Third generation work vessel for HvS

Maritime Journal has been privileged to follow the fortunes of HvS for many years and reported on each new vessel since 2003. Thanks to the foresight of the owner, Arjan van Stee, the family firm has introduced new and innovative vessels, timed to ‘stay ahead of the game’ when the demands of the marine construction and dredging industries are changing.

That approach resulted in the introduction of Zwerver II, a powerful triple-screw Damen ‘Multicat’ in 2003, with massive lifting power, bollard pull, and increased versatility. In 2007 a new Zwerver I was constructed by Scheepswerf Gebr. Kooiman BV of Zwijndrecht. This was a similar but slightly larger triple-screw vessel intended to combine a shallow draft with massive buoyancy for lifting and transportation, good sea-keeping qualities and a better than average towing capability. When the order for another new vessel from Kooiman was announced for delivery in November 2011, there was no doubt that a great deal of research would have gone into this ‘third generation’ of HvS work vessel.

Named Zwerver III, this latest addition to the HvS fleet has been designed, unsurprisingly, with wind farm and other renewable energy projects very much in mind. Many of the requirements demanded by the renewable energy market have been addressed, including general support for the installation of turbines and floating objects, anchorhandling, towing, cable laying support, survey, diving and ROV operation. In order to meet those requirements, many of which demand excellent manoeuvrability and station keeping, a highly innovative propulsion system has been adopted along with a DP-1 Dynamic Positioning system. At first sight this smart new vessel differs little from the many multipurpose work vessels being delivered at present but a closer examination reveals quite a different creature ‘beneath the skin’.

The pontoon style hull is larger than its predecessors with an overall length of 35.10m, a moulded breadth of 15.00m, a depth (half loaded) of 4.07m and a minimum and maximum draft of 2.7m and 3.00m. In plan view the hull is virtually rectangular, with heavily radiused corners and fendering extending aft to protect the forward shoulders. Two substantial push knees, extending well below the surface, are part of the structure and also house two transverse bow thrusters. The hull design aft ensures an adequate water-flow to the triple screw propulsion system and a shallow rise in the bottom plating towards the bow is intended to enhance the vessel’s sea-keeping characteristics.

Zwerver III has an open bow equipped with a massive full width roller of 2.0m in diameter and with a safe working load (SWL) of 250 tons. A unique feature is the hydraulically operated bow door, which is flush with the deck when stowed and rises to form a substantial 1.0m high bulwark to avoid ingress of water on deck when underway. During trials, the decks stayed dry and the door was reported to be a real benefit in rough seas. The open stern also has a centrally located roller of 1.3m diameter, 4m wide and 250 tons SWL, for use during towing operations.

An impressive inventory of high powered deck machinery illustrates the importance placed on towing and heavy duty anchorhandling. Two, single drum, Kraaijeveld winches are installed for towing and anchorhandling, both on the vessel’s centreline. The two winches are housed in a single integral structure, designed in cooperation with Kooiman, which also incorporates the pedestal for the aft crane. The towing drum has a line pull of 100 tons, a maximum brake holding load of 200 tons, and can accommodate a 1,000m steel wire towline of 48mm diameter. A similar drum for anchorhandling has a line pull of 200 tons and a brake load capacity of 250 tons. The work wire for anchorhandling is 1,000m in length and a diameter of 64mm. Both winches can be controlled remotely from the wheelhouse.

Line handling is simplified by the installation of two hydraulically operated guide pins of 150 tons SWL, one set of towing pins and a line handling fork of 200 tons SWL located adjacent to the forward roller. A similar installation is provided aft, forward of the stern roller. Three Brevini tugger winches are installed, each with a 15 ton line pull and 100m of 22mm diameter wire.

Zwerver III also has two identical hydraulic deck cranes, one mounted on a pedestal on the port bow and the other above the towing winch. The cranes chosen are HS Marine Cranes, model AKC-370 HE3, capable of lifting 10 tons at an outreach 20m. Both cranes are controlled remotely from the wheelhouse or portable consoles.

In spite of the impressive outfit of deck machinery, there is 300 sq/m of deck space for cargo and equipment and flush twist-lock fittings for securing containers. Other hull features include a 1.0m diameter ‘Moonpool’ and two 600mm diameter ‘Spud’ holes.

Provision has been made to fit an ‘Ampelmann’ personnel transfer system, that actively compensates for all vessel motions, should it be required. This would enable Zwerver III to act as a transfer vessel on site, taking advantage of its DP-1 system and adequate deck space to safely deliver personnel during construction and maintenance work.

At the very heart of this new vessel is the highly innovative propulsion system. Three Mitsubishi S12R-MPTK main engines, generating a total of 2,820 kW (3,782 bhp) drive two conventional propellers and one HRP thruster unit via three Reintjes WAF 665 gearboxes. The HRP model WM-6111 thruster, located on the centreline, is fully steerable and incorporates a 1,750mm diameter propeller and its associated nozzle. The conventional propellers are positioned on either side. Each propeller is 2,000mm diameter and has five fixed pitch ‘skewed’ blades rotating within a fixed nozzle. A twin rudder system is installed aft of each nozzle, with controls enabling the rudders to be controlled in unison or independently. In addition, two HRP 3001 TT transverse thrusters are mounted in the bow, one below each push knee.

On trials this unique propulsion system gave Zwerver III a bollard pull ahead of 56.8 tons, 40.8 tons astern and a maximum speed of 11.2 knots, which in the words of Arjan van Stee “were very comfortable and good results with a draft of only 2.7m. The vessel was sailing much better than expected, tests such as ‘crash stop’ and steering were amazing, with the vessel turning around and stopping in its own ships length. We hoped that the vessel would manoeuvre easier than the smaller multi-purpose support vessels and it really did. Even without the use of bowthruster(s), it was turning and manoeuvring very well.”

Electrical power aboard Zwerver III is supplied at 230/400 volts by two Mitsubishi 6D16T 120kVA auxiliary generators, one of which is fitted with an acoustic housing. Two Mitsubishi S6R MPTA - 570kW diesels drive the necessary pumps required to power the vessel’s hydraulic systems and deck machinery.

Integral tanks can accommodate 260 cu/m of fuel oil, 50 cu/m of fresh water, 8 cu/m of lubricating oil and hydraulic oil, 9 cu/m of dirty oil, 22 cu/m of grey water and 21 cu/m of water ballast. Provision is made to transfer fuel and water to other vessels or plant via high rate discharge pumps at 50 cu/m per hour.

In keeping with previous HvS vessels, the wheelhouse has been optimised to enable almost every aspect of work on deck and around the vessel to be clearly visible. The comprehensive array of engine and propulsion controls is more complex than usual, by the very nature of the vessel’s unique propulsion system. Matters are simplified enormously by the installation of an Alphatron/Navis DP-1 integrated control system, enabling precise ‘single lever’ control and accurate position keeping.

A navigational and communications package installed includes two JRC JMA 5300 Mk 2 ARPA radars; two Alpha Minicourse Gyro compasses; and three DGPS systems; a Veripos LID3-G1, a Saab DGPS-R4, and a Saab DGPS?AIS R4. The autopilot facility is provided by the DP-1 system and the charting system is an Alphachart T ECDIS (Transas). JRC equipment has also been chosen for the echosounder, speedlog and Navtex. All of the communications equipment is from Sailor, including two Immarsat-C Sailor 6110+LRIT.

Comfortable air conditioned accommodation has been provided for up to twelve persons in seven cabins. All of the normal facilities are available, including a galley, mess room, sanitary spaces and an office.

At the time of writing, final trials and commissioning were taking place prior to Zwerver III entering service. Commenting on the vessel’s performance, Arjan van Stee said, “We are very happy with the complete vessel, which is largely due to Scheepswerf Gebr. Kooiman BV, who were responsible for the engineering and construction. They carried out a wonderful job and created a vessel, which is unique in the market and equipped for maximum versatility on today’s marine and offshore projects. She will be excellent for the renewable energy market and the offshore market.”