Faced with problems maintaining the Paris Metro’s underground tunnel network, Ateliers de la Chainette (ADC) has developed an overhead crane fitted with a semi-circular arched beam which is designed to work close to the inside of an arched roof.

The specially designed lifting mechanism traverses the flange of the curved crane beam while the hook and load travel horizontally. Custom designed software is used to lower the hook automatically when the hoist unit is climbing the arch and raising the hook when it is descending the arch.

The Cherbourg naval dockyard ordered a similar unit to operate inside the roof of submarines, along with other defence related applications.