CARGO DREDGER FOR DUTCH FLEET
Dutch expertise in dredge technology and construction has a new reference in the 106-metre trailing suction hopper dredger Anchorage, built for the coastal marine aggregate trade, writes David Tinsley.
A product of the expansion-minded shipbuilding and repair group Thecla Bodewes Shipyards, the 6,300dwt Anchorage has been purpose-designed to extract, transport and self-discharge sand and gravel to North European terminals serving the building industry. The vessel employs a diesel-electric power and propulsion system and is equipped to draw aggregate from depths up to 60 metres.
She was originally ordered in 2017 from Barkmeijer Stroobos as the first of two ‘trailers’ for Hanson Marine of the UK, but the contract was annulled after the shipbuilding company’s bankruptcy in October 2018. Thecla Bodewes subsequently took over the Stroobos yard and the dredger newbuilds, and the nascent lead vessel was sold to Dutch building materials supplier De Hoop Terneuzen.
Following April 2019 launching from the Barkmeijer premises on the northern Netherlands inland waterway system at Stroobos, the hull of the Anchorage was towed to the Thecla Bodewes yard at Harlingen, where installation of all engine room and dredging equipment, electrical work and final outfitting was undertaken. While the group’s yards at Harlingen, Kampen and Meppel trade under the Thecla Bodewes name, Stroobos continues its activities as Barkmeijer Shipyards.
An extensive study of ports and berths on the north Continent and in the UK determined the main parameters for the vessel type, so as to maximise operational flexibility, with Groningen-based Conoship International providing input on hull design and stability calculations. The freeboard is comparatively large for a dredger, given operation in open seas, and powering for a fully-laden speed of 14 knots reduces transit times between the deeper offshore concessions and the discharge ports.
The trailing suction dredging pipe, deployed from the starboard side, incorporates a submersible pump at its bottom end, drawing sand and gravel up into the single hopper hold through an adjustable screen. During the trip to the receiving terminal, the water is removed from the aggregate cargo, so that dry discharge can be effected using a conveyor system.
Both the conveyor belts and the unloader carriage are electrically-driven by frequency controllers, and the arrangements provide for an average discharge rate of 1,200m3 per hour. Rapidity of port turnarounds and the complete round-voyage cycle is a vital factor in the marine aggregates business.
The diesel-electric powering and propulsion system was developed in close cooperation between Barkmeijer Shipyards and the Ridderkerk firm D&A Electric, to provide efficient regulation of energy supply for sailing, dredging and unloading. The scope of the latter’s supply featured the proprietary Eprop frequency-controlled power train and dynamic power management system.
The plant is based on three generators driven by Mitsubishi SU-series medium-speed diesels. Two of the sets are rated at 2,550kW and one is of 1,275kW, and the installation allows for one, two or all three to be run in accordance with energy requirements at any stage in the operating profile. This allows usage and individual genset loading in the most efficient manner.
For control and monitoring of the dredging process and shipboard systems, Barkmeijer collaborated with Alewijnse Marine in the development of an ‘intelligent’ and integrated automation package. As well as achieving the requisite dredging performance, the arrangements ensure that only seven or eight crew members are required at any one time to sail, load and unload and maintain the ship.
PRINCIPAL PARTICULARS - Anchorage
Dredging depth, maximum
Dredge pump power
Main diesel genset power
2 x 2,550kW + 1 x 1,275kW
Main propulsion thrusters
2 x 2,100kW
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