Exploring the Subsea Cable Market

Sales Director, Graham Wilkie of Hydro Group plc, a global design and manufacturer of underwater cables and connectors for subsea, topside and harsh environment applications, details how they have stayed ahead in the rapidly changing subsea cable market.

Thanks to the low oil price, the subsea sector is enduring a challenging period. Operators are being forced to venture into more remote and harsher locations, requiring top tier equipment to meet demanding and dynamic environments.

Systems being deployed require reliable power and communications connections suited to meet these demands. Today, the team at Hydro Group are being asked more and more for increasingly complex composite and physically demanding cable designs, the days have gone when the company was simply asked to provide an underwater electrical connection.

Dynamic Design

Most subsea cables designed and manufactured at Hydro Group’s Aberdeen, Scotland facility incorporate numerous specialist elements such as fiber optics, twisted pairs, triples or quads, Coaxial, VHF and high frequency RF, components.

As subsea equipment is becoming more complex with data management and collection systems transferring significantly higher volumes of information at faster rates the Transmission Characteristics, Low Loss and Shielding requirements need to be addressed in the design and composition of the cables.

To ensure the performance of the designs, increasing use of complex software modelling and analysis tools are employed. Hydro Group engineers routinely utilize packages such as Comsol multiphysics software to model designs and provide virtual realization of the cable characteristics under a variety of simulated conditions. Transmission characteristics and performance are also simulated with the use of Optem software tools.

Hydro Group regularly incorporates stainless steel tubes, rather than PBT tubes, for all Subsea Cable designs incorporating fiber optics. The benefits of utilizing optical fibers contained within stainless steel tubes are primarily two fold –

• The attenuation (signal loss) seen in the fiber due to the compressive forces on the glass is minimized as the stainless steel tube protects from the crushing action of the water pressure on the fiber itself.
• The addition of a hydrogen scavenging/absorbing gel is used within the St/St Tube to prevent the potential darkening of the optical fibers due to the natural ingression of small amounts of hydrogen which are present in these extreme conditions.

Both of these advantages over PBT Tubed fiber optics are deemed crucial in the demanding conditions seen by subsea optical cables.

Mechanical factors are extremely significant in the overall performance of subsea cable designs. Often these present a much higher risk in the reliability and durability of the design than all other constraints.  The application of FEA design and modelling tools such as Comsol and Orcaflex allow simulation and analysis of the design to ensure construction and incorporation of components that will meet the dynamic application requirements.

Under Pressure

Understanding the static and dynamic forces that will be applied allow the incorporation of features and components such as Vectran braids and cords for tensile strength in light weight and more flexible applications and Contra Helical steel wire armoring packages where significantly higher mechanical forces will be experienced.

Hydro Group recently invested in a new state-of-the-art hydrostatic pressure vessel, which offers a broader range of testing with a more accurate output. The 2.5 by 1.5 meter vessel has the capacity to pressure test large cable assemblies and equipment up to100 bar, simulating depths of 1000 meters below sea level. This complements the suite of existing pressure vessels that allow simulation of depths to 7000 meters of seawater.

Housed in the company’s Aberdeen headquarters, the equipment provides Hydro Group with the ability to design and pressure test complete cable assemblies built for deep waters projects, particularly for the subsea and defense industry.