Subsea Mechatronics
Inspection and cleaning procedures in flooded confined spaces

When Dario Sosa, founder and CEO of Subsea Mechatronics (SSM), got in touch about an exciting, new project, we were keen to hear more. The biggest challenge as they embarked on a new innovation was a visibility near zero, making regular video footage useless for documentation. Luis Sanchez, CTO of Subsea Mechatronics, stated “Deploying human divers to carry out these inspections would not only yield poor results; it would be a health and safety hazard.” Needless to say, we did not require much convincing to participate in this intriguing project.

Competing to innovate Iberdrola’s processes for inspecting and cleaning the water supply pipes of their power plants

The project in question was actually a competition organized by Iberdrola, a major, Spanish energy company. In a time when energy is an increasingly important commodity, every single energy producer is looking to secure their production to ensure minimal disruption for their consumers - to provide stability in an otherwise volatile world.
 
In power plants, the production of energy generates a lot of heat. Heat that needs dissipating in order to keep the plant at an optimal temperature. The cooling system that is required to handle this job is both vast and extremely intricate. One basic hallmark of this type of power plant is that their cooling circuits use water that is recirculated from natural sources such as nearby rivers, seas and oceans.
 
For this cooling system to operate optimally, the flow rate of the water has to be maintained at a satisfactory level. Natural water in exposed pipelines, especially at the temperature this water holds, will stimulate organism growth and sedimentation build-ups, which affect the flow-rate of the water considerably.
 
The entire plant is shut down twice a year for maintenance purposes. The maintenance process involves various efforts to reduce sedimentation build up in the cooling system. These efforts are planned based on visual pipeline inspections, where the goal is to clean the pipeline in the most efficient way in the areas with the highest amounts of sedimentation.

Good reasons to replace divers with ROVs

Such visual inspections have historically been carried out by human divers. There are many reasons why divers are not the best solution for this job and why one should opt for a more mechanical solution:

Health and safety of the divers

The pipelines that comprise the cooling system are confined, tight spaces. The pipelines vary from 1-4m in diameter - often on the narrower end of this scale. Human divers put themselves in unnecessary danger by diving in these conditions.

The visibility in some cases, when chemical products are used to combat biofouling, is close to zero. The diver’s main task is to evaluate sedimentation build-up and plant growth to quantify flow restrictions. Having less than 10 cm visibility makes it difficult to quantify sedimentation build-up in any qualitative way.

Positioning/orientation

It is not sufficient to simply say that “Yes, foreign objects that impede flow rate exist in the pipeline”. One has to be able to accurately locate the area of the findings in order for the inspection data to be useful. Knowing exactly where an area of interest is makes it possible to not only intensify cleaning efforts on said area, but one can measure the area’s development over time to evaluate and optimize the chemical combatting and the cleaning efforts.

These are just some of the reasons why Iberdrola was looking for new, improved ways to carry out these tasks. And what better way to engage the many bright minds in the industry than to make it a competition?

The objectives of the Iberdrola competition

In short, the challenge at hand was “to find innovative solutions for inspecting and cleaning large water supply pipes in electricity power plants.”
 
More specifically, the objectives of the challenge were
 
“To be able to perform underwater inspections more efficiently while the system is operating, or at least maximize the availability of the system. For the inspections, the aim is:

        1. To gain comprehensive information about the depth of deposits in specific areas                    along the pipeline

        2. Estimate the amount of dirt adhered to the pipes

        3. Know what type of dirt this is: tubularia, sludge, mussels, etc.”

The company who solved this challenge in the best way could be offered an opportunity to scale up the solution in collaboration with Iberdrola, adapting it by means of commercial agreement.

Customizing equipment that can navigate even the narrowest parts of the pipeline, provide accurate ‘stand-alone’ positioning, provide reliable visual documentation and clean the pipe

Being highly experienced in complex subsea research tasks, SSM made a clear plan for what kind of equipment was required in order to complete the challenge. This was no ordinary subsea research task, with lots of external factors rendering the use of conventional equipment ineffective. This called for a customized solution comprising cherry picked equipment such as the vehicle, the imaging technology as well as the positioning.

Vehicle

Due to the restricted space of the manhole, the total size of the vehicle was limited due to the need for the vehicle to enter the pipeline - which is 1 meter in diameter. This naturally put some limitations on how big the vehicle could be. In addition, it also put some limitations on what kind of tools could be utilized.

Imaging

Due to the near zero visibility caused by the vast amount of particles in the water, a regular underwater camera would not be suitable to visually document findings in an adequate way

Positioning

Tight, confined spaces paired with zero signal penetration/reception ruled out using any form of GPS or USBL positioning systems for the task.

A custom built SSM SOLEA-ROV paired with a Water Linked DVL A50 for positioning and an Imagenex sonar for visuals

In a time when every single KWh counts, Subsea Mechatronics not only had a business opportunity on their hands; they could also help improve the growing energy concerns becoming a crisis. The guys at SSM knew they had to get creative to fulfill this brief.


Vehicle

Given the small diameter of the pipeline entry in which the ROV, the vehicle used for this project had to be as small as possible. SSM’s fleet of vehicles ranges from industrial sized ROVs to miniature ROVs, all with different capabilities and features. The vehicle that was selected for this project is a custom built SSM SOLEA-ROV from the range of PIPEYE ROVs, complete with skid tracks for navigation in the pipeline.



Opting for a tracked, skid steered vehicle was a conscious choice. Due to the confined space of the pipeline, navigating a tracked vehicle and keeping it steady is much more convenient than operating a thruster controlled vehicle specially for the cleaning works. The sonar imagery is also much steadier when captured on a tracked vehicle.

Imaging

As previously mentioned, the visibility in these waters is as poor as you can imagine. With a bit of optimism, you could suggest that the visibility for this project was 10 cm. The 4K, high refresh rate camera SSM team uses for all their underwater video recordings was part of the payload, but the images it produced was underwhelming.