VOITH LINEAR JET DATA DEMONSTRATES IT’S NOW A PROVEN PRODUCT INDUSTRY ROUND-UP
Extensive data from 12 months’ operation of the Voith Linear Jet demonstrates that the new marine propulsion system is a proven product for crew transfer vessels working on offshore wind farms.
That’s the conclusion that Voith marine engineers have reached after studying detailed information from the VLJ installed in Turbine Transfers’ “Trearddur Bay,” a 21 metre long, 7 metre beam support catamaran.
Mark Harvey, Voith Turbo’s Marine Manager, told a Press conference at Seawork International:
The VLJ cannot only save owners and operators £75,000 in a season, but it can also produce better transit speed, more bollard pull, more thrust, and less noise and vibration.
Above: Turbine Transfers’ ‘Trearddur Bay.’
www.voith.com
VLJ spent 60 per cent of its time in transit at about 28 knots, and the rest of the time pushing up again structures.
“Conventional water jets can achieve 8 tonnes bollard pull at 90% maximum continuous rating, but the VLJ can do 8 tonnes at only 50 to 60% MCR,” said Mark.
“So the VLJ is not putting as much stress on the engine, resulting in less engine wear and less fuel being used.
“It also means that the VLJ is safer because, should more power be needed, the VLJ has plenty while a water jet has hardly anything left in reserve.
Below: The Voith Linear Jet. Above: Mark Harvey, Voith Marine Manager.
He said that logs from 907 hours’ operation working for Dong Energy in a wide variety of conditions in the North Sea proved that the VLJ out-performs similar vessels using conventional propulsion systems.
The VLJ, launched at Seawork International last year, harnesses the best elements of two existing technologies, conventional screw propellers and water jets.
Mark said that at a Royal Institute of Naval Architects’ conference last year it was stated that bollard pull was high on the list of key propulsion system features for the design and construction of windfarm support vessels.
Operational data, he said, showed that the
“Not only does this reduce the possible damage to the docking structure but it also results in a safe transfer of crew.”
He said the results from out of water inspections of the VLJ were exceptional, despite the fact that the vessel had spent much of its time working in the sand of the Grimsby area.
“The inspections showed almost no marine growth, no measurable wear on bearings, no “blade” tip wear, no damage to the leading edge, and no corrosion,” said Mark.
“The nozzle, shaft, and rotor are manufactured in Duplex stainless steel and are designed to last the life of the vessel,” said Mark. “This only leaves the wear parts of seals, bearings and nozzle, and we are confident about their reliability.
“That means we can offer a 10 years’ spares package. It will enable operators to stores these parts on board to ensure maximum up time of the vessel.
“In fact while a conventional jet could achieve eight tonnes bollard pull, the VLJ could get to 12.5 tonnes at the same MCR.”
Mark said that on operability the VLJ not only provided a more comfortable and safer journey for its passengers, but was also able to operate in conditions that other vessels would have found impossible.
“The high bollard pull, coupled with low vibrations, keeps the boat comfortable and stable against the windmill in swells,” said Mark.
July 2016 |
www.dockyard-mag.com | p47
“It will also give them confidence that in normal operations the maintenance costs are relatively small.”
Below: Computational Fluid Dynamics showing the VLJ in static bollard pull condition. Red shows positive pressures (thrust), and blue shows negative pressures.
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