Contour Repairs Corrosion Under Insulation at a Gas Station

Pipe Details

  • 76-mm (3-inch) diameter
  • API 5L Grade B steel
  • 70 bar (1,015 psi) design pressure
  • 60° C (140° F) design temperature.
  • 5.5 mm (2.2 inch) original wall thickness
  • 2 mm (0.08 inch) remaining wall thickness
  • Corrosion under insulation
  • Natural gas distribution station


  • A natural gas line at a distribution station had corroded from an original wall thickness of 5.5 mm (2.2 inch) to only 2 mm (0.08 inch).
  • Trained local technicians carried out repairs, installing CSNRI Contour, without taking the line out of service
  • CSNRI Contour repairs were performed in 1 day
  • The company safely resumed normal operations within 2 working days.

Nondestructive testing on a line at a natural gas distribution station uncovered corrosion under insulation on a 76-mm (3-inch) API 5L Grade B steel pipeline designed for 70 bar (1,015 psi) pressure and an operating temperature of 60° C (140° F).  The original wall thickness of 5.5 mm  (2.2 inch) had eroded, leaving only 2 mm (0.08 inch) remaining.

Because it was important for the section of pipe to remain operational while the corrosion was addressed, the owner selected a CSNRI Contour repair.

Using the specific characteristics of the pipe, CSNRI designed a repair to ISO 24817 2015 guidelines, which provide requirements and recommendations for qualifying, designing, installing, testing and inspecting the external application of composite repair systems to corroded or damaged pipework, pipelines, tanks, and vessels used in the petroleum and natural gas industries.

Contour Defect after removal of insulation
Defect after removal of insulation
Surface preparation by bristle blaster
Surface preparation by bristle blaster
Contour Completed repair
Completed repair

Local trained and certified technicians cleaned the pipeline with a bristle blaster to a finish equivalent to SA2.5 and then washed it with solvent and installed four layers of Contour. Once the installation was complete, the pipe was re-insulated.

The repair was completed with the pipe online and without any disruption to the local gas supply.