Tugboats prepared to handle larger tonnage in congested ports

Container ship challenges 

Capt Robarts explained the challenges of manoeuvring 24,000-TEU, 400-m ships into the UK’s largest container port, Felixstowe, which is part of the Harwich Haven. “We use tugs for escort towage and to assist in docking ships,” he said. “The challenges include the UK weather, which has increased in severity, increasing windage on the upper exposed areas, and tidal forces on ship hulls.” 

These forces have a dramatic effect on towage and handling container ships, especially berthing and undocking in adverse weather in the confines of the haven. “In confined areas there is only so much room to move,” said Capt Robarts. “We need multiple tugs and planning.” 

In Harwich and Felixstowe, pilots use medium-range escort tugs with azimuth stern drive and bollard pulls of around 85 tonnes. “We have developed standard operating systems through understanding the navigation, escort and ship assist modes. We use two tugs and the ship’s engine and rudder during turns.” This provides redundancy in manoeuvring in case weather and tides impact these turns “This removes a single point of failure.” 

Capt Robarts said team training was vital for ship handling in the Harwich Haven. Pilots, tug captains and harbour masters train together at HR Wallingford’s facilities in Oxford, UK using simulators to practice scenarios. “This is team glue,” he said. “We develop best practices for ship pilotage and towage, even the port director is involved.” 

Communications and devices for improving situational awareness are also important in ship handling. “A pilot cannot see the tugs, so training and communications is important. During indirect turns, we need the constant feed in communications to prevent snapped lines, prevent the tug overtaking the ship and to prevent failures.” 

Pilots use portable tablets with harbour navigational charts and AIS data for vessel positioning to improve situational awareness. “Pilots could have to control four to five tugs, that is six people communicating to do one manoeuvre,” said Capt Robarts. 

There is planning prior to container ship manoeuvres and dynamic risk assessments to ensure there are procedures when operations do not go to plan. “When 400-m container ships are in high-risk areas, there could be blackouts and towline failures,” he continued. “But tugs will save the ship, so it is manoeuvred to the berth with no damage. If there are the right resources, right training and right equipment, it will go right.” 

Dynamic towage 

Mr Oggel agreed ULCSs have high surfaces exposed to wind and are susceptible to changes in tide and currents. They need to sail at speeds of more than 7 knots to remain in control, but when entering ports, they are slowed and then controlled by tugs. “There is little room for error,” he said. “If things go wrong, there is a problem, such as Ever Given in the Suez Canal.” This ULCS was grounded in the Egyptian shipping canal for nearly a week when high winds pushed it into the soft sides in March 2021. 

Tugs need to use the dynamic forces of the ship and their friction in water to slow these large vessels. Carrousel RAVE tugs use their whole profile to generate lift and control the ship. 

“Ship inertia means tugs need to reduce their speed as they come into ports,” said Mr Oggel. “Tugs need to stop the ship in time and manoeuvre them in ports. They need to extend operating windows for adverse weather and tides when ports can receive ships without increasing the footprint of infrastructure.”  

These tugs are designed to use this inertia instead of battling it with higher-powered engines.  

“We can harvest their kinetic energy and momentum in the tow, by using the resistance of hull forces on the line,” said Mr Oggel. “These tugs use energy already there instead of generating energy in the opposite direction.” Carrousel RAVE tugs are used to escort and handle ULCSs in the port of Antwerp, Belgium by Multraship Towage.

On the panel were (left to right): Novatug managing director Julian Oggel, Kotug International manager for training and consultancy Daan Merkelbach and Harwich Haven Authority senior pilot Captain Mike Robarts