Sailing like a BOSS
The reduction of fuel consumption is a hot topic in the maritime industry. It’s an area of focus both as a means of improving environmental performance and of reducing costs.
One significant way of reducing fuel consumption is through reducing rudder movements. Van Der Velden Marine Systems, which has been a specialist in maritime manoeuvring and propulsion technology for more than 50 years, has been examining the issue of excess rudder movements and improving manoeuvrability for decades and has carried out many measurement campaigns on board vessels. These studies – driven by the demand for cuts in fuel consumption and emissions – have resulted in the ‘Barke Optimised Steering System’ or so-called BOSS™ which has been designed for both large, oceangoing vessels and for the inland sector – in this case the ‘BOSS™eco’.
Edwin van Buren, Director R&D at Van Der Velden Marine Systems, explains the thinking behind the development of the BOSS™. “Fundamentally any rudder technology is needed to keep the ship on a straight course, to make small corrections, especially when in wind and waves, and to manoeuvre the vessel when in an access channel/harbour etc. but then of course, the rudder angles are bigger.”
Over the decades Van Der Velden Marine Systems, part of Damen Shipyards Group since 2013, has been performing measurements on board vessels. “This has enabled us to get a better understanding of our products and compare the designs with the full-scale results,” he says.
“We found that there was much more rudder movement than expected when a ship sails ‘directly’ from A to B and much of this is not really necessary. This is leading to higher fuel consumption, resulting in unnecessary costs.”
For example, when a ship sails on autopilot and it has been adjusted for a heavy sea state and the vessel then enters flat water, often the autopilot is still on a setting suited to heavy weather.
“There is a similar issue when sailing manually. There is often no real attention on how the vessel is moving through the water. The captain steers the rudder angle in one direction following a straight course but actually they continually ‘float over’ the course line, resulting in unnecessary overshoots to be corrected by extra rudder movement.”
By measuring these unnecessary movements we can highlight that this is leading to extra fuel consumption, he adds. “We can make the captain aware that they are not using the rudder in an efficient way.”
BOSS™ – for oceangoing vessels
Van Der Velden Marine Systems initially tackled the rudder movement issue on seagoing vessels, particularly containerships, with sea trials taking place in the East China Sea.
BOSS™ sea trail with 10.600TEU container vessel CMA-CGM Ural at East Chinese Sea
Before the system’s development, the rudder force generated for specific angles was not measured or displayed by any of the ship’s navigation systems. Therefore, to optimise manoeuvrability when steering manually or automatically, BOSS™ is able to calculate the rudder forces by measuring the bending of the rudder stock.
In the case of larger vessels, strain gauges are built into the rudder to measure the loads taking place. The sensors measure the bending and torque of the stock and then calculates the lift and drag force of the rudder. A complex algorithm recalculates the measurements and provides a transversal and longitudinal force acting on the ship, which can then be displayed on a LCD touchscreen on the bridge.
By reducing rudder movements, manoeuvrability is improved and sailing on Autopilot mode reduces the overshoots, shortening the travelled distance and so reducing fuel consumption.
“Getting an insight into the rudder movement shows the resistance and we can quantify this. And crucially the BOSS™ makes the helmsman aware of what is happening so he can avoid excess rudder movement. Then the forces are translated directly into fuel consumption,” he stresses.
The drag force is displayed and this is very important for reducing fuel costs. “The algorithm is in real time, resulting in a very active system in both sea states and smooth water.”
Additionally, when a vessel manoeuvres in a harbour or berths alongside the quay, and is consequently using much bigger rudder angles, the BOSS™ has an alarm if there could be danger of the vessel losing rudder force due to stalling. “These stall moments when big rudder angles are being performed are very rare but this means the captain can lose control of the rudder, and if they are operating at speed this can be extremely dangerous.” The BOSS™ enables the captain to see when this moment is going to come and sends out an alert.
Van Der Velden Marine Systems is believed to be the only company in the market that offers this stall moment alert.
The patented system is also unique because the sensors cables go up through the rudder stock into the hull of the ship. “Clearly the BOSS™ is operating in a very harsh environment, so it was vital to find a solution to take the cables internally in through the rudder itself and bring them into the hull in a safe and a very well protected way. The solution has to be suitable for the lifetime of the vessel.”
“The device is integrated permanently into the rudder system to give real-time analysis and the data therefore comes into the IT backbone of the ship.”
Today, around 20 BOSS™ systems have been installed on oceangoing vessels.
CMA_CGM 10.600TEU container vessel equipped with BOSS™
Inland vessels – the BOSS™eco
More recently, Van Der Velden Marine Systems has also focused its attention on developing the BOSS™ system specifically for the inland sector and this led to the launch of BOSS™eco in May.
“The technical solution incorporating sensors into the rudders for large vessels has been a success but for small, inland waterway vessels this is too expensive.
BOSS™eco on board of IWW vessel.
“Again it is the same driver – to make the skipper aware of the unnecessary rudder movement and the fuel saving potential. BOSS™eco makes the relationship between the rudder movement and dynamic behaviour of the ship itself evident.”
The system provides insight into excessive rudder movements mainly using existing ship sensors. A touchscreen display with special software continuously calculates and shows the most efficient rudder movement tailored to the navigational situation. Preliminary results have shown a fuel saving of approximately 12%.
By preventing excessive steering corrections of the river pilot, fuel can be saved. The unique patented algorithms developed by Van Der Velden Marine Systems, which measure among other things the effect of rudder movements on the rate of turn indicator measured twice every second, calculate and advise the most efficient rudder movement tailored to the navigational situation at the time.
“For inland vessels there are no sensors in the rudder, instead we measure the number of degrees turned along the navigational course by the displacement per minute. Essentially, we measure the reaction of the ship to the rudder and this is combined with the operational profile and the environment i.e. is there a bend in the river, is the vessel going upstream/downstream, is the ship loaded/unloaded.”
There are two lines shown on the LCD display presenting the rudder movement and then another showing how the ship is actually being sailed. “The idea is to have these lines as close to one another as possible to minimise rudder movements and maximise efficiency. Of course, resulting efficiencies are very dependent on the skipper who has to make the relevant adjustments to the autopilot.”
While only launched in May, the BOSS™eco has already proved a big hit with nearly 20 inland waterway vessels due to have it installed or ordered.
For the owners and operators, the beauty of the system is that they can even see the results on their smartphone/tablet or from behind their desks. And unlike the BOSS™ it can be retrofitted for existing inland waterway vessels.
Remote iphone APP for BOSS™eco
Better insight is gained into fuel consumption and also the reduction of the CO2 percentage in exhaust gasses. With a built-in CO2 calculator and the trip registration system the information is directly available. This enables owners to view actual and average fuel consumption and average fuel savings per week, month and year. Additionally, the total cargo tonnage transported per tonne kilometre is shown and CO2 emissions are calculated.
Overall, Mr van Buren points out that BOSS™ is part of a larger picture for Van Der Velden Marine Systems, which is aiming to offer customers a complete monitoring system eventually. “BOSS™ concerns the rudder but it is all about digitalising the ship, big data etc. Owners want more data about the behaviour of their ship and the performance of individual components such as engines and manoeuvring equipment.
“Efficient manoeuvring is vital and the owner wants more control and to be able to permanently see what the condition and performance of the system is. We are working on a complete monitoring system; for example, we are developing systems to look at the clearance of the rudder bearings, and ways to measure the quality of the hydraulic oil from the steering gear. The next modules for a full monitoring system are the hydraulic oil condition and the rudder clearance modules, which should be ready by the end of year, and this will be followed by more condition and product performance modules in 2018.
“We are developing devices to collect data which will enable the captain and owner to see if the vessel is being sailed efficiently and so the vessel can stay in good condition. Fairly soon this will all be happening remotely (ship to shore) as well!”
This is just one example of the activities currently being undertaken by the Damen Shipyards Group in order to give operators more real-time information to assist them in achieving optimal performance from their vessels. A later article will consider this subject in more detail, considering the activities of Damen Digital.