Long range pipelines and tunnels

Inspection of the gallery of Les Mées

EDF - Les Mées (04), France - 2020

The mission aimed at collecting the necessary data to evaluate the general condition of the civil engineering in the tunnels, the drain valves, the turbines as well as the silting level in the canal. One of the technical difficulties consisted in carrying out this inspection over 2.7 km distance with a limited number of access points, thus requiring the implementation of a solution capable of travelling long distances, sometimes facing the current. In addition, the visibility conditions were very limited, so a video-only inspection was likely to be very tedious and time consuming.

The solution proposed by Subsea Tech to meet these operational constraints was based on the use of a Tortuga ROV, fitted for the occasion with a 3,300m long fiber optic umbilical and equipped with an Oculus M750d dual frequency (700 kHz – 1200 kHz) acoustic camera and an Imagenex 831A profiling sonar. Thanks to an horizontal aperture of 130° and a range of up to 120m, the Oculus offers a dynamic image of the environment in front of the ROV and allows the detection of structural disorders where video is ineffective. The 1200 kHz frequency resolution of the sonar allows the detection and dimensioning of defects of the order of 20mm at a distance of several meters. The profiling sonar allows the detection of irregularities over the entire tunnel section by performing circular scans.

Inspection of the Assassin Tunnel on the canal of Marseille

SEMM - Marseille (13), France - 2021

Subsea Tech has developed for the Société des Eaux de Marseille Métropole a floating inspection system specially designed for the inspection of partially flooded tunnels over long distances. This new system, named NAVIGOH, allows the simultaneous inspection of the above-water part (vault and side walls), thanks to two 4K cameras opening at 180° and a powerful LED lighting, and of the underwater parts (invert and side walls), thanks to a profiling sonar and an imaging sonar. The system is completely autonomous in energy and is only connected to the operator by a Dyneema cable of very small diameter but offering a breaking strength > 400 kg. NAVIGOH is deployed upstream of the tunnel and simply uses the channel current as a propulsion. The downstream speed is controlled by an electric winch, which also allows controlling the odometry within the tunnel.

The mission, conducted in January 2021, successfully completed the entire 3,400m of the tunnel. The recorded data allowed addressing the requirements expressed by the SEMM in terms of identification and localization of the disorders.

Visual inspection and ovality control of drinking water mains in Algiers

H2O ProServices - Algiers, Algeria- 2019

Subsea Tech performed the internal inspection of 2 drinking water mains of 2,000mm diameter over respectively 1,600m and 1,100m distances. For the purpose of this mission, Subsea Tech deployed its autonomous underwater robot Torpedo, designed in 2018 on another mission. Torpedo is capable of traveling up to 5,000m in >500mm diameter pipelines to perform visual/sonar inspections and highlight structural and functional issues.

The system consists of a torpedo-shaped vehicle equipped with batteries that give it an autonomy of several hours, and a motorized winch with a 5,000m spool of ultra-resistant cable. The winch allows not only to control the speed of the robot and to recover it at the end of the mission but also to measure the distance covered thanks to an odometer and thus to locate precisely the disorders observed in the pipe.

The robot is slightly floating in fresh water and is equipped with skis to stabilize it on the pipe roof during its evolution. The very small diameter of the cable (2.1mm) and the hydrodynamic form factor of the machine allow it to evolve in optimal conditions.

Torpedo is equipped with a very high sensitivity HD front camera with LED lighting and can also carry an imaging sonar (e.g. Blueview M900-130 or Oculus M750D) for inspections in extremely low visibility conditions as well as a profiling sonar (e.g. Imagenex 831A) for pipe ovality checks. All camera and sensor data is recorded locally. Given the large diameter of the pipe and in order to improve the quality of the video footage, an external camera system and associated lighting (GoPro camera, supplied by H2O Pro Services) was added under the front of the vehicle.

Torpedo has also been successfully involved in several inspections in France and abroad, over distances up to 4,500m:

Agglomeration of Thau: sea outfall of 1,100mm diameter over a distance of 2 x 2,500m (entering on each side of the outfall)

Egypt: Sea outfall of 800 mm diameter over a distance of 2,100m

Angola: oil pipeline of 1,000 mm diameter over 4,500 m distance

Inspection of two seawater pipes – EDF PEI Bellefontaine power plant

EDF - Bellefontaine, Martinique (France) - 2018

Subsea Tech was mandated by EDF to perform the internal inspection of 2 Ø1400 mm pipelines used to supply a seawater desalination plant in Bellefontaine, Martinique. The total length to be inspected was 480 linear meters for each pipe.

Among other operational constraints, the presence of a mixture of fresh and salt water in the pipe with a clear separation between the two phases and zero visibility in the lower part (sea water). This constraint made it necessary to navigate in the upper part of the pipe where sharp concretions threatened the umbilical and the ROV fairing. The inspection of the lower and lateral part of the pipe was ensured thanks to the Oculus M750d imaging sonar. In addition, an Imagenex 831A profiling sonar attached to the Tortuga was used to check for ovality along the entire length of the pipe. Another difficulty was the presence of a total of 4 bends in each pipe, 2 of which were at 45°, creating significant friction on the ROV tether.

These constraints were nevertheless overcome and the Tortuga demonstrated that it was capable of evolving in a confined environment over long distances, carrying several sensors, despite the presence of numerous singularities.

Some references

• MERCERON TP – Capbreton (40): Visual inspection and 3D profiles of an HDPE pipe Ø400, length 50 m to evaluate its wear by sand transport
• SUEZ – Menton (06): Underwater inspection by ROV of a sea outfall from a dredging chamber and from the discharge at 48m depth
• VEOLIA – Caluire (69): Underwater inspection by ROV of a drinking water pipe over 300m for the Eau du Grand Lyon
• BRL – Lunel (34): Assessment of the geometry and evaluation of the quantity of sediments deposited in 5 siphons
• CREOCEAN – Ajaccio (2A): Visual inspection of a sea outfall over 800 ml in the Gulf of Ajaccio
• ORLLATI – Geneva (Switzerland): Inspection of a storm water outfall, over a distance of 120 meters, discharging into the Lake Geneva
• SAFEGE – Marseille (13): Inspection of the stormwater network of Barbusse-République – Canebière – Prado
• EDF – Casterino (06): Underwater inspection of the Casterino feeder tunnel (horseshoe section of about 1.5m x 1.9m and length of about 1,200m)

 And more than 35 other references for public and private clients