The realm of offshore operations has witnessed remarkable advancements in technology, particularly in the field of remotely operated vehicles (ROVs). These miniature marvels have revolutionized the way underwater inspections, maintenance, and explorations are conducted.
In this article, we delve into the fascinating world of mini ROVs, highlighting their capabilities, applications, and the significant role played by internet and Ethernet technologies in their operation.
In the offshore industry, we tend toward the maxim of bigger is always better
or might is usually right
and while the industry’s need for large, powerful machinery is undeniable, lbf/kgf, in isolation, is merely a statistic that logically cannot decide every application. This is especially true when it comes to Remotely Operated Vehicles (ROVs).
Through field experience we have learned that above and underwater working conditions, including available space, fiscal and time costs, power to weight ratios, and tether drag all need to be considered when using ROVs. And for these reasons, the myth of needing to always employ full work-class ROVs, as a way to ensure one has the capabilities and options to handle any application, now floats in the wake of miniaturized pragmatism.
A new, nimbler class of Remotely Operated Vehicles, called Mini ROVs, is cutting and crawling a path through today’s offshore industry.
In the process, they have not only rounded out the capabilities of their larger, work-horse brethren, but they have also proven superior for certain offshore applications (e.g. valve replacement, hull inspection, etc.), as the following technical overview will reveal.
What are Mini ROVs, Exactly?
Mini ROVs are larger than pocket-sized micro ROVs,
which have neither the thrust to work in currents nor the available payload to carry more than a single camera, lights and perhaps 1 or 2 sensors. With their larger size, Mini ROVs can carry a broader, more potent suite of sensors, tools, and other technologies, some of which will be detailed below.
However, Mini ROVs are smaller than standard observation class ROVs, which generally require large, complex, and expensive Launch & Recovery Systems (LARS). Mini ROVs require no such system. Indeed, they can be deployed and retrieved using their own tether if the tether is strong enough, though many can handle a 100 Kg payload. Further advancements have been made to the technology, and they only become increasingly significant.
Key Mini ROV Technologies
Mini ROVs were initially designed for shallow water applications, simply because there were a number of challenges that needed to be met before they could operate at depths greater than 1,000 meters. These included the miniaturization of control electronics, the design of lighter weight pressure housings, power and data transmission over very long cable/tether/umbilical lengths, and more.
Over the past decade, the ROV industry has managed to overcome these challenges, effectively helping Mini ROVs emulate the capabilities of much larger systems. Additionally, some Mini ROV manufacturers have developed previously unthought-of technologies that have proven to be uniquely useful to offshore applications.
Applications of Mini ROVs
- Offshore Inspections: Mini ROVs are extensively used for inspecting underwater structures such as oil rigs, pipelines, and subsea infrastructure. Their compact size and maneuverability enable them to access confined spaces and perform visual inspections with high precision.
- Search and Rescue Operations: Mini ROVs prove invaluable in search and rescue missions, aiding in locating and recovering submerged objects or individuals.
- Environmental Surveys: These ROVs assist in conducting environmental surveys, monitoring marine life, and assessing underwater ecosystems, providing valuable data for conservation efforts.
- Underwater Filmmaking and Exploration: Mini ROVs have opened up exciting possibilities in underwater cinematography and exploration, capturing breathtaking footage and unveiling the mysteries of the deep sea.
Low Drag Tethers and Ethernet Extension
Tethers become a big problem for Mini ROVs in deep water. The longer, thicker, and coarser a Mini ROV’s tether is, the greater the cumulative drag from that tether and, therefore, the greater the thrust these smaller ROVs require to maneuver reliably.
Smoothing a tether is a non-issue, as cable sheaths are now rather smooth, but thinning the cross-section of a tether has been a difficult proposition. Mini ROVs must transmit and receive many signals, and, sometimes, a considerable amount of power. This has typically required many layers of wiring, shielding, and fiber.
However, now, largely thanks to Ethernet extension technology, the cross-section of tethers has thinned to just 8.99 mm, considerably thinner than traditional ROV tethers, which average at least 20mm. Once Enable-IT Inc., inventors of Ethernet extension technology, were able to miniaturize deep sea-worthy Ethernet extenders, Mini ROV manufacturers have been able to multiplex their transmissions –and send Power over Ethernet (or PoE
)- to Mini ROVs using just 1-2 pairs of standard copper wiring. What is more, these Ethernet extenders seamlessly drive this data and power many thousands of feet, well past Ethernet’s distance limit of just 100 meters (328 feet) and with no bridging in between. This means significantly fewer wires and results in a very thin, all-copper tether with significantly less drag upon the Mini ROV. Furthermore, this means that these Mini ROVs can often be lowered into the water by hand, without the need for expensive launching systems.
Vortex Generators (Non-Magnetic)
Another highly useful advancement is that of non-magnetic vortex generators, which, when utilized as part of a “crawler” attachment, effectively grant Mini ROVs the ability to crawl pipelines, hulls, and other structures (See Figure 1). Using an impeller, instead of magnets or thrusters, vortex generators create a low pressure pocket (i.e. venturi effect) beneath their crawling Mini ROV, yielding up to 28kgf (62 lbf) of attractive force against any flat and hard surface.
Such a system holds several attractive benefits for its operators. For one, it yields so much attractive force that it maintains precise operations while a vessel is already in motion at sea or is experiencing strong currents while anchored. Therefore, this allows operators to survey their vessels more safely and economically than they otherwise could have, as they would have had to employ dive teams, sometimes even in particularly hostile environments. It also means that cameras and other imaging equipment (e.g. imaging sonar) produce very high quality images and data, because these devices are kept at a consistent distance from the target structure. Furthermore, with such stability, Mini ROV operators can enjoy much less fatigue and the occasional choice to focus solely on incoming data.
Automated Navigation
Previously, the technologies required for automated navigation, such as Doppler velocity logging, were too difficult to sufficiently miniaturize for Mini ROV use. Needless to say, some operators will be pleasantly surprised to learn that automated navigation of Mini ROVs has indeed become a reality within the past five years. Using a form of sonar tracking, Mini ROVs are now able to lock onto a target and navigate by way point, hold a position, conduct a programmed search, and more. In fact, at least one Mini ROV can reliably orbit around its locked-on target.
The benefits of automated navigation are quite clear. Lessening operator effort lessens their fatigue, thereby increasing their chances of efficiently completing their other tasks, such as data monitoring. Additionally, to the degree that an application can be automated, such navigation logically holds the potential to save operators inordinate amounts of time and money.
Mini ROVs in Action
Larger ROV Support
Due to their size, agility, and newfound capabilities, Mini ROVs do well at rounding out the abilities of their larger brethren. Such was the case of FMC Technologies, a prominent oil and gas supply service company, and their need to cap three sub-sea manifolds which were missing small valve caps but were already installed. Oil production could not begin without these small caps, and the proposition of recovering three 160 ton manifolds to install these caps involved many millions of dollars. FMC naturally turned to ROVs to try and solve the problem but quickly realized that neither work-class nor observation class ROVs could adequately match the operation parameters, one being too large for the space, and the other too small for the job.
FMC then turned to Mini ROVs and decided upon an operation whereby a Mini ROV would be outfitted with a special torque tool (to attach and tighten each cap). Then, due to the North Sea’s bad weather, FMC would use a work-class ROV to place the Mini ROV, which was to be in a basket, close to each manifold and release its tether. Thereafter, the larger ROV was to provide support as the Mini ROV got to work. And work it did.
Navigating through the first manifold was tight but straightforward. The Mini ROV operator was able to reach the appropriate valve, use the torque tool to tighten the cap, and recover the Mini ROV relatively quickly. The second and third manifolds were a bit more difficult.
It turned out that the second and third manifolds already had temporary test caps attached to their relevant valves, so the Mini ROV had to remove this cap and be recovered before it could try again and attach the actual cap. On the second manifold, this was complicated by the fact that the WROV accidentally opened the Mini ROV’s basket on the way up, but it was ultimately recovered quickly. By the third manifold, the operator attached a small mirror to the torque tool, so one could see the test cap better, and, after recovering the Mini ROV and dropping it back down, he smoothly attached the final cap.
Supplanting Larger ROVs
In another example, Mini ROVs proved to be uniquely suited for some applications. This is especially true in applications that require crawling and/or attachment, such as the 2009 case of an Inspectahire survey of an oil rig’s legs in the Persian Gulf. Inspectahire, out of the UK, was tasked with surveying the legs of an oil rig that belonged to one of the world’s largest oil and gas exploration and production companies.
Figure 2. A Mini ROV launched into the waters below an offshore platform. Photo courtesy of Teledyne Benthos, Inc.
As the rig experienced the Persian Gulf’s unforgiving thermally-induced tides, previous attempts to survey the rig’s legs by flying an observation class ROV down to them were unsuccessful. Inspectahire needed something new.
After learning about crawling, adhering to Mini ROVs, they decided to give them a try. Suffice to say, the results were impressive. Due to their portability and tethering, not only were they able to successfully complete their inspections, but they were able to launch and direct their Mini ROV from the platform directly above each leg.
As Cailean Forrester, Managing Director at Inspectahire, said, “The LBC [Little Benthic Crawler] is an innovative piece of equipment, and in this instance allowed us to undertake a challenging survey in a safe and effective manner, and overcome some of the issues which had previously been faced. An alternative method would have been to use divers, but they would have had to use magnetic clamps to ensure they didn’t get swept away in the current.”
Mini ROVs: More-than-Ready for Offshore
Over the years, Mini ROV manufacturers have soundly overcome the significant challenges faced when deploying these smaller, nimbler ROVs in deeper, offshore applications. In the process, they have advanced operators’ capabilities with innovative technologies. Vortex generators, for example, now allow Mini ROVs to firmly attach to and crawl around structures, saving operators from always having to employ diving teams for tasks like surveys. Similarly, low-drag tethering, via Ethernet extension, helps Mini ROVs maintain their extreme maneuverability while offering the ability to be launched by hand.
As such, Mini ROVs have proven to deftly and efficiently complement the capabilities of larger, work-class ROVs. Even more promising, in certain applications and as evidenced above, a Mini ROV may be the only ROV an offshore deployment needs.
Interesting Facts about Mini ROVs
- Depth Capabilities: Mini ROVs can operate at impressive depths, with some models capable of descending to 1000 meters or more.
- Versatile Attachments: These ROVs can be equipped with various attachments such as cutting tools, sonar systems, water samplers, and magnetometers, enabling a wide range of applications.
- Cost-Effectiveness: Compared to larger, more complex ROVs, mini ROVs offer a cost-effective solution for underwater inspections and operations, making them accessible to a broader range of users.
- Training and Portability: Mini ROVs are relatively easy to operate and transport, allowing for quick deployment and reducing the training required for operators.
Conclusion
Mini ROVs have emerged as indispensable assets in the offshore industry, offering highly efficient and economical solutions for underwater inspections, explorations, and maintenance operations. The incorporation of internet and Ethernet technologies has played a pivotal role in amplifying their functionalities. This integration allows for real-time video streaming, remote control, seamless data transfer, and collaborative efforts. As these technologies continue to advance, the potential of mini ROVs in the marine sector will expand further, unlocking novel opportunities for underwater exploration and effective resource management.
