Port environmental concerns, stability regulations and rising bollard pull requirements will influence tug designs this decade
Naval architects are introducing hybrid and LNG-fuelled tug designs and redesigning harbour and escort tugs to increase their power and towage capabilities without affecting their stability.
Workboat Association chief executive Kerrie Forster says harbour towage providers, with designers’ help, will find solutions to port operators’ pressure to reduce emissions.
“For harbour towage, designers need to further embrace hybrid and emissions reduction technologies,” Mr Forster tells Tug Technology & Business. “This is extremely important in this sector as these vessels often perform shorter operations and remain closer to port allowing for vessels to recharge or refuel more frequently,” he says.
Outside harbours, replacing conventional propulsion with alternative fuels or batteries could be more challenging, says Mr Forster.
“This is harder to practice in the larger workboat industry due to larger operating times and further distances from shore, but another sector looking at alternative fuels is the pilot boat sector,” he says.
“The rest of the industry looks upon the technology developed by these vessels to benefit the larger community in the future,” Mr Forster adds.
LNG is the main alternative to diesel fuel for propulsion currently being used on dual-fuel tugs. Med Marine procurement and technical group manager Ertuğrul Çetin thinks diesel could be taken out completely in future tug designs.
“LNG may be one of the most important fuels in the near future,” he explains. “We are already responding to the demands for LNG-powered tugs. We believe dual-fuelled tug demands will change into full LNG-fuelled ones.”
Mr Çetin thinks other fuels could be considered in tug design. “LPG, methanol, biofuel and hydrogen are considered the most promising solutions. Battery systems and fuel cells might also be among the alternative energy sources.”
Electric power would be considered in tug design if solutions are found to concerns over battery capacity, life, costs and recycling. “We think fully electric tugs will be the most commonly used tug type,” says Mr Çetin. “We are expecting solutions to battery life, expired battery disposal and the high initial investment costs, and are preparing our designs and capacities accordingly.
“We are pursuing our hybrid and fully electric tug designs and production strategies with our clients, suppliers and designer companies.” Med Marine works with naval architects at Robert Allan to offer adapted designs for harbour and escort tugs operating worldwide.
Mr Çetin says demands for higher bollard pull from tugs to support larger container ships is also influencing tug design.
“The size of vessels arriving at ports is growing in parallel with the port size and facilities. So, the bollard pull value expected from tugboats will increase in the future,” he says. “We are ready to respond to those needs and to stability requirements.”
In response, Med Marine and Robert Allan developed MED-A2360 (or RAmparts 2300 MM) series for harbour towage.
“The trend in harbour tugs is shifting to smaller but stronger tugboats,” Mr Çetin says. “When MED-A2360 series tugs are compared with other 60-tonne bollard pull designs, they are shorter, more compact and have better manoeuvrability. They are preferred for port operations due to their versatile and multi-purpose nature.”
Med Marine has expanded its portfolio with a compact azimuth stern drive (ASD) line-handling tug using Robert Allan’s RAscal 2100 design. This 21.4-m tug has a 10.7 m beam, 5.1 m hull depth and 4 m operational draught. It is designed with 40-50 tonnes bollard pull for towing, pushing, mooring and fire fighting.
Med Marine also has both Z-drive and twin-screw RAscal 1800 design tugs under construction at its shipyard in Turkey. For escort tugs, Med Marine offers RAstar and TRAktor designs of 24-36 m long. The shipyard has taken into consideration new IMO stability rules that came into force in January 2020. “These regulations will lead to safer escort operations,” he says. “We are building our tugs and expanding our designs in light of these rules.”
More Turkish newbuildings
Sanmar has also adapted Robert Allan designs to produce its own classes. Some of its latest orders and deliveries have been Bogacay and Sırapınar class harbour tugs based on RAmparts designs.
Bogacay-class tug Galluzzo was delivered to Italian owner Rimorchiatori Napoletani in October 2019. This is a 24.4 m long ASD tug with bollard pull of around 75 tonnes and a foldable mast with hydraulic controls in the wheelhouse for when the tug is operating close to ships’ flared bow.
For Marin Tug, Turkey, Sanmar built two Bogacay-class ASD harbour tugs with bollard pulls of 60 tonnes and another with 70 tonnes in 2019. It also supplied a Sirapinar-class (Ramparts 2200) harbour tug with 50 tonnes of bollard pull and a 28-m, RAstar 2800 design, terminal tug with 80 tonnes of bollard pull.
Sanmar is also building two 30.5-m escort tugs of TRAktor 3000-Z design for Bukser og Berging. They will have 70 tonnes of bollard pull and generate a steering force in excess of 80 tonnes.
Robert Allan uses virtual reality (VR) to design and engineer its tugs. It provides first-person perspective of being on board its tugs to verify owner and shipyard expectations. It is especially valuable to evaluate complex areas, such as wheelhouses, control centres and machinery spaces where spatial aspects of the layout are difficult to capture in traditional 2D and 3D media. VR models are being used to produce realistic renderings, interactive panoramas, walkthrough/flyover videos, and standalone virtual tours.
Production ramped up for new, manoeuvrable design tug
Damen Shipyards has ramped up production of its new reverse stern drive (RSD) tugs in response to demands for manoeuvrable vessels. It has delivered two RSD 2513 design tugs with 70 tonnes of bollard pull for European operations, one for Multraship Towage and another for Boluda, in the last two years. It is producing Mark-2 RSD tugs with more power and 85 tonnes of bollard pull, says Damen Benelux sales manager Joost van der Weiden.
“To achieve this, we increased the engine size and installed larger propellers, increasing the diameter from 2.7 m to 3 m in the Mark-2,” he says. RSD tugs are designed to provide ship handling and towage from both fore and aft ends of the hull, which is different from azimuth stern drive (ASD) tugs.
“These are compact and powerful tugs that can handle high bollard pull,” says Mr van der Weiden. “RSDs can operate in both directions in ports, which is very positive for customers. They can side-step with higher speeds (6 knots) than traditional ASDs because there is no centre line skeg.” RSD tugs have flat bottom hulls and twin fins at the stern.
Damen has also included its new human-machine interfaces and remote monitoring technology in the RSD tugs. The technology is also installed in its new ASDs that are built in Damen’s shipyards in Romania, the Netherlands and Vietnam.
Mr van der Weiden was involved in developing and project managing the RSD tugs; the first of these, formerly Innovation, is operating in Rotterdam. The second RSD built, Multratug 6, is in Antwerp, Belgium.
“All of our first series is built in Romania and our Mark-2 RSD tugs are being built in Vietnam,” Mr van der Weiden says. “Five were built in Romania, plus four are built in Vietnam, with the majority of these already sold,” he says.