Yard coins ‘retro-upgrade’ term for offshore job

03 Sep 2014
The two GulfMark PSV’s in Shipdock Amsterdam’s Panamax dock

The two GulfMark PSV’s in Shipdock Amsterdam’s Panamax dock

Damen’s Shipdock Amsterdam yard describes a recent repair and conversion job on two offshore supply ships a ‘retro-upgrade’ – combining a general upgrade with retrofitting of anti-roll stabilising tanks.

The yard says it is particularly proud of the short timescale between receiving the order and completing the work on GulfMark UK’s Highland Defender and Highland Guardian. The job required close cooperation between Shipdock Amsterdam and sister Damen compny Niron Stall, which was responsible for manufacturing the anti-roll tank and new hull sections.  

“The contract was completed within a six week lead-time only, from the initial steel cutting to the vessels’ delivery. The lead-in time was practically zero”, said Flip van der Waal, Shipdock Amsterdam MD. “Niron and Shipdock started almost upon receipt of GulfMark’s steel cutting-drawings. The prefabrication part took three weeks to construct the two 75 tonne sections, painting included.”  

The 87m sister ships encountered downtime of six weeks only, including four weeks docked together in Shipdock’s 250m drydock followed by sea trials and return to base at Aberdeen.  

The antiroll tank units were retrofitted to improve the vessels’ roll characteristics, resulting in greater crew comfort as well as enhancing operational capability by reducing roll motion and roll angle in adverse weather. The tanks were placed abeam so that their internal baffles slow the rate of water transfer from the port side to the starboard side. As a large amount of water is restricted on one side of the vessel, this creates an asymmetrical force that opposes the natural but significant rolling motion imparted by a heavy sea swell.

The antiroll sections were installed directly against the aft face of the vessels’ accommodation. Damen says that the tanks were constructed as a complete single section, extending across the entire weather deck from port to starboard side, extending upward from B deck to the Bridge deck. The antiroll tanks are now a seamless and fully integrated part of the ships’ structure.  

The additional upgrade work was intended to further enhance the operational characteristics. “Our vessels are now even better equipped to face the harsh environments they will encounter within the operational arenas that they were designed for,” said Jim Bradford, GulfMark general manager operations.  

“The antiroll retrofit and the general upgrade put together, we’d like to dub this contract a retro-upgrade”, concluded Mr van der Waal.

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