Mermaid Podded Propulsion Installed
Sedco Express — the first of a new fleet of DPS3 semi-submersible oil and gas drilling exploration rigs for operation in depths to 8,500 ft. — is the first use of the Mermaid podded thruster drive in an offshore application. Mermaid was jointly developed by Kamewa and Cegelec. The system aboard Sedco Express consists of four sets, each comprising synchronous 7 MW AC motor, pod cubicle and slipping unit, large and small pod domes, 12 pulse synchroconvertor and 11 kV supply transformer.Mermaid units reportedly can reduce required generating capacity by up to 17 percent, and cooling requirements by about 25 percent. Mermaid units are designed to save time and money on the repair and maintenance fronts as well, as the units can be fitted and replaced underwater. Shaft seals and propellers can also be changed underwater. For the project, Cegelec was tasked with a wide range of vessel power and control systems, including the overall power system, the AC drilling package, integrated control system and dynamic positioning equipment. The dynamic positioning (DP) system consists of a thruster, power system and operator interfaces, hydro-acoustic position reference system, DGPS system, anemometer, gyro compasses and vertical reference units for automated control of the vessel's position. The DP system provides joystick manual control of all thrusters.