Challenges of HDD Projects and Common Causes of Coating Damage During Pullback Operations

Horizontal Directional Drilling (HDD) is widely used to install pipelines in environmentally sensitive areas and difficult terrains, with crossings now reaching lengths of up to 2000 m and accommodating large-diameter pipelines. However, the combination of abrasion, impact, gouging and bending forces during pullback makes HDD one of the most demanding installation methods for pipeline coatings.

One of the primary challenges is that conventional corrosion protection barrier coatings, such as Fusion Bonded Epoxy (FBE), Three-Layer Polyethylene (3LPE), Three-Layer Polypropylene (3LPP), and liquid epoxy field-joint coatings, are often designed for corrosion resistance rather than the severe mechanical stresses encountered during HDD installations. During pullback, pipelines are exposed to high friction, impact forces, abrasion, bending stresses, and contact with harsh ground conditions, which can exceed the mechanical limits of these coatings.

Common causes of coating damage during pullback include:

  • Abrasion from aggressive soil conditions, such as sand, clay, fragmented granite, cobble, and rocky formations, which can wear through protective coatings.
  • Mechanical impacts and gouging caused by the collapse of the tunnel during installation projecting rocks, drilling tools, or debris within the bore path.
  • Shearing, tearing, and crack formation in field-joint coatings due to tensile and friction forces experienced as the pipeline is pulled through the bore.
  • Mishandling during installation, which can damage coatings before or during pullback operations.
  • Dragging or contact with drilling equipment, such as carbide cones or other hardware, which can scar the coating and expose bare steel.

The consequences of coating damage can be severe. Exposed steel may become susceptible to corrosion, leading to failed post-construction inspections, costly repairs, pipeline removal and reinstallation, project delays, and significant cost overruns—sometimes reaching millions of dollars.

Traditional dual layer FBE or FBE ARO coatings do not always provide adequate protection in demanding HDD environments. Testing and field experience showed that composite protection systems offer substantially greater strength, stiffness, and fracture toughness than conventional FBE coatings, helping to prevent coating failures caused by pullback-related stresses and abrasion.

Key takeaway:

HDD projects are particularly vulnerable to coating damage due to abrasion, impact, bending, and harsh subsurface conditions during pullback. Selecting coatings with sufficient mechanical protection is critical to maintaining pipeline integrity and avoiding expensive project delays and rework.

Related Solution

For HDD installations involving aggressive ground conditions, composite mechanical protection systems such as ScarGuard can be used to provide additional resistance to abrasion, gouging, impact and pullback-related damage.

Learn more about ScarGuard →