A 10t double girder bridge crane in a unit has its power indicator light on, and the indicator of the operation linkage table is on, but it cannot be started. After the maintenance personnel went to the site for inspection, it was found that the safety door from the driver's cab to the walking platform was not closed. When the maintenance personnel close the safety door, everything in the crane is normal, which is a false fault.
In the safety protection of the crane, there is a door switch on the hatch door, the driver's door and the access door. When the crane driver or maintenance personnel go to the crane for maintenance, the hatch door must be opened to the crane platform, or Open the access door to the crane rail beam. At this time, the normally closed contact of the electrical switch on the opened door is disconnected, and the main contactor of the electrical box is released, thereby cutting off the power of the crane and preventing the crane from starting. At the same time, this protection protects the maintenance personnel from the danger of charging the trolley on the bridge, and also prevents others from starting the car and inspecting the maintenance personnel. It can be seen that the protection of the safety door switch is necessary.
