Introduction
One of the major problems for smart ports and automated shipping is the bit when the boat collides with the dock. That sounds more dramatic than it is, but all ship mooring (actually, docking) starts with a “controlled” collision between the pier and the ship and then comes the job of keeping the ship relatively stationary, so that it can be unloaded. Traditionally (over 28,000 years), this has been done with hawsers (mooring ropes) and a lot of manual labour. This is problematic for integrated unmanned smart shipping systems.
Analysis
Automating mooring systems is no simple task, although well worth the effort. A major problem with rope hawsers, despite their width and strength, is that they break. With new materials and automatic tensioners, this is becoming less common, but it still happens. When they break, there is a whiplash effect that can cause these large ropes to snap back across the dock at huge speed destroying any equipment and people in their path. Although no international figures are available, those countries that do publish accident statistics for dockside injuries have significant numbers of deaths and severe injuries documented from snap-back accidents.
The neat thing about automated systems is the speed of docking and undocking, which would be measured in seconds and minutes, rather than minutes and hours.
Initially one may consider using a robot handling system to replace the stevedores or longshoremen and such systems exist using shipboard robotic arms which, combined with mobile cleats, should allow unmanned mooring but would not solve the snap-back problem. Companies such as MacGregor and Trelleborg (Dynamoor) supply this type of equipment
Most marine cargo ships and cruise liners are made of steel so magnetic mooring systems exist made by Mampaey Offshore Industries, and Cavotec in association with Mooring Systems Limited (MSL) of New Zealand. It is believed Chinese companies are also proposing similar systems. These use electromagnetic grips to attach to either the vessel hull, or specially placed steel plates. Of course, there may be problems with residual magnetic flux getting inboard the ship and affecting sensors or cargo, but that could easily be engineered away.
Another potential issue is hull thickness. Firstly too thin a hull, say around an empty cargo hold, might cause the steel to buckle or, for older ships, excessive paint and rust and even residual marine growth may cause an enlarged air-gap causing the magnetic grip to be insufficient. This could be a problem for smaller ports and the tramp end of the merchant navy. Modern ports entertaining ideas for smart ports might use magnetic grips for modern ships that can improve suitability.
The systems seem reluctant to specify the amount of power required and what happens in the event of power failure – brochures generally feature stand-alone generators powering each set of magnetic grips. Alternatively, the magnetic grips could be mounted on board the ship and the port would only have to supply a stable steel structure to grasp.
Nature provides some solutions for holding objects in marine environments, if we consider barnacles, seaweed and the octopus. Barnacles either use glue or grow into the substrate; seaweed extends “holdfasts” root like structures that just grip and have no nutrient channels; while the octopus uses suction cups to hold onto its prey.
Gluing ships to a dock would probably not be suitable as ships heave, sway, surge, roll, pitch and yaw, even alongside a dock. Using a holdfast, or web, to capture a ship and hold it a fixed distance from the dock to facilitate loading and unloading has yet to be designed. Suction cups, however, are certainly an option and vacuum mooring systems are already popular in some ports.
Vacuum systems exist and are eminently suitable for many dockings. They have been in use for more than 20 years and are installed in many ports. Companies that make and install these systems are Cavotec, AMS, Trelleborg and Macgregor. They are generally installed in larger ports that deal with newer cargo vessels, cruise liners and ferries.
The same comments that addressed issues with the electro-magnetic grips apply to the vacuum grips. The hull strength (thickness) must be sufficient, there must be no water or residual fouling on the surface because vacuum pumps can easily pump our gases, but they are poor if there is liquid in the system that must be evaporated by low pressure, although a robust but lesser vacuum can be pulled using a venture system. A tight seal is imperative, so residual fouling would be a nuisance. There is a similar issue with changes in draught due to loading and unloading, as ballast water cannot be discharged willy-nilly inshore because of the danger of contamination by invasive species of marine life.
The major benefits of both vacuum and electromagnetic grips are safety and speed. The greater dampening effect of these systems, when compared to rope (or chain), allows swifter loading operations. Even CO2, generated by the energy consumed by either generating the magnetic field or vacuum, is easily offset by that saved by the increased speed and throughput of vessels. There is an additional issue of maintenance, as these are complex electro-mechanical systems that must weighed against rope wear and the fact that rope (fibre) showing wear (which will only occur at chafing points generally) should be replaced in its entirety. In addition, these systems are easy to automate and incorporate into a smart system.
Summary
Rope mooring is unlikely ever to be totally replaced, especially in smaller ports where ship visits are more sporadic. But in major ports dealing with high-volume shipping and contemplating the transition to smart operation, it would seem an obvious choice to move away from rope mooring to vacuum or electro-magnetic.
Major shipping companies should give serious consideration to the mounting of these systems on board wherever possible, so their ships have more freedom of choice between ports that may not have the budgets for fully functioning automation, but may be able to swing for steel plating enabling ships to self-moor.
Our report on The Future of Smart Shipping will explore this topic in more detail and is due be published Q4 of 2023. Please contact a member of our team if you would like to pre-purchase the report with a discount, or nominate your company to take part in our interview and research process.
