With a vertical pipelay system that can tilt 10 degrees from the vertical, the Seven Waves vessel is performing pipelay operations for Petrobras in waters up to 2,500 m (8,200 ft) deep offshore Brazil, according to Subsea 7, the vessel’s owner.
The vessel is considered the first of a new generation of pipelayers contracted to Petrobras, the company said. The fifth of seven vessels contracted by Subsea 7 to IHC Merwede’s Offshore and Marine Division, the Seven Waves began commercial operations under a five-year contract in Brazil in mid-May 2014, about three months ahead of schedule, said Subsea 7 in its second-quarter 2014 results.
The vessel’s pipelay system includes two below-deck storage carousels with capacities of 2,500 tonnes and 1,500 tonnes, respectively. The vertical lay system can operate at angles up to 10 degrees from vertical. It is designed to lay flexible pipe in water depths to 3,000 m (9,840 ft).
The system has a top tension capacity of 550 tonnes (two 275-tonne tensioners). The tensioners can be retracted from the firing line. The vessel can handle flexible pipe in diameters from 315⁄16 in. to 24.8 in. To maintain the ship’s orientation during pipelay operations, the vessel is dynamically positioned (DP Class II). The propulsion system includes three stern azimuth thrusters, two retractable bow azimuth thrusters and two bow tunnel thrusters.
The moonpool is designed for hanging off equipment up to 600 tonnes. Equipment in the moonpool can be rotated under full load. The cargo deck area is about 1,200 sq m (12,916 sq ft). The main deck crane is a Huisman Mast Crane with a capacity of 400 tonnes. The crane is fitted with an active heave-compensating system and a deepwater lowering system. The wire length for the crane is 2,500 m. There are also two abandonment and recovery winches built for 600 tonnes and 200 tonnes, each with 2,500 m of wire.
The vessel includes two Hercules type ROVs rated to 3,000 m, which can be launched over the side. There are accommodations for 120 persons.
The Seven Waves is the first of four flexible pipelay support vessels (PLSVs) under long-term day-rate contracts in Brazil, Subsea 7 said in its 2014 annual report. The construction of the remaining three PLSVs (Seven Rio, Seven Cruzeiro and Seven Sun) was proceeding according to plan with delivery scheduled for 2015 and 2016.
The work scopes of these multiyear contracts include new field development and inspection, repair and maintenance of existing fields.
Sector: Vertical Pipelay
Owner: Subsea 7
Name: Seven Waves
Shipyard: IHC Merwede, Krimpen aan den IJssel, The Netherlands
Length: 145.9 m (478.5 ft)
Molded Breadth: 29.9 m (98 ft)
Depth: 13 m (42.6 ft)
Operational Draft: 7.2 m (23.6 ft)
Maximum Draft: 8.3 m (27.2 ft)
Deadweight: 11,312 tonnes
Operating water depth: 2,500 m
Pipe Carousel Capacities: 2,500 tonnes and 1,500 tonnes
Service Speed: 13 knots
Propulsion: Six Wartsila diesel-electric engines; three stern azimuth thrusters; two retractable bow azimuth thrusters; two bow tunnel thrusters; DP Class II
Total Power: 18+ MW
First Operations: 2014
Operating Arena: Brazil
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