Precision Engineering Offshore: Solving Critical Uplift & Warpage on 11 Jacking Units

Introduction: The Challenge

A critical offshore asset, the rig, faced a significant operational threat due to widespread issues across its jacking system. A series of pending overhauls from a previous shipyard project—delayed due to spare parts unavailability—were compounded by new damage sustained during jacking operations as the rig transited to its current location.

The result was a cascade of failures across the Forward, Starboard, and Port legs. Problems ranged from oil leaks and excessive gear uplift to catastrophic component failures, including sheared climbing pinions, cracked bull gears, and severe plastic deformation on critical shafts. With the rig's stability and mobility compromised, an immediate and comprehensive remedial campaign was required to restore the jacking system to full working order and ensure operational safety.

Project Scope & Objectives

Formura Offshore Services was tasked with a large-scale repair campaign to address all outstanding issues. The project scope was extensive, covering multiple drive systems across 11 individual units.

The primary objectives were:

• Comprehensive Overhaul: Execute pending overhauls on primary, secondary, and final drive units as originally planned during the shipyard project.
• Rectify Operational Damage: Repair or replace components damaged during recent jacking operations, such as the sheared pinion in Unit G3 and the cracked bull gear in Unit I3.
• Restore Mechanical Integrity: Dismantle, inspect, and rebuild units to OEM standards, replacing worn bearings, seals, and gears to eliminate oil leaks and excessive uplift.
• Ensure Long-Term Reliability: Go beyond immediate repairs by proactively replacing wear items and utilizing Non-Destructive Testing (NDT) to guarantee the integrity of reused components.

Key Challenges & Solutions

The Formura team, encountered and overcame several significant technical and logistical challenges over the 38-day project (Sept 6 to Oct 13, 2023).

Challenge - Widespread & Severe Damage: Components across multiple units showed critical failures. For example, Unit I3's final drive had 27mm warpage, and Unit L4's bull gear was cracked and stuck.

Formura's Solution - Systematic Diagnosis & Precision Repair: Each unit was meticulously dismantled and inspected. Heavily damaged items (e.g., Unit B1 output shaft, Unit E4 46T gear) were replaced. Critical components like the 32T bull gear for Unit I3 were salvaged from Unit J1 and certified through Dye Penetrant Testing before reuse.

Challenge - Spare Parts Shortages: The project was initiated specifically because previous shipyard work was delayed by a lack of spares, creating a challenging repair environment.

Formura's Solution - Innovative Rework & Salvage: The team employed on-site ingenuity to keep the project moving. Hubs were refurbished, and components were swapped between units where possible (e.g., hubs for Unit J1 final drive were reused from Unit G3). The cropped bull gear on Unit L4 was carefully removed using high-pressure hydraulics to salvage other components.

Challenge - Complex Tolerances & Alignment: Critical parameters like gear uplift and housing warpage were outside acceptable limits on multiple drives (e.g., Unit D2 had 1.72mm uplift, Unit I3 final drive had 27mm warpage).

Formura's Solution - Meticulous Reassembly & Measurement: After overhauls, the team focused on precise alignment. Uplift was systematically reduced to within tolerance across all units (e.g., Unit D2 reduced to 0.45mm, Unit I3 final drive warpage reduced from 27mm to just 3mm), ensuring smooth operation and preventing premature wear.

Challenge - Unforeseen Internal Damage: Upon opening units, hidden issues were discovered. Unit H2's secondary drive bearings were found damaged after an abnormal noise was heard during initial inspection.

Formura's Solution - Thorough Investigation: The team didn't rely solely on external reports. They investigated abnormalities, leading to the discovery of the damaged bearings in Unit H2, which were then replaced, preventing a future catastrophic failure.

Project Results

Formura Offshore Services successfully delivered a complex, multi-unit overhaul campaign and completing the project within the scheduled offshore window.

Key Results:

• 11 Critical Units Restored: All primary, secondary, and final drive systems on the identified units were successfully overhauled and returned to service.
• Operational Integrity Achieved: Critical parameters like gear uplift and warpage were corrected to well within tolerance across the board, ensuring smooth and reliable jacking operations.
• Rig Mobility Restored: The successful overhaul of units like G3 (sheared pinion) and L4 (cracked bull gear) directly addressed the damage sustained during transit, fully restoring the rig's ability to safely jack and position itself.
• Future Failures Prevented: The proactive replacement of seals and bearings, combined with the investigation of anomalies like the noise in Unit H2, has significantly enhanced the long-term reliability of the entire jacking system.

Conclusion

This project stands as a testament to Formura Offshore Services' capability to manage and execute large-scale, technically complex repairs in an offshore environment. Faced with a combination of pending work and unexpected damage, the team delivered a solution that was not only technically proficient but also resourceful in overcoming parts shortages. The successful restoration of jacking system underscores Formura's position as a trusted partner for ensuring the safety, reliability, and longevity of critical offshore assets.