The Van der Velden® FLEX Tunnel – a ‘quantum leap’ for inland shipping
German shipping operator Rhenus PartnerShip was the first company to install a Van der Velden® FLEX Tunnel; on its inland vessel Rhenus Duisburg. The company deploys this 110-metre long vessel with three push barges to transport coal from the ARA (Amsterdam-Rotterdam-Antwerp) ports to the Port of Lünen in the German Ruhr Area.
In a recent interview, Herbert Berger, Rhenus Schiffsmanagement Managing Director, calls on draught, tonnage, travel time and fuel consumption data from over 200 trips to answer some questions about his hands-on operational experience with the Van der Velden® FLEX Tunnel. Enabling a side-by-side comparison, the company uses an identical sister vessel (the Rhenus Lünen) that is not equipped with the Van der Velden® FLEX Tunnel on the same route for the same purpose.
How satisfied are you with the Van der Velden® FLEX Tunnel in general?
The Van der Velden® FLEX Tunnel is a quantum leap in fuel reduction on inland waterway vessels. Achieving direct fuel savings with only one additional component is usually not successful, but with the Van der Velden® FLEX Tunnel, by only pressing one button we immediately see 9% fuel savings. It is also maintenance free and therefore without any maintenance costs. Up to now we have had no problems – the Van der Velden® FLEX Tunnel has always been reliable.
How did it cope with the low water levels this summer?
I have never seen such low water levels in the Lower Rhine. And, compared to 2003, we had a very long period of low water levels this year. These started in July and lasted through the summer months. This meant that loads of 280cm were no longer possible. While this has been unique, in my view this will not be an exception in the future.
With a draught of 230cm and less, the Van der Velden® FLEX Tunnel remains extended during the loaded journey. Consequently the main engines are also operated with less power. Too much power will cause vibrations in the stern of the boat.
What were the lowest water levels in which you could still operate?
On the Rotterdam-Lünen route, both the Rhenus Duisburg and Rhenus Lünen could be kept in operation. With a draught of 150cm, however, the ship’s captain considered it no longer useful to operate with three push barges.
And, in terms of loading capacity, what does this equate to?
To date, the lowest loading depth has been 155cm. 1,700 tons of cargo could still to be transported with three push barges. At normal water levels this tonnage can be carried by only one push barge.
Can you give us numbers in terms of fuel economy?
In daily practice, compared to the sister ship Rhenus Lünen on the route from Rotterdam to Wesel, the Rhenus Duisburg displays an average of 11% fuel savings. This corresponds to a saving of 277 tonnes CO2 per year.
Considering these results, does the Van der Velden® FLEX Tunnel meet your expectations?
Yes. The basis for our decision to consider the Van der Velden® FLEX Tunnel for the Rhenus Duisburg was the tests at DST [Development Centre for Ship Technology and Transport Systems] as well as the courage to make that decision. There were no empirical values that could be accessed. The logical conclusion that the trouble-free inflow to the propellers and thus using a larger propeller made the decision easier. Yes, the Van der Velden® FLEX Tunnel meets my expectations. At no time have we regretted the decision.
In which situations would you recommend the Van der Velden® FLEX Tunnel?
The Van der Velden® FLEX Tunnel does not show its advantages in all shipping routes. For example, in canals the ship’s captain has not seen any difference whether the Van der Velden® FLEX Tunnel is extended or retracted. Since canals require limited speed it is expected that savings will be zero in this situation. This matches with the design purpose. Basically, the Van der Velden® FLEX Tunnel has its advantages on all flowing rivers. Furthermore, if a vessel is used predominantly on flowing rivers, the advantages are greater.
Attention should be paid to configure the stern of the vessel – including the Van der Velden® FLEX Tunnel and the propeller size based on the area of application of the vessel. With regards to the Rhenus Duisburg, DST in Duisburg found an optimal solution for us.
The Van der Velden® FLEX Tunnel – a brief explanation
The founding concept of the Van der Velden® FLEX Tunnel is its ability to retract. The system can fold back into the vessel hull. This lowers resistance and increases efficiency. A vessel sailing in shallow waters can deploy the tunnel to ensure sufficient water flow to the propellers and maintain their efficiency. This means that, in shallow waters, vessels fitted with the retractable tunnel remain operational for longer than other vessels. The retractable tunnel is seamlessly constructed over the nozzle, stopping any false air infiltration between the nozzle and tunnel. Moreover, the Van der Velden® FLEX Tunnel is approximately 66% the size of a conventional tunnel, resulting in lower resistance. With a clear focus on efficiency, the hull design (including cargo space and loading capacity) can be optimised.