Why Ballasting Shells Are One of The Best Possible Submarine Cables Protections?

Energy

Tuesday, April 23, 2019

While carrying 99% of all international communication, submarine cables are of critical importance to our daily lives. Deployed as well in the offshore industry by oil and gas rigs and marine renewable installations, they provide power shore-to-platform and internal fiber-optic communications and oceanographic monitoring and surveillance.

But despite being examples of advanced technology, submarine cables remain vulnerable and relatively easy to damage.

For that reason, submarine cables need to be designed and built with additional protection, making them resistant and reliable enough. Submarine cables protection is of crucial importance for every offshore project.

Most Recent Available Submarine Cables Protection Solutions

Depending on the industry, the seabed conditions and the depth, there are various submarine protection systems available right now at the market. All of them share the same objective: protecting the submarine cables from fatigue, overbending and external factors.

The CPS or The Cable Protection System

An entire Cable Protection System (CPS) usually consists of bend restrictors, bend stiffeners and protecting shells (Split Pipes), used at the bottom of the foundations to protect the cable near the platform:

Bend Restrictors

Bend restrictors are applied to ensure that the bending radius of the cable will not exceed the minimum bending radius defined by the manufacturer.

Bend Stiffeners

Bend stiffeners are especially designed and manufactured for use in dynamic applications to prevent failure as a result of cyclic loading.

Cylindrical Half Shells or Split Pipes

Cylindrical half shells or split pipes usually include as well bend restrictor functions and other connection elements, but also a protection and potential ballasting function and therefore are most of the time used as part of a complete cable protection system. They are especially adapted for the crossing of the scour protection at the bottom of the platforms but also for rocky or challenging seabeds thanks to their abrasion resistance and stabilizing/ballasting abilities.

Most of the time, the mentioned solutions are made of composite materials and most specifically polymers such as polyurethane. The main advantage of polyurethane is its corrosion resistance. Cast iron can handle corrosion as well but additionally provides the solution with a ballasting/stabilisation function.

Protecting Solutions for Longer Sections of Cables

Concrete mattress, rock dumping and rock bags are used to protect longer cable section. However the most used solution to protect the longer section of cables (inter-array, export cables or interconnection cables) is the burial of the cable onto the seabed. The rock dumping or the concrete mattress can be used when the burial is not possible or in addition with. The installation of the concrete mattresses is however very challenging due to the concerns related to the alignment and the “butting up” tolerances. This system requires as well some specific means as frames, ROVs, etc.

Protecting and Ballasting Shells Made of Cast Iron

The shells are the only one solution that is frequently used in both applications - in CPS but also to protect longer cable section. The protecting and ballasting shells are a simple, effective and easy to assemble solution. They are positioned along the cable and can additionally ballast the installation.

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FMGC – The European Counterweights Leader apply Its Expertise in Ballast Solutions to the Offshore Sector

Today, FMGC has developed a full range of offshore ballast solutions as protecting and ballasting shells, gravity based ballast and clump weights. Cast Iron withstands the harshness of marine environment , resisting to high impact or fatigue sollicitation. Moreover the impact of the corrosion and abrasion on the cast iron is really limited and do not impact the environment.

In the case of the protecting and ballasting shells, the main goal of the development team was to combine the protection, the stabilization and the bend restrictor aspect in only one product, which can be directly installed on the deck of the laying vessel. Thanks to the specific design the need for other dedicated means and additional ships is drastically reduced.

These shells can be used as a part of a cable protection system (CPS) in addition with polyurethane products but also for the protection and stabilization of longer section of cable for the shore landing or for rocky or challenging seabed where burial is not possible.

The solution can be easily adapted to various types of cables: from telecom cable of 20 mm to export cable of 250 mm.

Leading French companies as Enedis, Sabella, Jifmar and Perenco have already incorporated FMGC protecting and ballasting shells in some of their projects.

 

This is the feedback of Perenco who have used as well as the protecting and ballasting shells for submarine cables developed by FMGC:

“As part of a project to install medium voltage submarine electrical cable in 2018, we have installed FMGC protecting and ballasting shells directly into the platform feet immediately after the risers. The Offshore conditions of the project were particular: little water (5 to 25m of water), very bad visibility for the divers and a rather rare current. The cast iron shells of FMGC perfectly met our demand by allowing us to establish a good stability of our cables in the platform feet. The team has reacted very quickly and adjusted the centralizer on the cable outlet diameter received and which was not the one requested first. This reactivity allowed us to pose the cables before the beginning of the bad season.”

 

A reliable cable protection system secures the performance of an offshore project by protecting submarine power cables against various factors. FMGC is aware of the challenges of the sector and is committed to delivering innovative, reliable and cost efficient solutions.




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