Uncharted Waters: A Deep Dive into Assessing the Fatigue Life of Subsea Pipelines

Subsea cables and pipelines are the backbone of the offshore infrastructure, playing a critical role in transporting energy and fuel. These pipelines and cables are essential for keeping the lights on and powering our homes and businesses, but with this importance comes a great responsibility to ensure their safe and reliable operation.

One of the biggest threats to the structural integrity of these pipelines is VIV, which stands for vortex-induced vibrations. VIV creates significant stress on the pipelines, which if compounded over time, can lead to fatigue failure. This is a serious concern as failure of these pipelines can have severe environmental and economic consequences, as well as cause fatalities.

To anticipate and control failure risk, integrity assessment of subsea pipeline free spans is a frequently used method. However, assessing the structural integrity of these pipelines is a complex task, especially when considering the low-cycle and high-cycle corrosion failures. Current industry standards for crucial engineering evaluations such as corrosion fatigue are not fully adequate to address this issue.

This is why a research methodology was developed to study the fatigue behavior of the free-spans based on DNV-RP-F105. This methodology was integrated into a PYTHON code to check the response behavior of free-spans and its effects on fatigue life. A case study was presented by selecting a free-span and the results showed that the adjacent span plays a critical role in determining the fatigue life of the free-spans.

In conclusion, this study highlights the importance of assessing the structural integrity of subsea pipelines and cables and the need for a more robust and effective approach to evaluate the fatigue life of these pipelines. The research methodology and PYTHON code developed in this study can be used as a tool for integrity assessment of subsea pipelines and cables. Additionally, the study showed that at areas where span lengths are increasing due to adjacent spans, span interventions methods are advised. This is a crucial step towards ensuring the safety and reliability of our offshore infrastructure and protecting the environment and human lives.