Cables

Cables and umbilicals are used to transport the electricity or signals from offshore wind and oil and gas. They are critical components during the operation safeguarding a stable and robust energy production. For offshore wind they are particularly of importance as 80% of all insurance claims stem from cables. This means that the design and operation of cables and umbilicals are key for success.

The DNV Subsea Toolkit includes a software tool based on many years of research and full-scale testing where the objective is to calculate capacity (ULS) and fatigue (FLS) of dynamic cables and umbilicals with cross sections spanning from simple steel pipes to complex sections composed of helically wound cores, insulation and durable sheath.

In today’s offshore field developments, significant investment is spent on designing, modelling and analysing offshore cables and umbilicals. This represents a substantial financial commitment to offshore wind and oil and gas production. Using the DNV Subsea Toolkit, it is possible to confidently build and assess the structural strength of such subsea equipment during design and operation throughout the lifetime.

We believe success relies on the ability to have engineering workflows that allow for integration with software tools for dynamic motion analysis, continuous increase in the fidelity of analytical data models and analyses from options study through conceptual design, basic design and detailed design yielding confidence in the compliance, safety and structural integrity of new and ageing offshore cables and umbilicals.

DNV Subsea Toolkit

Software calculating capacity and fatigue of offshore cables and umbilicals

DNV has developed its Subsea Toolkit for decades to simplify and speed up the engineering task to design submarine pipelines conforming with the DNV rules and cross-sectional capacity and fatigue calculations of cables and umbilicals. This means that owners and designers can use existing and validated commercial software from DNV instead of making their own implementation for ULS and FLS calculations.

The software facilitates a complete and user-friendly process primarily focusing ULS and FLS during the phases in the structural design of offshore cables and umbilicals from option studies through operation to lifetime extensions. For long term extreme conditions, the software interacts with software like DNV’s Sesam Marine Dynamic Package or others like OrcaFlex and FlexCom.

The Subsea Toolkit is applicable for the design and operation of offshore power cables, umbilicals, and flexible pipes – in addition to submarine pipelines.

Great for:

• Cross-sectional capacity to calculate capacity curves and allowable tension/curvature
• Cross-sectional stiffness including axial and torsional stiffness, moment/curvature hysteresis and hysteresis damping. The modelling includes strength/functional elements arranged in a helix geometry where the slip of helix elements to release stresses is essential to obtain the required high bending flexibility
• Extreme design (ULS) documenting acceptable stress in components and capacity curves. The helix stick/slip behaviour introduces a complex stress picture of the components which is accounted for
• Extreme loading environment including 100-years load conditions, environmental contour lines and non-Gaussian extreme response statistics
• Fatigue design allowing for helix elements of cables and umbilicals and tensile armour of flexible pipes
• Long-term fatigue (FLS) where the loading environment is defined by wave scatter diagrams and directions. This could often be 100-300 short-term conditions where the stresses come from time domain dynamic analysis performed in software tools like DNV’s Sesam Marine Dynamic Package or others like OrcaFlex and FlexCom
• Static and time domain dynamic on-bottom stability design of submarine pipelines according to DNV-RP-F109 On-Bottom Stability Design of Submarine Pipelines, Cables and Umbilicals (edition May 2021). The submarine pipeline dimensions, and weight are calculated by specifying wall thickness, cut back length, material densities and soil properties
• To sum up, the DNV Subsea Toolkit will help you to do cross-section analysis of mechanical properties like bend stiffness, torque balance, cable geometry inclusive of helix arrangement, material properties, tension, curvature and load capacities such as allowable tension and fatigue damage.