It's MAD world!

Although marine aggregates are increasingly in demand given the scarcity of land-based resources, the marine aggregates dredging fleet worldwide is largely an aging one, with a significant portion of vessels over 30 years old.

With its decades of experience building dredgers of all types, Damen decided to explore the aggregates market to see if it could develop a tailor-made, future-proof dredger series, specifically for this sector.

Olivier Marcus, Product Director Dredging, comments: “The marine aggregates business is served by a very old fleet, particularly in the UK. For many years Damen’s repair yards in the Netherlands have been performing the maintenance on these dredgers, so we have the expertise needed to build a new generation of vessels that are optimised for the marine aggregates market. We set out to make a dredger that is safer, more efficient and sustainable, and indeed, vessels that offer the lowest cost per tonne of dredged material.”

A stable platform, even in the harshest weather conditions

Crucially, the Damen Dredging team looked to the Group’s Offshore Vessels for their design inspiration, given their renowned seakeeping behaviour and ability to handle heavy sea states – a vital requirement given the offshore sand mining concessions the aggregates dredgers have to serve. It was vital that the new dredger design had to provide a very stable platform in poor weather conditions. An optimised hull design and the enclosed bow shape ensures that these vessels can operate in harsh weather, and protect the sand and gravel from green water ingress.

Damen also teamed up with Cemex UK, one of the leading marine aggregates suppliers in Europe, and Cemex became the launching customer for the first Damen Marine Aggregate Dredger (MAD) 3500. The ‘Cemex Go Innovation’ successfully entered service in April 2021. Damen Product Group Design & Proposal Engineer, Frank de Hoogh, says: “Cemex was very familiar with our dredging installations such as our trailing suction pipes. We worked closely together to further optimise the MAD concept for the British marine aggregates market.”

The MAD 3500 has been tailored to achieve the optimum balance between payload and efficiency. They are also made of higher tensile steel, making them stronger and lighter, which in turn enables them to carry as much cargo as possible. Equipped with a 700 millimeters trailing pipe system, the hopper dredger is designed for mining marine aggregates in the North Sea and English Channel at -55 metres below sea level.

Working with leading UK operators

And in further fine-tuning for the UK market the new Cemex dredger was adapted so it can operate within the limited dimensions required for the vessel to traverse Shoreham Lock on the south coast of England. Cemex Go Innovation is designed to fit the lock perfectly, and at 103 metres long and 16.4 metres wide, there is only 50 centimeters clearance either side and the lock is approximately 10 metres longer than the vessel itself.

Future-proof engines

The MAD vessels also feature future-proof Tier III engines and they are fully compliant with the latest IMO regulations and prepared for SCR units. In an industry first, Damen has introduced a Permanent Magnet e-motor, making them much more compact, lighter and efficient when compared to conventional vessels. The submersed Damen dredge pump is directly driven by an electric motor, without a gearbox in between. Moreover, the electric motor forms an integral part of the trailing pipe structure.

The order for the Cemex MAD 3500 was swiftly followed by an order for another one, and again for a leading aggregates operator – Hanson. The MAD 3500 'Hanson Thames' was delivered to the owner at the end of November.

Fixed screening installation

Several key features have been introduced to maximise efficiency. Damen has developed an innovative, fixed screening installation, which ultimately leads to a better quality load, representing significant savings for the operator. Mooring is carried out by spud poles rather than lines, which gives customers the flexibility to offload anywhere, even without the need of a quay.

Autonomous operations

Easy maintenance is another important consideration. The winches of the suction pipe are under the deck and the tower is modular, therefore it can be taken apart and replaced with a spare so the crew does not have to risk working at height when performing regular maintenance duties. This also significantly reduces downtime due to maintenance.

As well as this, the new MAD is designed with the environment in mind. Traditionally, older dredgers discharge the unusable material over the side. However, in the MAD series, all the discharge takes place through the bottom of the ship. This eliminates the large plumes that would normally occur.

MAD 3500 & 6400

In addition to the MAD 3500, we have launched the MAD 6400. This vessel can dredge up to 60 metres depth and has a hopper capacity of 5,600 m3 and a trailing suction hopper pipe of 750 millimeters.

Olivier and Frank emphasise: “The MAD 3500 has lived up to all the industry’s expectations and even exceeded them. Its seakeeping behaviour is exemplary and the quality of the cargo load is excellent. And importantly these new dredgers will enable our customers to increase their annual production substantially. These are complex vessels, but by working closely with our customers and listening to their requirements, we have designed a marine aggregates dredger that is ideal for the decades to come.”