<b>Cranes</b>
Since the containerization, ports and shipyards have expanded their capacities more and more in order to maximize their performance. Construction, maintenance and processing times have been minimized in order to increase productivity. Cranes with a higher capacity are an essential element of shipyards and ports for construction, maintenance and cargo handling. The installation, maintenance and equipping of such cranes require specialist knowledge and equipment. The steady development towards larger ships and cargo handling devices around the world are presenting shipbuilders, port owners and shipyards with new challenges.
Terminal cranes are essential to discharge cargo from ships and on to load ships. For the handling of containers most big ports have huge container bridges who can replace themselves along a ship. The cranes are also called container handling gantry cranes or ship-to-shore cranes.
Once a container is unloaded by ship-to-shore crane in most ports a straddle carrier is picking up the container. Straddle carrier is a vehicle that carries its cargo underneath its “straddle”. It then can move on rubber tires around and pick up containers and discharge without any external assistance.
Mobile cranes combine the function of a tower crane with the mobility of a truck crane. Heavy-lift cranes are specialised to move heavy-lift cargo.
Crawler cranes provide stability and mobility with an undercarriage pair of tracks for the operation of less developed facilities or to support developing construction.
Rig cranes can be mobilised quickly, are flexible in configuration with a long reach and with a combining lifting capacity up to 5,000 tons. They are the workhorses for heavy projects.
Gantry cranes or overhead cranes are built on top of a gantry, a structure to mount a workspace or object. A gantry crane can be either an entire structure on rails like in shipyards, a supporting structure fixed in a location on the ceiling of a building with a movable hoist running along a beam or rails and can be installed on ships to move e.g. hatch covers.
On board a vessel, several cranes can be installed e.g gantry crane to move hatch covers, deck crane to handle provisions, cargo cranes to handle bulk cargo, containers, general cargo, palletised cargo etc.
Depending on the type of ship, loading and discharging is done through different handling equipment. These can be land or ship bound. Land-based handling facilities are, for example, container cranes for container handling or e.g. also pneumatic conveyors and belt conveyors for loading and unloading grain and similar bulk goods.
General cargo, bulk cargo or even containers can be lifted on and off board by on-board crane systems. On-board cranes (also known as deck cranes) with rope luffing mechanisms are preferred; slewing cranes with a lifting capacity of > 150t are called heavy lift cranes that can carry up to 800t or more.
The inclination of the crane jib is varied with the luffing mechanism. The statics are designed so that the incline can be changed under load. The boom is swiveled around the crane axis with the slewing gear. If there are several cranes on board, they are arranged in such a way that their conveying areas overlap in order to be able to serve the entire deck area.
In order to avoid additional lifting work due to a vertical load movement when the crane arm is extended, the load path is kept as horizontal as possible during luffing. This is achieved by cleverly guiding the suspension and luffing cables.
Crane structures are designed in solid wall or half-timbered construction. The former includes both those consisting of normal profiles or sheet metal girders and those made in cell, box or shell construction. Trusses are built out of triangles in a statically determined manner and viewed as trusses.
In order to lift the load from or on board, it must be possible to turn the crane boom around the vertical crane axis. This is done by the slewing gear of the crane. This is where the bearing of the rotatable tower and the drive of the slewing gear are located.
Cranes
Advertisement: