A marine aggregate dredger under construction for UK shipowner CEMEX Marine will deploy the first dredge pump driven by a permanent magnet electric motor.
The 1,400-kW motor will drive the submersed pump on CEMEX Go Innovation, being built at Damen Shipyard Group’s Galati shipyard in Romania. It is expected to deliver efficiency of 97%, including energy lost through friction with bearings and the mechanical seal. The new motor extends the marine application of permanent magnets, which have previously used to drive thrusters, shaft generators and deck machinery including winches.
The air gap in permanent magnet motors makes them lighter than oil-filled asynchronous motors, while the greater efficiency allows them to be designed smaller. The dredging pump motor developed by Marotechniek and Damen Dredging Equipment is controlled by a water-cooled active front-end drive.
The hopper dredger is designed for mining marine aggregates at 55 m below sea level. The submerged pump is directly driven by the electric motor, which forms an integral part of the trailing pipe structure. The motor is located near the middle of the pipe, usually operating at a depth of 25 m.
The drivetrain including pump, motor and frequency converters have passed testing including an overspeed test at 20% higher than nominal rpm and a torque test at 30% beyond operational requirements. The equipment will now be shipped to the Netherlands where it will dredge pump will be connected and the motor and pump fitted to the trailing pipe system.
The hopper dredger, destined for deployment in the North Sea and the UK Channel, is expected to be delivered later this year.