The contract included three single-girder overhead travelling cranes, equipped with electric chain hoists with a capacity of 1,000kg and a profiled double-girder crane with a cable hoist with a capacity of 6,500kg. The first units were intended to handle the elements on the roof of the trams, including air-conditioning and pantographs.
Ultrasound sensors were added by Bouyer Manutention to detect the opened-up pantographs and to ensure that the hoisting is carried out only when it is in the folded down position. Manipulating an open pantograph would in fact run the risk of catching and tearing off the catenary system, said Verlinde. The 6,500kg crane is used for handling the bogies between the pit and the workshop when the wheels have to be reprofiled by grinding.?
Another special safety system was added to all the cranes to ensure that, when the pantographs, the air-conditions units, or the bogies are handled, the power supply line is not carrying current.
To power up the catenary system, five keys must first be correctly positioned. A primary key is set at the level of each overhead travelling crane, enabling the crane concerned to be started. It is freed by an electronic signal when the position of the crane is detected, when it is in a secure position.
When the key is withdrawn into a non-secure position it means the current will be cut off immediately. Once the four primary keys are correctly set, they unlock the mother key which enables the catenary system power supply to be operated.
