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Introduction

Onsite repairs of FPSOs while producing is preferred over taking it to a dry dock as this has cost implication due to loss of production and the reservoir related issues make it technically difficult.

Carrying out structural repairs and modifications inside tanks as well as at Non Cargo block areas of an operational or live FPSO should be looked at differently as this brings different challenges from structural repairs carried out on ships in dry docks. The structural integrity and safety have to be ensured, as adjacent tanks would most likely to have cargo. Removal of wasted structure for repairs pose additional challenges as the structure would be under stress due to waves and loading of the tanks. Logistic challenges due to long-term presence of the repair team offshore, material movement, material stowage and low production rate due to restriction on personnel onboard due to other operational commitments adds up to the woes. 
The below covers various stages involved in Special Survey repairs of an FPSO and areas requiring special attention at various stages of execution of steel repairs work while the FPSO continues to be in operation.

• Planning Stage
• Tank washing using ship’s installed cargo tank washing system and venting of tanks
• De-sanding/ cleaning of cargo tanks
  • Gas tests and monitoring
  • PPE/ gas masks
• Structural survey
  • CCTV
  • UTG
  • Visual survey
• Repair plan approved by the Classification Society.
• Steel forecast and procurement – steel plate standardisation
• Tools and equipment suitable for working on a live platform.
• Continuous gas monitoring
• Constraints in cleaning of structure for hot work inaccessible before scaffolding
• Constraints in material movement and lowering into tank due to restricted deck openings.
• Constraints in ventilation due to limited openings
• Adjacent tanks would be live and hence precautions during hot work.
• Wetback welding on adjacent bulkheads/ side shell
• Scaffolding erection at repair areas and walkway ladders etc.
• Rescue kit and escape sets and identification of escape route
• Working at heights and hot work in confined space – explosive mixture
• Structure in stress due to vessel loading and hence deflection during hot work possible. Precautions to be taken during renewal.
• Deck renewal – tower scaffolding, spatter containment and main deck habitats
• Welding processes
• NDT
• Preservation of renewed structure
• Closing out reports after job completion
• Handing over of tanks back to operation
• Rotation of manpower and ensure right mix of manpower.
• Logistics – replenishment of gas, consumables
• SPS as substitute for renewal