The Van der Velden® FLEX Tunnel – a valued solution for inland navigation
4 January 2019
The German shipping company Rhenus PartnerShip was the first company to install the Van der Velden® FLEX tunnel in 2015; on the inland navigation vessel Rhenus Duisburg. The shipping company uses this 110-metre-long vessel to transport coal from ports in the ARA (Amsterdam-Rotterdam-Antwerp) region to the port of Lünen in the German Ruhr region using three push barges.
In a recent interview, Herbert Berger, Managing Director Rhenus Schiffsmanagement, used design, tonnage, journey time and fuel consumption data from more than 200 trips to answer some questions about his operational experience with the Van der Velden® FLEX Tunnel. The comparison of fuel consumption and potential savings is based on the identical sister ship (Rhenus Lünen), which is not fitted with the Van der Velden® FLEX Tunnel. The ships carry the same cargo on the same route.
How satisfied are you in general with the Van der Velden® FLEX Tunnel?
The FLEX Tunnel offers massive fuel savings on inland vessels. Achieving immediate fuel savings is not usually possible with just one additional component, but with the FLEX Tunnel system we have seen immediate fuel savings of 9% at the touch of a button. It is a maintenance-free system, which results in reduced maintenance costs. To date (since 2015) we have had no problems – the FLEX Tunnel has always been reliable.
How did it go this summer with the low water levels?
I have never seen such low water levels in the Lower Rhine – compared to 2003, we have had a very long period of low water levels this year. It started in July and lasted throughout the summer months. This meant that a loading depth of 2.80m was no longer possible. Although this was unique, in my opinion it will not be exceptional in the future.
With a draught of 2.30m and less, the FLEX tunnel remains extended during the loaded voyage. As a result, less power is drawn from the main engines. Too much power causes vibrations in the stern of the ship.
What were the lowest water levels at which you were still able to operate?
We were able to keep both the Rhenus Duisburg and the Rhenus Lünen in operation on the Rotterdam-Lünen route. However, at a draught of 1.50m, the captain felt that pushing three barges was no longer efficient.
And what does that mean in terms of cargo capacity?
So far the lowest loaded depth was 1.55m. We were able to transport 1700 tons of cargo in three barges. At normal water levels, this tonnage can be transported in just one barge.
Can you give us figures for fuel consumption?
In daily practice, the Rhenus Duisburg recorded 11% fuel savings on average on the route from Rotterdam to Wesel compared to its sister ship the Rhenus Lünen. This corresponds to a reduction of 277 tonnes of CO2 per year.
Taking these results into account, does the Van der Velden® FLEX Tunnel meet your expectations?
Yes, absolutely. Our decision to consider the FLEX Tunnel for the Rhenus Duisburg was based on the studies by DST (Development Centre for Ship Technology and Transport Systems) as well as the confidence and courage to go for a new innovation, since no empirical results were available at the time. The logical conclusion from the reports, the smooth inflow to the propellers and the use of a larger propeller, finally led us to take the decision. The FLEX Tunnel meets my expectations: we have not regretted choosing this innovative product for a moment.
In which situations would you recommend the Van der Velden® FLEX Tunnel?
The advantages of the FLEX Tunnel are clear on virtually all shipping routes. On canals, for example, the captain of the ship did not see any difference when the FLEX Tunnel was folded or extended. Because canals require limited speed, savings are expected to be zero in this situation. This corresponds with the design objective. In short, the FLEX Tunnel has advantages in all types of flowing water. Moreover, when used on rivers, the benefits are greater.
Attention needs to be paid to the configuration of the stern, including the FLEX Tunnel and the propeller size, based on where the vessel is expected to be used. DST Duisburg and Damen Marine Components found an optimal solution for the Rhenus Duisburg.
The Van der Velden® FLEX tunnel – a brief explanation
The basic concept of the Van der Velden® FLEX tunnel allows for it to be folded or extended. The system can be folded flat within the hull. This reduces the overall resistance of the vessel and increases efficiency. A ship sailing in shallow waters can use the tunnel to create sufficient water flow to the propellers to maintain their efficiency. This means that, in shallow waters, ships fitted with the extendable tunnel will remain operational longer than other ships. When extended, the tunnel connects seamlessly to the nozzle and prevents any false air infiltration between nozzle and tunnel. In addition, the FLEX Tunnel is approximately 66% the size of a conventional tunnel. With a clear focus on efficiency, any ship design (including cargo space and cargo capacity) can be optimised.