Towing system unique in tug market In-depth | TOWING
T e fi rst Mampaey DOT system is now in operation. T
he world’s first harbour tug equipped with the Mampaey Dynamic Oval Towing (DOT)
system is now in operation at the Port of Peterhead. The first results of the vessel in operation demonstrate the added operational value of the DOT system. On the 19 June 2008 the vessel was named
Ugie Runner by Mrs Judith Mackie, the wife of the convenor of Peterhead port authority board. The vessel has a length of 13m and a beam of 5.40m and was specially designed for this client by MacDuff Ship Design Ltd. With the DOT system crane and
additional ‘A’ frame for plough dredging this multi-functional vessel is capable of performing a wide range of harbour duties. Two Scania engines, rated at 350bhp each, produce a bollard pull of 9.3tonnes. With the DOT system over the bow, the vessel can rely on a bollard pull of 5.4tonnes astern. To withstand the expected dynamic forces, the DOT system has a safe working load of 15tonnes.
Towing principle What is unique about this vessel is that it is the fi rst outfi tted with the innovative DOT system developed by Mampaey Off shore Industries BV, of The Netherlands. The towing system consists of a 360deg oval deck mounted rail with free running carriages on which the towing hook is fi tted. The main advantage of the DOT system lies in the fact that a tug has a different
The Mampaey DOT system installed upon Ugie Runner.
towing point when towing over the stern and when towing over the bow. The oval shape offers the ability to connect the distance between the two towing points into one towing system, which cannot be achieved by any other existing tug, it is claimed. The close match of the towline forces
above the water and the hydrodynamic forces below enable an
optimal
manoeuvring performance with full control during towing operations, even at assisting higher speeds. Towing operations can be freely changed from any direction; either from bow to stern use or vice versa, with one integrated towing system. The main advantage of this is that the tug
operator can be flexible in deciding what mode to use to assist the ship and maintain the connection to the tow at all times. The controllability and flexibility were the most important considerations in the choice of the DOT system for Peterhead port. In the confined old port, vessels can be assisted flexibly as the full power is available in all directions. When assisting vessels in the exposed
Ugie Runner is the world’s fi rst tug to be equipped with the Dynamic Oval Towing system.
18
outer harbour, the tug can help vessels in a controlled and safe manner at higher speeds with the DOT system over the raised bow. The radial support of the
towline attachment reduces the tug’s risk of capsizing due to towline forces, an effective safety measure.
Oval ring T e DOT system consists of a heavy deck mounted rail, and the DOT system itself. T e rail forms an integrated part of the ship’s structure. T e DOT system attaches the Mampaey disc type towing hook to the rail. T e tow forces are equally distributed to the rail by means of a spreader bar, the two carriages, and the rollers. The whole structural design and integration with the ship design was analysed with fi nite element method calculations and optimised for strength and costs.
Outlook T is tug is the fi rst result arising from a cooperation
between MacDuff
Ship Design and Mampaey Offshore Industries. MacDuff has now designed a range of DOT tugs that can be tailored to client requirements. MacDuff Ship Design was recently
awarded a contract to prepare a design package, including production drawings, for three 23m tugs which include a Mampaey DOT system for an unnamed Asian client. SBI
Ship & Boat International September/October 2008
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