What’s the best way to address inadequate thrust restraints on a pipeline?
When longitudinal forces aren’t properly resisted by thrust blocks, pipeline sections can be pulled apart by thrust forces which cause circumferential cracks at the pipe joints. This can lead to severe mortar delamination, corroded wires, cracked outer cores, and compromised steel cylinders. One of the biggest, and most impactful, complications of inadequate thrust constraints are pipeline leaks. As a result of the leaks, the system can catastrophically fail.
To address distressed pipelines, including those with inadequate thrust restraints, utilizing carbon fiber reinforced polymer composite (CFRP) lining systems is an appropriate solution. The use of CFRP composites for pipeline rehabilitation involves the application of epoxy saturated sheets of carbon fiber and glass fiber composites to the inside or outside of the pipeline, applied in the orientation designated on project design drawings.
Unidirectional carbon fiber fabrics, as shown in the photograph, are typically relied on for structural integrity. Glass fabrics typically serve as the electrical isolator layer on projects involving metallic pipelines, or in the end termination details for PCCP, to separate the carbon fibers from directly contact with any metallic substrate being rehabilitated. Once cured, these composite materials serve as the structural system and often are designed to take all structural loads without relying on the host pipe for structural integrity.
Proactively addressing and inspecting PCCP systems is an effective way of documenting and preventing any pipeline failures. The risks of inadequate thrust restraints can be mitigated with internal inspections, electromagnetic testing to ensure the integrity of the PCCP inventory, acoustic monitoring, and impact echo testing.