Unleashing the Power of Remotely Operated Vehicles (ROVs) in Subsea Component Inspections

Image of a Remotely Operated Vehicle (Image credits: ScienceDirect.com)

Introduction

Remotely Operated Vehicles, or ROVs were developed in the 1960s to retrieve underwater missiles, mines, and other naval weapons. ROVs have hence become a successful tool for various industries and are often used in deep-sea research, retrieval, and rescue missions. 

Similar technology, operated by Jean-Louis Michel and Robert Ballard aboard the French research vehicle RV Le Suroît, named Argo/Jason was used in the hunt for the RMS Titanic debris that sunk after a collision with an iceberg on its doomed maiden voyage. Argo is a remotely operated deep-sea vehicle, that used SONARs and cameras to map out the ocean floor and locate the position of the test subjects. The Argo is towed behind a ship that transports the ROV to the search location and has a two-body ROV called Jason, developed by the Woods Hole Oceanographic Institution (WHOI). Former prototypes of the ROV named Jason Jr. (1991), Hercules (2021), and Argus (2021) were lost at sea, however, Jason managed to recover the latter two ROVs as they were less than 200 miles away from its location.

ROVs bridge the gap between human ability and the forces of nature, enabling researchers, engineers, and those curious in accessing otherwise inaccessible locations of experimentation and research, further broadening mankind’s perspective of the world we operate in.

The Evolution of Subsea Component Inspections

ROVs are generally used in subsea component inspection in various industries like oil and gas, offshore renewable energy, underwater research, and marine salvage operations. Quality testing and structural health assessments of subsea infrastructure depend heavily on the abilities of ROVs.

The evolution of subsea components has been accelerated by the rapid advancements in technology, industry demands, and the need to operate in increasingly challenging subsea terrain. Significant developments in materials, design, manufacturing techniques, and monitoring systems for subsea technology and infrastructure over the past few decades have further expedited the process.

Some notable aspects of the evolution of subsea components are:

• Advancements in material science have led to the utilization of more resilient materials, which can withstand the unforgiving conditions in deep-sea, including high pressures, corrosive seawater, and extreme temperatures. Carbon steel which was the traditionally preferred material has now been replaced or supplemented by corrosion-resistant alloys (CRAs) which include stainless steel, nickel-based alloys, etc. Coatings such as epoxy or polyethylene are also applied to protect the material from corrosion.
• Structural analysis techniques like finite element analysis (FEM) have helped evolve the design of subsea components to ensure structural integrity and optimized designs for various loading conditions. Components are designed to withstand extreme external pressures, internal stress, and various external factors. Rigorous testing procedures such as pressure and fatigue testing are also carried out to assess their performance.
• Robust and watertight connections in challenging subsea environments are ensured with the use of specialized connectors and hydraulic couplings. Sealings and connector systems have undergone massive improvements with the use of elastomeric materials, metal-to-metal seals, and composite gaskets to ensure long-term sealing integrity.
• The evolution of subsea components has also led to advancements in intervention and maintenance techniques. ROVs and Autonomous Underwater Vehicles (AUVs) are extensively used for inspections, repairs, and maintenance activities on subsea infrastructure. This has greatly improved the accessibility and serviceability of subsea components, reducing the need for expensive and laborious interventions.
• Subsea control systems have also evolved with the facilitation of remote monitoring and control components. This technology enables operators to remotely operate valves, actuators, and other subsea equipment. Advances in control systems have led to the development of subsea control modules, umbilicals, and master control stations that improve their efficiency and reliability.
• Instrumentation and monitoring systems in the deep sea have become progressively sophisticated. Sensors and data acquisition systems monitor different parameters, including pressure, temperature, flow rates, corrosion rates, and structural integrity. Continuous monitoring and early detection of potential issues are now possible because of real-time data transmission and communication systems. These features enhance safety and operational efficiency.

The evolution of subsea components has been focused on increasing their durability, reliability, and performance in demanding subsea environments. The development of material sciences and materials, advanced designs, augmented sealing systems, enhanced control systems, and monitoring technologies have significantly contributed to the safe and efficient operation of subsea infrastructure.

Continuous improvement drives the evolution of subsea components, focusing on sustainability, cost-effectiveness, and environmental consciousness.

ROVs in Action: Examining Subsea Components

Thorough inspection, assessment, and analysis of various elements of underwater infrastructure are imperative in the examination of subsea components. This ensures their integrity, performance, and adherence to safety and regulatory standards. 

Examining subsea components includes the following aspects:

• Visual inspection is the primary method for examining subsea components. ROVs are primarily used in this process and are equipped with cameras to capture real-time visual footage of the components. The visual feed hence obtained helps the operator to identify any signs of damage, corrosion, leaks, etc. High-definition cameras and lighting systems aid in providing clear visibility in the deep-sea environment for better footage.
• Non-destructive techniques are preferred for a detailed assessment of the structural integrity of subsea components and to detect hidden defects present. Non-destructive testing methods commonly used for deep sea applications include Ultrasonic testing, Magnetic particle testing, Radiographic testing, and Eddy current testing. These methods enable the assessment of critical parameters such as wall thickness, material properties, and the presence of cracks or deformities.
• Subsea components are susceptible to corrosion due to the corrosive nature of seawater. Monitoring the corrosion in subsea components involves studying the corrosion rate, extent, and potential impact on the component’s structural integrity. A variety of methods like corrosion coupons, corrosion probes, and cathodic protection systems are employed to monitor and mitigate corrosion risks.
• Integrity assessments are conducted to determine the fitness of subsea components for service. The component’s design, structure, operational history, and maintenance records are analyzed in an integrity assessment. The analysis may also include testing stress and fatigue levels, gauging the remaining life of the components, and determining repair or replacement requirements.
• Subsea components undergo testing to ensure their applicability in the harsh subsea work environment. This is done by evaluating the mechanical properties, corrosion resistance, and fatigue behavior of the material used. Material testing methods such as tensile tests, hardness tests, and chemical analyses are employed to analyze the material’s performance and adherence to industry codes.
• The data generated during the analysis of subsea components (inspection reports, NDT results, and environmental parameters) is vast and data analysis techniques such as statistical analysis and trend monitoring are used to identify patterns, defects, and potential problem areas. A report is hence prepared, summarizing the inferences and providing recommendations for further actions such as maintenance and repair.
• Compliance with industry codes and standards is critical during the assessment of the structural integrity of subsea components. Organizations like the American Petroleum Institute (API), International Organization for Standardization (ISO), and relevant government organizations provide guidelines and criteria to adhere to for the employment of subsea equipment, their testing, and maintenance. 

Verification of the compliance of these subsea components requires the amalgamation of visual inspections, non-destructive testing, integrity assessments, material testing, and data analysis. These examination activities aid in the assessment of the condition, operational abilities, and safety of the components, enabling informed decision-making regarding maintenance, repairs, and asset management in subsea environments.

Overcoming Challenges and Advancements

The exponential growth in the use of Remotely Operated Vehicles has significantly aided the exploration and inspection of the challenges in underwater environments. The technology used in ROVs has been developed after numerous losses and challenges and has greatly benefitted from technological growth, hence enhancing the abilities of ROVs, and broadening their range of applications.

Some key breakthroughs in the use of ROVs are as follows:

• Developments in pressure-resistant housings, buoyant materials, and thruster technology have permitted ROVs to access and operate deeper in the ocean, accessing thousands of meters below what was earlier possible. Access to these regions is practically impossible for human divers due to the pressure and temperature changes. An improved understanding of the ocean, due to the benefits of ROVs has made deep-sea exploration, offshore energy development, and subsea infrastructure a reality for modern engineering.
• Former versions of ROVs were limited in power and endurance, as they relied on surface power and were connected via a tether. Advancements in battery technology and the use of hybrid power systems have significantly increased the duration of operation of modern ROVs. This reduces the issue of recharging and obtaining power from surface vessels repeatedly and enables longer missions.
• Progress in thruster design, control algorithms, and feedback systems have improved the responsiveness and stability of ROVs. Advanced navigation and positioning technology such as Doppler velocity logs, inertial navigation, and acoustic positioning systems, has improved the accuracy and reliability of ROV operations.
• Underwater communication technology has been upgraded in present times with the use of acoustic modems and fiber-optic solutions. The reliability and rate of data transfer have significantly improved. Operators receive high-resolution visual feed, sensor data, and control commands in real-time, facilitating efficient decision-making and remote access.
• Manipulators’ arms are often installed on ROVs to enable them to perform tasks such as the operation of valves, collection of samples, and deployment of tools. Progress in robotics has created improved manipulator arm designs and dexterity. Control systems are also progressing in terms of their effectiveness and accuracy. Newer ROVs can perform more nuanced and complex tasks, eliminating the need to risk human life in hazardous working environments.
• Modern ROVs are now equipped with high-definition cameras, 3D imaging technology, and advanced lighting systems. This provides the operator with clearer and more detailed visual data during testing and inspections. The newer ROVs are also equipped with special sensors and instruments such as SONARs, magnetometers, and multi-beam echo sounders. This has expanded the data-gathering ability of ROVs for mapping, navigation, and surveys.
• Modern ROVs are also equipped with autonomous abilities and artificial intelligence (AI) to perform autonomous tasks and further reduce human intervention. AI algorithms aid the ROV in avoiding obstructions, planning its path of motion, and enabling autonomous inspection processes. This reduces the workload of an operator and increases the efficiency of a mission. The complexity of operations can be increased in this regard.

These challenges and advancements in the operation, testing, and design of ROVs have made them efficient tools for multiple industries, and progress in technologies continues to enhance the versatility of ROVs in underwater operations.

ROVs: Enablers of Cost Efficiency and Risk Mitigation

ROVs have emerged as a facilitator of cost efficiency and risk mitigation in a variety of industries. Some ways that ROVs promote cost efficiency and risk mitigation are:

• The offshore oil and gas industry, renewable energy, and underwater infrastructure industries use ROVs in multiple applications. They can carry out visual inspections, data collection, and conduct non-destructive tests while eliminating the need for human interference and risk to human life. Inspection costs are hence lowered, and hazardous working conditions can be avoided.
• Unlike human beings, ROVs can operate without the limitations that are caused by human physiology and they do not need to take breaks or get fatigued. This not only improves productivity but also the efficiency of the operations.
• Accessibility is a major benefit provided using ROVs. They can access challenging environments enabling inspections, testing, repair, etc in such conditions.
• ROVs can be equipped with data collection equipment like sensors, cameras, etc. This data can be crucial for risk assessment, optimization, and decision-making. They also transmit data back to the control center for remote access to data and processes.
• Rescue and salvage missions, like that of the implosion of the Titan submersible, are often assisted by ROVs to map the ocean and help locate debris or other objects. ROVs were also used in prior expeditions to the original Titanic wreckage, aiding in the study of the remains of the ship. Their mobility and ability to potentially manipulate and recover objects provide better access to search sites and provide crucial data to operators.

The cost efficiency and abilities of ROVs make them indispensable for multiple applications and their risk mitigation capabilities have saved millions of dollars and multiple human lives.

Conclusion

The world of Remotely Operated Vehicles is captivating, and its capabilities evoke amazement at the potential for noteworthy discoveries. ROVs are a testament to the capabilities of modern technology that transcend human limitations, allowing us to venture into unfamiliar territories and unravel the mysteries that lie beneath. It is evidence of human resourcefulness and our unending pursuit of knowledge. 

Mankind will continue to be fascinated by the wealth of data that ROVs bring forth as they propel us onward in our relentless pursuit of knowledge and comprehension.