You’ve selected the perfect subsea cable design for your big project, but now the question arises: Which type of cable termination should you use?
The main function of a cable termination is to provide connection points for the electrical and optical components, while also transferring the necessary strength between the cable’s armor and the equipment.
The design of a termination depends completely on your specifications, including the size and type of cable and type of application. In this blog, we describe the basic categories of subsea cable terminations. For more details, download our ebook: Designing subsea cable terminations.
Deck-end, sea-end or both?
Marine cables are stored and transported on large drums and deployed on rotating winches. A deck-end termination connects the cable to the drum or winch. In this case, the mechanical strength component of the termination (steel or synthetic aramid fiber) is generally fixed to the winch. The cable core then extends through the mechanical termination with electrical and/or optical connectors to attach to the power supply.
Sea-end solutions are terminations where the cable connects to towed devices, such as an acoustic source for seismic acquisition, sonar arrays, or ROVs. Sea-end terminations vary much more than deck-end terminations because the types of equipment at the end of the cable and the amount of water pressure and friction from towing differ tremendously.
The four main types of sea-end terminations include:
- Faceplate design
- Inline termination
- Mechanical head termination
- Flexible termination
Four types of sea-end cable terminations
1. Faceplate Design
A faceplate design is a type of termination often used for the source umbilical cable in seismic acquisition, but also for other applications. For seismic acquisition, the cable contains electrical and sometimes optical lines, along with an air hose used to pump out seismic waves. The faceplate design is a large and robust termination to accommodate multiple electrical and/or optical connectors and the air hose fitting on the front of the metal plate.
2. Inline termination
An inline termination is a relatively simple design that can be used when there is no restriction on the rigid length of the termination. This type can be used in seismic acquisition or defense towed arrays to connect the hydrophones to the lead-in cables attached to the ship. These terminations are streamlined to reduce drag as the hydrophones move through the water.
3. Mechanical head termination
For some sea-end assemblies, the strength member of the cable must be mechanically terminated and then fixed onto the equipment with a mechanism such as a hook or an axle. Then the cable core containing the electrical and optical elements passes through this termination and is routed to a junction box on the seabed equipment.
4. Flexibel termination
Often, cable terminations have restrictions on the maximum permissible rigid length because the cable and termination must be spooled on a winch or pass over rollers. If the rigid length of the termination is too long the cable would bend too sharply over the radius of the winch, creating weak points where it could break. A flexible termination housing using linked metal shackles, like a string of vertebrae, can bend and move while retaining the necessary strength and protection for the cable.
Read more on Flexible Terminations.
Download our termination design guide
Cable terminations are critical to the success of any project that depends on marine cable. DeRegt can provide custom-designed turnkey cable and termination assemblies to match any application. The final design of your termination will depend on your exact requirements.
For more help in creating the right termination solutions for your subsea cable, download our free guide:
Download our free Ebook on Terminations.
