Reversed stern drive, Carrousel RAVE, azimuth stern drive and RApport designs enhance harbour towage, while hybrid and LNG bring green alternatives
Tug owners have a choice of new designs for improving harbour towage. This year has seen construction of tugs to ingenious designs that demonstrate the improvements in manoeuvrability and versatility of harbour tugs.
There will be new designs of Carrousel RAVE tugs, of which the first two are already in operation – Multratug 32 and Multratug 33, in Belgium and Germany. Naval architects at Robert Allan are designing a new variant of this innovative concept for Novatug, combining a Carrousel rotating towing system, Robert Allan hull design and Voith Turbo inline propulsion.
The two existing Carrousel RAVE tugs (CRT Large design) have an overall length of 32 m and 77 tonnes of bollard pull. Novatug’s next variant (CRT Medium) will have an overall length of 28 m and bollard pull of about 50 tonnes. It will still have Voith inline propulsion along the centreline of the hull and the Carrousel towing system.
Robert Allan and Novatug said this design will be fuel-efficient and provide “inherently safe towing assistance in dynamic conditions with manoeuvrability for operations in confined waterways, locks” and other tight spaces.
Competing with this concept for harbour towage and ship manoeuvring in tight areas is Damen’s reversed stern drive (RSD) tug design, the first of which, Innovation, was unveiled during Q2 2018. Tug Technology & Business witnessed its capabilities during a demonstration in Southampton, UK in June. This design combines elements of tractor tugs and azimuth stern drive (ASD) units. It has a patented twin-fin skeg and the ability to tow ships ahead or astern.
With expectations high for this design, Damen also constructed a hybrid propulsion version, said Damen sales manager for north, west and south Europe Arjen van Elk. He also said there are plans to build more of both IMO Tier II and Tier III diesel-only versions in different sizes, and hybrid tugs.
Innovation is a 25-m tug, built by Damen to a RSD Tug 2513 design and has a bollard pull of 75 tonnes ahead and 71 tonnes astern. Its 13-m beam is wider than other tugs of this size, which Mr van Elk said improves its stability. He said its 5.5 m draught means this tug can assist ships from its bow and stern in most harbours. He added that Innovation has a maximum speed ahead of 13 knots and slightly less, 12.8 knots, astern.
Mr van Elk went on to explain that Innovation has a higher freeboard than is usual on a tugboat of this size, which enhances safety and stability. It also has shatterproof glass around the wheelhouse to protect crew and a glued superstructure to counter noise and vibration.
In addition, Damen has extended its series of ASD tug designs with two multipurpose vessels. ASD 2312 has 60 tonnes of bollard pull from a 23-m harbour tug in push and pull modes. It has an aft deck area of 54 m2 and six-person accommodation. ASD 2813 tug has 80 tonnes of bollard pull from a 28-m tug, an aft deck area of 82 m2 and accommodation for 10 seafarers.
Damen has also broadened its benchmark ASD harbour tug design from 2810 to an ASD 2811 (11 m beam compared with 10 m of the previous design). ASD 2811 has 60 tonnes of bollard pull both in push and pull mode. Its harbour tugs come with conventional diesel-driven main engines that are IMO Tier II compliant. To become Tier III, Damen can install its marine NOx reduction system, which it unveiled in June.
Damen product manager tugs, Dirk Degroote said these ASD and RSD tugs are for the next generation of harbour towage operations. “Development of the next-generation series has been about taking the best of our existing vessels and adding innovation to deliver a range of vessels fit for the future,” he said.
Design: RSD 2513
Built: April 2018
Builder: Damen Shipyards
Owner: Damen Marine Services
Class: Bureau Veritas
Length, oa: 25 m
Beam, oa: 13 m
Draught: 5.5 m
Displacement: 525 tonnes
Bollard pull ahead: 75 tonnes
Bollard pull astern: 71 tonnes
Speed ahead: 13 knots
Speed astern: 12.8 knots
Rivalling these designs is new architecture from Robert Allan and Sanmar Shipyards on the first RApport 1600-SX tug, with Gökçay commencing operations in May. This is a steel twin-screw harbour tug designed for stability, manoeuvrability and affordability.
This Bureau Veritas-classed, 16.3-m tug has conventional twin-screw propulsion with twin nozzles and four rudders, providing Gökçay with a bollard pull of 21 tonnes and a top speed of 11.5 knots.
This power comes from two Caterpillar C18 engines, which each develop 650 kW of power and turn two five-bladed propellers of 145 cm diameter, through Reintjes 5.5:1 reverse and reduction gears. There are twin high-aspect ratio rudders fitted behind each nozzle.
Gökçay’s stability is assisted by the fuel storage involving a two-tank arrangement with wing tanks port and starboard, centrally located to minimise the effect on trim. On the aft deck there is a 25-tonne towhook with an electric-driven winch and pipe bollards are fitted in the bulwarks for mooring.
The wheelhouse has extra-large windows facing the aft and funnels have a low profile, meaning that most of the aft deck is visible to the operator. Gökçay has fendering for harbour operations including 250 mm D-shaped fenders at the sheer and vertical W fenders around the bow.
Designer: Robert Allan
Design: RApport 1600-SX
Class: Bureau Veritas
Length, oa: 16.3 m
Breadth, moulded: 7.4 m
Depth, moulded: 3.3 m
Draught: 2.7 m
Speed: 11.5 knots
Bollard pull: 21 tonnes
Fuel oil: 15 m3
Crew: 3 persons
Main engines: 2 x Cat C18, 650 kW
PSA Marine has chosen dual-fuel propulsion for its next harbour tug. In March, it contracted Wärtsilä to design and equip a harbour tug it ordered from PaxOcean Shipyard. This 28-m tug will run on LNG fuel that PSA Marine expects will reduce its carbon footprint and emissions of NOx and SOx gases.
This tug will have a bollard pull of around 50 tonnes from two Wärtsilä 20DF dual-fuel engines that will run primarily on LNG. Wärtsilä will also supply its LNGPac fuel storage and supply system, steerable thrusters and a Wärtsilä ProTouch control system. This equipment is due to be delivered to PaxOcean’s shipyard at the end of this year.
PSA’s dual-fuel tug is expected to commence operations in the port of Singapore around mid-2019. It will join two other LNG-fuelled tugs that will be already in operation by the end of this year including KST Liberty, a 32-m ASD tug built by Keppel Singmarine for Keppel Smit Towage christened in May. Keppel Singmarine is also building a similar dual-fuel tug for Maju Maritime for delivery in Q3 this year (Tug Technology & Business, Q2 2018).
Editor’s comment: Advantage of towing both ways
Damen Shipyards demonstrated that its reversed stern drive (RSD) tug has a future for harbour towage in restricted ports. I witnessed this brand-new Damen tug design when it was tested in Southampton, UK in June.
In my opinion, harbour towage will be revolutionised by this new design of tug that can operate in tight ports in both directions.
Whether this is of the first design, a RSD 2513, a smaller unit or a hybrid version, there will be more of these types of tugs operating in harbours worldwide within the next three years. Damen already has plans to produce several on speculative basis.
After seeing its capabilities first hand, I strongly feel this design has a future for operations in ports, terminals and coastal towage. Innovation is an April 2018-built and Bureau Veritas-classed tugboat designed for towage and ship assistance in harbours from both the stern and bow. Damen has shown that an RSD tug is unique in performance and manoeuvrability.
It has a tight 360˚ turning circle and an emergency stop that felt more like being on a fairground ride. With its ability to operate ahead and astern, and with this manoeuvrability, I expect Damen will be getting orders very soon for RSD tugs. I have witnessed the future of harbour towage and ship assistance operations and expect a great future for this tug design.
Innovation engineroom delivers the power and manoeuvrability
Innovation has a pair of Rolls-Royce MTU 4000 series M63L main engines with 16 valves and each produce 2,240 kW at 1,800 rpm. These drive Rolls-Royce US255 thrusters with 2.7 m diameter propellers, providing the reversed stern drive RSD 2513 design tug with its tight 360˚ turns and top speed of 13 knots. They also help generate bollard pull of 75 tonnes ahead and 71 tonnes astern.
Additional power comes from two Caterpillar C4.4TA generator sets that produce 81 kVA, 400/230 V at 50 Hz frequency. Also in the engineroom are Azcue bilge, fuel and service pumps. Damen has introduced a remote monitoring system for its engineroom machinery.
Deck equipment on Innovation includes a hydraulic towage winch that has a split drum and can deliver a pull of 31 tonnes at up to 11 m/min or a reduced pull at up to 38 m/min. It has a 175-tonne brake. There is also an electrically driven anchor winch that operates up to 10 m/min and a 360 kg anchor.
In the wheelhouse, Furuno Electric supplied a FAR-1518-BB radar, FE-800 echosounder, DS-80 speedlog, Navtex and automatic identification system equipment. There is also:
Innovation’s communications include VSAT with a Intellian v60G antenna that operates over Inmarsat’s Global Xpress network. Cobham Satcom supplied two Sailor 6222 VHF radios and Jotron supplied hand-held VHF.
New towage safety guidance published
In the wake of a number of towage accidents in the last two years, UK-based National Workboat Association (NWA) has released a second edition of Use of Workboats for Towage: Good Practice Guide to improve safety in the sector.
This provides advice and recommendations for safely operating tugs and is an updated version of NWA’s existing guidance which includes feedback from towage operators throughout the UK and Europe.
It was written after tugs capsized during towage operations leading to seafarer deaths. This included the sinking of tug Domingue, with two fatalities, while manoeuvring container ship CMA CGM Simba in Tulear, Madagascar on 20 September 2016.
NWA’s updated version includes additional guidance on the safe use of gog ropes to prevent girting, or capsizing workboats during towage and harbour operations.
While this is a rare occurrence, incidents of girting continue to pose a significant challenge to the safe completion of towage operations, said NWA. This leaves tug operators vulnerable to financial and reputational damage and is a danger to human life.
This second edition of Good Practice Guide was developed in collaboration with SMS Towage captain Gareth Bonner. It is designed to help tug masters interpret the stability books on board individual vessels.
It covers the basic principles of stability and defines regularly used terminology found in stability documentation on workboats, helping to prevent any lack of clarity that could pose a risk to the safe operation of tugs.
For more information about this guide use this link: http://bit.ly/TTB_NWA_Guide