Castoro Sei

  • HULL TYPEColumn stabilised semi-submersible
  • PIPELAY EQUIPMENT2 Rotating gantry cranes 134 tonnes capacity
  • POSITIONING SYSTEM3,000 m anchor wire on each winch of 76 mm
  • FIELD OF ACTIVITYOffshore Construction

Semi-submersible pipelay vessel

The Castoro Sei provides a safe, reliable and stable operating platform capable of laying subsea pipelines up to 60 inches in diameter, with additional facilities for offshore construction works and flotel capability. Optional piggyback and dual-lay configurations ensure that the Castoro Sei is capable of installing complex infield pipeline systems in addition to major trunkline systems. The Castoro Sei has an extensive track record of sustained high productivity in both shallow and deep water conditions on major trunkline projects, together with an impressive list of infield projects.


The semi-submersible hull construction with optional thruster assistance for enhanced position keeping enable operations to continue in adverse weather conditions. The upper hull encloses the accommodation, main engine room and main store rooms. It is divided transversely by three watertight bulkheads. A large proportion of the main deck is used for pipe storage with a rotating gantry crane mounted on either side of the firing line. The equipment and control systems onboard have been maintained to keep up with current technologies.



The Castoro Sei is built in accordance with the rules of the Italian Marine Ministry and is classed A1 by the American Bureau of Shipping. The flag state is the Bahamas and the Port of Registration is Nassau. The Castoro Sei also holds a Letter of Compliance issued by the Norwegian Maritime Directorate.



The firing line comprises the fixed pipelay ramp, enclosed in the central housing, running along the longitudinal centreline of the vessel. It is connected to an internal and external ramp, both of which have adjustable inclination to facilitate pipelay in varying water depths. A ramp extension unit is available for use in deep water or for severe seabed conditions. Located along the fixed and internal ramps are three 110 tonne tensioners, nine work stations (Welding, X-ray and Field Joint Coating) and a number of support rollers.


The pipe double-jointing system with six work stations is located in the deckhouse above the fixed ramp while the transfer and line-up station is enclosed within the superstructure at the stern.



The vessel has a twelve point mooring system to facilitate accurate positioning and movement during operations with a fully redundant control and monitoring system. It also has four Azimuthal variable pitch thruster units which can be utilised for propulsion or to further enhance position keeping if required.



A fully mechanised GMAW system known as “PASSO” is utilised for medium to large diameter pipe in the firing line whilst double joint line welding is accomplished using submerged arc equipment.



An aluminium helideck structure is located at the stern of the vessel. The helideck is designed to accommodate single main rotor helicopters up to and including the Sikorsky S61N type and is approved for use by the UK, Norwegian, Danish, German and Netherlands Civil Aviation Authorities. Offices and stores are located on either side of the central housing at main deck level. A separate superstructure mounted at the bow of the vessel encloses the bridge, offices, computer room and radio room.


Column stabilised semi-submersible



Length overall excluding ramps 152.0 m

Breadth overall 70.5 m

Depth to main deck 29.8 m

Transit draft 9.5 m

Operating draft (typical) 14.0 m

Survival draft 12.5 m

Dedicated pipe storage space 1,195 sq.m

Additional deck space 1,525 sq.m

Deck load 3,600 tonnes



American Bureau of Shipping






Four 37 tonne Azimuthal thrusters

Twelve 25 tonne anchors

Twelve 124 tonne anchor winches

3,000 m anchor wire on each winch of 76 mm



2 Rotating gantry cranes 134 tonnes capacity

Longitudinal conveyor, gantry transfer conveyors, line-up station

Three 130 tonne pipe tensioners

Fixed ramp, articulated ramp, mini ramp extension

Bevelling stations

Double jointing system

Welding stations utilising a semi automatic system

X-ray or AUT equipped NDT stations

Field joint coating system

Abandonment & recovery winch (400 tonnes)

Piggyback lay welding line facility

Dual-lay welding line and ramp


Suitable for helicopters up to and including the Sikorsky S61N type



Fully equipped radio room GMDSS

Satellite communications & TV

2 ARPA radars

GPS / DGPS navigation & positioning




6 Main generators 20.5 Mw total

1 Emergency generator 800 Kw



Ballast capacity 11,518 cu.m

Lube oil capacity 138 cu.m

Fuel oil capacity 3,123 cu.m

Potable water capacity 1,000 cu.m

Fresh water generators 180 tonnes / day



Accommodation for 347 people

Client offices, Conference rooms, Hospital, Gymnasium, Galley mess room, Coffee bar, Cinema, Recreation rooms, Satellite television

Castoro 6 - Brochure
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