Over 200 anodes onboard the Thunder Horse platform had suffered fatigue related failure and a replacement of the anodes to the hull was required without interrupting production.
Proserv’s friction welding technology was used to replace like for like anodes, using an ROV. This was a challenge considering the anodes were 400lb in weight. Extensive testing was carried out in advance to qualify the performance of the friction weld including fatigue, tensile and electrical continuity tests. The installation was completed using the ROV that was permanently on board the FPS and was done in conjunction with other planned ROV operations. This helped save money as no construction vessel was required.
Proserv’s HMS 3000 hydraulic friction welding system was integrated to a customised ROV tooling package for this work scope. The ROV prepared each location and positioned the anode against the hull. Each 400lb anode required two tripartite friction welds for secure attachment. Continuity was achieved by welding a stud to the existing doubler plates, through a machined hole in the new anode strap. The final weld was qualified to the client’s specification with programmed weld parameters. Once offshore, the HMS 3000 friction welding system consistently executed the same weld and produced graphs for client record.
This unique method of remote anode replacement, utilising tripartite friction stud welds, was an industry first and it provided a high integrity connection between the anode and the hull. Its successful completion carries implications for aging FPSOs, platforms, pipelines and vessels worldwide.
- This unique method was an industry first as it was ROV deployed
- Significant cost savings as launched by ROV off the platform – no vessel required
- Low risk to personnel through use of ROVs
- Uninterrupted production
- The lower temperatures associated with friction welding can be qualified for use in zoned areas
- The welds were monitored in real-time and their integrity recorded