Tugboat (ship type)
Tractor , also known as tugboats, (Engl. Tugboat or tug ) are vessels with powerful propulsion system, the other for pushing and pulling ships or large floatable objects are used. Mostly towing cables are used for pulling , which are hung on hooks on the tractor or rolled up on cable winches.
In Germany there are 450 pieces together with the push boats (status: 2000).
Types of tugs
Tugs can be differentiated according to their design and purpose, whereby the features can also overlap.
Differentiation according to purpose
- Deep -sea tugs: sea-going tugs which are used for the transport of deep -sea lighters , wrecked ships or other objects.
- Anchor handling tug (AHT - anchor handling tug): seagoing tractor with high bollard pull leading to the entrainment of drilling rigs are used; they sometimes also serve as a supplier for oil rigs (AHTS - Anchor Handling Tug Supply)
- Salvage tugs : seaworthy tugs with high bollard pull that are used for salvaging wrecked ships; partly also used as an emergency tug onbehalf of the state
- Port, assistance or tugboat tugs: relatively small, very manoeuvrable tugs that maneuver larger ships in ports to the berth (i.e. tow, push, push, etc.).
- River or inland tugs : not seagoing tugs, the motorless barges and barges hauling by canals and rivers. Sometimes the barges or barges were also referred to as tugs.
Differentiation according to type
Basically, a distinction can be made between tugs with a conventionally constructed drive system (motor, gearbox, shaft system, propeller, rudder) and tugs with all-round controllable drives ( propeller pods or Voith-Schneider drive ). With the latter design, a distinction is made according to the installation position of the drive systems.
- Rear tractor (ASD - azimuth Hing Star Drive, dt. Pivotable rear-wheel drive ): One or two drive systems, installation in the rear
- Tractor tug : One or two propulsion systems, installation under the bow
- “Rotor” tug : three propulsion systems, two under the bow, another in the stern. The tractor can turn on the spot. The name "Rotortug" is a protected name of the Dutch company KST.
Power, bollard pull, propeller characteristics
The performance of the tractor varies depending on the type. An essential measure is the so-called bollard pull , which is measured in tons. Ocean tugs have engine outputs of 15,000 kW and more, the bollard pull can be over 250 tons. Modern larger harbor tugs develop a bollard pull of 20 to 80 tons with engine outputs of 2,000 kW to 4,000 kW.
The fact that a tug has to provide much greater thrust than just its own resistance at the respective speed means that its propellers have to have their optimal operating point with a relatively small rate of progress. That is why the propellers of tugs are mostly designed as jet propellers, i. i.e. they are encased in a Kort nozzle .
The most powerful anchor-handling tugs of German shipping companies are the Uranus and Orcus from the Hamburg company Harms Bergung Transport & Heavylift GmbH & Co. KG with a bollard pull of 285 tons, followed by Janus and Ursus (219 tons each) from the same shipping company.
The world's most powerful salvage tugs are also in use for German shipping companies. The Nordic used as an emergency tug has a bollard pull of 201 tons, its predecessor Oceanic of 180 tons. Both ships are or were operated by the Hamburger Bugsier-, Reederei- und Bergungsgesellschaft mbH & Co. KG .
Harbor tugs have to be particularly agile because of the limited action areas in the narrow harbor basin. Therefore, in contrast to earlier designs with conventional propulsion systems, propeller pods, so-called Schottel rudder propellers, are often used for the drive, which can rotate around the vertical axis without limitation . These can be used both as main propulsion or as primary maneuvering propulsion.
Another variant is the Voith Schneider drive , in which knife-like blades pointing downwards are used for the drive thanks to a sophisticated mechanism. Tugs with this drive are also known as "Voith water tractors".
In many cases, the tug is not used by pulling cables, but by exerting pressure directly on the ship's hull, so-called tugging. This saves the line connection and enables maneuvering in very tight spaces, for example in docks. The hull of the maneuvered ship must be specially reinforced at suitable points in order to avoid deformation. The relevant points on the drop side are marked accordingly, for example with the word “TUG”. For example, tugs (not to be confused with the Bugsier shipping company ) have, in addition to the usual rubbing strips, large rubber buffers at the bow and, depending on the drive system, also at the stern.
Rubber buffers on the bow of an old tractor in Brunsbüttel
As a new innovation, hybrid tractors with batteries and electric motors combined with diesel engines are being built. The port of Antwerp is building a tugboat powered by hydrogen and diesel.
New Zealand is building the first battery-powered electric tug for the port of Auckland.
The Dutch company Novatug developed the Carrousel Rave Tug , the "carousel tug ", in which the towing winch is not attached to a fixed point on the deck, but can rotate freely around the central deckhouse on a huge turntable . This increases the maneuverability and efficiency of the tractor use, especially when braking and with steering assistance. Because the tow rope is always optimally positioned, there is no risk of the tractor capsizing, regardless of its position in relation to the direction of pull. The prototype MULTRATUG 32 , which went into operation in 2018, is 31.90 m long, has a total engine power of 5300 kW and a VSP drive each under the bow and the stern.
- Peter Andryszak: Das kleine Buch vom Schlepper , Oceanum Verlag, Wiefelstede, 2014, ISBN 978-3-86927-411-9
- Jan Mordhorst: Tug. Use in port and on the high seas. Koehlers Verlagsgesellschaft, Hamburg 2008, ISBN 978-3-7822-0974-8
- Ralf Witthohn: The "bull" pulls with revolutionary technology . In: Deutsche Seeschifffahrt, Issue 9/2009 , pp. 56–57. Storck-Verlag, Hamburg 2009, .
- Steam tug at Ruhrort harbor, around 1940. digit.wdr.de, with further photos of the ship
- Information on the KST Rotortug ( Memento of the original from October 27, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed March 6, 2011
- Technical data of the "Multratug 32" on the website of novatug.nl, accessed on August 16, 2020