DNV GL revises pipeline free span guidance


DNV GL has updated its recommended practice on offshore pipeline spans, to reflect project and research experience from the last decade on free span dynamic response, particularly on structural modeling.

DNVGL-RP-F105 is said to enable significant costs savings, in the newbuilding and operational phase.

The RP provides rational design criteria and guidance for assessment of dynamic response of pipeline free spans due to combined wave and current loading.

It specifies detailed design criteria for ultimate limit state and fatigue limit state due to in-line and cross-flow vortex induced vibrations (VIV) and direct wave loading.

Linlin Jiao, senior pipeline engineer, DNV GL - Oil & Gas, said: “New research through PhDs, published literature, and extensive accumulated project experience have advanced the field, and allowed us to significantly refine and improve the recommended practice with more reliable results and a greater range of applications.”

The main changes are:

  • A new force model for direct wave action, which allows for multi-mode and multi-span analyses
  • Accurate modal response quantity calculation procedures for short spans
  • General guidance on how to apply and interpret sensor technology on free spans
  • General guidance on how to apply the RP to spools, jumpers, flexible loops and piping systems
  • A new response model for cross-flow VIV in waves with low Keulegan-Carpenter numbers.

Cathrine Torp, communication director, DNV GL - Oil & Gas, added: “With these key updates, the DNVGL-RP-F105 will increasingly benefit our customers by reducing the enormous cost due to unnecessary span interventions and potential fatigue failure.”