FEATURE SPONSOR
CABLE INSTALLATION
THE RIGHT APPROACH TO INSTALLATION ANALYSIS
The primary rationale for performing simulations of power cable lay and pull-in operations is that vessel time and broken cables are expensive compared to engineering studies
So how should these studies be performed and what are the key deliverables?
ANALYSIS
It is vital to know the limitations of an operation and de-risk it before mobilising so analysis should be performed on every aspect of the installation campaign. However, a hazard of this type of engineering study is ‘rubbish in, rubbish out’. This is why AgileTek developed a suite of tools to ensure cable, cable protection system (CPS) and vessel are all modelled as realistically as possible.
CABLE RESPONSE
Cable response is dominated by bend stiffness, which should be modelled as a non-linear hysteretic relationship between moment and curvature. This curve is an output of AgileTek’s AELCableProp software for any cable design. CPS elements should be modelled as a separate line to the cable, with stress- strain curves used to characterise material response. For some sections, response to bending should be determined by local finite-element analysis of the assembly at the required tensions.
VESSEL RESPONSE
Vessel response to waves should have been derived at the water depth and wave heights being analysed. Overboarding chutes and quadrants should have geometries representative of real vessel equipment, and cranes and A-frames must be modelled dynamically to handle the quadrant and cable as they would during offshore operations. Modelling the cable response accurately for pull-in operations requires fully dynamic simulations covering the complete installation procedure: starting with the pull-head on deck, through CPS
overboarding and engagement at the foundation, to pull-head past the hang-off deck and ending with the cable laid down on the seabed.
PRACTICAL UNDERSTANDING
It is also important that analysts practically understand the input data assumptions as these are a possible source of error. Misreading a procedure can incorrectly eliminate or create dynamic responses of the cable / CPS. Following these steps helps ensure that operations are given the most advantageous weather windows possible but may come at the cost of needing to run lots of long simulations. By using their highly scalable on-demand AELCloud system, AgileTek can deliver weeks of simulation time in a few hours.
AgileTek
www.windenergynetwork.co.uk
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