Wind turbine installation is a highly specialised activity requiring custom-built ships: aptly called wind turbine installation ships (WTIS). energize spoke with Jan Schreiber, GL’s new Ship Type Expert for Offshore Service and Working Vessels, about pioneering projects, newly developed rules and future challenges.
energize: Recently, the wind turbine installation ship ”Pacific Orca” was delivered by Samsung Heavy Industries to Swire Pacific Offshore Operations. What makes this ship special?
Jan Schreiber: First of all, she is the largest wind farm installation ship ever built, with a length of 161 metres, a breadth of 49 metres and a depth of 10.4 metres. Her capacity is enormous: she is capable of carrying and installing up to twelve wind turbine units of the 3.6 MW class. Furthermore, the Pacific Orca can install foundations and erect turbines in water depths of up to 60 metres. Looking at future projects, this WTIS will also be able to install very large wind turbines with a rated output of 10 MW. Another impressive feature is the ship’s ability to lift herself up to 17 metres above sea level. This minimises the impact of waves and wind during installation operations.
energize: How did GL contribute to this project?
Schreiber: This was a truly collaborative project involving several business segments of the GL Group. Our colleagues from GL Noble Denton undertook the engineering and design work for the legs, spud-cans and the jacking system, including FMEA, as well as integration of these components into the ship’s hull. They also provided the shipyard consultancy and site-specific assessment services. Future- Ship, a GL company, carried out the global strength and fatigue analyses for the ship afloat and was responsible for owner consultancy. And GL as a classification society conducted the in-place analysis in jacked-up mode and provides the classification services for the “Pacific Orca”.
energize: Did GL have to develop a new set of classification rules specifically for this special ship type?
Schreiber: Yes. GL had published new rules for Hull Structures of offshore service vessels as early as 2010. These rules have recently been supplemented by a set of classification rules for crew boats and offshore wind farm service craft. This was done to consolidate all relevant GL rules, inter national codes and recommendations applicable to the classification of crew boats into one coherent framework. Using this compendium, designers developing vessels for the needs of their clients will be able to rely on one single collection of rules and guidelines with full confidence that their design will comply with classification requirements.
energize: Are these rules being applied in any current projects as yet?
Schreiber: Just recently we announced that the new “WindServer” wind farm service trimarans designed by Fjellstrand for World Marine Offshore will be classed by GL. This project comprises two 30 m and four 25 m ships. Their designer improved access to offshore installations in difficult weather conditions, enhanced the fuel efficiency, reduced the running costs and ensured the safety of the personnel on board, all pursuant to GL’s rules. The boats will have a service speed of 25 knots and the capacity to carry 25 and 12 service personnel, respectively. The trimarans are scheduled to go into service as early as March 2013.