Pipeline Free-Span Analysis

In-service pipelines could potentially suffer from fatigue damage (FLS) and local buckling failure (ULS) due to the free.

Pipeline vibration due to vortex shedding (in-line and cross-flow VIV) and direct wave actions causes accumulative fatigue in a free span. Pipeline static bending, vortex induced vibration, direct wave and current effects and trawl gear interaction are the main contributors of a local buckling failure in a free span.

Z-Subsea possesses comprehensive experience in assessment of free spans of in-service pipelines. Z-Subsea’s approach is in full in compliance with “DNV-RP-F105 – Free Spanning Pipelines” recommended practice. Allowable free span length need to fulfill the integrity of the pipeline against fatigue damage, local buckling failure and trawl gear interaction.

To calculate allowable free span length against fatigue damage, Z-Subsea employs following levels of assessment:

  • Screening
  • Response Model
  • Finite Element (FE)