Flaws and defects in pipelines can significantly reduce the structural integrity of a pipe, potentially resulting in a loss of containment.
Pipeline operators have a few options to repair these flaws:
- Replace the section of pipe;
- Weld a metal sleeve over an extended area; or
- Use one of many possible non-welded repair technologies.
A key challenge is choosing the right repair solution for specific operating conditions.
Why Not Repair the Flaw with a Steel Sleeve?
Welding a metal sleeve is the traditional repair approach, but it can also create problems. Welding can cause moisture to be absorbed, increasing the embrittlement of the pipe.
There is also an increased risk of hydrogen-assisted and hydrogen-induced cracking as the metal cools.
This embrittlement is impacted by:
- the combined stress caused by shrinkage,
- hydrogen molecules diffusing or spreading out from the weld,
- and the formation of hard martensite.
Steel sleeves are also limited to relatively straight and uniform pipe geometries. The repair of wrinkled pipe, bent pipe, tees and elbows using this traditional repair approach is challenging and in most cases impractical.
Using non-welding repair technologies addresses this limitation. Installation often includes a wet layup process. This allows these technologies to take the form of the underlying structure. These composite repairs are often installed faster and with less equipment than traditional metal sleeves.
For these reasons, many operators are turning towards non-welding repairs.
Join the Joint Industry Project (JIP)
C-FER Technologies is leading a joint industry project for pipeline operators interested in testing the new repair technologies. Members will learn what the best and safest technologies are for their operations and help direct testing.
Operators can conduct a side-by-side comparison of these non-welding repair technologies tested at pressure in an objective, non-biased, and highly instrumented laboratory environment.
To C-FER’s knowledge, this testing approach is the most representative completed to date of conditions during actual field installations for the repair of circumferential cracks.
Considering Non-welding Technologies
There are novel composite or metal repair technologies that do not require welding to the carrier pipe. When selected, designed and installed properly, these technologies can provide significant load-carrying capacity.
Non-welding repair technologies have focused on the repair of axial defects in pipelines (i.e. hoop reinforcement) such as corrosion, seam welds defects, dents under internal pressure cycling or burst pressure. These technologies have been developed and evaluated for this application, leading to standardization in ASME PCC 2 and ISO 24817. However, their evaluation for the repair of circumferential cracks for axial reinforcement or slope/ground movements for bending reinforcement has been limited.
Composite repair materials are usually anisotropic (i.e. material properties vary with orientation), leading to more design and installation considerations.
These considerations make it very difficult to know if a specific technology is acceptable for individual pipelines. The consequences of picking the wrong technology for the wrong condition or flaw can be significant.
Evaluating Non-welding Pipeline Technologies
C-FER has experience evaluating non-welding repair technologies, including recent full-scale testing using biaxial, burst and bending load configurations. These tests are some of the first to accurately replicate real pipeline conditions by including internal pressure during repair installation.
C-FER’s laboratories can also simulate almost any full-scale environment with our high-capacity load frames, pressure equipment, instrumentation and data acquisition systems.
Conceptual Drawings and photographs of test Configurations
Internal Burst Loading
Biaxial loading
