Application: Touchdown monitoring
Vehicle: C-Worker 7
Payload: Veripos LD7 DGPS, Dual head R2 Sonic 2024 MBES. EdgeTech DS2000 combined Sub-Bottom Profiler and Side Scan Sonar. Valeport CTD sensors. The payload bay also incorporated acquisition PCs, data storage RAID drives and full air-conditioning systems.
Navigational sensor suite comprising 360-degree camera box with visible and infrared cameras, AIS and radar.
Summary: The C-Worker 7 autonomous surface vessel was deployed to the Mediterranean to support a pipelay operation for Subsea 7. The C-Worker 7 was used for pre-lay survey, touchdown monitoring and As-Laid Survey.
Benefit: Using the autonomous C-Worker 7 offered significant cost savings to the customer as it replaced the need for an additional survey vessel. The C-Worker 7 also provided greater operational flexibility; being unmanned meant it could be deployed for longer periods of time therefore widening the operational window. In addition, use of the C-Worker 7 resolved the technical challenge of surveying in very shallow waters whilst also removing the risk to personnel working at sea in small craft.
This project began with the design and build of the payload system to house the customer specified sensors. A custom payload frame was designed and fabricated in house. The modular frame slotted into the C-Worker 7’s moonpool to mount and deploy the multibeam and side scan sonars. The equipment deployment RAMS were designed to ensure accurate repeatable operational positions thus removing the need for re-calibration after each use.
Upon completion of the integrated payload system, the C-Worker 7 completed acceptance trials in the Solent. The vessel was then mobilised from ASV and handed over to the customer for transport.
The C-Worker 7 was transported by road to Gibraltar to meet the Seven Antares pipelay barge, which then transited to the operational area. The vessel was secured using a customer supplied bespoke cradle on the deck of the 119m pipelay vessel.
A 20ft control cabin was set up on the aft deck of the Seven Antares. This provided a secure area for survey control and the vessel navigation operations. Systems installed within the control cabin enabled the Subsea 7 team to navigate the C-Worker 7 and control the survey data acquisition. Having the survey team in full control of the vehicle ensured that the data requirements could be easily completed and any additional requirements dealt with quickly and efficiently without the need to mobilise additional personnel or equipment.
ASV Global’s proprietary control system ASView was used to control the C-Worker 7 and to monitor its condition throughout the operation. Communication to the C-Worker 7 was maintained via a COFDM IP link. The radio system was setup to flexibly allow the addition of mesh nodes to enhance the range of the vehicle as required and to mitigate any blind spots created by infrastructure on the pipelay barge.
The C-Worker 7 was launched via the ships crane using a 3-point lift and a remote release hook before beginning each mission.
Very Shallow waters prevented the use of a WROV to monitor pipelay operations so the primary role of the C-Worker 7 was to perform touchdown monitoring. The survey suite deployed by the C-Worker 7 enabled it to precisely determine the location of the TDP and compile a comprehensive As-Laid survey of the newly laid pipe. The C-Worker 7 also carried out a range of other survey tasks including pre-lay surveys before the Seven Antares reached critical crossing points in the operation. These surveys were used to identify the precise location and condition of previously installed crossing support mattresses.
An additional Seamesh IP system was installed by Subsea 7 to remotely control survey data collection aboard CW7 from the lay vessel.
The C-Worker 7 was operational for a total of 37 days. Using the autonomous vessel removed the need for a manned survey vessel which reduced the customer costs significantly. The C-Worker 7 also provided greater operational flexibility; being unmanned meant it could be deployed for longer periods of time therefore widening the operational window. In addition, use of the C-Worker 7 resolved the technical challenge of surveying in very shallow waters whilst also removing the risk to personnel working at sea in small craft.
A spokesperson from Subsea 7 reported “The C-Worker 7 has proven to be a very capable vessel providing an excellent stable survey platform controlled by the Pipelay Vessel”.
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