In this webinar, experts provided guidance on the approach to thruster selection and why there is a move away from absolute power to maintenance and thruster performance
In Riviera Maritime Media’s webinar Thrusters: future-proofing your vessel and investment, Berg Propulsion managing director west Jonas Nyberg, Global Ship Support director Duncan Payne and Wärtsilä director of thrusters and propulsion control systems Lauri Tiainen assessed important thruster operational factors.
Berg Propulsion was the premier partner of the webinar with sponsorship provided by Wärtsilä. The webinar was part of the Marine Propulsion Webinar Week.
Mr Nyberg represents an independent company which provides products to the shipping and marine industries. With so many shapes and forms of azimuth thrusters, how should a thruster be sized for the vessel and how should the assets be operated? “Equipment designed for efficiency is a way of future-proofing the investment,” he said.
Berg Propulsion looked at the efficiency equation from three different angles: product efficiency, system efficiency, and operational efficiency. Product efficiency comes from the interaction of the product’s components. “The way the cooling system is set up impacts fuel consumption. Is hydraulic steering specified or more efficient electric steering?”
System efficiency is often forgotten or misrepresented, which he illustrated with a case study of a tugboat owner assessing the specification for a new craft with an 80-tonne bollard pull. The traditional way is to specify the power output of the engine, and then find an azimuth thruster to suit. A more efficient system-based approach is to start with the biggest propeller that can fit the vessel within draft and other limitations. Then specify the engine – an approach that could produce a 10% saving in fuel requirements.
In a poll: Which component has the biggest impact of fuel consumption? 51% chose the engine, and 49% believed it was the propeller.
The third aspect is operational efficiency. One example is an escort tug required to be on station – steam full speed and wait or reduce load and cruise to arrive within an acceptable window?
Providing the owner’s perspective was former seagoing engineer and shoreside vessel manager with decades of experience in thruster operation and maintenance Mr Payne. Shipowners, he warned, need to pay special attention to shipyard activities around the vessel during thruster installation. “We have all been to shipyards and we know that shipyards will try to do everything as quickly as possible and at the same time,” he said. Insist on installation when there is no grit-blasting, painting or grinding taking place nearby. Maintain an accurate installation log and witness the thruster testing and commissioning.
With regards to crew, they should be trained beyond the barest standards and the control layouts should be intuitive with adequate feedback without unnecessary alarms and interruptions during operation.
Regular technical bulletins from the thruster manufacturers is a significant help in maintaining a smooth operation, said Mr Payne. He went further, saying that in this era of carbon reduction and the strive for efficiency, the end-user should not wait for legislation, or from upgrades from the OEM, but the end user should be at the forefront of change, demanding solutions for the OEMs.
This advice was not fully taken on board, and in a poll 46% felt that legislation should take a lead in driving advances in technology to increase efficiency and reduce emissions. End user requirements, as voiced by Mr Payne, were chosen by 29% and OEM innovations by 25%.
Mr Tiainen looked at the range of available thruster applications from the in port manoeuvrability required by large container ships to the highest levels of dynamic positioning required by large offshore construction vessels. In general, the higher up the scale, the larger the performance demand, and increase in capex and opex.
While the larger applications tend to favour the steerable thruster, ducted thrusters should not be dismissed. “The ducted version can still be beneficial up to 16 knots,” he said.
In a poll: Which of the following will be the industry’s preferred thruster? Controllable pitch was chosen by 51% and fixed pitch by 37%. A small number plumped for the rim drive (8%) and 4% other.
With regards to controllable pitch propellers and tunnel thrusters, these are still in demand in large commercial vessels. Where noise is an issue, such as on cruise ships, the fixed pitch propeller is more efficient, less noisy, and is suited to longer operations. At the highest level, the deepsea offshore construction vessel with DP, fixed pitch was the first choice, noted Mr Tiainen. The same applied to the controls, which become more sophisticated as the number of thrusters increase.
Thrusters are an essential component for the development of autonomous vessels, and delegates were asked: In the future will we see more autonomous harbour manoeuvring? 30% strongly agreed, 56% agreed, 10% thought that levels would remain as today and 4% thought the tide would swing back to manual approaches.
In a related question, now that IMO has identified four degrees of autonomy, which level of autonomy would delegates feel comfortable with on a shortsea ferry?
Wärtsilä also has the SmartDocking solution for vessels on a regular route. Mr Tiainen said the system allows safe repetition of manoeuvres, freeing the Captain and crew to be more observant of surroundings.
The theme of the webinar was on future-proofing the vessel and to a large extent advice from the experts was heeded, with 92% choosing vessel performance when asked: For optimum efficiency and future-proofing the vessel is it best to focus on? The remainder (8%) chose the traditional approach of installed power.
In the question and answers session, Mr Payne responded to the same question saying owners and operators would always prefer to have the vessel operating and vessel performance would be the first choice.
Mr Nyberg noted there had been a shift in thinking on this question. “It reveals a very interesting paradigm shift in the industry. In the past, in the commodity offshore field, customers and owners, were bidding on certain horsepower segments for their anchor handlers,” he said. “Which actually doesn’t tell you that much about the performance of the vessel, only how much power is installed, but a 5,000-hp tug might have a bollard pull of 60 to 80 tonnes,” he said. The change taking place is for more focus on performance, and less on installed horsepower. “This is good for efficiency and very good for what we are trying to achieve holistically in the industry,” said Mr Nyberg.
Load response, mechanical efficiency and green issues were the thrust of the questions from delegates. Mr Nyberg noted that switching fuels during operations, such as marine fuel to LNG, can have an impact on load response. If power plants are becoming less responsive, a switch to controllable pitch propellers could be a solution to managing load response.
Mr Tiainen said solutions also exist in the form of hybrid power plants, where batteries could provide the initial response power to cope with the gaps when diesel generators are starting up and provide the initial acceleration or deceleration. Mr Tiainen pointed out that when it came to future-proofing, having electric as the final drive in the thruster or to the propeller gives a side range of options in the whole of the propulsion system.
As energy sources develop, these could be retrofitted ahead of the electric motor – diesel generator for LNG, methanol, fuel cells or a combination.
He added that would mean that there would still be a need for reduction gears. “Often there is a dilemma between the power and rpm and the torque.”
Mr Nyberg agreed on the electric propulsion issue. “The safest way is making sure propulsion is electric, we will see much more of this going forward.”
The multiplicity of energy and propulsion options going forward is daunting but Mr Nyberg had some good advice on how to keep the strategic purpose of the design in mind throughout the process from initial considerations to commissioning the system.
Mr Nyberg said, “To be successful in a project, at the design stage you need to produce documentation that describes the philosophy of the vessel in a simple manner – almost an operational manual for the crew. Start with this before anything is designed. What this does is create a common widespread understanding between the person that builds the electrical equipment, the vessel designer, the yard, the operator and the equipment maker. Everyone has the same view.”
This was also his main takeaway, along with advice to owners and operators to use their leverage with OEMs to be provided with the latest information on developments, and to always use the data that is coming from operations. “Do not underestimate the power of the connection between man and machine,” he said.
Mr Payne’s takeaway concerned future-proofing the crew and avoiding “erodeable skills.” He said, “My main takeaway from this is that we all want to see technology improve and emissions reduced, keep the crew fully involved.”
Mr Tiainen noted that the biggest gains for the future are on that system level. “Look to the vessel performance first and find the best technical solution for your needs,” he said. He added automation products are available today to reduce the pressure on crew and allow them to focus on safety awareness.