Floating Storage Unit Turns Into Self-Propelled Barge

Brokers are the invisible and often-criticised participants in the marine industry. However, there is no doubt that in this project, bringing together a Nigerian customer, an unused French oil barge and a Dutch shipyard, the broker was instrumental.

It was the Kamar Shipping Group who brought all parties to the table to enable this remarkable transformation, resulting in a ship corresponding exactly with the requirements of the customers.

The non-self-propelled barge Limosa II was initially conceived for the state of France. Its principle goal was to provide a floating buffer capacity for fuel oil which could be used in the case of war. Since its construction in 2006, the barge had been filled only once or twice and hardly moved from the dock. For strategic planning reasons, the barge became redundant and was available on the market.

Transport solution

The opportunity was on the radar of Kamar Shipping Group, a Dutch shipping company with over 30 years of experience in inland shipping, predominantly in ownership of barges, shipbuilding, brokerage, bulk storage and transport. One of their customers was searching for a solution to transport oil from inland to the sea through the Nigerian river delta. A high load capacity with limited outside dimensions was required. Furthermore the barge should be able to run downstream fully loaded and upstream as efficiently as possible, while taking into account the shallow water in some parts of the river. A pushboat and barge combination would seem the obvious choice, but this is unsuitable for the coastal waters where the cargo needs to be delivered.

The answer was found in the modification of a 2006-built barge to a self-propelled barge. For this task, Kamar contacted Trico, a Rotterdam-based shipyard with extensive experience in shipbuilding for inland shipping which has proven not to shy away from innovative concepts. Recent Trico deliveries include notable vessels such as the hybrid-powered Duandra and the LNG-propelled Argonon.

Unique propulsion system

As it is impossible to fit in a conventional shaft-line propulsion installation into a barge without major changes to the aft ship (including deep propeller tunnels), the choice for a diesel-electric propulsion installation was almost self-evident.

But the combination of shallow water leading to a minimum of water under the keel when the vessel is loaded and the requirement not to ballast the ship for the empty return trip led to a very unique propulsion installation, a world-first according to the shipyard.

The electric power generated by three Caterpillar C18 gensets in the engine room is distributed to three azimuthing thrusters, each of them housed in a steel box on the transom. These steel boxes can be raised or lowered, as they slide on a rail system. On either side of each box, a winch moves the box up or down by driving a steel chain. This movement can even be done while the vessel is making headway.

Electric outboards

The whole arrangement can best be visualised as three electrically-powered outboard engines which can be vertically raised or lowered, but obviously in a size and horsepower rating never seen in outboard engines. Besides providing adequate propulsion power in two extremely different sailing conditions, there are some other advantages to the set-up. There is of course the redundancy: even if one of the pods would be out of service, there are still two to do the job. Then there is the efficiency: in light-loaded condition, sometimes one or two pods will be sufficient. The units not in use can be raised out of the water and do not cause any drag. Last but not least, there is a very high degree of manoeuvrability provided. Each of the units contains an azimuthing thruster, type V-Pod from Verhaar Omega, which can provide thrust in any direction. Each of the V-pods has a rating of 400 kW.

Flexible hoses on top of each of the boxes guide the power cables from the inboard variable frequency drives used for speed control of the thrusters to the thruster motors in V-Pods. The electric motor of the pod does not need any external cooling, as it is housed in the pod of the thruster under water. The cooling for the generator and AC installation is by means of boxcoolers which were created on the sides of the engine room, along the newly created fuel tanks. Given the high seawater temperature of 30 degrees in the Niger Delta, the boxcoolers were dimensioned significantly larger than would be the case for ships built for the Northern European market.

Deckhouse

During the build, the aftmost cofferdam was moved four metres forward. The removal of the aft ballast tanks created the space needed for the engine room and a tween deck above. Above the main deck, a deckhouse was created with accommodation for the crew of six, along with a wheelhouse. As the Limosa II will encounter some low bridges on her regular sailing route, the wheelhouse is built on a hydraulic pedestal and can be lowered into a recess provided in the centre of the deckhouse.

As the ship will sail in coastal waters, which can involve sailing in waves, cables and lashing points are provided to fix the wheelhouse firmly in position when raised. Given the tropical sailing area, an air-conditioning installation for the accommodation was indispensable.

Modifications

While the original towing oil barge was already built under BV class, the conversion required a significant amount of drawings to be reapproved, both to qualify as a self-propelled inland vessel and to extend the sailing area to coastal areas.

To provide safety at sea, a central walkway was built and placed on the deck. The bowrudder was removed and a bowthruster of the channel type was installed in a purpose-built gondola on the bow. This diesel-driven thruster sucks water from below the bottom and ejects it into a rotatable steering grid, making it possible to give thrust in any direction. The bow thruster was also supplied by Verhaar Omega. Further modifications done by Trico Shipyard include the supply and installation of a 2,000 kilogramme SWL cargo hose crane from Van Wijk.

Large undertaking

For the shipyard, which has ample experience both with shiprepair work and new construction, this was a larger undertaking than any previous job. The typical outfitting of inland ships on hulls built in the Far East takes only one a third of the working hours spent on the conversion of Limosa II.

Nevertheless, John van de Wijgaart, one of the three entrepreneurs behind Trico Shipyard, believes that the conversion was more effective both in terms of costs and delivery time than a complete newbuilding for the same purpose.

The outfitting quay in Rotterdam is brimming with activity. To compensate for the fluctuations in the inland shipping market, the company has now also placed its focus on seagoing vessels, in particular for the offshore market. An example of this is lying at the outfitting quay already: a seismic research support vessel under construction for a Dutch ship owner.

Bruno Bouckaert