Underwater Hull Inspection for FPSOs and Marine Vessels
Robotic NDT for wall-thickness measurement, corrosion mapping and bilge keel weld inspection
TSC Subsea provides robotic non-destructive testing (NDT) solutions for inspecting the hulls and structural welds of FPSOs, ships and other floating assets while they remain in service.
Our inspection technologies provide quantitative wall-thickness measurements, corrosion mapping and crack detection and sizing, supporting hull integrity assessments, maintenance planning and Underwater Inspection in Lieu of Dry-Docking (UWILD) programmes.
Using robotic systems such as ORCA™, we can carry out hull inspections above and below the waterline, reducing the need for divers, coating removal and costly vessel downtime.
Hull Surveys: Wall-Thickness Measurement and Corrosion Mapping
Acoustic Resonance Technology (ART)
ART provides quantitative wall-thickness measurements and corrosion mapping through typical marine coatings, without the need for coating removal.
Unlike conventional contact ultrasonic methods, ART uses non-contact sensors and is more tolerant of surface conditions, including soft marine growth. This reduces surface preparation requirements while enabling inspection of both internal and external corrosion from the outside of the hull.
ART data detailing internal corrosion collected from the external surface
ART stitched wall thickness data and corrosion mapping
Key capabilities:
- Quantitative wall-thickness measurements with sub-millimetre accuracy.
- Detection and mapping of internal and external corrosion.
- Inspection through typical marine and antifouling coatings.
- Reduced surface preparation and coating removal.
- High-resolution corrosion mapping for hull condition assessment.
- Identification of coating degradation and disbondment.
Robotic Hull Inspection Using ORCA
Our ORCA™ robotic crawler enables hull inspections above and below the waterline, deployed directly from the vessel deck without the need for divers or an ROV. Its omnidirectional movement allows efficient scan patterns and precise positioning around hull features such as sea chests.
Equipped with ART, ORCA supports spot measurements, continuous line scans and targeted corrosion mapping. Scan resolution can be adjusted during a single deployment, allowing faster coverage of larger areas and more detailed inspection where needed.
ORCA conducting an underwater hull inspection
Lloyd’s Register Validation
Acoustic Resonance Technology (ART) has been validated by Lloyd’s Register for quantitative ultrasonic thickness measurement of carbon steel ship hull plating through coatings, including the assessment of internal and external corrosion defects.
Hull and Bilge Keel Weld Inspection
Alternating Current Field Measurement (ACFM)
Structural welds, including bilge keel connections, are subject to loading and fatigue that can lead to cracking over time.
TSC Subsea uses ACFM to detect and size surface-breaking cracks in hull and structural welds, including through suitable protective coatings.
ACFM provides recorded, auditable inspection data, supporting weld integrity assessments without the need for extensive coating removal.
Robotic crawler deployed from the vessels deck
ACFM data detailing crack detection and sizing
ACFM Inspection Capabilities
- Detection and sizing of surface-breaking cracks.
- Inspection through suitable non-conductive coatings.
- Inspection of bilge keel and other critical structural welds.
- Recorded and auditable inspection results.
- Recognised by leading classification societies
- Deployed by ROV or via deck launch.
Robotic Deployment of ACFM
Our MagCrawler™ robotic system deploys ACFM array probes to detect and size surface-breaking cracks in bilge keel attachment welds, supporting underwater hull integrity and UWILD inspections.
MagCrawler can be positioned using a work-class ROV or a compact ROV launched directly from the vessel deck, providing flexible deployment options without the need for divers.
MagCrawler conducting a bilge keel weld inspection
Industry Recognition and Approvals
ACFM is an established inspection technique recognised by leading classification societies, including Lloyd’s Register, DNV, ABS and Bureau Veritas, and is referenced in international inspection standards.
Supporting Hull Integrity and UWILD Programmes
Underwater hull inspection provides operators with quantitative condition data to support integrity assessments, maintenance planning and decisions about further inspection or repair.
Our robotic NDT solutions can support UWILD programmes by providing detailed wall-thickness measurements, corrosion mapping and weld inspection data as part of an agreed inspection scope.
Where applicable, this allows inspections to be undertaken while vessels remain operational, reducing inspection-related downtime and the need for dry-docking.
Proven FPSO Hull Inspection
TSC Subsea deployed ORCA to carry out underwater hull inspection on an operational FPSO, collecting quantitative wall-thickness measurements to assess hull corrosion.
The deck-launched system enabled inspection below the waterline without requiring divers or an additional ROV support vessel, demonstrating an alternative approach to conventional hull inspection.
Discuss Your Hull Inspection Requirements
Whether you require hull corrosion mapping, structural weld inspection or support for a UWILD programme, our team can help identify a suitable inspection approach.
Case Studies
Simplifying Offshore Inspection Through Deck-Launched Robotics
1. Challenge Diverless UWILD crack detection and sizing across 70 structural locations. Supporting a life extension survey. 2. Solution Deck-launched deployment using a compact ROV and robotic MagCrawler equipped with ACFM® array probes. 3. Result Delivered...
Transforming FPSO Hull Inspections: A Cost-Effective, In-Service Solution with ORCA.
The FPSO in question is a single-hull vessel originally built in 1981 and later converted into a disconnectable FPSO in 2008. It is classed by Lloyd’s Register and has operated under a periodic inspection regime since its conversion, with a dry dock Special Survey 8...
ARTEMIS: Through-Coating Inspection for Large-Diameter Subsea Pipelines.
A primary objective was to assess areas expected to become dead legs as a result of future pipework rearrangements. These dead legs, along with the commingling point for flow back to Nyhamna, have been assessed as susceptible to Flow-Assisted Corrosion (FAC),...
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