Globalisation, privatisation, competition and cost pressures are driving changes in the cargo handling business and in the design and construction of mobile harbour cranes, as David Foxwell finds out
Manufacturers of mobile harbour cranes say they are increasingly in demand for handling fruit,coal and steel,and suggest that demand is growing for new types of larger mobile cranes that are capable of meeting the need for heavy lifts of items of cargo such as steam and gas turbines, generators and boilers.
One of the best known manufacturers sold 76 cranes in 2005, a significant advance compared with 66 in 2004, and 62 in 2003. But that same manufacturer claims that users have become more demanding. "Clients are only prepared to invest in cranes which are made to suit their own applications," a leading manufacturer tells Port Strategy. "These applications are both varied and different, and the issues that need to be addressed include not only the size and type of vessel, handling rates, planning and scheduling parameters, and the proportion of different types of cargoes handled (containers, bulk materials and general cargo) in terms of total volumes, but duration of use and local conditions."
Typically, say manufacturers, users are asking for cranes with the following features: more intensive, rapid container handling on all sizes of vessels, including twinlift operation; container handling for specific vessel sizes, such as panamax and postpanamax ships; high handling speeds at low lifting capacities, when handling pallets of fruit, for example; container handling and a significant share of heavy lifts at multiple-cargo terminals in the vicinity of centres of heavy industry; large grab capacities for uninterrupted bulk handling with a high crane classification and, as a result, longer service life; and the ability to switch from one type of handling operation to another - from container to general cargo to bulk handling, particularly at smaller and medium sized multiplepurpose ports.
Also, as ships get larger and stacks higher, there is increased demand for higher towers, and higher tower mounted cabs, and ports and harbours want more flexibility to configure their cranes in terms of capacity, drives and hoisting speed.
When a need arises for additional handling capacity, delivery time is of central importance, as are features such as advanced propping technology with pressure monitoring. Automatic operation has the advantage that it makes it possible to quickly level a crane, and reduce the time required to move a crane and prop it alongside a ship.
With environmental issues becoming ever more important, diesel electric drive is becoming the norm, say manufacturers, offering as it does, unmatched efficiency, and reduced emissions and noise levels compared with the alternatives. Several manufacturers also configure mobile harbour cranes for operation on an external power supply, reducing running hours for the diesel engines and generators - and thus reducing maintenance requirements.
Asked what new features and improvements to existing mobile harbour cranes are being sought by terminals, manufacturers highlight features such as individually-steered axles that facilitate exact positioning of a mobile harbour crane by means of the crab steering function.Other features being introduced include radio remote control, to facilitate lifting gear change, or options such as load guidance systems or 'anti-sway' systems to increase handling performance.
Depending on the application and ambient conditions, handling performance can be increased by up to 20% with the latest generation of advanced harbour cranes, manufacturers say.
Weight has traditionally been a concern with mobile harbour cranes, particularly on unreinforced quays, but this can be tackled by adding axles to the chassis to spread the load, and manufacturers agree that weight is no longer the problematic issue it once was."The weight of a mobile harbour crane is not an issue," Peter Klein, spokesperson for Gottwald Port Technology in Germany, confirms.
"Our cranes are equipped with a number of axles which, in most cases, meets the requirements of a quay and, if necessary, additional axles can be fitted,and of course propping pads can also be modified, where necessary, to meet the requirements of the quay."
As Mr Gottwald also explains, in new generation cranes such as Gottwald's Generation 5, a wide range of cranes are based on a uniform design that is applied across a range of crane models, but variants have been developed with varying numbers of axles.Typically,two of the axles are driven by high-performance hydraulic motors,but where particularly high levels of performance are required a third drive is available as an option.
Innovative axle concepts developed for the latest generation of mobile harbour cranes enable each of the axles to be steered individually - this allows the crane not only to achieve the smallest possible turning radii, but also to perform 'crab' steering at an angle to the longitudinal axis of the crane, making the crane easier to manoeuvre and position alongside the ship, even in the tightest spaces. Individually steerable axles also reduce tyre wear,and the use of larger wheels,with diameters of up to 1,500 mm,make it possible to travel over obstacles, rails, and quays with uneven terrain.
Some models also incorporate helpful features such as refuelling during operation, and with the main fuel tank located in the chassis the centre of gravity of the crane is lower, thus minimising vibration caused by movement of the fuel when in operation.
A mobile harbour crane's propping system is obviously of central importance, and the concept adopted must be able to transfer forces to the quay substructure in an appropriate manner. Stabiliser pads may, where necessary, be modified to meet the requirements of a quay, and as highlighted above, an automatic pressure monitoring system ensures that a crane can be levelled as quickly as possible.
