Tugs with as much as 90 tonnes bollard pull are now being specified to ensure the requirements of the container terminal sector can be fully catered for
Terminal tugs need to be larger and more powerful because of the delivery of extremely large container ships, some capable of carrying more than 20,000 TEU. This has clearly had a major impact on the design and specification of harbour tugs over the past few years, and continues to do so. The need for tug operators to handle such large vessels safely and in all weather conditions has necessitated an increase in the bollard pull of tugs that may be called upon to work in container terminal environments.
Indeed, a significant proportion of the tugs being built and ordered today are over 60 tonnes bollard pull with a growing number rated at 80 tonnes and above. The main reason for this market trend is the increased average size of new generation container vessels along with the cascade-effect, which has pushed older but still substantial size vessels of 10,000 TEU and upwards onto all trades. It is a simple fact that ports in all regions of the world are handling much bigger container ships than they were five years ago and they need the appropriate harbour towage assets to support them.
Container terminal demand is largely driving the market for new tugs as a result. As Turkish tug builder, Sanmar projects director Ali Gurun observed, “Most of our newbuilding deliveries over the past few years were either for dedicated container terminals or for multi-purpose terminals that handle containers.” Recent orders reported by Sanmar have included a 60 tonnes azimuthing stern drive (ASD) tug for Rimorchiatori Riuniti and a 70 tonnes Voith Tractor tug for Rimorchiatori Tripmare of Italy, both of which are expected to serve Italian container terminals.
It is the weight and height of the latest generation behemoths of the seas, such as 2017-delivered 21,413 TEU OOCL Hong Kong, that have required tug operators to build new and more powerful tugs to service them. Without a substantial amount of investment, towage companies would simply not have been able to safely and efficiently meet the needs of their container shipping and terminal operating clients in berthing these ships.
Having more power at their disposal is the key requirement of most tug newbuild contracts as a result. As Mr Gurun pointed out “all our container terminal deliveries in recent times have been in excess of 60 tonnes, mostly over 70 tonnes, and some up to 80 tonnes.” There have also been requests for ASD tugs with more than 80 tonnes of bollard pull, “which can [also] deliver this level of power astern, when pulling over the bow of the tug.”
“All our container terminal deliveries in recent times have been in excess of 60 tonnes”
It is not just additional power that is being required of the latest generation tugs that will be used to handle container vessels, said Robert Allan design supervisor Lawren Best. He said the structure of modern and large ships are optimised for operational efficiency in service and “as a result is less capable of withstanding the high direct pushing forces that the tugs are capable of.”
The consequence of this is that tug fendering needs to be designed “to ensure that contact pressure within the container ship’s hull structure is within limitations.” As an alternative to pushing directly on the ship’s hull, the Rotortug configuration on a new generation of tugs allows the ship to be pushed and pulled into its berth without any contact from the tug.
There are some other specific features of contemporary container vessels that also influence tug design, explained Mr Gurun. “We are being asked for tug designs where the wheelhouse and deckhouse are optimised to minimise any risk of hitting the flare of [new] container vessels, which tend to have rather high flare angles.” Sanmar also receives requirements for tractor tugs that can offer better performance on heavily-flared vessels and are a good solution as a ‘bow tug’, “for operations where the attended vessel is being handled by one bow and one stern tug in a channel.”
Tug designers and builders are continuing to respond to the container ship market’s specific needs through new designs and design enhancements. Naval architects at Canada’s Robert Allan have designed RAstar 2900-SX as a tug that has been optimised for handling container ships – specifically at the APM Tangier-Med 2 terminal in Morocco.
Sanmar is building four of these new tugs in Turkey for Svitzer, with delivery scheduled for the last three months of 2018. The 90 tonnes bollard pull tugs will probably be the highest power-rated yet for a dedicated container terminal tug. They will incorporate escort winches, engineered fenders and a hull and superstructure arrangement that has been designed for container terminal applications.
Sanmar is building 90 tonnes bollard pull tugs for Svitzer - probably the highest power-rated yet for a dedicated container terminal
The new ASD design is 29.4 m in length, with a moulded beam of 13.4 m and an overall draught of 6 m. The four new tugs will each be powered by a pair of MTU 16V4000 M73L engines, delivering a combined 2,700 kW to the Schottel SRP 560 azimuth drive’s 3 m diameter propellers.
One of the world’s leading container terminal operators, PSA in Singapore, commissioned Robert Allan to design a tug specifically for its container terminal operations. This resulted in the Z-Tech class, of which another two tugs have recently been ordered from Cheoy Lee Shipyard in Hong Kong. PSA has also recently ordered two new RAmparts 3200-W type tugs from Pax Ocean.
Another Southeast Asian terminal, Pelindo III (PT Pelabuhan Indonesia – Persero) now has a total of 15 new RAzer class vessels under construction for service at its ports in Surabaya. These will be used to handle a wide range of vessel types, including container ships.
All of Robert Allan’s designed harbour and terminal tugs can assist large container vessels, when they are properly configured. This is equally true of a versatile new 25 m harbour tug design that Sanmar has developed so that its hulls can be outfitted as either a tractor tug with an aft working deck or as a Rotortug with both fore and aft working decks. Tractor tug versions of this new design, with the designation TRAktor 2500-SX, are available with various bollard pulls up to 70 tonnes, while the ART 60-25SX Rotortug versions are available with up to 60 tonnes bollard pull.
Sanmar has secured an initial order for a 60 tonnes bollard pull tractor version of this design from the Port of Taranaki in New Zealand, and is now building a trio of 70 tonne bollard pull tractor versions of the so-called Deliçay series. The first of the three is in an advanced stage of construction with delivery scheduled for February 2018.
Robert Allan has also been collaborating with Cheoy Lee Shipyards on a new tug series that will be designated the RAmparts 2500-CL and which could also find employment in container terminals. This is an evolution of the successful RAmparts 2500-W design, which has been enhanced to provide improved manoeuvring and side stepping capabilities. The new 25.4 m tug type will be available with various propulsion packages to achieve 50 tonnes, 60 tonnes and 70 tonnes bollard pull ratings.
Spanish tug operator Boluda Towage and Salvage has selected a Robert Allan design to enhance its capabilities in the key container transhipment port of Algeciras. The company took delivery, in the middle of this year, of VB Juangonzalez, the third in a series of 10 new generation tugs ordered from Astilleros Zamakona that are designed to provide excellent manoeuvrability both in port and at sea. It follows into service sisterships, VB Xaloc and VB Xerea, which were deployed in the port of Valencia at the end of 2016 and early 2017 respectively. Before the end of 2017, the fourth tug in the powerful new series, VB Cebalos, will also enter service in Algeciras. These 31.8 m long, 12.8 m beam tugs are powered by Caterpillar MAK main engines and have a bollard pull of 80 tonnes.
Damen Shipyards continues to build many designs of tugs that are well-suited for container operations. This was recently exemplified by two Damen-built sister tugs, the ASD 2913 type Rotterdam and Southampton, which were taken into service by Kotug Smit within the ports of Rotterdam and Zeebrugge respectively. Each of these 29 m tugs has a bollard pull in excess of 80 tonnes, allowing Kotug Smit to provide assistance to the largest container vessels calling into these Northern European ports.