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What Are Subsea Electronics?
Subsea electronics involves the design and marinisation of electronic systems for underwater applications. The field encompasses a wide range of uses, with the oil and gas industry serving as a pioneer for several decades. More recently, the renewables sector has emerged as an increasingly significant player in this domain.
To deploy electronics underwater, it is common practice to shield them from the environment using one-atmosphere pressure vessels. These housings not only provide waterproofing but also protect the electronics from immense pressure. For context, subsea electronics can be deployed at depths exceeding 3,000 metres, where pressures reach approximately 300 bar (4,400 psi). To visualise this, 300 bar is equivalent to the weight of a large passenger jet pressing down on the area of an A4 sheet of paper—or roughly the weight of three elephants standing on your nose.
Subsea electronics are critical for controlling and monitoring a diverse array of applications, including valve operation, communications, sensor monitoring, motor control, and even the remote operation of entire subsea factories. The challenges and innovations in this field make it an exciting area of engineering with applications that continue to expand across industries.
The diagram below shows an example of a Subsea Electronics Module (SEM), a metal cylinder with end caps and two connectors with protective caps.
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Pressure Vessel
• The pressure vessel houses the electronics and acts as a barrier against seawater pressure. It is typically made of metal, although plastic versions are available for shallower water applications (up to a few hundred metres).
• Metal Pressure Vessels: Metal pressure vessels are manufactured from various materials, depending on the application: Aluminium: Commonly used for shallow and medium-depth applications with short deployment times due to its lightweight and cost-effectiveness. Stainless Steel: The most widely used material, offering an excellent balance of cost, strength, and corrosion resistance.Titanium: Ideal for specialised applications where stainless steel is unsuitable, such as when lower weight, smaller size, or enhanced corrosion resistance is required for extended deployments. Copper Beryllium: Occasionally used for its superior thermal properties, which aid in power dissipation, and its resistance to marine growth compared to other metals.
• Corrosion Protection: Metallic pressure vessels require protection from seawater corrosion, which can be achieved through several methods: Housing within another structure: For example, placing the vessel inside an oil-filled subsea control module. Corrosion-resistant materials: Titanium is a common choice for such applications. Cathodic Protection: Using sacrificial anodes, such as zinc, which corrode preferentially to protect the pressure vessel.
End Caps
• End caps seal the ends of the pressure vessel. Typically, one cap is ported (to accommodate connectors) while the other remains unported.
• Ported End Cap: Features holes that are precisely machined to fit specific connector types.
• Sealing: Double O-rings are used to seal both the end caps and the connectors, ensuring a reliable pressure-tight barrier.
• Pressure Relief Valve: A safety feature installed on the ported end cap, allowing safe venting of pressure that might inadvertently build up within the vessel while at depth.
• Lifting Eyes: To enhance safety during manual handling, lifting eyes can be added. This is especially important for deep-rated pressure vessels, which can be extremely heavy (e.g., those rated for 3,000m depths).
Connectors
• Overview: Subsea connectors play a vital role in transmitting signals and power into and out of pressure vessels, ensuring the integrity of underwater systems. These connectors are designed to maintain watertight integrity and resist corrosion, using robust materials such as titanium, stainless steel, or marine-grade polymers. Many connectors employ dual O-rings for reliable sealing. Several types are available, including dry-mate, wet-mate, ROV-operated wet-mate, optical, and penetrator connections.
• Wet-Mate Electrical Connectors: Wet-mate connectors enable underwater mating and de-mating, simplifying system architectures and allowing large systems to be segmented for easier deployment and retrieval. Some are designed for diver operation, while others are ROV-operated for deeper water applications. ROV-operated wet-mate connectors are typically larger, more expensive, and have fewer pins per unit area than their diver-friendly counterparts.
• Dry-Mate Connections: Dry-mate connectors are simpler in design and require mating and de-mating out of the water. For most applications, this is entirely acceptable and provides cost and size advantages over wet-mate connectors.
• Subsea Optical Connectors: In recent years, there has been a growing adoption of subsea optical connectors due to their ability to provide much higher signal bandwidth compared to electrical systems. They also offer improved isolation for sensitive applications. Modern designs have enhanced sealing, alignment, and self-cleaning mechanisms, addressing the limitations of earlier generations.
• Penetrators: Penetrators are sealed devices that allow electrical conductors to pass through a bulkhead, such as a pressure vessel wall, without water ingress. Unlike connectors, which support repeated mating and de-mating, penetrators provide a permanent or semi-permanent interface between the interior of a subsea housing and the external environment. They are considered highly reliable for long-term applications.
Card Frame
• The Role of the Card Frame The card frame plays a crucial role in securely housing electronic circuit boards while also providing an efficient thermal pathway to dissipate heat from the electronics.
• Environmental Considerations Once deployed, the subsea environment is generally quite stable and benign. However, during transportation to remote locations, the electronics can be subjected to extreme levels of shock and vibration. The card frame must ensure that the electronic cards are securely housed to dampen vibrations and avoid resonances. To verify the suitability of the electronics and the card frame, the subsea oil and gas industry enforces rigorous shock and vibration testing as part of qualification procedures.
• Thermal Management Another critical function of the card frame is to provide a thermal pathway from the electronics to the end caps or the walls of the pressure vessel. As the electronics are sealed, nearly all heat is removed via conduction rather than convection or radiation. This is particularly vital for high-power applications, where effective thermal management prevents overheating, thereby preserving the operating life of the electronics.
Circuit Boards
The circuit boards (i.e., the electronics) used in subsea electronics modules (SEMs) are critical for a wide range of functions, depending on the specific application. These can include:
• Power electronics for energy conversion (e.g., DC to DC, AC to DC).
• Communication electronics, such as copper and optical modems, RS485, Ethernet, and CAN bus interfaces.
• Digital electronics, including FPGAs, DSPs, and microprocessors.
• Analogue electronics for interfacing with sensors.
Given the extreme environments in which subsea electronics operate—and the high cost and difficulty of replacing components—reliability is of paramount importance. In the offshore industry, electronics are often qualified and production-tested to meet standards such as ISO 13628-6 and API 17F. These standards require rigorous thermal, shock, and vibration testing to ensure performance under demanding conditions.
Additionally, other key standards include:
• SIIS (Subsea Instrumentation Interface Standardisation): Covers sensor-to-control system interfaces and communication protocols.
• IWIS (Intelligent Well Interface Standardisation): Focuses on interfaces between production control system electronics and intelligent well electronics.
• IEC 61508 (Functional Safety for Electronic Systems): Applies to safety-critical applications, such as HIPPS valves, and defines the Safety Integrity Level (SIL) of electronics.
Design Constraints and Reliability Measures
The cylindrical nature of SEMs and their typically small internal volumes mean that space is at a premium, resulting in project-specific PCB shapes. However, some standards, such as IWIS, have introduced common form factors like the Eurocard format.
For certain applications, such as ROV payloads, the required mission time of the electronics may be relatively short. In contrast, subsea production control systems often demand mission times of 25 years or more, making reliability absolutely critical. To achieve this:
• Redundancy is frequently incorporated.
• Components are carefully derated to reduce stress.
• PCBs are conformally coated for protection against moisture and contaminants.
• The SEM is filled with dry nitrogen to prevent internal condensation.
By adhering to stringent standards and employing robust design practices, subsea electronics can perform reliably even in the most challenging environments.
Where are they used?
Subsea electronics are utilised across a variety of industries, including oil and gas, renewables, marine research and oceanography, defence and security, environmental monitoring and conservation, telecommunications, mining and mineral exploration, and aquaculture, to name just a few.
In the oil and gas sector, subsea technology plays a crucial role in operations such as wellhead control, pipeline inspection, and the remote operation of safety systems. Key equipment includes subsea control modules (SCMs), underwater sensors for pressure and flow, and remotely operated vehicles (ROVs) for maintenance tasks. Similarly, the renewable energy sector relies on subsea technologies to monitor offshore wind farms, manage wave and tidal energy systems, and ensure the reliability of subsea power cables. Underwater acoustic sensors, communication systems, and power distribution units are essential tools in this domain.
In the telecommunications industry, subsea technology underpins the installation and maintenance of undersea fibre optic cables, enabling global connectivity through equipment such as fibre optic multiplexers, data logging systems, and signal amplification units.
Beyond industrial applications, subsea technology significantly enhances scientific research, environmental protection, and sustainable practices. In marine research and oceanography, autonomous underwater vehicles (AUVs) and environmental sensors facilitate the study of marine ecosystems, ocean currents, and climate-related data. The defence and security sectors utilise sonar systems and inertial navigation tools for underwater surveillance and infrastructure monitoring. Similarly, aquaculture operations leverage subsea cameras, oxygen sensors, and automated feeding systems to optimise fish farming conditions. Subsea technologies also enable deep-sea mining, providing tools such as specialised ROVs and geological sensors for exploring rare mineral deposits.
The influence of subsea technology extends to areas such as shipping, environmental conservation, and even entertainment. Marine transportation benefits from underwater sonar systems and corrosion sensors to monitor vessel integrity, while environmental monitoring employs acoustic sensors to track marine life and detect pollutants. Subsea imaging and lighting systems bring the underwater world closer to audiences, whether through documentaries or live viewing in aquariums and tourist submarines.
Across these diverse applications, subsea technology continues to drive innovation, addressing complex underwater challenges and contributing to advancements in energy, science, and industry.
History of Subsea Electronics in the offshore Energy industry
Subsea electronics have been pivotal to the development of offshore energy, from oil and gas exploration to renewable energy systems. Over the decades, these technologies have evolved to meet the demands of deeper, harsher environments while expanding their applications to support sustainability. Here’s is a brief overview:
Early Beginnings (1940s–1960s)
Offshore oil and gas exploration began in the 1940s, primarily in shallow waters such as the Gulf of Mexico. Early systems relied on mechanical and hydraulic controls, with minimal use of electronics. By the 1950s, basic subsea electronics were introduced to monitor wellhead conditions such as pressure and temperature. These systems, tethered to surface platforms via simple electrical connections, laid the groundwork for future advancements.
Expansion and Innovation (1970s–1980s)
During the 1970s and 1980s, offshore exploration pushed into deeper waters, driving innovation. Subsea Control Modules (SCMs) were developed, enabling remote operation of valves and pumps. Hydraulic-electric multiplexing allowed multiple wellheads to be managed via a single umbilical line, streamlining operations. Remotely Operated Vehicles (ROVs) became essential for inspection, maintenance, and repair, equipped with cameras, sensors, and manipulators. These developments expanded the industry’s operational capabilities.
Modernisation (1990s–2000s)
By the 1990s, subsea electronics had advanced significantly, enabling ultradeep water operations. Fibre optics replaced copper cables, improving data transmission speeds and reliability. Integrated subsea systems, including subsea trees and manifolds, became the norm, relying on advanced sensors and controls for efficiency. Electronics were also engineered to withstand extreme pressure, low temperatures, and corrosive environments, ensuring reliable performance in harsh conditions.
Present Day (2010s–2020s)
Today, subsea electronics underpin complex systems in both oil and gas and renewable energy sectors. Key developments include:
• Subsea Processing: Technologies such as separation and boosting process hydrocarbons directly on the seabed, utilising advanced monitoring and control systems.
• Autonomous Underwater Vehicles (AUVs): AUVs are now widely used for pipeline inspection, environmental monitoring, and site surveys, equipped with sophisticated navigation and data collection systems.
• Condition-Based Monitoring (CBM): Real-time data collection and predictive analytics optimise maintenance schedules, preventing equipment failures.
• Renewables Integration: Subsea electronics are critical to offshore wind farms, tidal energy, and wave power systems. They monitor high-voltage power cables, regulate energy distribution, and track environmental impact, supporting efficient and sustainable operations.
Future Directions
The future of subsea electronics lies in supporting autonomous “subsea factories” that can extract and process hydrocarbons on the seabed. Renewable energy systems will continue to benefit, with enhanced integration of wind, wave, and tidal power. Digitalisation and the Internet of Things (IoT) will enable remote optimisation, while subsea electronics will also play a vital role in carbon capture and storage, aiding climate change mitigation.
Subsea electronics have revolutionised offshore energy, enabling efficient operations in oil and gas while driving innovation in renewable energy. As these technologies continue to evolve, they promise to support a cleaner, more sustainable future for global energy production.
How can Spark Product Innovation help?
Spark Product Innovation is uniquely equipped to support the development of advanced subsea electronic systems, including Subsea Electronics Modules (SEMs), Compact Electronics Modules (CEMs), Subsea Control Modules (SCMs), and High-Integrity Pressure Protection Systems (HIPPS). With a strong foundation in engineering and product design, Spark helps clients meet the demanding requirements of subsea environments by adhering to internationally recognised standards such as ISO 13628-6 and API 17F. These standards ensure the reliability of subsea electronics under extreme pressures, temperatures, and corrosive conditions.
Spark’s expertise encompasses the development of energy conversion and energy harvesting technologies, as well as advanced communication systems such as modems, Comms On Power Systems (COPS), and Comms And Power Systems (CAPS). Its multidisciplinary team excels in designing rugged, high-performance electronics capable of operating reliably in challenging underwater environments. Whether enabling remote operation through Remotely Operated Vehicles (ROVs) or integrating advanced technologies into subsea systems, Spark delivers tailored solutions. With a focus on cutting-edge thermal management, custom heatsinks, card frames, and energy-efficient designs, Spark ensures the longevity and resilience of subsea systems.
By collaborating with Spark, organisations across industries such as oil and gas, renewable energy, and marine research can benefit from innovative approaches to subsea technology. The company’s work spans areas such as power distribution, energy harvesting, and the integration of subsea control systems, underpinned by a focus on engineering excellence and technical precision. Its commitment to robust design ensures subsea electronics meet the demands of challenging environments while supporting the advancement of critical underwater operations.
