What has been accepted for decades is no longer so as risk assessments now consider the potential risk of accidents in relation to the load being hooked to the structure of the surrounding hall or vehicle, office container or tooling in the path of the load during lifting, lowering, long-travel or short- travel movements. As the cranes are usually optimised for their operating scope of work, any accidental blocking of the load may lead to dynamic overload which, in the worst case scenario, can result in hot steel being poured out, load drop, wire rope rupture with dramatic human and material damage, the permanent deformation of structures, etc. The same applies for a rotor on a power unit or a tool in a press that remains blocked while an attempt is made to lift it.

In order to prevent such incident/accident, it has become mandatory to instal overload protection devices in those countries which have implemented this regulation in their laws and strongly advised in those countries where no such safety regulation applies – so far.

Such heavy hoisting systems are generally equipped with auxiliary hoists which, if their capacity is not as high as the main hoists, the combined loads of both main and auxiliary hoists may exceed the nominal capacity of the EOT crane. For this reason, in addition to the individual overload protection device, a summing module will also be necessary. Each load limiter will protect its corresponding hoist against overload, while the summing module will receive load informations from the individual limiters analog outputs to ensure the overload protection of combined loads.