2.5.3 Multi Lifting

Electric bridge and gantry cranes are sometimes used for multi lifting operations where the load is shared between two or more cranes which must operate in unison. The cranes must each have a SWL equal to or in excess of their share of the load taking into account any possible variations of share. They must also be able to operate at the required distance apart, taking account of the load rating of the supporting structure or tracks at that proximity. The speeds of the cranes should be compatible particularly if the operation involves long travel movement in which case the long travel speeds must be matched.

When purchasing new cranes for this application the cranes should be regarded as a single machine. There should be the facility to control all cranes from one control station using a single set of controls. The crane systems should be linked so that when any motion command is given, they communicate to verify that all cranes are executing the same movement. An integrated control system of this type will eliminate the potential risks arising from a malfunction of one of the crane control systems and a lack of coordination between the individual crane operators.

When using more than one existing crane or purchasing an additional crane to work with an existing one for this application, consider integrating the control systems as described above, especially if the operation is frequent. It is often possible to perform multi-lifting operations with separately controlled cranes, but this requires careful planning, training, and procedures to manage the associated risks.