Diverse Challenges, One Solution: Overhauling 13 Critical Units

Introduction: The Challenge

The Rig continued its critical maintenance journey with the next phase of its Phase 1 remedial campaign. Following previous interventions, the rig still faced significant jacking system integrity issues that demanded expert attention. A comprehensive inspection revealed a wide array of problems across all three legs: primary gearboxes with output shafts suffering from severe pitting and dents up to 4mm, final drives with excessive warpage and uplift measuring up to 29mm, multiple motor pinions with chipped teeth, and red gears showing severe spalling and wear. With the rig operating, a focused and efficient campaign was required to address these diverse issues and return to a state of full operational readiness.

Project Scope & Objectives

Formura Offshore Services was tasked with executing this continuation of the Phase 1 remedial campaign on the Rig. The project scope was extensive, covering primary drives, secondary components, and final drive systems across 13 individual units on all three legs.

The primary objectives were:

• Complete Phase 1 Scope: Execute all planned repairs on primary drives, final drives, and motor pinions as per the maintenance schedule.
• Rectify Severe Gear Damage: Address primary gearboxes with damaged teeth (Unit A1, L2) and replace motor pinions with chipped teeth (Units E2, H3, H4).
• Correct Final Drive Distortion: Overhaul multiple final drives (F4, G4, I2, K4) with warpage ranging from 24mm to 29mm and uplift up to 7.92mm.
• Eliminate Oil Leaks: Replace motor pinion seals on units with active leaks (E3, G2, G4, H2) to prevent lubricant loss.
• Restore OEM Specifications: Dismantle, inspect, and rebuild all units to OEM standards, utilizing spare components where necessary to replace irreparable parts.

Key Challenges & Solutions

The Formura team, executed this demanding campaign over a 5-week period (January 15 to February 14, 2025).

Challenge - Severe Primary Gearbox Damage: Unit A1's output shaft had "severe pitting and dents of more than 3 to 4mm" with damaged splines. The primary and final drive gears had chipped teeth. Unit L2's primary gear also had chipped teeth.

Complete Primary Gearbox Overhauls: Both gearboxes were fully dismantled. Unit A1 received a spare primary gear, final drive gear, and 7T1P pinion, with all retainers, nuts, bearings, and seals replaced. Unit L2 received a spare primary gear while reusing the output shaft and final drive gear. Both were restored to like-new condition.

Challenge - Multiple Final Drives with Excessive Distortion: Four final drives required major intervention. Unit I2 had 29mm warpage and 7.92mm uplift; Units F4 and G4 had 24mm warpage with 6.72mm and 5.59mm uplift respectively; Unit K4 had been left disassembled with poor bull gear splines.

Systematic Final Drive Overhauls: Each final drive was completely rebuilt. For Unit I2, the inboard hub, outboard hub, and 7T¼ P pinion were replaced with spares. All four units achieved consistent post-overhaul results: warpage reduced to 8mm and uplift to 0.64mm (Units F4, G4, I2) or 0.27mm (Unit K4), bringing them all safely within tolerance.

Challenge - Widespread Motor Pinion Failures: Multiple units required motor pinion replacements due to chipped teeth and severe pitting (E2, H3, H4), while others needed seal replacements for active oil leaks (E3, G2, G4, H2).

Efficient Component Replacement Campaign: The team executed all seven motor pinion-related repairs with precision. On Unit H3, they replaced a pinion with chipped teeth and severe pitting. On Unit G4, they combined a final drive overhaul with a motor pinion seal replacement, demonstrating efficient multi-tasking.

Challenge - Unexpected Gearbox Findings: While working on Unit I1, scheduled for red gear replacement and seal work, the team discovered the primary gear and final drive gear were "turning freely," indicating potential internal issues.

Adaptive Scope Expansion: With the Company Man's approval, the team disassembled the gearbox for inspection. They found the output shaft seal damaged and replaced it, along with the motor pinion seal, while confirming the output shaft and gears were in good condition. This proactive approach prevented future failure.

Project Results

Formura Offshore Services successfully delivered a comprehensive Phase 1 continuation campaign for the Rig, addressing a wide range of jacking system issues and restoring the asset to full operational integrity within the scheduled anchorage window.

Key Results:

• 13 Units Addressed: All primary, final drive, and motor pinion repairs on the identified units were successfully completed.
• Primary Gearboxes Restored: Units A1 and L2 received complete or partial gearbox overhauls, with damaged gears and shafts replaced, eliminating the risk of catastrophic failure.
• Final Drive Distortion Corrected: Four final drives were brought back into safe tolerance with consistent, measurable results.
  • Unit F4 final drive: Warpage reduced from 24mm to 8mm; Uplift reduced from 6.72mm to 0.64mm.
  • Unit G4 final drive: Warpage reduced from 24mm to 8mm; Uplift reduced from 5.59mm to 0.64mm.
  • Unit I2 final drive: Warpage reduced from 29mm to 8mm; Uplift reduced from 7.92mm to 0.64mm.
  • Unit K4 final drive: Reassembled with all spare components; Uplift measured at 0.27mm.
• All Pinion & Seal Issues Resolved:Three motor pinions with chipped teeth were replaced, and four motor pinion seals were replaced, stopping all active oil leaks.
• Proactive Issue Detection:The team's diagnostic diligence on Unit I1 prevented potential future gearbox failure by identifying and rectifying a damaged output shaft seal.

Conclusion

This project exemplifies Formura Offshore Services' consistent capability to deliver high-quality remedial campaigns for the Rig. By successfully addressing a diverse portfolio of issues—from major gearbox overhauls and severe final drive distortions to precision pinion replacements—the team demonstrated technical breadth, adaptive problem-solving, and a steadfast commitment to operational excellence. The successful completion of this Phase 1 continuation further solidifies Formura's trusted partnership in maintaining the safety and reliability of their critical offshore assets.