Free spans of pipelines may develop due to several reasons such as installation on uneven seabed or due to scouring effects. Such spans may be subjected to fatigue damage caused by direct wave and Vortex-Induced Vibrations (VIVs).
DNV GL is developing a new online tool for assessment of fatigue due to VIV and direct wave loading on pipelines. The pipeline fatigue assessment tool can efficiently evaluate entire pipelines based on multiple surveys or operation conditions. Fatigue damage is calculated per KP location along the pipe, allowing for more accurate, and less conservative assessment of pipelines with changing free span lengths and locations. This can significantly reduce or avoid costly intervention work for pipelines on shifting seabed. The fatigue assessment of free spans is compliant with the latest revision of DNVGL-RP-F105.
The main benefits are:
- Reduced unnecessary conservatism for span assessments since damage is logged per location (and when spans change, critical locations change)
- Easy to account for variation along the line (pipe direction, water depth, pipe dimensions etc.)
- More efficient and robust means of identifying multi-span configurations
- Improvements to DNVGL-RP-F105, input data, changes to data or confidence levels can be seamlessly implemented
- More effective and robust means of identifying multi-span configurations
- Possibility to easily re-calculate results from previous assessments (due to e.g. new information)
- Efficient follow up of free spans based on survey through the life time of the pipeline and ease to add and assess new surveys
- Calculate fatigue life based on the operation history by weighting different operation conditions, installation damage and temporary phases.