Tugs are vessels used to tow barges and ships.The tug is characterized by firm structure, good stability, small hull, large main engine power, large traction and good handling performance, but it has no loading and unloading capacity.It is mainly used to tow barges and various operation ships carrying materials.Tugs can be divided into ocean tugs, inland river tugs, coastal tugs, harbor tugs, marine rescue tugs and other types according to different areas of use.[1]
Chinese name
Tugboat
Foreign name
tug
Definition
Ships for towing floating structures
Features
Firm structure, good stability, etc
Role
Carry out towing and transportation operations and perform rescue tasks
The draft of the tug shall be as close as possible to the depth of the channel, and the concave bottom of the ship where the propeller is installed is usually tunnel shaped, so that the diameter of the propeller is larger than the draft of the ship.propellerWhen working, the concave part is filled with water, so that the propeller is fully immersed in water to give full play to the power of the main engine and improvePromotion efficiency。If the water depth of the channel is less than 0.6m, tandem propellers should be used or replacedWater jet propulsion。
The towing equipment is generally a towing hook.The engine power of large ocean tugs can reach 20000horsepowerThe displacement is more than 5000 tons, which can be used for rescue at sea, towing huge ships and other large water structures, such as offshore platforms andFloating dockEtc.
Large ocean tugs are equipped with large power at the tailStreamerIt can automatically retract and release the streamer as the tension of the streamer changes in the wind and waves.Inland river tugboatMost of them are double engines, with engine power ranging from tens of horsepower to thousands of horsepower.
There are tugs and barges in inland ships. Barges are used to load goods. Most of the barges have no power, but the tugs have strong power, but their own carrying capacity is very small. Generally, barges are grouped into a fleet, and the tugs provide power to navigate.
classification
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Tugs can be divided into the following four categories according to their main use tasks.
(1) Transport tug
It is an inland and sea tug with the main task of towing barges.The advantage of this mode of transportation is that it is economical.With the further development of tug transportation, push fleets are used in inland rivers with good channel conditions (wide and small curvature) and coastal areas with moderate wind and waves.The main advantage of the push fleet is that the total resistance of the fleet is reduced, the wake of the tug propeller does not affect the resistance of the barge, and the drag loss caused by the towline is eliminated. Therefore, the hydrodynamic performance is better than that of the tug fleet;The number of crew on the barge can be reduced, or even made into an unmanned barge, which is more economical.Drawing on the experience of foreign countries in the use of push barge fleets, China has studied and promoted push barge fleets since the late 1970s, and has achieved good results in river sea intermodal transport in Hanshui, the Yangtze River, Heilongjiang, the Yellow River and the Bohai Sea, which has become the main mode of inland waterway freight transport.
(2) Auxiliary operation tug
These include tugs at ports used to assist large ships in entering and leaving ports, berthing and disembarkation, turning around, etc., tugs used by shipyards to mobilize ship berths, repair and dock, assist in trials, etc.
(3) Salvage tug
It is mainly used for rescuing shipwrecked ships at sea. It is equipped with facilities for drainage, fire fighting, diving and other operations for the shipwrecked ships. It has the ability to supply oil, water and power to the shipwrecked ships, and can tow the shipwrecked ships back.
(4) Tugs for marine development
be used forOffshore drilling platformIt is generally a multi-purpose tug for towing, anchoring, feeding, land and water transportation and towing engineering ships.
The above is divided according to their purposes. For example, according to the navigation area, they can be divided into inland river tugs, port tugs, coastal tugs and ocean tugs.[2]
Design features
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The common requirements of tugs in terms of performance are high stability requirements and more important maneuverability during towing.At the same time, each type of tug has its own special design problems according to the different use tasks.Therefore, there are different design characteristics.
(1) Transport tugs and pushers
The basic premise shall be to ensure the maximum towing force when towing or pushing, and shall have good heading stability, rudder force and reversing performance (especially pushing the ship) to control the barge fleet.
From the perspective of rapidity.When towing or pushing, the resistance of the towing and pushing boat itself accounts for a small percentage of the total resistance of the fleet, so the design focus is to ensure good propulsion performance when towing and pushing.For this reason, the draft of the stern should strive to ensure that the stern can accommodate the propeller with the best diameter and ensure the smoothness of the water flow when towing and pushing.
In terms of maneuverability, large tail draft and thinner tail body help to increase rudder area, which is beneficial to heading stability, reversing performance and slewing performance. Pushing the ship to improve its reversing performance.Reversing rudder is available.In order to improve the maneuverability of pushers and tugs, twin propellers and ducted propellers (also called Z-thrusters) that can rotate 360 ° can be used.
Tugs or pushers are generally single deck ships.Inland river tugs are equipped with deckhouses or half height sheds, and sea tugs are generally equipped with the first floor.The pusher has a permanent multi-storey superstructure to facilitate the driving vision.
(2) Auxiliary operation tug
Its maneuverability and reversing performance are very important for operation, so the captain should be short.360 ° full rotation ducted propeller should be adopted.In addition to paying attention to the towing force during towing, proper consideration shall be given toFree speed。
The arrangement shall ensure that the upper deck is relatively open to facilitate operation, so generally onlyDeckhouse。Due to the small number of crew members, the status of the former living quarters is also small.
Due to the relatively small quantity of fuel, fresh water and domestic supplies, it is easy to deal with in the layout.Some also use the port as a tugboat and also as a short distance coastal towing.
(3) Salvage tug
No matter how bad the sea conditions are.It can arrive at the scene of the accident as soon as possible to carry out rescue, so wind resistance is particularly important.In addition, the requirements for free speed and seakeeping performance are also high, and the towing force during towing is also important.Therefore, this type of tug is usually equipped with a large power main engine and adopts double propellers and controllable pitch propellers.Due to the large power of the main engine, the long distance of the continued voyage, and the requirements of rescue equipment and rescue supply of oil, water, food, etc., there are relatively more crew members, so more building status and buoyancy are required.Compared with other types of tugs, its displacement and main dimensions are larger.Long forecastle type and large ballast tank volume (floating state and stability after adjusting oil and water consumption) are often used in the building. When the length is more than 50m, the requirement of unsinkable tank 1 shall be met.
(4) Tugs for marine development
In addition to the performance requirements of ocean tugs (stability, towing force, maneuverability), it should also have some technical performance of small transport ships.For this reason, the superstructure should be concentrated in the front as far as possible, so as to leave a large rear open deck position to arrange cargo tanks and stack deck cargo. The power of the main engine is mainly considered according to the requirements of the towing drilling platform.The controllable pitch propeller is also suitable for propulsion.The trim adjustment of this type of tug in different service conditions is a complicated problem, so attention should be paid to the front and rear distribution of its oil, water tank and ballast tank.[2]
