Dredger of the month: Vox Maxima

TSHDs Rotterdam and Vox Maxima. Credit: Van Oord

The launch of Van Oord’s TSHD Vox Máxima was a first for Katerina Kerr. She takes a look at the award winning vessel’s work history to date

Rewind the clock to 2010 and the newly delivered Vox Máxima had just started work on Maasvlakte 2 at the port of Rotterdam. With a hopper capacity of 31,200 m3, the trailing suction hopper dredger (TSHD) was one of the largest dredgers ever built in the Netherlands. Vox Máxima was designed and built by Royal IHC at its shipyard in Kinderdijk. The ship was one and a half times larger than the largest ship the yard had previously had on its slipway.

The biggest TSHD to be constructed at the Dutch yard before Vox Máxima had been Van Oord’s 1998-built Volvox Terranova with a hopper capacity of about 20,000 m3. When Vox Máxima was launched into water in 2009, there was less than half a metre of space left on either side of the construction hall doors, and it had not reached its final dimensions. The wheelhouse and deck were still to be installed. It remains the largest TSHD to be built by Royal IHC.

Its dimensions are quite impressive: the ship is 203 m long, 31 m wide, and has a deadweight of 564,000 tonnes. The two main engines have a power of 14,400 kW each.
Dredging is carried out with a 1.4 m diameter suction pipe, operated by three gantry cranes and winches on the starboard side of the ship.

According to Van Oord’s project manager Gerard Alkema, a second suction pipe is not necessary. He said at the time of the launch, “The reliability of these types of systems has improved a lot in recent years. We opted for one suction pipe, to reduce investment costs and because you get a higher efficiency from the total pump power.”

With a building period of more than two years after the first steel plate was cut in 2007, Vox Máxima was delivered to Van Oord on 21 January 2010. That same year, the vessel was awarded the Ship of the Year award at the fifth annual Maritime Awards Gala. Presented to IHC Dredgers, then part of IHC Merwede, now Royal IHC, judges noted its design and excellent transport capacity.

Designed in close co-operation with Van Oord, IHC Dredgers succeeded in creating a high-speed ship with a large hopper capacity and a full hull. It also contains several innovations, such as a single-suction tube with an underwater pump, and an ergonomic bridge layout.

Maasvlakte 2

After Vox Máxima was built, it departed to Rotterdam, where it was deployed on the Maasvlakte 2 port expansion project. As one of the most important ports in the world and the largest port in Europe, Rotterdam makes an important contribution to the Dutch economy. About 2,000 ha of land was to be reclaimed for the new port development.

Vox Máxima can dredge up to a depth of 70 m. When the vessel starts loading sand, the suction pipe is lowered with winches and dragged over the seabed next to the ship. To loosen the seabed, a draghead at the end of the suction pipe is equipped with jet water nozzles.

The vessel then sucks up the sand and water mixture through the pipe and transports it through a pipe system on deck to the hopper. An underwater pump, powered by a 6,000 kW electric motor, is fitted in the suction pipe. “An electric motor underwater is of course difficult. In this case, the electric motor is filled with oil to ensure that no water can flow in,” said Alkema.

The dredged sand can be unloaded from the vessel in three ways. The TSHD has 18 bottom doors, through which the sand can be released in one go. There is an option to pump the sand through a floating pipe to the shore, or to place it on shore via rainbowing.

Two 6,650 kW dredge pumps are installed to pump sediment ashore and for rainbowing operations. “The distance and speed with which the pumping ashore operations takes place depends on the type of sand,” explained Alkema. “In general, you can achieve discharge distances of up to about 3 km and the hopper will be empty within 70 minutes.”

Vox Maxima. Credit: Van Oord

Van Oord and Boskalis employees celebrated the completion of Maasvlakte 2’s 11 km-long seawall in July 2012, which Vox Máxima had spent weeks working on, along with a wide range of other dredgers and equipment. In total, 10 million m3 of sand was needed to fill the gap in the seawall, while 325 million m3 of sand was applied to the entire Maasvlakte 2 area. That is about as much sand as would be needed to fill 1,000 large football stadiums.

Closure of the seawall could only take place at dead tide, which occurs once every two weeks, as the difference between ebb and flow is at its smallest and the current through the gap in the seawall, the least strong. With a lot of current, the applied sand would be immediately sucked away again.

Maasvlakte 2 was an impressive first project for Vox Máxima, which has continued to be deployed on numerous large reclamation projects. Global warming is producing effects such as rising sea level, changing weather patterns, extreme weather conditions, soil subsidence, and endangered biodiversity.

Vox Máxima and other vessels in Van Oord’s fleet have been kept busy on sea-level mitigation and land reclamation projects. “We are rising to the challenge by taking the lead in partnerships that focus on developing such solutions, contributing to a better world for future generations,” said Van Oord in a White Paper – Accelerating Climate Initiatives – in 2019.

Future fleet

Van Oord has three TSHDs under construction. The first two, Vox Ariane and Vox Apolonia, will be delivered in 2021. The third vessel will be delivered in 2022. The new TSHDs will replace existing vessels and will fit in with Van Oord’s aim of making its fleet state of the art and more energy efficient.

Van Oord’s TSHD Vox Amalia successfully started its first project at the end of March in Den Helder, the Netherlands, where the vessel is reinforcing the coastline by placing more than 3.5 million m3 of sand in a deep trench just off the coast.

With a length of 158 m, a width of 36 m, and a load capacity of 18,000 m3, the Spanish-built vessel is used for land reclamation, construction or expansion of port infrastructure, and coastal reinforcement. It is part of Van Oord’s new generation of TSHDs that offer energy efficiency with the smallest possible carbon footprint. With a new generation of energy-efficient TSHD’s operational, let’s see what the future will bring.