Conversion, upgrades, and retroft solutions

ALL PHOTOS COURTESY OF ULSTEIN GROUP.

Alarge number of ofshore vessels still remain cold stacked or idled. Nevertheless, there is potential for an alternative utilisation of this feet in other markets, retroft to alternative fuels, or further enhancement for more efcient operations in their current markets.

The hulls of ofshore vessels have become a part of the skyline of many ofshore shipping regions. Over 1,900 ofshore vessels are out of service, many of them for more than 6 years already. This laid-up feet represents 30% of the total ofshore vessel feet of more than 6,000 units, thus, not all these vessels will fnd their way into the market again. Over 600 units are platform supply vessels (PSV), ranging from 50 and up to 99m lengths, more than 50 of these have not left the construction yard yet. Fiftyfve per cent were delivered after 2005, which are vessels with a long life expectancy remaining. Platform supply >>

vessels represent a versatile platform that can be adapted to multiple userapplications and situations. Anchor handling tug supply vessels (AHTS) and ofshore construction vessels (OCV) also present multiple possibilities for their alternative use in other markets.

Ulstein Group has, in recent years, explored 30 alternative market uses for existing platform supply vessels by means of conversion, upgrades, and retroft solutions. In case of conversion, a vessel is renewed, redesigned, and rebuilt to new technical and functional requirements. With an upgrade, the vessel is updated, renewed and/or the onboard systems and equipment are updated to higher standards regarding function, capacity, and capability to rebrand the vessel, and in case of a retroft, new technologies or features are added to existing systems and equipment. These 30 applications relate to four diferent vessel markets: the energy markets, the leisure market, the ocean biomass and other miscellaneous industrial and contingency applications.

Five potential applications of platform supply vessels are highlighted in the following table. These are based on the ULSTEIN PX121 design, a medium-sized PSV which has demonstrated to be a fexible platform for alternative uses. The refurbishment of the ‘Ocean Adventurer’ expedition cruise vessel included a general modernisation throughout the vessel, with signifcant >>

technical upgrades, securing a vessel with increased fuel efciency and, subsequently, a minimized carbon footprint.

Ulstein can transform an ofshore vessel, such as a PSV, into another ofshore type vessel, typically a multipurpose support vessel, light subsea construction vessel or ofshore wind service vessel, or into a non-ofshore vessel like a fsh carrier (wellboat) or expedition cruise vessel. The platform supply vessels of the ULSTEIN PX121 design, ‘Esvagt Leah’ and ‘Esvagt Heidi’, were originally built at Ulstein Verft and returned to the yard in 2021 to be upgraded to more environmentally friendly power solutions, and to a new life as ERRV vessels. The scope of work by Ulstein included project management, procurement, engineering, production and power & control deliveries. A battery deckhouse with a grid support unit for hybrid power has been prepared, the methanol tanks rebuilt to carry liquids under the OSV Chemical Code, and on the main deck, new prefabricated deck houses have been installed accommodating rescue zones, and new Esvagt type Fast Rescue Boats. Ulstein Power & Control delivered the power and automation solutions to the vessels as newbuilds. Their delivery now included the upgrade of the power and automation systems, the battery package, frequency converters, drives and switchboard reconstruction as well as its installation and commissioning.

It is not uncommon to see newbuilding and aftermarket activities being carried out in parallel at Ulstein Verft. Lifecycle services, including conversions, retrofts and upgrades, are good complements to newbuilding projects, and allow for a better utilization of the resources of the yard. The upgrade projects can be minor to large works. Mobilization and demobilization of topside equipment such as cranes and towers, installation of ballast water treatment systems or periodical dockings are common at the site.