An offshore drilling rig operating in the Gulf of Mexico required the safe removal and recovery of its forward and aft moonpool flaps. These large structural components, critical to moonpool integrity and underwater operations, had to be detached, lifted, lowered to the seafloor, and ultimately brought to the surface for inspection and handling. Subsea Global Solutions was selected to complete this complex underwater project due to our proven record of delivering technically challenging subsea repairs with precision, safety, and reliability.

Work was performed over a two-week offshore campaign by our US Gulf Coast team, supported by INSEA auditors and the rig crew. The project was completed successfully, safely, and on schedule.

The Challenge

The rig required full removal and recovery of both moonpool flaps, large steel structures secured by hinges, locking pin padeyes, retention chains, and welded connections. The primary challenges included:

1. Extreme Offshore Conditions

• Multiple days of inclement weather delayed mobilization, equipment installation, and dive operations.

• Strong winds and storms restricted diver access and topside lifting work.

2. Complex Structural Removal

• The flaps required cutting through thick padeyes and angle sections, some of which proved resistant to gouging equipment.

• Hinges, retention chains, landing pads, and flap sections all required sequential removal with zero room for error.

3. Rigging, Lifting & Recovery

• Each flap had to be safely rigged to a spreader bar, cut free, lowered to the seabed, and then lifted to the surface.

• All operations required strict coordination with the rig crew for winch operations, lifting points, and deck handling.

4. Safety & Compliance Requirements

• Full IMCA audits, LOTO verification, NDE/MPI testing of padeyes, and pre-job emergency drills were mandatory before work could begin.

• A diver recovery and injured-diver drill was required to certify readiness for underwater work.

Our Solution

Subsea Global Solutions deployed a full dive spread, experienced underwater technicians, and a detailed step-by-step work plan to complete the moonpool flap removals. Our approach included:

1. Mobilization & Equipment Setup

• LARS installed, welded in place, load tested, and verified by NDE.

• Dive station fully established and audited to IMCA Standards.

• Full lockout/tagout (LOTO) completed and verified.

• Emergency drills and diver recovery exercises performed prior to the first dive.

2. Inspection & Prep Work

• Divers conducted MPI and visual inspections of all lifting padeyes.

• Cleaning and preparation of rigging points completed on forward and aft flaps.

• Safety hazards, such as loose rigging chains, were removed immediately.

3. Aft Flap Removal & Recovery

• Side flaps and landing pads detached and lifted.

• Angle cuts completed (starboard and port), including lessons learned applied to optimize cutting efficiency.

• Five bottom hinges cut.

• Locking pin padeyes cut despite thickness challenges requiring adjusted cutting methods.

• Aft flap lowered to the seafloor, then later recovered to the surface once weather allowed.

• On deck, all ancillary components were removed.

4. Forward Flap Removal & Recovery

• Similar removal procedure completed, including padeye preparation, angle cuts, hinge cuts, and chain removals.

• Forward flap lowered below the hull and subsequently recovered to the surface.

• Minor abrasions were documented at lowering locations, with no structural concerns.

5. Demobilization

• After final recovery, equipment breakdown was completed, and the team demobilized safely.

Outcome

Even with intermittent shutdowns caused by storms, crew changes, and equipment challenges, Subsea Global Solutions successfully:

• Removed and recovered both moonpool flaps

• Completed all cutting, rigging, inspection, and lifting activities safely

• Documented all abrasions and findings

• Coordinated seamlessly with the client, rig crew, and IMCA auditors

• Completed the project within the planned operational window

This project demonstrated our ability to perform complex structural removals on offshore assets while maintaining the highest levels of safety, compliance, and diving excellence in challenging conditions.

Underwater Repairs with Subsea Global Solutions

Subsea Global Solutions specializes in comprehensive underwater repair solutions that eliminate the need for drydocking, including precision structural cutting, subsea component removal, rigging and lifting, and inspection services such as UWILD’s and NDE. Our commercial dive teams execute complex repairs in challenging offshore environments using certified equipment, rigorous safety protocols, and proven methodologies that ensure operational continuity and asset integrity. From structural modifications to recovery operations, we deliver reliable, class-approved underwater repairs tailored to the needs of offshore vessels and energy assets.

‍