Ulstein unveils ‘U-STERN’ foundation installation vessel

The company describes the ULSTEIN U-STERN as “a safer, smarter and more competitive solution for transporting, upending and installing large monopiles in dynamic positioning mode.

The U-STERN enables longitudinal storage of monopiles and upending on the ship’s centre line. This allows the ship to head into waves during the installation process, minimising motions and fuel consumption. The U-STERN design also provides excellent shielding from waves during the installation process.

“Combining the U-STERN with transverse and longitudinal skidding systems, offshore lifts for monopiles are eliminated, as the main crane is only used to support the upending and lowering of the foundation,” the company explained.

“The U-STERN looks like a simple recess in the stern, but it is much more than that,” said Ulstein Design & Solutions product manager and lead naval architect Ko Stroo. “The shape and location of the recess are finely tuned with CFD and motion analysis to make it work in harmony with the crane and mission equipment.”

“More than two years of R&D have enhanced our understanding of how to improve the dynamics associated with DP monopile installation. This has resulted in the U-STERN having significant benefits over conventional monopile installation over the side of a vessel.”

Ulstein says the concept provides increased operability due to a 25% reduction in motions, excellent wave shielding in the ‘moonbay’ and controlled upending of monopiles. It also provides a 50% power reduction in DP operations due to weathervaning and ensures safer lifting operations offshore.

“The idea of longitudinal monopile installation originates in our experience in developing heavy-lift pipelay vessels with a centreline firing line,” said Ulstein Design & Solutions managing director Edwin van Leeuwen.

“However, the U-STERN is not a ‘one-trick pony’, as the vessel is also suitable for jacket installation and other heavy lift installation work. We have presented the U-STERN to major contractors and operators, many recognising this as a highly viable solution for installing the next-generation monopile foundations.”