Productivity and sustainability in an era of rising demand

While dredging is often seen as a dirty and unattractive business, it plays a vital role in keeping ports and waterways around the world open for commerce, transport and recreation.

Every year, billions of tonnes of sediment are carried down rivers and along coastlines where they settle onto sea and river beds, reducing depth and hindering access.

Once a simple fact of life requiring occasional maintenance dredging by water and port authorities, global warming and the resulting additional rainfall is now increasingly making it a serious problem in many harbours and terminals.

For some, the removal of that sediment has become a near continuous process with the attendant inconvenience and costs that go with it. Growing populations and increasing soil loss as more land is given over to agriculture only serve to accelerate this process even further. Meanwhile, rising sea levels bring additional demands for maintenance dredging as well as action to protect vulnerable coastlines.

The result of this perfect storm is that demand for dredging solutions has never been higher. Damen Shipyards is taking a lead in the development of sustainable solutions that meet the needs of today’s owners and operators.

Sustainability is a word that is hard to escape these days, but it lies at the core of everything that Damen does because it makes sense economically as well as societally and environmentally.

The past year has seen a notable number of advances in Damen’s ongoing dredger development programme. In December 2020, the first of Damen’s Marine Aggregate Dredger (MAD) 3500 class was handed over to its owner following successful trials in the Black Sea.

The vessel is the first of a new generation of efficient and economical dredgers specialising in the extraction of sand and gravel from the seabed. Designed to mine at depths of up to 55 metres it has a capacity of 3,500m3.

The MAD concept as a whole has been designed around the need for 21st century vessels that can deliver sustainability, safety, efficiency and maximum crew comfort.

The award of Lloyd’s Register’s ECO Notation was achieved through a range of methods that include the fitting of exceptionally effective silencers, the use of biodegradable oil in all the hydraulics and a highly efficient propulsion system to minimise fuel consumption and emissions.

A second Damen MAD 3500 is currently in build at Damen Shipyards Galati, Romania.

Summer 2020 saw Damen’s commitment to the shift to electricity extend to dredging with the unveiling its first Electric Cutter Suction Dredger, the ECSD 650. Ideal for operations in urban and environmentally-sensitive settings, the electrical power also provides a significant reduction in noise compared to diesel engines .

The new class is an adaptation of the conventional CSD 650. As modular vessels, both can be broken down into containerised components for transportation and subsequent reassembly on-site. The difference is that in the ECSD 650 the standard diesel engines have been exchanged for electrical engines and the void in the aft starboard side pontoon has been repurposed to host the electrical control centre.

The dredger’s electrical system is easily maintained without the need for special crew training and the associated reduction in vibrations during dredging ensures a more comfortable experience for the crew.

The dredging team at Damen is well aware that dredging close to inhabited and other sensitive areas can not only generate a range of unwelcome chemical emissions, but also excess noise from the operation of the dredge pumps.

To address this issue, they have developed a new generation of electrical submersible dredge pumps (EDOP) that are both clean and quiet, using the latest in compact electric motors and frequency converters. These advances combined with Damen’s policy of standardising components have minimised costs and optimised the designs, such that they deliver a 93% drive efficiency.

As well as being quick and straightforward to connect to a power supply such as a genset, the EDOP dredge pumps are also easier to maintain than their hydraulic equivalents.

Alongside these innovations, Damen’s new sustainable TSHD designs announced in 2019 have been attracting plenty of interest. The design focus is to create the optimal dredger for maintenance dredging of ports and channels.

The five Port Maintenance models; the TSHD650, TSHD900, TSHD1500, TSHD2000 and TSHD 2500 are compact yet highly efficient and cost-effective vessels with excellent manoeuvrability thanks to their twin azimuth plus bow thruster propulsion systems.

Hopper capacity is up to 2500 m3. Nearly all maintenance can be done afloat and options include IMO Tier III compliance and diesel-electric power plants. The Multi-Purpose range offers hopper capacities from 2000 to 5000 m3 across four models down to a depth of 30 metres and are ideal for maintenance works in larger ports and channels, as well as capital dredging.

All the vessels in the Damen dredging portfolio are designed and built with the sustainability requirements of both today and the future firmly in mind, but competitive pricing and minimisation of operating costs are also continuously reviewed.

Digitalisation and the use of remote monitoring to drive preventative maintenance all help to maximise performance and minimise downtime.