Seatools recently delivered its third Carrera 4, mass flow, remote-operated excavation system to Bergen-based Ocean- team Shipping. The latest system is being mobilized to work offshore Vietnam, while the previous two are on duty in the Gulf of Mexico. One of the projects involves pipeline de-burial for Pemex to implement anode replacement. Another involves excavation in variable soil conditions in the Cantarell field.
According to Seatools, an important advantage of mass flow excavation is that there is no physical contact between system and seabed. Structures such as valves and pipes within the soil may be exposed without risk of damage. Mass flow excavation also allows soils to be removed from around and within complex structures with relative ease. Additionally, the shape, depth, and rate of excavation may be varied according to tool altitude over the seabed, power selected, and transit speed.
Carrera 4 is a multipurpose tool for pipeline burial/deburial, trenching, excavation, and stabilization/scour protection removal. The system operates at 2-5 m above the seabed and is designed for installation and deployment from any DP-equipped surface platform.
The Carrera 4 and its associated equipment is designed for shipment in a 20 ft container.
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The system is operable in blowing or cutting mode (or a combination of the two). By adjusting the operating height and flow rate, it can also perform both "spot" and volume clearing and excavation.
Carrera 4 can also tackle combined soil conditions. The speeds of the system's turbines can be adjusted to optimize the balance between flow and speed when dredging variable soils.
These turbines are installed in a dual-channel configuration (previous Carrera mass flow excavation systems have a single channel). Each tunnel is equipped with two turbines. The upper turbine creates a large variable flow of 5.5 cu m/s per tunnel, while the lower turbine accelerates the speeds up to a maximum of 28 m/sec, enabling the equipment to cut stiff clays of up to 50 kPa. The twin units contra-rotate for zero external torque. They are linked by a central hinge that allows tool width to be varied from 0-15°, providing a trench width of up to around 4 m in a single pass.
Launch and recovery of the machine is achieved via a single hoist wire running from the hoist point via the underwater unit and back again. No special spreading or lifting equipment is required.
Engineering feasibility studies are under way relating to the Norwegian Shelf and to complex soil conditions in the Far East.
