UMC carry out an underwater transducer retrofit to keep hoegh fleet services vessel ‘hual trotter’ on schedule.
Posted: 25 July 2005
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Quite often UMC are contacted to assist with the scenario of having to replace an existing transducer with one of a different make and size. Rather than rely on the existing aperture, often the wrong size, the following procedure eliminates improvisation and allows for a painless transformation. The full procedure was submitted to Hoegh Fleet Services Norway and DNV for pre qualification, and accordingly accepted by both parties.
The new transducer and housing were delivered to UMC prior to the  vessel arriving at Amsterdam . The flange was welded to a new section of hull bottom plating, which measured 500mm x 500mm being 20mm thick grade A steel. The plate, with the new transducer housing already attached, and the new transducer, accompanied the specialist diving team as they met the vessel upon arrival.
Following initial discussions onboard, the diving team quickly affixed a cofferdam to the underside of the vessel in way of the existing transducer. The water was evacuated from the cofferdam and the existing plate, surrounding the old transducer, was removed from the hull. The UMC internal team then prepared the peripheral hull plating to accept the new plate complete with new transducer housing. After the initial full penetration Tungsten Inert Gas root weld had been finished, and subsequent NDT of the weld approved, the internal team continued building up the internal weld as per UMC’s class approved procedure for this type of repair. Once the  welding on the insert was complete, and following an acceptable cool down period, the diving team removed the cofferdam and applied an underwater coating to the exposed areas. Divers then inserted the transducer into its housing feeding the cable through for internal connection. The cable was duly tested and the new transducer commissioned accordingly.
The actual operation, from divers initially fixing the cofferdam to ultimate DNV approval of the full job scope completion, was 30 hours. All work was carried out during the vessels scheduled call, ensuring no off hire time experienced.
Posted by Editor Pipeline Magazine
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