Waterjets For Ctvs: debunking the myths

With more and more wind farms in Europe, Asia, and now here in the United States, a steady stream of Crew Transfer Vessels (CTVs) will be needed to support their construction, maintenance, and operation. Typically aluminum catamarans, these vessels are deployed to ferry personnel and light equipment to and from offshore wind farms on a daily basis.

While a good portion of CTVs in the established offshore wind market in Europe are powered by water jets, Adam Mills, Sales Manager at Marine Jet Power, says there are still many misconceptions about the waterjet solution. propulsion circulating in the industry.

A common myth, Mills says, is that water jets don’t work well on the high seas or in extreme wind and tide conditions. “Our water jets perform exceptionally well in harsh conditions,” he says.

“There are more than 60 CTVs equipped with MJP water jets; we understand the industry and the mission of ships. – Adam Mills, Sales Manager at Marine Jet Power. (Photo: Marine Jet Power)

CTVs operating on the high seas often encounter turbulent, ever-changing sea conditions that subject the vessel to all six ship motions, but it’s primarily pitch, roll and heave that affect the propulsion system, Mills says. “The effect of these movements only becomes of concern if the vessel has a shallow hull, a shallow draft and operates at extremely high speeds where air can be drawn into the water intakes,” says- he. “In our 35 years of experience, it is extremely rare for this to become a concern. On a vessel operating at CTV transit speeds in extreme conditions, the waterjet water intake remains comfortably deep enough to ensure the pump is properly primed and an unaerated laminar flow of water is ingested .

Mills adds that MJP’s efficient pump design and steering system provide high thrust and maneuverability, ensuring the vessel stays on course in extreme conditions. “This is especially important when approaching the turbine in rough seas to transfer the crew,” Mills notes. “The water jets operate independently, allowing true glide motion of the vessel, between bucket and steering nozzle. The operator has precise 360 ​​degree maneuverability. With water jets installed, a vessel can rotate 360 degrees along its own boat length.For CTVs in prevailing wind conditions, this makes crew transfer much more precise and safer.

(Photo: Marine Jet Power)

While the initial cost of purchasing waterjets can often seem higher than fixed propeller options, Mills says CTV owners and operators should consider the full life cycle cost when evaluating their propulsion options. “In general, water jets do not overload the engine in different sea states and loading conditions like conventional propellers. Therefore, with a hydrojet vessel, you won’t need to replace your engines,” he says.

According to Mills, users of MJP waterjets will experience very low annual service costs due to their duplex stainless steel construction and the company’s standard five-year warranty. “You can run our waterjets for 5,000 hours in the first year and only the anodes and oil filter will need to be replaced. Now life cycle costs are starting to look a lot more attractive in favor of waterjets. »

Mills says MJP’s “highly efficient” mixed-flow pump design and duplex stainless steel construction gives an extra boost in efficiency that not only translates into fuel savings, but time savings as well. “Transit times can be reduced, which means more time to service and maintain wind turbines.”

Improved efficiency thanks to mixed flow: The impeller diameter is larger than the inlet diameter. Therefore, as the flow comes in, the water wraps radially around the pump, causing radial flow and axial flow, creating mixed flow. “At high speeds, the efficiency is much higher,” says Mills. “Because, like a centrifugal pump, mixed flow more efficiently manages the flows entering the pump. This results in a more efficient water jet, either operating with less energy or saving fuel. (Photo: Marine Jet Power)

Additionally, Mills says MJP recently expanded its X-Series waterjet line to offer sizes up to 500X/2070kW, meaning builders can benefit from an approved waterjet of higher class which is a one-piece bolted or welded installation. “The X-Series waterjets are very easy to install, shipped in one piece and installed in one piece, significantly reducing the man-hours needed to complete the vessel. This has been done through extensive research and feedback from builders around the world.

Crew comfort
Mills says another common myth about water jets is that they reduce captain and crew comfort, but he notes that MJP’s recently launched Dynamic Positioning (DP) system for its control solution JetMaster 3 electronics was created with CTV operations in mind. “There are more than 60 CTVs equipped with MJP water jets; we understand the industry and the mission of the ships,” says Mills.

The Adaptive DP system has four modes of operation and is designed to make stationkeeping in prevailing wind and tide conditions comfortable for out and about vessels. “Our DP system is designed so that once the maintenance crew has been safely transferred to the turbine, the captain can step away from the helm with confidence that the vessel will stay in station and maintain course. while waiting for the crew to complete their maintenance work on the turbine, sometimes for several hours.The DP system therefore helps to reduce captain fatigue while saving fuel as it applies precise control when needed .

Rhoscolyn Head’, a 15m fast wind farm service catamaran fitted with twin MJP UltraJets, built by South Boats for Turbine Transfers Ltd. (Photo: Marine Jet Power)

It’s common for people to believe that jets of water can be harmful to marine mammals and other forms of sea life, but Mills says that’s simply not the case. “When it comes to protecting wildlife, water jets are the best propulsion solution as they have intake grilles and all rotating parts inside the vessel and above the bottom of the hull “, he says. “That’s why water jets are often the preferred solution when operating in areas where marine life is prevalent and protected, and also when a vessels operation is picking up personnel from surrounding waters, such as boats diving and search and rescue vessels.

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