The key allows an operator to effectively turn off the rated capacity limiter so that the crane is able to lift a load that could lead to structural damage or tip it over.
The key will be replaced with a set-up button. The button will override the LMI during the rigging process, and in other conditions where no load charts are supplied by the manufacturer. The set-up button will not allow the operator to override the crane computer in conditions where there is a load chart.
The changes have been made by the crane and lifting equipment product group of the European manufacturers’ association FEM, Fédération Européene de la Manutention.
The FEM stepped in to save the new European design standard, EN 13000, when several governments objected to the override keys and refused to entirely confirm EN 13000 in 2005. A committee led by engineers from Liebherr, Terex-Demag, Faun and Locatelli, among others, met to try to solve the problem.
Now, a solution, which the FEM calls “an entirely new safety concept”, is within reach. Any cranes marked with a CE label will need to have made these changes, or equivalent ones.
The plan does allow the operator to up-rate the crane in a few unusual circumstances.
In a deadlock situation, where the rated capacity limiter has cut off movements that prevent the crane from returning to normal conditions, operators will be able to press the set-up button to raise the RCI’s shut-off limit capacity to 110%. During this time, crane motions will be limited to 15% of their maximum working speed.
In case of an emergency, the crane can also include a bypass switch outside of the crane cab, which, if activated, also cuts crane speeds to 15% of maximum. This switch automatically resets after every load cycle.
Every time an operator activates the set-up button or overrides the LMI, a data logger will record how much the crane is overloaded (including all values above 100% nominal capacity of the load chart), and other conditions that might be useful in evaluating an accident.
For a more in-depth report on the issue, see Cranes Today June 2006, pp15-18.
