunching of Felt: Sometimes, felt can bunch inside the pipe due to a loss of air pressure through the packer. Careful monitoring of air pressure is essential.
  3. Packer Stuck Inside Pipe: The packer may get stuck inside the lateral or mainline for assorted reasons. Pre-installation CCTV checks can help detect and address issues before commencing work.
  4. Roots Intrusion: Roots inside the lateral connection must be removed before LJR installation.
  5. Depth and Location Challenges: When lateral connections are located at great depths or under structures that cannot be excavated, dealing with issues can be challenging. Faulty LJR installation may necessitate expensive excavation for correction.

Comparing Lateral Junction Repair Options

There are two common options for Junction repair options, t-seals & top hat seals . Below are the considerations for both options: 

T-Seal:

  • Material Strength: Uses silicate Supercil reinforced with woven glass for superior strength and thinner walls compared to traditional glass felts. 
  • Mixing Consistency: It offers error-proof, pre-packaged Supercil for consistent mixing quality. 
  • Environmental Advantages: Emphasizes application controls to prevent spillage and site mess. 
  • Innovative Packer System: Uses an innovative, patent-pending packer system to make the installation process safer and significantly faster. 
LatSeal Packer
Image Source: Ibtech Australia

Top hat seal

  • Proven Technology: The top hat shape have been used extensively for a decade, indicating reliability. 
  • Rapid Setting Resin: Different seal options can come with proprietary materials and  resins with a rapid set but a long pot life, allowing for efficient product placement. 
  • Expansion to Larger Pipes: This technology has extended to larger carrier-size pipes, ensuring structural integrity. 
  • Non-Obstructive Installation: Top hat style seals can be installed with minimal flow obstruction. 
Interfit TopHat
Image Source: M Tucker & Sons Australia

Conclusion

In the world of infrastructure maintenance, LJR serves as a vital tool for safeguarding the integrity of sewer networks and ensuring the efficient operation of wastewater systems. Proper planning, thorough pre-checks, and confirmation of the feasibility of LJR installation are essential to minimize risks associated with this crucial repair process. When considering LJR, one must weigh the potential costs of a faulty installation against the benefits of avoiding excavation and repair. 

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About the Author

Mark Lee is the Business Development Manager (AUS/NZ) at VAPAR and a former Senior Asset Engineer who has spent more than a decade managing the asset lifecycle of infrastructure. He has extensive experience managing pipeline networks, including design, construction, condition assessment and decommissioning.

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