X-Stern Extender enhances subsea safety
The X-Stern Extender features an extendable moon pool in the aft, allowing crew to place the stern towards weather and waves when using dynamic positioning, as opposed to the higher bow. The moon pool feature has been proved to enable safer subsea installations via cranes or an A-frame, as opposed to installations over the side or aft of the vessel, Ulstein noted.
Hydrodynamic simulations in common wave conditions for the North Sea have shown that the water motions inside the moon pool are reduced by 50% compared to outside the moon pool, ensuring a safety margin against green water.
“We believe this is a much better solution than working over the ship’s side, which can be a risky and strongly weather-dependent operation,” commented Tore Ulstein, deputy CEO and head of market and innovation at Ulstein Group. “Even for a subsea vessel that normally has a moon pool in the midst of the ship, valuable central deck space and hull volume will be freed up with the moon pool placed aft.”
Importantly, the X-Stern Extender is an add-on – it is not part of the ship’s structure and not counted in the ship’s length. This innovation results in lower deadweight, fuel consumption and operational costs for a fully functional subsea vessel.
Ulstein noted that the Extender also features the central characteristics of the established X-Stern: notably an aft deck protected from weather, extra volume and smoother motions.
