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Wednesday, August 25, 2021 

Subsea Global Solutions (SGS) was recently contacted by a customer, when a vessel's starboard tailshaft shifted during the vesselís port call in Puerto Seybaplaya, Mexico, while the shipís crew were carrying out maintenance on the shaft coupling.

The movement resulted in the aft water seal losing contact with the liner, causing large amounts of water ingress into the stern tube. Local divers were called in to seal the aft seal housing with rags and underwater epoxy, temporarily stabilising the water ingress. The client ordered new OEM seals for both the forward and aft systems to allow for complete replacement. In preparation for the underwater aft seal replacement, the SGS Transhab system and SGS commercial diver technicians were mobilised and once on site, the dive team confirmed the tailshaft had slid aft by about 200 mm and needed to be pulled forward and re-coupled before the tailshaft seals could be replaced.

The SGS centralised Technical Repair Department as an OEM service provider worked closely with the client to develop a custom tailshaft re-positioning procedure. This included both the underwater and internal works, followed by our standard underwater seal replacement procedure. The work was expected to be completed in five 12-hour shifts with six commercial diver technicians and one project manager from SGS Vancouver, SGS Houston, SGS Long Beach, SGS Port Angeles, and SGS Tampa.

SGS’s internal team began by installing hold back clamps on the forward seal housing while the dive team began removing the rope guard. The tailshaft was secured internally by a clamp while the propeller, tailshaft, and seal housing were prepared for repositioning. The repositioning of the tailshaft was a critical step as it required all parties to work in unison for a successful outcome. SGS’s diver technicians supported the coupling of the shaft and the repair of the damaged controllable pitch mechanism internally. The shaft was successfully returned to its original position without any risk of water ingress to the vessel. With the tailshaft back in position, the aft and forward seal systems could be reinstalled. After the system was pressure checked, it was thoroughly flushed and readied for testing. The controllable pitch system was tested and calibrated. The whole project was completed without the need for drydocking, and the vessel performed sea trials without any issues.

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