The dynamic anti-collision system, a new element in Liebherr’s Litronic system, controls the simultaneous operation of crane motions. The basic idea behind anti-collision systems is to prevent collision between the cranes or fixed obstacles. When a number of cranes are operating simultaneously, the action of each crane can be controlled based on information of the current position of the neighbouring crane.
Liebherr says the unique feature of this new system is that the system automatically calculates actual position, speed and the acceleration of each crane as well as the load moment limitation. This provides the crane driver with maximum flexibility backed with full safety. Conventional anti-collision systems define a virtual border in order to prevent the cranes from colliding. However, this results in a restriction of the working radius of each crane. With the new dynamic anti-collision system the working radii are not restricted as the system calculates actual and anticipated crane movements.
Automated tandem lifts are another important feature of the Liebherr control system and can be carried out in three different modes. Standard mode tandem lifts require each of the two cranes to have its own driver and each driver is informed of the main functions (speeds etc.) of both cranes on their respective screen in order to control simultaneous speeds.
A more efficient alternative is the automatic parallel mode with only one crane driver controlling both cranes. In this mode the traverse remains parallel to the ship or to the starting position and an automatic control system calculates the movement of the boom head of both cranes. Speeds are derived from calculated boom head speed. The traverse remains horizontal. As the length and hook height difference is kept constant during motion there will be no diagonal line pull in the cables. Another big advantage is that the communication reduces from two crane drivers and one banksman to just one crane driver and the banksman. This allows a safe and quick lift, Liebherr says.
A third option for tandem lifts is the automatic rotation mode with the traverse being able to rotate. The crane driver only has to control the direction and/or rotation of the traverse while the control system automatically calculates the required movement of the boom heads of both cranes. Speeds are again derived from calculated boom head speed. The traverse remains horizontal.
Furthermore the Anti-Heeling System of the vessel can be supported through the control system. The total moment of all cranes can be calculated in relation to the vessel’s longitudinal axis, depending on the load and working radius of each crane and displayed on the vessel’s bridge.
Another innovative feature for these cranes is the Vertical Line Finder, which is provided as an optional control assistance in order to avoid side pull of the load resulting from long distances between operator and load or asymmetric gravity centre point. This new device controls the crane jib position by indicating the exact vertical rope position before lifting off the load. This ensures maximum accuracy and avoids potential side pull of the load. The benefit is that load swing is avoided from the outset so reducing the risk of damage to load or crane and ensuring maximum safety for operator and environment.
The first ship cranes implementing both anti-collision and automated tandem operation are the heavy lift cranes of the CBB rope-luffing cranes range. The control system records data about all individual components in load collectives, all alarm signals and failures as well as peak values. The lifetime of components can thus be analysed and plans for preventative maintenance and spare parts supply can be established.
To complement the support of Liebherr’s world-wide service network, the CBB crane is equipped with a modem for data-transfer enabling remote diagnosis. This allows for system checks as well as fault-finding which can cost-effectively be carried out without the presence of a service engineer.
