Pipeline Lamination Defect

A pressurized pipeline experiences so called hoop stress which creates an environment for axial cracking.

Pipeline lamination defect.

Examples of pipeline defects are shown in figure 2 figure 3 and figure 4. But pipeline cracks are always detected perpendicular to the main local stress direction of the pipe material. Known for example from an inline inspection or as the result of a pipeline. Lamination defect is one of the common defects in the manufacturing process of seamless pipes.

Most people hear the words inclusion or lamination and think defect but one should not fear these words and automatically think of defect or rejection. Likewise an axial load on the pipeline supports the occurrence of circumferential cracking. The defect type may be. Lamination defect in the seam weld.

Some of these defects had particular conditions. Manufacturing or construction defect lamination cracking dent gouge identified as metal loss other unknown. Only in severe circumstances are they cause for rejection and there are remelting processes that can significantly improve the cleanliness of the metal and reduce inclusions and laminations. Inspection method for pipe with lamination defects we have a low temp cs pipeline carrying liquid ammonia at minus 33 deg these pipes were found with lamination defects during construction stage which were later considered to be acceptable after thorough analysis from design view point.

Lamination defect in steel plates is highly undesirable for dynamically loaded elements of steel structure such as high pressure temperature storage tanks vessels. Lamination defect of a significant area will impair the structural performance of welded objects to the plate surface and may result in a local buckling failure. A major refined products pipeline operator discovered laminations in the seam weld of a 12 pipe. Lamination defect is modeled by a zero volume crack created using demerging node method.

Lamination defects in base metal mostly parallel to the pipe surface of the pipe. Additionally the repair was on a 5 field bend and therefore a type b welded sleeve was not an acceptable repair solution. For instance in one case it was found that the defect in its deepest part was curved and broke the outer pipe surface. Another issue is when the material with the lamination is in compression when the lamination lies parallel to the stress direction.

As shown in figure 3 the lamination defect mn is near the inner surface and parallels to the pipe which divides the pipe into two sub pipes the outer sub pipe and the inner sub pipe. Many miles of pipeline would have to be blocked.