Offshore vessel Seven Viking is the result of the stringent technical requirements that characterize most sophisticated offshore vessels. What makes this Ulstein designed vessel outstanding is the focus that has been placed on ensuring that the crew can deliver peak operational performance from this complex and versatile asset no matter what task is set for it.
Seven Viking is a tailor-made solution for inspection, maintenance and repair (IMR), survey and light construction and is employed on long-term charter with Statoil (STO) in the North Sea. Its work scope also includes alongside scale treatment and pre-commissioning. This broad range of duties necessitated the inclusion of a complex equipment package, but, with Ulstein’s approach to design, operational functionality has not had to be compromised as a result. Rather, the vessel closes an innovation gap in the offshore market through its success in providing the crew with a work environment that is as versatile as it is specialized.
At just 106.5m long and 24.5m wide, the vessel’s equipment has had to be accommodated extremely efficiently and most is situated in a hangar space. All operational personnel are stationed in one area directly above the hangar to facilitate cooperation and communication. Panoramic windows provide visual access to operations and the area has a direct view of the customized module handling system and moonpool in the hangar space. This joint operation control room has stations for shift supervisor, module handling system control, ROV control, scale treatment control, third party control and survey control.
The ship has been developed to meet the highest working environment standards and has been designated comfort class COMF-V (3) by classification society DNV. Minimal noise levels are achieved by the use of electric winches for the vessel’s three ROVs, the module handling system and other equipment. To minimize working at heights and manual handling, man-riding baskets and utility cranes are installed in the hangar area.
Ulstein has worked in close partnership with the vessel’s owners Eidesvik Seven, a joint venture between Eidesvik and Subsea 7, to achieve the landmark design. “Ulstein helps owners think innovatively, to bring forward new, quality vessels ready for the future,” says Tore Ulstein Deputy CEO Ulstein Group and Managing Director of Ulstein International. “Combining Ulstein’s ingenuity and experience with the commercial drive of shipowners working for first-class clients, we have created a vessel that stands out in an industry characterized by sophisticated tonnage. Seven Viking will change the expectations of charterers in the IMR market.”
While Eidesvik has focused on the vessel’s maritime qualities in order to develop the best possible operational platform, co-owner Subsea 7 has worked specifically on the technical solutions of an operational nature, including freeboard, deck space, hangar, operational control room, workshops and offices. Ulstein brought all the requirements together and both designer and yard, Ulstein Verft, put a lot of additional effort into engineering and integration. In the most hectic production phase, almost 400 people were working on the vessel. The result is a prototype vessel with a big future, says Ulstein.
Seven Viking is designated ICE-C class and built specifically for operations in harsh and cold environments. It can accommodate 90 persons and can maintain a service speed of 16 knots fully mobilized for IMR operations.
Ulstein’s X-BOW hull line design reduces hull motion in transit and gives increased stability. The bow shape ensures soft entry into waves, thus reducing speed loss, pitch and heave accelerations, as well as eliminating the slamming and vibration problems associated with conventional bow flare.
The increased stability has not meant a compromise in agility and Seven Viking can manoeuvre with ease even within the confined spaces between platforms that larger vessels would find difficult to access.
The ship is dynamic positioning class 2 (DP2) and can work on DP in 5m significant wave height. The ship’s power system is divided in three, and includes three thrusters aft and three fore, as well as three auxiliary systems. The three-way main switchboard is the largest switchboard ever delivered from Ulstein Power & Control, and in the case of a single major failure, the vessel will still have two thirds of its thruster power available. A key feature of the vessel’s electronics is the integrated automation system, ULSTEIN IAS, built on Ulstein’s flexible modular architecture. This architecture features redundancy at all levels.
The 135 ton active heave compensated offshore crane on deck will mainly be used for lowering and lifting heavy equipment to and from the sea bottom. Two work ROVs and one observation ROV can be lowered from the ship’s side. All ROV systems in enclosed in a ROV hangar and launched using A-frames. The two work class ROVs (Schilling HD) are rated to 3,000m and the observation ROV (SubAtlantic Mohican) is rated to 2,000m.
In the hangar, the module handling system has a cursor system for the controlled launch and recovery of modules up to 10m high and weighting up to 70 tons. These operations can be conducted in water depths up to 2,000m.
The vessel’s skidding system has storage capacity for up to eight skidding pallets including four indoor storage positions.
Twist locks are integrated onto part of the 830m2 working deck for quicker mobilization and demobilization of standard containers.
The scale treatment pumping spread and special product tanks are integrated into the vessel and provide for a pumping capacity of 30-2,800 l/min @ 0-345 bar. Seven Viking’s tank capacity includes 2072 cu. m. for fuel oil (MDO), 1,493 cu. m. for potable water, 3340 cu. m. for ballast/drill water, and 554 cu. m. for brine.
Several notable environmental initiatives have been taken when designing the vessel which carries the Clean Design notation. These include the diesel electric propulsion which reduces atmospheric emissions, and the ship’s electrical winches which mean there will be no hydraulic oil leakage.
“The Seven Viking may be battling the North Sea for many months of the year but it certainly won’t be harming it,” says Ulstein. “Being considered an industry vanguard means being out front and consistently staying ahead of the pack. To Ulstein it means developing innovative and dependable solutions that solve unique and often complicated offshore demands - thus we have Seven Viking.”
(As published in the December 2012 edition of Maritime Reporter - www.marinelink.com)