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Innovations in tug design and propulsion

Wed 11 Oct 2017 by Martyn Wingrove

Innovations in tug design and propulsion
Mike Fitzpatrick (Robert Allan): “Hybrid is much better for tugs. It is less costly in capital” (credit: Martyn Wingrove)

Robert Allan president and chief executive Mike Fitzpatrick identified the latest design trends as new propulsion configurations, fuel choices and autonomous control

Robert Allan is at the forefront of new tugboat naval architecture with variants of its escort and harbour tug designs incorporating the latest in marine innovations. The Vancouver, Canada-based marine engineering group has designed some of the more enterprising and innovative tugs to be built this year.

In an exclusive interview, Robert Allan president and chief executive Mike Fitzpatrick described some of the latest trends in design to Tug Technology & Business. He identified the key technology trends by pointing to new configurations of azimuthing thrusters, the use of liquefied natural gas (LNG) and energy storage systems on tugs, changes in power/displacement ratios and the ongoing development of remote control and autonomous vessels.

Robert Allan’s innovative work has been focused on developing new concepts, such as the Carrousel Rave tug design. This has a low-drag hull, Voith propulsion in an in-line configuration and Novatug’s carrousel towing system that can freely rotate around the tug’s superstructure. Mr Fitzpatrick said this would be ideal for harbour and canal towage where there is limited manoeuvring space.

Two tugs to this design were ordered by Multraship Towage and Salvage and built in Germany. The first of these, Multratug 32, was delivered in June and went on sea trials in September this year. At the time of writing, in early October, it was due to enter service in November. A second, Multratug 33, is due to enter service in February 2018.

This design maximises the manoeuvrability of the tug and its bollard pull without jeopardising its safety, Mr Fitzpatrick said, comparing it with Robert Allan’s RAmparts design tug, which was also designed for harbour and terminal operations where the highest bollard pull is required from small tugs.

He said developments in bollard pull capabilities can only go so far before stability becomes a safety issue. “We needed to look at what was safe so we developed our own internal guidelines for what is too much bollard pull in a small tug.” He explained that 70 tonnes of bollard pull from a 24 m tug would be a good and safe power/size ratio, but not all tug operators want a 70 tonne bollard pull vessel, which is why there are around 30 distinct versions of the RAmparts design.

“We needed to look at what was safe so we developed our own internal guidelines for what is too much bollard pull in a small tug”

Variants in fuel and power components are also becoming more influential in tug design, as demonstrated by the Robert Allan-designed RAstar 40 m LNG-fuelled escort tugs for Østensjø Rederi for operations in Hammerfest in northern Norway. Mr Fitzpatrick expects more LNG-fuelled tugs to be brought into service – at least one is being built in China and another in the United Arab Emirates – but he said there were technical and financial reasons why another energy innovation is more likely to take off.

“It is much more difficult for LNG fuel systems to be designed on smaller vessels,” he said, explaining that these could increase construction costs by US$4M. This may not be a great change for large commercial vessels, but makes a big difference to the price of building a new tug.

“Hybrid is much better for tugs,” he said. “It is less costly in capital and there is not much variation in [machinery] arrangements.” He added that it would cost between US$500,000 to US$1M extra to install energy storage for hybrid propulsion.

“Hybrid is much better for tugs. It is less costly in capital and there is not much variation in arrangements”

There are other benefits for tug operators: “Hybrid systems could mean tugs operate up to 80% of their time on one engine, leading to fuel savings and less engine run-time,” he explained. “It is easier to build an economic case to add batteries with no effect on the size of the tug.”

Robert Allan has also taken the lead in developing autonomous tugs, with its RAmora design concept for a remote control vessel. “We are making slow progress with our design and we are working with a prominent tug owner on RAmora,” said Mr Fitzpatrick. A model has been tested on Transas simulators at the Pacific Maritime Institute.

He expects faster progress will be made on developing autonomous fireboats, of which Robert Allan is a leading designer. “There is enough interest that we expect to build an unmanned fireboat for real service before a remote-controlled tug,” he added.

Mr Fitzpatrick admitted that there had been a slowdown in tug newbuilding orders this year, which reduced the company’s work on designs for shipyards. “We are now working at around 80% capacity compared to a year ago when we were working at 125%,” he said. However, this has enabled Robert Allan to review existing designs and innovate. This is shown in its designs for Carrousel-Rave tugs and work on RAmora.

Biography

Mike Fitzpatrick has worked for Robert Allan for 14 years in many roles, reaching vice president of projects in 2007 and chief executive in 2015. He graduated with a bachelor of engineering in naval architecture from the University of New South Wales in Australia in 1995 and then worked as a naval architect at InCat Designs in Sydney, Australia, until he joined Robert Allan in 2003.

Mike is responsible for corporate direction, business development, management of senior project managers, and project priorities, schedules and profitability.

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