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Pump jet technology originally used in submarines is being used in offshore platform support vessels for the first time.
Pump jets, which are also now being used in high-speed surface vessels, draw in water and then forcibly eject it out through a nozzle. A traditional propulsion system uses a propeller to push on the water.
GE said its Inovelis pump jet, is 10% more efficient and can save up to £160,000 a year compared to conventional Azimuth propulsion when used in offshore Platform Support Vessels (PSVs).
The Inovelis pump jet houses an electrically powered propeller and its motor within a steerable pod, which is mounted beneath the hull of an offshore vessel. Like a podded thruster, it is said to have improved manoeuvrability, responsiveness and fuel efficiency compared to conventional propulsion systems.
The pump jet uses fixed stator vanes and a nozzle to guide the water flow across the impeller blades and enhance propulsion efficiency. It has also been designed to be as compact as possible to further influence the ships’ fuel economy and emissions. GE calls the Inovelis “the marine equivalent of a jet engine”, with the difference that the Inovelis can be pointed in any direction on a horizontal plane.
According to GE, the Inovelis has higher thrust capability than a conventional propulsion system, as well as improved hydrodynamics. The propulsion system is therefore able to perform better in both dynamic positioning (DP) mode, such as when a PSV is stationary for drilling, and also while in transit.
Paul English, marine leader of GE Power Conversion, said: “There is a clear trend towards larger, more capable offshore support vessels and a second trend towards the search for oil and gas taking these vessels ever further from home ports.
“Ship operators are looking for systems that support cost-effective, fuel-efficient, rapid transit, without sacrificing the capability to operate effectively and efficiently once on site in DP mode. This raises a dilemma as many current designs are a compromise between these two differing requirements.”
In addition, Inovelis uses GE’s induction motor technology and has a “no man access” design, which helps reduce overall size and provides an additional differentiation from other designs. The company said that a PSV driven by two 2.5-megawatt Inovelis pods, operating 30% of the time in transit at full speed could save up to £160,000 a year compared to conventional systems.
GE said it has received a number of Inovelis orders for large PSVs. The first is scheduled for delivery in the second quarter of this year, with ship commissioning around the end of the year.