ABB of Norway, a manufacturer of marine Dynamic Positioning technology (DP), has chosen a Sonardyne USBL (Ultra-Short Base Line) package as the principal position reference system for a major ship construction project. The Sonardyne system will be installed aboard the Havila Crown, which is an advanced multi-purpose support vessel to give it the ability to perform a wide range of offshore oilfield support tasks.
The ship is currently under construction for Havila Supply at the Langsten Slip yard in Norway and is due for delivery in April 2001. The system is being supplied by ABB as a complete package valued at NOK 6,5 million. This includes the Sonardyne USBL and a Vertical Reference Unit manufactured by TSS (UK) Ltd. The Sonardyne USBL and the TSS sensor will be integrated with the DP system and will enable the ship to hold station in even the most demanding sea conditions. This will be a valuable capability that will make the new ship suitable for a wide range of contract work including anchor handling, pipe and cable laying and construction support tasks.
The Sonardyne USBL system works in conjunction with one or more acoustic transponders on the seabed equipped with an acoustic release mechanism to permit their recovery after use. By measuring the transit time of the acoustic signal between the ship and the transponder the system is able to calculate the ship’s relative position with a high degree of accuracy – typically better than 0.5 per cent of slant range. This information is then automatically relayed to the DP control which commands the thrusters that hold the ship on-location.