What is pipeline roof topping?
Pipeline roof topping, also referred to as pipeline tenting, peaking, or angular misalignment, is a geometric anomaly that occurs at the seam weld of longitudinally welded pipes. Considered a pipe-mill defect, it is typically introduced during the manufacturing process.1
How does roof topping occur?
Pipeline roof topping occurs when the edges of the pipe plate are not properly crimped before the U-and-O forming process. Rather than forming a perfect circle, the edges meet at an angular apex. This causes the seam weld to protrude beyond the pipe’s circular contour. This creates a non-circular shape that resembles a “roof.” Roof topping is more common in older pipelines.1
How does roof topping impact pipeline safety?
Minor pipeline roof topping may be acceptable within specified limits and under non-severe service conditions. However, significant misalignment can compromise the safety and integrity of the pipeline. In such cases, the pipe should be rejected to prevent potential future failures.1
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Source reference
1 The Encyclopedia of Pipeline Defects, ROSEN UK, Edition 3, 2017.