Wet mate connectors are used in applications where connections need to be made and broken underwater, such as oil and gas wells, remotely operated vehicles (ROVs), marine and oceanographic exploration, aquaculture and fish farming, underwater lighting and video monitoring systems, and offshore renewable energy.
This article reviews several wet-mate options, including gold-plated and niobium-based electrical connectors, electro-hydraulic connectors, and fiber optic connectors.
Gold is good
Wet mate connectors with gold-plated contacts are used in a wide range of applications, from ROVs and oceanographic research instrumentation to submarine launch tubes and mine detection sleds. The gold plating is resistant to corrosion and provides a low contact resistance. These connectors often need to be unenergized before unmating underwater.
Circular wet-mate connectors are available with contact pins with radiused shoulders to facilitate smooth mating and prevent damage from debris in the water. When mated, the design forces water out and creates a secure electrical connection despite the wet environment. A key feature of the design is that these connectors are built to withstand high-pressure environments, typically rated for thousands of PSI.
One family of wet-mate connectors has up to 16 gold-plated contacts and a pressure rating of 10,000 psi. Depending on the configuration, they can support voltages up to 600 Vdc and currents up to 7 A. Configurations are available for high-speed data connectivity, such as Ethernet.
The Niobium option
Wet-mate power and signal connectors with niobium contacts are also available. Niobium is similar in strength to titanium and has conductivity like copper and aluminum alloys. However, it reacts differently with water.
When energized niobium contacts are exposed to water, a passive insulating film about 150 nm thick isolates the contacts. The contacts are designed so that when they are mated, the film is wiped away, and electrical contact is made. The film is spontaneously reformed within milliseconds when the connector is unmated underwater.
Unlike gold-plated contacts that can handle high voltages, niobium contacts are typically limited to a maximum of 60 Vdc. That makes them suitable for battery and signal connections. For example, niobium power connector benefits include the following, as shown in Figure 1:
- The lack of seals improves reliability
- There is no inherent depth limit or limit on the number of mate/unmate cycles without maintenance, and while power is oIt can be designed for loose alignment tolerances and support blind mating
- Low mating force
- Not susceptible to corrosion
Electro-hydraulic connections
Some applications, like smart well completion systems, need electrical and hydraulic connections. Those systems are used in oil and gas extraction and have downhole sensors for monitoring the operation and remotely controlled hydraulic valves for optimizing the flow from a well in real-time.
Wet-mate electro-hydraulic connectors are available with various electrical and hydraulic connectivity options. They support the disconnection and reconnection of tubing strings and associated electric and hydraulic line umbilical connections. They also offer eight field-configurable disconnect methods to maximize system integrity and operational flexibility (Figure 2).
Optical wet mate
Some marine systems, such as ROVs, need the high-speed connectivity provided by fiber optics. Optical wet mate connectors with up to four fiber connections can be used for those systems. One design uses a unique “rolling seal” configuration that supports high-reliability connectivity even in the presence of debris, sediments, or other contaminants.
When mating, the seals on the connector faces rotate, pushing away any sediment or seawater from the contact area. Then, the optical fibers connect within a clean, oil-filled chamber, providing a protected environment for low-loss signal transmission. Some key specifications include:
- Operating temperature of 0 to +40 °C in seawater
- Titanium connector shells
- 30-year design life
- 10,000 psi maximum operating pressure
- Up to 100 mate/unmate cycles without refurbishment
- Optical performance:
- Insertion Loss ≤0.5 dB for 1310/1550/1625 nm (single-mode) or ≤1.0 dB for 850/1300 nm (multi-mode)
- Return Loss ≥30 dB per channel for 1310/1550/1625 nm
Summary
Wet mate connectors that support electrical, optical, and combined electro-hydraulic connections for a wide range of oceanographic, commercial, and military systems. Electric contacts are available with gold plating or made with niobium, which is inherently water-safe.
References
Downhole wet-mate connectors, Halliburton
NiobiCon Wet-Mate Electrical Connector, Northrop Grumman
NiobiCONN Application Series: The Underwater Power & Signal Connector, ICONN Systems
Rolling Seal 4 (RS4) Optical Connector, Teledyne Marine
Subsea connectors and cable assemblies, Eaton
What are underwater connectors, and what functions do they serve?, DWTEK
EEWorld Online related content
How are sensors improving maritime navigation?
Undersea optical-fiber cables do double-duty as seismic sensors, Part 1: Context
What’s the difference between transceivers and transponders?
What are submersible sensors?
What’s the difference between sensors used in underwater, flying, and creeping robots or drones? Pt 1.
