Abstract:On February, 15th 2005, Gondán S.A. shipyard in the north-west of Spain handed over the escort tractor Voith tug “VELOX” to the Norwegian shipowner Østensjø Rederi AS, the first of this type in the world to incorporate a bulbous bow. After generally making a reference to the benefits obtained by the incorporation of a bulbous bow regarding the reduction of the ship's resistance, we specifically analyse the consequences derived from the incorporation of this appendage in an escort tractor Voith tug concerning i… Show more
“…On the other hand, taking into consideration the tendency of curves at higher speeds, especially with a rudder angle of 25 • , it could be concluded that at present, there are no escort tugs available in the market with that BP required. Nevertheless, this circumstance is solved in real life using two tugs working in tandem [39], so the BP of each escort tug is added as it is regulated in Los Angeles/Long Beach port [40,41].…”
Due to the lack of information about the concept of Tons of Steering Pull (TSP) of many escort tugs, and the lack of research works relating the TSP demanded by a tethered vessel with respect to the TSP provided by tugs, the present paper shows an original study with mathematical models on how to solve these problems. What is more, an important percentage of the towing sector always employs Bollard Pull (BP), which is considered the only parameter capable of defining performance, so this paper aims to relate BP with TSP. The present research was carried out based on more than 25 escort tugs of different towing companies. Furthermore, a real case study of different tanker vessels was used for modelling purposes of tethered vessels’ TSP. Finally, once the proposed models were obtained, they were compared with International Maritime Organization (IMO) guidelines. The results showed charts with the main independent variables of tugs and vessels in order to be as useful and practical as possible to the shipping industry, mainly to ship owners and tug operators, from a safety point of view.
“…On the other hand, taking into consideration the tendency of curves at higher speeds, especially with a rudder angle of 25 • , it could be concluded that at present, there are no escort tugs available in the market with that BP required. Nevertheless, this circumstance is solved in real life using two tugs working in tandem [39], so the BP of each escort tug is added as it is regulated in Los Angeles/Long Beach port [40,41].…”
Due to the lack of information about the concept of Tons of Steering Pull (TSP) of many escort tugs, and the lack of research works relating the TSP demanded by a tethered vessel with respect to the TSP provided by tugs, the present paper shows an original study with mathematical models on how to solve these problems. What is more, an important percentage of the towing sector always employs Bollard Pull (BP), which is considered the only parameter capable of defining performance, so this paper aims to relate BP with TSP. The present research was carried out based on more than 25 escort tugs of different towing companies. Furthermore, a real case study of different tanker vessels was used for modelling purposes of tethered vessels’ TSP. Finally, once the proposed models were obtained, they were compared with International Maritime Organization (IMO) guidelines. The results showed charts with the main independent variables of tugs and vessels in order to be as useful and practical as possible to the shipping industry, mainly to ship owners and tug operators, from a safety point of view.
“…The consequences of this manoeuvre are presented by Baniela and Diaz (2008): Relatively high-speed navigation is required.Braking or braking and steering is controlled by the tug to maintain a reference angle corresponding to the water flow direction, as opposed to the direction taken by the vessel on tow.…”
Section: Operating Tugs For Escort Assistancementioning
confidence: 99%
“…Figure 14 shows the balance of lateral forces acting on the escort tractor Voith tug involved in indirect operations. It is known that (Baniela and Diaz, 2008; Van der Laan, 2002) three forces act on tugs involved in indirect operations. The balance between them will be represented in an equation for the tug's movement under these conditions: The resultant hydrodynamic forces for lift and drag of the skeg and hull, applied to the Centre of Lateral Pressure (COP) above the quick work of the tug: H f The resultant thrust related to the two cycloidal propellers, whose point of application varies according to the thrust of each propeller: PtThe tug force related to the towline action applied in the staple: T f Figure 14.Balance of forces acting on the escort tractor Voith tug during the escort manoeuvre.…”
Section: Controlling Towing Manoeuvres By Operating the Towing Winchmentioning
confidence: 99%
“…This situation is to be related to the case of indirect towing operations. The resultant equation (Baniela and Diaz, 2008) indicates the relationship between towline forces ( T f ) and the resultant hydrodynamic forces ( H f ): This study is intended to analyse what effect automatic manoeuvre control has on equilibrium in navigation. To this end, this table has been developed to relate the different operational modes (without winch control, with a constant tension and with controlled tension and distance, as seen in Table 2).…”
Section: Controlling Towing Manoeuvres By Operating the Towing Winchmentioning
An escort tugboat comes to the aid of a vessel when that vessel is navigating in confined waters and at a speed that is usually higher than six knots. In the escort manoeuvre, two systems come into play. One is the propulsion and steering of the vessel. The other involves the tug winch in terms of the tension it exerts and the length of towline released. In this way, the tug winch becomes a key piece of equipment. Along with the difficulties of carrying out the manoeuvre itself are the risks resulting from the operation of the winch. For this reason, automatic manoeuvring systems have been developed to facilitate this operation. They consist of information technology applications that help the skipper with manoeuvring the tug. At the same time, they make it possible to display and monitor the most important parameters of the towing winch. This study will describe a control system for the towline so that it can help carry out the towing manoeuvre with an escort tug. It indicates the control parameters for the manoeuvre, as well as the operational variables of the winch on which the system runs. K E Y WO R D S 1. Escort tug.2. Towing manoeuvre control. 3. Towing winch monitoring.
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