PRODUCTIVE NEW CARGO DREDGER FOR UK

The £30 million (US$41m) investment by Southampton-based Cemex UK represents the state-of-the-art in sea-going, suction hopper dredger technology, and has been designed to draw sand and gravel from depths up to 55m around the British coast. Cargoes will be shipped to river and coastal terminals in the southern UK and on the near-continent, in the arduous, tide-governed business of maintaining year-round supplies of aggregate to the construction market.

Main contractor Damen Shipyards Group assigned the newbuild project to its Romanian division. The keel was laid at the Mangalia yard in October 2018, and the floated hull was transferred in August 2019 to the Galati complex for outfitting. Following trials in the Black Sea, the vessel departed Constanta towards the end of December last year, arriving at Damen Ship Repair in Amsterdam during early January for some final work.

Cemex Go Innovation is the first new ship to have been commissioned by Cemex UK for 22 years. Embodying the Damen MAD (Marine Aggregate Dredger) 3500 design, she offers a 20% capacity increase, as well as substantially greater dredge depth capability and offshore range relative to the 1990-built vessel that she is replacing.

Twin engines of the small-bore, medium-speed Wartsila 26 series, proven in demanding operating profiles such as those of coastal cargo dredgers, deliver the requisite redundancy as well as power. The installation has been prepared for integration of selective catalytic reduction (SCR) technology, so as to ensure Tier III NOx compliance while running on fuel oil.

Drive is through reduction gearboxes to controllable pitch propellers of the Wartsila 4D775 type, mounted in nozzles to maximise thrust. The arrangements should ensure laden speeds up to 12 knots from the licensed dredging areas.

Damen awarded the complete electrical outfitting and dredging automation systems to compatriot Alewijnse Marine which, in turn, selected the Italian company Marelli Motor to design and manufacture the bow thruster motors, each of which has a nominal power of 300kW at 690V/50Hz.

The trailing dredge pipe is deployed over the ship’s port side and the submersible dredge pump is direct-driven by a continuous electric motor, of the permanent magnet (PM) type, fitted at about midway in the pipe. Electric drive obviates the need for an intervening gearbox and the air-filled motor is more compact, lighter and more efficient than the asynchronous, oil-filled alternative. Controlled by water-cooled AFE (active front end) drive, the motor was developed by Damen Dredging Equipment in cooperation with Marotechniek.

In addition to the dredger’s pivotal requirement for a powerful pump to draw sand and gravel from the seabed, slurry pumps are need to return the excess water back to the sea. The latter must be capable of ensuring reliability and availability while handling the abrasive fluids. For the Cemex newbuild, the company specified two SlurryPro centrifugal pumps designed and manufactured by the UK firm Atlantic Pumps of Derbyshire.

All dredge piping is arranged above deck, enhancing safety by obviating the flooding risks associated with fracturing and holing of inboard pipes resulting from the handling over time of the abrasive seabed material.

The screening plant differs from that of previous generations of ‘sand suckers’, which typically use two separate, rotatable towers. With wear and tear on all components in contact with aggregate being a fact of life, the re-designed, fixed installation is intended to last through flow direction optimisation, added wall thickness, and rubber-lined elements in the loading chutes. The screen surface area as a whole has been much increased, improving delivered cargo quality and reducing loading time.

Dry discharge is effected by the ship’s own grab-type unloader machine, at rates up to 20% greater than throughputs achieved with existing vessels.

In parallel with the newbuild investment, Cemex UK has ploughed £1.8 million (US$2.5m) into the modernisation and expansion of its wharf at Shoreham, on the southern English coast. The length of the Cemex Go Innovation is the maximum for access through the sea lock at Shoreham. Furthermore, a new dry discharge system has been brought on stream at Northfleet Wharf in Kent, one of Cemex UK’s three Thames-side facilities at a cost of £3.8 million (US$5.2m).

The MAD 3500 design was also chosen by another leading UK operator, Hanson Marine, for its 2020-built Hanson Thames.

PRINCIPAL PARTICULARS – Cemex Go Innovation