Author: Stephen Auld, Global Business Manager, Subsea Asset Monitoring

In my last blog, the first in a three-part series, I looked at how our 6G enabled SMART and AMT acoustic hardware can provide the information you need to understand both high and low frequency movement of your subsea assets’ integrity and fatigue life.

These sensors provide seamless, wireless, monitoring for vibration and motion subsea as part of a stand-alone system, without any need for local power or communications umbilical.

So, once you’ve got your monitoring sensors in place, how do you access the information they’re generating? In short, there’s no single answer – that’s because there are now options to suit every scenario, including using marine autonomous systems (MAS).

Vessel or ROV deployed options

Conventionally, there are three main ways you’d get your sensor data: via a subsea transceiver connected into your control system; by a vessel with an over-the-side Dunker; or by using a remotely operated vehicle (ROV) with acoustic telemetry equipment. Let’s look at all three in a little more detail.

• With a hardwired system, you’d have a transceiver, such as our Dunker 6 or SMART-Dunker, mounted within a tripod on the seabed, connected to a subsea control module or other termination assembly. This subsea transceiver would gather the sensor data acoustically and then send it topside via the main umbilical. For monitoring systems that are spread over a large area, we can create an acoustic daisy chain to hop data to a central transceiver, which then delivers each sensor’s data via the one umbilical.
• For vessel-based data harvesting, if your ship already has Sonardyne 6G enabled transceivers on board, such as our Ranger 2 and Mini-Ranger 2 Ultra-Short BaseLine (USBL) systems, you can use them to acoustically upload the data from any of our sensors – because they all speak the same language. If you don’t have a transceiver on your vessel, you could rent or purchase a Dunker 6 transceiver, which could then be hung over the side of your ship, rig or platform and into the water, to acoustically retrieve your subsea sensor data.
• If you have a ROVNav 6+ fitted on your ROV, you have everything you need to harvest data from our 6G SMART and AMT monitoring instruments. The ROVNav 6+ on the ROV just needs to be within acoustic range to gather the data which it then sends topside via the ROV’s umbilical.

These are the conventional methods we’re all used to. But there are now alternatives. Increasingly, we’re using new ways of harvesting data remotely and wirelessly, at far lower costs and with vastly lower carbon emissions, using unmanned surface and subsea systems.

Data harvesting with unmanned surface vessels (USVs)

First, let’s look at unmanned surface vessels (USVs), sometimes called surface gateways – as they provide a relay, or gateway, for your data. The number of USVs on the market has exploded in just a few years and we’re increasingly able to use them for data gathering operations.

We’ve already been working with a wide range of providers, including L3 Harris ASV, XOCEAN and Maritime Robotics, using a number of different platforms, including Wave Gliders, to head offshore and gather data. Read about work we’ve done with each of these by clicking the links on their names.

The benefits of installing our systems on USVs for data harvesting include a vastly reduced carbon footprint, enabling staff to work remotely, which is crucial in the current Covid-19 environment, as well as reducing costs, making more frequent harvesting missions eminently viable. But there are also operational benefits. For example, we’ve been able to enter the 500 m exclusion zone in order to harvest data, because these systems, being so much smaller than any manned vessel, pose minimal threat to production systems.

Their efficiency is also enhanced thanks to low hull and propulsion noise, so data can be harvested faster than from a noisy manned vessel. Just like a manned vessel, they can also beam the data they gather to shore via Iridium satellite or 4G, depending on local communications availability.

Your data collection options

To make any USV “data-harvest-ready” with our systems is quite simple. Depending on the size of the USV and how much you want it to do, we have a number of options:

• Modem 6 – our acoustic modem family
• Dunker 6 – our LBL and telemetry transceiver for deployment from vessels or USVs
• Or one of our Ranger USBL family of High Performance Transceivers (HPT), depending on the water depth you’re working in and the precision that you want.
• If you’re also doing positioning, you may want our Gyro USBL – removes calibration requirements so great for using on dynamic vessels of opportunity.
• Acoustic Communications Module – ideal for gliders, all the electronics you need, housed in a compact form factor, with a remote transducer
• Wave Glider Transceiver (WGT) – all the electronics you need, including a satellite link, with a remote transducer

Each of these systems can interface in several different ways with the vehicle’s management system for access to the previously recovered data. When instructed to do so, the unmanned vehicle can then transmit the recovered data via Iridium or for example a 4G cellular network back to shore.

Get in touch if you want to learn more about this amazing technology.

Letting the underwater drones do the work

Another option is to use underwater drones, or autonomous/unmanned underwater vehicles (AUV/UUV) for your data gathering missions. In fact, your AUV/UUV may already be equipped for data collection, if it has an AvTrak 6 or AvTrak 6 OEM Nano telemetry transceiver on board.

• AvTrak 6 OEM – our vehicle-ready, self-contained vehicle tracking and communications transponder
• AvTrak 6 – as above, but within our subsea housing

Once the data has been harvested, your AUV can either transit to a wired subsea transceiver or meet up with a USV, to offload its data. Of course, it could also be recovered by a conventional vessel using a Sonardyne transceiver or by downloading the data once the AUV has been recovered on the back deck.

If there’s a substantial amount of data to be retrieved, our BlueComm free space optical modem enables multiple megabytes of it to be offloaded, quickly. This is perhaps more relevant in seismic data acquisition operations, but could also be useful when monitoring requires a high level of data transfer, for example, downloading raw or time series subsea asset motion data.

Just as you can with an AvTrak, with an integrated BlueComm your vehicle can gather data then offload it either to a BlueComm hardwired into the subsea infrastructure to then send down the umbilical or to a manned or unmanned surface vessel, with a corresponding BlueComm receiver. To put it another way, we no longer have a problem handling high bandwidth data subsea!

Conclusion

So, what’s the upshot of all of this? In a nutshell, when you’re monitoring subsea assets using our equipment there are numerous ways, both conventionally and now also using MAS, such as USVs and AUVs, to access as much data as you would like wirelessly. And this isn’t just for subsea asset monitoring, it can be for data collection from any type of subsea sensor.

In my next blog, I’ll take you through what happens now you have your data and who helps you to understand what’s happening in your subsea system.

We can help and assist on all aspects of data harvesting missions, including organising the most appropriate and efficient data gathering platform for the task. Get in touch to find out how we can help you.