For those about to dock, cranes that suit you

Container ships are getting larger and larger: the seemingly limitless demand for imported products, particularly in Europe, has meant vessel size has been on a constant increase for many years. In July of this year Danish shipbuilder Maersk's giant Triple E container vessel sets sail on its maiden voyage. The ship represents the latest generation of giant container ships, with a length of 400m, width of 59m and a depth of 15.5m. Its impending arrival has left many major ports scrambling to improve their infrastructure to facilitate it.

Key to this development of port infrastructure are ship-to-shore (STS) container cranes, which load and unload container vessels, and need to possess enough height and outreach to work efficiently on larger ships.

"There are cranes that are only four-to-five years old which will struggle with the height of the new Triple E vessels," says Andrew Bowen, head of engineering at London Gateway. The new port recently took the delivery of several giant STS cranes from Chinese manufacturer ZMPC, which have a 25-container outreach and are 138m high. These cranes aren't just designed for the current set of large container ships, but have been future-proofed in anticipation of further increases in vessel size. Bowen continues, "It's difficult to predict how things will develop, but with talk of 22,000 TEU ships in the future it is important for London Gateway to be ready for those type of increases."

The market is complex. Increases in ship sizes affect different ports in different ways, depending on the terminal's position within the global container shipping supply chain. Maurizio Altieri, Terex's general manager, material handling and port solutions, says: "The generalised size increase of container ships is posing serious challenges to all major ports, called to cope with the need of increased draft and bigger cranes. But secondary and feeder ports remain reasonably unaffected"

"In this way, the market demand of STS cranes has seen an increased number of requests for huge Super-Post-Panamax's, but has also maintained a steady demand for 'conventional' Post-Panamax cranes. The share between the two groups is about 50% each on the total STS market volume."

With half of the market requiring consistently larger cranes, design challenges have emerged. "The most visible change in the STS design has been the increased size of the crane. Twin, tandem and double twin lifting capabilities have demanded more from the machineries and structures, which has created challenges with the weight and wheel loads, especially with the deliveries to existing terminals" says Tuomas Saastamoninen, sales and marketing director, Konecranes Port Cranes.

As a result, many dockside jobs require a manufacturer to build highly customised units. As Jeremy Bowen explains, "On a project such as this we specify what we want from the manufacturer, from the types of brakes we need, to the specific gearbox we require."

The sheer size of these cranes, as well as the cost and logistical complexity involved means there are understandably only a select number of companies capable of producing these types of machines. London Gateway's Jeremy Bowen, explains: "It's a pretty specialised industry. There aren't many manufacturers who are capable of producing cranes on this scale. In our case, we went through a tendering process which was won by the Chinese manufacturer ZPMC." It's no wonder then that Terex, Liebherr, Konecranes and ZPMC all describe experience as one of the major assets they bring to the construction of STS container cranes.

More than just a giant
Speed is a major factor for any business involved in container shipping and this has just as much impact as size when it comes to new STS cranes. Being able to process a vessel quickly is what makes one port stand out from another. "We know that Felixstowe and Southampton have both increased the speed at which they unload vessels in anticipation of us opening the port in the Q4 2013. It's natural for this to happen, they want to demonstrate they can compete," says Andrew Bowen.

Automation has had a significant impact on improved efficiency in container terminals, however the evolution of STS cranes has followed a slightly different path. Maurizio Altieri, describes the process "STS design is and has for a long time remained quite stable. While other port machinery has seen new trends and technology changes, the last real breakthroughs with STS cranes have been the introduction of the twin-lift and the phase-out of the DC drives in favour of AC systems, both of which date back a decade or two ago."

There are certain logistical obstacles that stop STS cranes becoming too automated. A moored container ship still moves in an unpredictable manner that even sophisticated computer systems struggle to cope with, particularly when weather conditions are poor. The cranes therefore require operators to pick up containers, although in the even larger modern cranes they benefit from a certain level of technological support, as Jeremy Bowen says:

"Computer assistance is necessary with such tall cranes, because the operator's depth perception is affected by the height at which they are situated. From the moment the container is picked up, computer systems assist them in passing the load down the quayside to other cranes, which are completely automated."

TEUs and vessel size
The relative standardisation of the twenty-foot equivalent unit (TEU) container has also determined the evolution of STS cranes. Whereas a TEU's height may vary, rarely does the container's width and length. As Maurizio Alteri continues: "The so-called tandem lift, where 2x40ft or 4x20ft containers can be simultaneously lifted, had been regarded as a major innovation at the time of its launch. However, in reality it has remained a niche solution not setting any real trend. Except in a few ports where the TEU ratio is substantially unbalanced toward 40ft containers, a 2x40ft lift is normally not particularly advantageous. Otherwise, the 4x20ft lift has proven to not be particularly effective, because the time required to engage and lock four containers simultaneously normally heavily jeopardises the gain on overall cycle time. Containers are predominantly 20ft and the greater cost of these cranes has meant the technology failed to gain traction."

Undeniably, the particular ways in which vessel expansion occurs drives the way the STS cranes have developed too. "Looking at the trends in vessel expansion, traditionally they had been getting wider, but recently this appears to have stabilised," says London Gateway's Andrew Bowen,

"Significant developments are now coming in terms of height, with more and more being stacked on deck. The cranes here at London Gateway are future-proofed against numerous different increases in vessel size."

Increases in width are restricted by natural geographical constraints, such as the width of straits, which for obvious reasons expand at a slower rate. However, London Gateway is still preparing for any increases in this area. The new London crane's outreach, at 25 containers wide, still extends two containers beyond the width of a Triple E ship.

Slow to develop
Not all features of the STS crane have developed at the same rate as size has increased, Maurizio Altieri explains: "While the overall trend shows an increase of operating outreach and corresponding lifting height, other parameters have remained quite stable. In particular, the Safe Working Load, which averages 50t for the "small" STS and 60-65t for larger models.

"Another area is dynamic performance, main speeds are quite variable for the smaller cranes, but are almost fixed for top values at 90/180 m/min for the hoist speed and 240m/min for the trolley speed in the biggest STS cranes."

"We see this directly from the quotation requests and projects we deal with. Basically these top parameters have not been increased in almost a decade, most probably because a further increase, would also require a corresponding increase in the relevant acceleration. This makes it a challenge to maintain structures stiff enough to avoid excessive deflections and minimize the weight increase of the machine themselves."

Old and new
On older ports, quay strength and minimum berth depth can be a limiting factor for upgrades. Altieri explains: "The first challenge ports face in coping with the latest generation ultra large container carriers is the requested minimum draft required for a new quay.

"The dead weight of the STS is increasingly important, especially in equipping an existing berth. The constraints on the STS weight have become much tighter on existing berths, originally designed for smaller cranes. This means that quay rail reinforcement, which is sometimes unavoidable, comes to represent a substantial cost."

"The main challenge for crane designers and manufacturers becomes optimising the structural design to minimise the wheel load increases due to the bigger sizes. However, the cranes must also maintain enough rigidity to not affect the performance of the operator with excessive deflections and oscillation. The recent advances in semi-automation and automation of STS cranes, while still at a pioneering stage, will hopefully allow manufacturers to overcome this problem in future."

Future-proofed
Much of this market is based on what the future holds for the shipping industry, so it is important to discover what developments manufacturers are anticipating. Size is hard to predict. Just a few years ago, forecasts suggested increases would falter. This has proved untrue.

"The future holds a mixed bag in terms of quay side cranes," says, Gerry Bunyan, Liebherr Container Cranes, sales and marketing manager, "The number of larger cranes will increase, particularly in green field sites. On the other hand, smaller ports will drive a demand for more efficiency and productivity. This will have knock-on effects in terms of optimisation and semi-automation on STS cranes for these ports. Information management in terms of box positions, logistics and integration of both the land and sea side operations will drive future changes."

With container shipping continuing to thrive it's fair to suggest that manufacturers and ports will have to continue modifying equipment to meet the demands of those using maritime facilities. As Maersk's Triple E ship sets sail, STS container crane manufacturers and ports already have to prepare for what will eventually replace the vessel at the forefront of container shipping.