New 'Friction Free' Tugboat Point Lessens Dangers of Towlines for Salvage Interests

NETHERLANDS – WORLDWIDE – Anyone who has witnessed a cable part under tension, particularly a steel hawser whilst recovering a fishing net or, worse still, towing a large vessel, will be aware of the potentially devastating results of any ensuing accident. Yesterday at the 22nd International Tug, Salvage and OSV (ITS) convention in Barcelona a new device to lessen the dangers of towlines was unveiled which assists in the prevention of chafing whilst under way.

The Rotterdam based shipping company Rotortug and ASD Ship Design from Alblasserdam in co-operation with Ridderinkhof in Hasselt have developed the so called ‘azimuth friction free towing point’ which is equipped with a rotating wheel to guide the towline without friction (patent pending. The new device is particularly useful when synthetic towlines are used.

Conventional towing point designs are usually a rigid construction fitted with polished and stainless steel cladding in line contact areas guiding a towline to a towing winch. Using state of the art towing winches, towlines are winched in and out automatically by using a pre‐set line force to prevent both dynamic overloads and slack wires.

Synthetic towlines are gradually replacing steel wire towlines. They are generally seven times lighter compared to equivalent steel wire towlines. In fact synthetic towlines are so light (and thus easy to handle) they float in water. A downside to synthetic towlines is their sensitivity to chafing and maximum safe working temperatures.

Synthetic towlines can easily fail due to chafing and friction with increased risks for safety. The rapid switches of direction as line is fed in and out with traditional winches causes high temperatures, especially to the inner core of synthetic towlines. This becomes an even bigger issue when operating in high outdoor temperatures. The friction and the high resultant temperature cause much wear and ultimately the failure of a towline connection.

The three companies involved all have pedigrees in the industry Rotortug bv, as the name suggest builds rotary tugs with three azimuth thrusters to provide greater manoeuvrability, ASD Ship Design has been responsible for over thirty new types of vessel and Ridderinkhof has developed the so called Wave Winch for sea and port tugs, a high dynamic winch that secures a tight towing rope even in difficult circumstances. Ridderinkhof has been awarded the exclusive production rights for the azimuth friction free towing point for the first years of production.