A panel of experts debated what is required to deliver more powerful, stable, manoeuvrable, cost-effective and safe tugs during Riviera Maritime Media’s Tug vessel classification and design: safety, stability and notations webinar
This webinar was held on 30 March 2021 as part of Riviera’s ITS TUGTECHNOLOGY Webinar Week, which was supported by the European Tugowners Association and UK Maritime Pilots Association.
The panel consisted of Robert Allan Ltd director of design development Lawren Best, Svitzer Europe head of marine standards Scott Baker, The Workboat Association chief executive Kerrie Forster and United Kingdom Maritime Pilots Association chairman Captain Mike Morris.
They examined the latest rule requirements for tug safety and stability and the trade-offs that are made when balancing design, cost and compliance considerations.
The panel also outlined technologies inspiring a new generation of future-proofed tugs, which could put the seafarer at the centre of the design.
Mr Best explained what is required for escort tug stability, where engine, thruster and hydrostatic forces need to equal the towline and hydrodynamic forces on the vessel.
He explained how important it was to inform tug masters of the steering and braking forces and translate these into towing-system load ratings. “Most critically, is informing the tug master of the safe operational stability limits,” said Mr Best.
He said Robert Allan has devised two main methods of doing this. It has written escort safety limit placards specific to individual tugs to be displayed in wheelhouses, providing stability and safety information to masters. “We also provide electronic inclinometers to give operators feedback of the degree of heel,” said Mr Best.
He also outlined IMO’s implemented Tug Stability Criteria, which was previously introduced by classification society Bureau Veritas and adopted by others, including Lloyd’s Register and ABS.
“Class harmonisation of criteria through IMO is a great improvement,” said Mr Best. It has been adopted by many individual flag states and others are undergoing this process. “There has been progress,” he commented, “But a couple of flag states are holding out, with their own tug-stability criteria.”
Mr Forster outlined how naval architects need to consider seafarers who will be working on these tugs over a 30-year lifetime in their designs.
“Do we feel seafarers are part of the design of vessels as well as the end-users?” he asked. One positive in tug design for masters and other crew is the position of the bridge. “Wheelhouses are raised with good visibility of the working decks and for good eyesight of the stability of the vessel,” said Mr Forster.
But he highlighted how interior arrangements are less well designed. “When raising wheelhouses high, what about the access stairs and companion ways?” he asked.
Stairs are often steep, passageways are narrow and there are tight corners for tug crew to get around. These can be awkward to move around even when tugs are berthed.
“Some tugs are poorly designed for the people on board,” said Mr Forster, adding the industry needs “seafarer-centric tugs” where layout of the living and working areas is better considered.
Svitzer Europe’s Mr Baker explained how tug capabilities do not always match requirements for handling ever-larger container ships, which are more than 400-m in length and 60 m in breadth.
Ships are built for a lifetime of 20-25 years, but tugs can continue operating for more than 40 years. “Tugs have lifecycles beyond commercial ships,” said Mr Baker. “And ships are built in excess of what tugs can cope with.”
This is why there is continuous need for tug operators to update their fleets with more powerful and stable tugs, with higher bollard pulls.
Mr Baker also highlighted how in some ports, the space for manoeuvring these larger ships is unchanged, resulting in ship-handling challenges. “In some ports there is barely enough space for tugs to assist ships,” he said.
Capt Morris agreed there is limited space in ports and waterways, such as the Manchester Ship Canal in the UK. He provided a perspective on tug design from a pilot’s viewpoint. Which on many ship bridges does not include visualisation of the tugs handling them.
“What pilots need from tugs is that they can do the job required,” said Capt Morris. “Some designs are better for different jobs, therefore we need the correct tug for the job.”
Another important consideration is close co-operation and communication between pilot, ship captain and tug master. “On the majority of ships, pilots cannot see the tugs from the bridge and tug masters cannot see the ship bridge,” said Capt Morris. “Pilots need to be aware if there are issues. Tug masters need to tell the pilot if there are problems with the tug, or if there is a need to reduce speed.”
In an interactive webinar, attendees were asked their views on various elements of tug stability. First they were asked what they thought the average commercial life expectancy of modern harbour tugs is. Just 1% of those responding said up to 10 years, and 17% voted 10-20 years. The majority (62%) thought it was 20-30 years, and 20% voted for more than 30 years.
Attendees were then asked what would deliver the greatest improvement in the safety of escort tug operations. Of the responses, 20% were for crew training, 7% for electronic inclinometers, 3% for escort tug safety placards and 70% voted for all of these together.
They were also asked how owners and operators regard placing reasonable maximum angle limitations on downflooding when determining a tug design’s maximum bollard pull. 35% thought it was very important, 42% said important, 16% voted for ’of middling importance’, 5% said of no great importance and 2% thought of no importance.
In another poll, attendees were asked how owners and operators regard having IMO-harmonised stability criteria across all classes and all flag states. 51% said it was very important, 43% thought it was important, 4% said it was of no great importance and 2% of middling importance.
Panellist at Riviera’s Tug vessel classification and design: safety, stability and notations webinar were (left to right) Robert Allan Ltd director of design development Lawren Best, Svitzer Europe head of marine standards Scott Baker, The Workboat Association chief executive officer Kerrie Forster and United Kingdom Maritime Pilots Association chairman Capt Mike Morris
To view details of upcoming Riviera webinars and virtual conferences use this link to the events page