All change please
Handling extreme peaks and troughs in box movements demands meticulous planning, as Alex Hughes explains
The arrival of ultra large container ships (ULCS) at ports around the globe is changing the face of the industry, bringing with them tremendous peaks in box exchanges that are challenging even the most experienced of handlers.
In Italy, for example, every week ULCSs call at Medcenter in Gioia Tauro, generating an average box exchange of 3,500-4,000 units. However, this could rise to 6,000 containers per call when vessels deployed by the 2M alliance commence operations.
According to Medcenter managing director Domenico Bagala, the largest ever box exchange reported in Gioia Tauro to date involved a massive 7,597 moves. “This concentration of work doesn't lead to congestion at the terminal. Quite the reverse!" he says. "When we start handling large amounts of containers in one call we expect crane productivity to increase, since one crane will be able to work for several hours in the same bay, minimising the number of times it will have to be shifted and reducing the fragmentation of work that can accrue on smaller vessels.”
Nevertheless, for a terminal to handle such big box exchanges, it needs deep draft, large yard capacity and quayside equipment able to operate up to 23 rows of deck-stowed containers. Medcenter, says Mr Bagala, not only has the necessary infrastructure already in place, but has also recently improved both the rails and quay wall structure to support larger gantry cranes and improved the alongside draft.
The terminal has upgraded its nine ZPMC gantry cranes from being able to handle 22 rows of containers to coping with 23 rows. Similarly, one of its existing Liebherr gantry cranes has been extended from 19 to 20 rows, while three others are to be converted shortly to enable them to operate across a standard 14,000 teu vessel.
To support quayside activity, MCT has also invested in new yard-handling equipment. In November, ten of the latest technology ESC340 Kalmar E-drive straddle carriers were put into service at a cost of €7m, courtesy of Cargotec. Nevertheless, Mr Bagala concedes that to maintain fast vessel turnaround time terminals need to maximise the number of cranes deployed on ULCSs.
A box exchange of up to 5,000 containers is also not unknown at Abu Dhabi's Khalifa Port Container Terminal (KPCT), even on calls by 14,000 teu vessels.
Vessels with these high move counts can produce a high waterside peak, which can be exacerbated with dual cycling, says Angelo de Jong, the terminal's procurement manager. This leads to a high load or discharge rate from cranes, which has its impact on ground transport and yard productivity. In addition to which stack utilisation rises quite quickly.
“A 5,000 box exchange would still not cause us major logistical problems. In fact, overall, big box exchanges are view positively, since there is less waste in the operational process. Indeed, if it was a case of five ships generating 1,000 boxes each, or one requiring around 5,000 boxes to be moved, we would definitely prefer the latter,” he says.
Terminal utilisation is a key factor in preparing for a call with a high number of moves, says Mr de Jong. If the yard is already operating at 70%-75% capacity, then contingency plans are necessary. However, anything under that would imply “business as usual”, requiring no special measures to be implemented. “And there have been times when the yard has been full up to 85%,” he says.
The layout at Khalifa was designed for such eventualities: the main stacking yard is automated, while an adjacent facility, worked by reachstackers and terminal tractors, mainly handles empties. On the relatively rare occasions when utilisation of the automated stacks exceeds 80%, cargo is temporarily diverted to the empties yard.
Khalifa deems another industry trick – that of pre-loading the quay – unnecessary, given that the automated yard is just 120 metres from the quay, so travelling distances are extremely short. If a very large box exchange is anticipated, the housekeeping features of the terminal operating system creates space at the front end of the stack and pre-positions load boxes to be able to handle the peak.
“We simply ask the system to create space in certain areas, after which the cranes will begin moving boxes out of there as part of an overall housekeeping exercise. So, when the vessel arrives, everything is prepared for loading,” says Mr de Jong, who notes that, in an RTG operation, pre-loading of the quay would probably have to be done to ensure sufficient containers were stacked close to the quayside. Having stacks perpendicular to the quay wall further supports a smooth traffic flow on the apron. “Not having to undertake that extra work shows the advantages inherent in an automated stacking yard when handling really large container vessels,” he adds.
But Mr de Jong says that terminals cannot become complacent, since when stacking yards do start to become full there is undoubtedly a negative impact on vessel turnaround times. In these types of situations, quay cranes are invariably left waiting for the arrival of containers from the yard. In an RTG-based yard, the drop off in productivity occurs when uptake of yard capacity is in the region of 75%; for an automated yard, productivity is affected at over 82%.
“There is a tipping point,” says Mr de Jong. “Using RTGs, you can achieve productivity of 30 moves per hour or more at levels of yard utilisation of below 75%. Once capacity uptake reaches more than 78%, productivity suddenly drops significantly. Just a short hike in yard utilisation has a massive impact."
However, this is not a problem restricted purely to ultra large container ships. Turnaround times might be lengthened on a vessel call generating around 5,000 moves, but this would also be true on a call by a 10,000 teu vessel with a similar box exchange. “It's not a given that it's just big vessels that can have a negative impact on productivity,” he says.
Ship size growth introduces air draft issues
As vessel sizes have grown, so to have quayside gantry crane sizes to enable them to access taller and wider stacks of onboard stowed containers. Some ports have experienced air draft issues, generated by cranes having to avoid deck-mounted structures.
MCT has yet to encounter any major air draft issues with its gantry cranes and has therefore not had to heighten its cranes as yet, but Domenico Bagala does not rule out future modifications if necessary.
“Height capability of gantry cranes depends on the actual vessel draft, combined with the height of the quay above the level of the sea. Gioia Tauro does not have a significant tidal range, so the lifting height above rail of our largest ZPMC gantries is 43 metres. Since, Medcenter tends to be the first port of call for ULCSs arriving from the Far East - and the last port of call for large vessels bound for Suez – invariably the arrival/departure drafts of these very large ships are very high. This combination allows our cranes to easily operate top tiers on deck,” he says.
KPCT, for its part, currently has nine cranes with a 44-metre lift height. However, any new cranes will be higher so as to avoid any potential air draft issues on 23,000 teu vessels.
“We haven't heightened the existing cranes, but we have increased the outreach, although this hasn't involved any structural modifications,” he says. Instead, the limit switch on the end of the boom has been repositioned, in what was a rather simple modification. So, rather than stopping over the 22nd row of vessel-stowed boxes, the trolley now continues to the 23rd row.
Some terminals around the world underestimated the ability of their cranes to handle ULCSs and have had to heighten various units to avoid air draft issues. Mr de Jong comments that this is an expensive operation and one to be avoided if at all possible.
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