Taking the next generation to the next level
When asked what drove Damen to come up with the new ASD Tug 2813, design and proposal manager Erik van Schaik gives a straightforward answer: “safety, reliability and efficiency”.
“To elaborate, there are two markets for 80-tonne bollard pull multipurpose ASD tugs; those over 30 metres and those under. The vessels over 30 metres typically spend most of their time offshore where their length is needed to ensure good seakeeping behavior in heavy seas. For this market, we offer the Damen ASD Tug 3212.
“However, if your tugs are operating most of the time in locks and harbours you need something that, while maintaining sufficient propulsion power, is more compact and manoeuvrable. In the past we supported this sector with the ASD Tug 2913, but with the increasing size of container ships we needed to be able to offer operators a vessel with the necessary power but which was also more competitive. Shaving a single metre off the length of a tug might sound an unremarkable step, but doing so took the design below the critical 400 GRT threshold, without making any concessions on functionality or capability.
Some of the results of creating a shorter tug might, initially at least, seem surprising. “In fact,” says Erik, “despite being shorter, as the hull form of the ASD Tug 2813 features less tapering and less beam amidships, the new design actually increases stability!” The hull form of the vessel forms a key part of the ASD Tug’s enhanced safety characteristics in general. For example, its smooth, rounded shape allows the water to flow effortlessly around the hull. This results in a continual, predictable availability of thrust.
“The freeboard’s 1.6-metre height gives the foredeck three metres clearance from the water under load, ensuring that it remains dry in most conditions, continues Erik. The shape of the aft deck also avoids the collection of water, which keeps things dry astern as well,” explains Erik. “Also contributing to the safety is the large single skeg. This makes the steering easy and stable, even with just the one thruster, and the freeboard has been well thought-out with the tumblehome up to 40 degrees.”
“The wheelhouse, which is also very compact, has been designed to provide maximum visibility. Large, tinted windows provide a complete, unobstructed view fore and aft, while sky windows give an optimal view of the assisted vessel. With the wheelhouse leaning inward, it makes the ASD Tug 2813 ideal for working under the flare of a container vessel.”
The glass used in these windows is the patented Damen Safety Glass. This glass is laminated and shatterproof, and so gives protection to those inside in the event of a towing line snapping. It meets the NEN-EN 356 standard for glass used in buildings, defined as ‘resistance against manual attack’. The test for this involves dropping a ball weighing 4.11 kilogrammes three times on to the surface of a window from a height of 6 metres.
“Safety is always a focus on Damen vessels and is only going to increase in importance as our tugs continue to evolve. For example, we are currently developing electronic stability protection for the entire range. This will clearly alert the crew when a vessel is approaching its stability limits during operations so that they can take timely action.” The vessel, like all in Damen’s next generation range of tugs, is prepared for the more rigorous stability regulations that are coming into force next year, and it boasts numerous other features that make it easier to operate, allowing for a greater focus and further increasing safety.
“The user interface has been evolving continuously since it was first unveiled last year on the RSD Tug 2513,” says Erik. “We received a lot of helpful feedback about it, which we have consolidated and taken on board to deliver version 2.0.” The interface is ergonomically designed with user-friendly consoles, operating panels with controls, monitoring and alarm functionality as well as nautical information, main engine data feeds, and winch and auxiliary controls. All the data is presented in an easy to access manner, with the user able to select relevant information to be displayed as required.
“The ASD Tug 2813 has been designed throughout for the best use of space. This contributes effectively to the goals of both safety and efficiency. From a safety perspective, the flush foredeck, which is optimised for various towing modes, gives excellent accessibility to the winches, bollards and fairleads. The aft deck is also open and clear with no obstructions. In the engine room the spacious, uncluttered theme continues. Here, the engines are mounted on shock absorbers and the piping system fitted in such a way as to ensure low vibration and noise levels. For maximum safety, all the equipment in the engine room can be controlled from the main deck. The crew can also monitor the alarms, analyse any problems and take the necessary action, all from a safe location.
Reliability as standard
Erik says that the fact that the tug is a new design is no barrier to its claim to reliability. “Although it’s a new design featuring a lot of innovation, the ASD Tug 2813 draws heavily on its proven Damen heritage and uses a lot of tried and tested technology,” he asserts.
To ensure the reliability of the tug, Damen has taken great care to ensure its ease of maintenance. For example, all the steel parts are well rounded, welding is performed without underlap or undercutting and the bulwark is closed. The fendering has also been a point of close attention. “It’s a challenge to design a fender that will not damage the skin of an assisted vessel that is working at sea with a pushing force of 85 tonnes. The waves make it necessary for it to absorb a tremendous amount of energy. With the ASD Tug 2813, the cylindrical fendering absorbs the initial impact, which is then distributed over the block fenders. This way the average fender pressure never goes over 20 tonnes per square metre.”
In addition, throughout its tug range Damen uses closed cooling water systems, designed for 35-degree seawater temperatures, for both the engines and the air-conditioning. “We fit these as standard on our tugs. We see this as an investment in reliability; it avoids the risk of pollution and corrosion. And, due to the quality of the equipment we use, the closed cooling systems play an important role in minimizing maintenance requirements.”
Energy, ergonomically & environmentally efficient
“The ASD Tug 2813 is efficient in every way – starting with the design process. Damen’s TugSim software allows us to calculate the escort forces on the towing line and so predict the effects that these will have on the performance of a tug. The findings are then incorporated into the design for optimal efficiency and predictable behaviour. “The theme of efficiency continues with the build,” says Erik. “We’ve streamlined this to use the minimal possible number of components, so construction takes less time.”
The tug is also an efficient working space. It features a carefully planned layout that aims for smooth working logistics. Starting with the uncluttered, spacious decking, every detail has been taken into consideration. For example, when you enter the accommodation, the first thing you encounter is a changing room – forming a crossover space between the living and working areas.
The laminated Damen Safety Glass windows provide effective insulation and bring down the required use of air-conditioning capacity by a consider able 50%.
“In the accommodation areas we’ve given plenty of thought to crew requirements. Their living areas are spacious, in spite of the vessel’s compact nature, and constructed of durable, waterproof materials. Electrical sockets are well spaced to give easy access for charging mobile phones, for example, and each cabin has its own en-suite facilities.” The vessel also has very low noise and vibration levels, with COMF-NOISE 3 and COMF-VIB 1 notations, and a comfortable mess room provides a communal living space with settees, radio and TV.
Back on deck, the vessel is prepared to be fitted with Damen’s highly-efficient Render & Recovery Winch. This compact system contributes to the vessel’s spaciousness and facilitates excellent views from the wheelhouse. It has no gearbox, no additional clutches, no water-cooled disc brakes and no different speed/pull settings. This, combined with its control via the ergonomic human-machine interface, makes for a highly user-friendly operation.
Strong, stable & sustainable
Where the vessel’s efficiency truly reaches its peak, however, is in its sustainability. “By its very nature, such a compact vessel uses significantly less fuel at normal operating speeds and the smooth hull provides a high level of agility that contributes further to this. When the vessel performs in direct towage it requires less fuel for higher line forces.”
To meet Damen’s, and its clients’, goals of increased maritime sustainability, the design of the ASD Tug 2813 has once again gone into every conceivable detail to identify enhancements. “By creating a vessel that functions at the optimum size, less auxiliary power is required, once again reducing fuel consumption. All of these measures drive down fuel consumption, thereby considerably reducing both the OPEX and emissions.
“In the same way, the laminated Damen Safety Glass windows provide effective insulation and bring down the required use of air-conditioning capacity by a considerable 50%.” There are also options with the vessel that can further extend its environmental credentials. For instance, it can be supplied with its own sewage treatment system and bilge water separator if required.” Another option is a Marine NOX Reduction System, which will ensure that it is fully compliant with IMO Tier III regulations.”
This works by injecting urea into the exhaust. This triggers a chemical reaction with the gases that reduces the NOx emissions by substantially more than the 80% required to comply with the regulations. The vessel can also be supplied with Bureau Veritas Clean Ship Notation or Lloyd’s Eco Notation. The ASD Tug 2813 offers not only a sustainable performance by today’s standards, but also by those of tomorrow. It’s ahead of the game,” he concludes.