Going forward in reverse

Elaine Maslin reports on a new breed of service and operations vessels entering the market, which can go ahead and aft just as happily as they entered.

Ulstein’s Windea La Cour, a new 88m-long service operation vessel, during sea trials. Photos from Ulstein.

“It can go backwards at 12 knots,” is not a claim you hear often about an offshore vessel. And yet, it might be something we soon hear more.

It’s the speed achieved during sea trials by Ulstein’s latest SX175 design, Windea La Cour, an 88m-long service operation vessel (SOV) for offshore wind farms. It’s the first Ulstein vessel to sport both the firm’s unique X-Bow design, but also an X-Stern.

Its ability to go “backwards” is no mistake. The design makes it suited to working close to offshore wind farm structures, whichever way it is headed and the weather is coming from.

The vessel’s genesis comes partly from Ulstein’s work for the offshore sector, for which it initially had the idea to have platform supply vessels with an X-Bow and X-Stern. But, it’s also been very much influenced by detailed work designing a dedicated SOV for the wind industry and a sign of Ulstein’s philosophy that more offshore wind farm work could be done by monohull vessels, including foundation installation.

“We feel that for installation work, especially for the foundations, the most effective tool is a floating platform and this is actually already been proven by Seaway Heavy Lifting, which has successfully installed many turbine foundations and transition pieces from their floating vessels,” says Edwin van Leeuwen, product director, Ulstein Design & Solutions. “It makes installation faster as it is less restricted by jacking operations. Then, it can make sense to install the nacelle and turbine blades from a jackup, as it has more precision high up.”

In fact, Ulstein’s SOV development stems back to work conducted on the Windlifter design monohull DP (dynamic positioning) installation vessel. At the time, the market wasn’t ready for such a concept, but the idea sparked an interest with UK firm SeaEnergy and later on resulted in work in developing a dedicated SOV, which then triggered Siemens, a big player in the wind market.

Ulstein’s ideas exceeded Siemens’ initial concept requirements. “That was the first time so much effort was put into a dedicated offshore wind SOV design together with a client,” says Nick Wessels, marketing and sales manager, Ulstein Design & Solutions. “We had changed their mindset and it opened up the possibilities.”

The first of two SX175 units being built, the Windea La Cour, was delivered on 23 June 2016. The vessel then sailed out for its first service campaign on 1 September to work on the massive, 150-turbine Gemini offshore wind park, which is being built 85km off the Netherlands, on contract to Siemens. The second vessel, due in 2017, will work on the Sandbank and Dan Tysk wind farms, also for Siemens.

Windea La Cour has accommodations for 60 people in single cabins, with 40 dedicated to technicians, a motion-compensated gangway system and a 10-person daughter craft for transferal to wind turbines.

“The X-Stern also allows us to have the gangway on the starboard instead of the center line and allows better outreach. You can have either the stern or bow heading into the weather. We also found the motion pitch behavior was improved by doing this,” van Leeuwen says.

It’s not Ulstein’s first SOV, however. An X-bow designed vessel, the Siem Moxie, was delivered to Siem Offshore Contractors in 2014, with a string of new features, including propulsion and hull system choice, a new type of crane and cable-lay support capability.

But, Ulstein has also been eyeing the offshore wind installation market, as they have a large background in developing offshore heavy lift installation vessels. The firm came up with the already mentioned Windlifter design, a vessel to carry multiple entire turbine top sections – complete with nacelle and blades – for installation in one piece. More recently, Ulstein started working on jackup designs including a heavy lift jackup able to lift 1500-1800-tonne, both jacked up and while afloat.

Ulstein’s van Leeuwen says the firm is looking at a completely new design, together with a client, for installing wind turbine foundations, which may or may not be a jackup.

“Given the trend in the industry for even bigger wind turbines, larger installation units will be required or different installation methodologies,” van Leeuwen says.

Beside specialized vessel designs, Ulstein is also very active in the design and supply of handling tools via its subsidiary Ulstein Equipment. In 2011-12, they developed the industry’s largest pile gripper frames (PGF), used at two different jackups and with one back in use again today on a third jackup. The foldable PGF design from Ulstein allows the installation of monopiles and transition pieces from a jackup vessel to be performed in a single jackup cycle, hence reducing the number of jackup cycles and the risk involved in these operations. Ulstein is of course considering if the system can be used on a DP vessel as well, for which it has to be motion compensated.

To complete the portfolio of offshore wind installation handling tools, Ulstein delivers pile upending tools and recently designed and built a complete new flange lifting tool for transition piece lifting. Being a complete mechanical system, securing and releasing from a transition piece is just a matter of using a simple mechanism. The simpler, the better is the general opinion at Ulstein Equipment.

A new concept is also emerging – Ulstein Colibri, a system that can be added on to existing cranes as a retrofit, to compensate crane motions to keep the load on the hook stationary. “It’s not heave compensation, but motion compensation,” Wessels says. Instead of compensating the entire crane, this system only compensates the movement of the crane tip, so it only has to deal with the load hanging off it. A prototype is being developed as we speak.

With the offshore wind industry further developing, Ulstein launched a new cable-lay vessel idea, as it thinks there will be a need for cable-lay capacity. They came up with something new for the market – a unit with the biggest capacity for a single length cable in one vessel. But OE will have to look at that another day.