Advanced cable solutions and how they are built – Which type of ROV Cable fits your application best?
Each subsea project is different and the same is true for the corresponding (ROV) cable construction. After all, ROV systems are used for a broad range of purposes. Which type of ROV cable is best for your subsea project?
To answer this question, it is important to know how an ROV cable is built. Which elements determine the geometry of a cable? And which cable specifications are important for your ROV system?
Our experts produce cables for a variety of ROV systems. As each purpose requires a different cable construction, there is no such thing as a catalog; your requirements are translated into fit-for-purpose designs.
On this page, we explain why each ROV cable is custom constructed.
In the example below – an ROV cable – components are laid up in helices with extruded plastic sheets and tapes separating the layers. The electrical and optical components are laid up in the core. Around the core, a strength member is wrapped. In this case a steel armor with 2 layers.
Another common material used as a strength member in ROV cables is aramid fiber, which is much lighter.
Conducting electricity and data
Electrical conductors are usually made of copper with thermoplastic insulation. Data is usually sent via optical fibers these days. Fragile components like optical fibers are placed towards the center for crush resistance. The helical structure makes it possible to bend and stretch the cable construction without permanently deforming or breaking the components.
Weight and Elongation
ROV cables are designed in a way that the load is transferred through the strength member instead of the electrical and optical components. This is done by applying a smaller lay angle for the strength member than for the components. In deeper waters, the number of heavy materials should be limited as the ROV cable should be able to lift its own weight.
Another important aspect is to design ROV cables so that they do not stretch more than 0,6% at the maximum workload. This way, components are prevented from failing. Stretching beyond should be limited in order to prevent the copper from deforming and/or creating an overlength of copper in the cable.
We always design ROV cables in a way that the cable does not rotate under tension, named “torsion balance”. This is done by tuning the lay angles and balancing each layer in a specific direction.Watch our free webinar
Now you know how ROV cable construction works, it is important to know what determines the design for your own subsea project. Which cables are there for ROV systems and what type of cable fits which subsea project?
For example, what type of power should your cable be able to transfer? And how deep does your ROV operate? The latter has a large impact on the material used for your strength member, as steel is often too heavy for deep-water operations. In such cases, aramid fibers or other lightweight synthetic fibers might be the best option.
The fact that ROVs are operating at greater depths is a trend that we see a lot , but selecting an extra-long cable “just to be safe” is a common mistake. This means that large pieces of cable remain on deck when not using its full length. If a lot of cable is left on the reel and the system runs on full power, the cable can get too hot.
This example shows how important fit-for-purpose is. Not only length is very important; weight and conductivity also play a major role. Think carefully about the application of your ROV cable and what specifications fit this purpose!
The application of your ROV equipment must always be leading. For this reason, our specialists are happy to think along with you about the actual use of the cable and the optimal cable specifications.
Different scenarios can be addressed in an early stage of the development and by analyzing the impact of the requirements on the cable design many operational problems can be prevented. For example, by performing thermal analyses the heat generated by the cable on the winch can be predicted. This can be used to determine the maximum power versus the number of layers on the winch and if forced cooling is required.
Other analyses and calculations can also lead to a better fit-for-purpose. This has a direct impact on the downtime and life expectancy of your ROV equipment. For example, the strength, elongation & rotation versus load and weight (see “cable construction”) play a major role in extending the life expectancy of the ROV cable. Design criteria might lead to savings in the long run, which is why it is very important to focus on Cable Specifications at an early stage in your subsea project!Read more
As mentioned, each subsea project is different and the same is true for the corresponding (ROV) cable construction. As ROV systems are used for a broad range of purposes, these purposes affect the design of the cable and vice versa.Read more
How do several design considerations, such as system and cable requirements, impact each other? And when should you bring certain manufacturers to the table in order to make the best cable selection possible? Our R&D Manager answers these questions and more in our exclusive Webinar On-Demand.