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Thursday, February 25, 2021 

A Chinese partner agency of US-headquartered company Subsea Global Solutions (SGS) identified a problem with propeller damage to a vessel, sustained through contact while under way to Busan, Korea.

The client reported severe engine loading and excessive vibration, and SGS prepared various repair options.  An initial underwater inspection revealed large aft-ward deflections up to 100 degrees on all four propeller blade trailing edge tips. SGS responded quickly with repair options, cold static load propeller blade straightening being recommended. The client was reluctant to proceed at first, as they had received competing quotes from alternate commercial diving companies which seemed more economical. It was understood that this was because the procedures proposed by the alternative commercial diving companies included methods such as underwater propeller blade cropping. SGS preferred to avoid cropping, feeling that all four propeller blades were ideal candidates for restoration to near OEM design geometry without cropping. The client decided to go with the SGS proposal.

The SGS Busan team mobilised three experienced commercial diver technicians: two trained commercial diver propeller technicians working with virtual support of a Senior Technician from the SGS Vancouver office, where training technicians are based, providing education for the company's 165 divers through the SGS Maritime Academy.

The underwater repair process began with a close visual inspection for any linear surface defects in the deflected section tension sides (suction faces)—none were sighted. Using the design drawings, key locations to position our underwater propeller blade press were decided,  considering section thickness, fold lines, deflection angle radii, and the correct target geometry for propeller blade restoration, all without removing any material from the propeller blades. After completing each blade’s underwater straightening process, a subsequent close visual inspection was performed to ensure that no micro fractures or other linear defects had developed.

With a 12-hour repair window, all four blades were successfully restored to near design geometry and as per iACS Rules, allowing the vessel to continue operating until the next scheduled dry docking, at which a detailed inspection supported by dye penetrant can be undertaken. Upon departure, the client reported a successful sea trial with all engine parameters and vessel performance restored to pre-damage values.

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