A shuttering machine is a specialized lifting equipment used for opening and closing gates (silt traps) in hydraulic structures. Like general-purpose cranes, it is a cyclic intermittent lifting machine. As a crane for special purposes, the shuttering machine has the following characteristics:

LARGE LOAD FLUCTUATIONS. The previous chapters have introduced the calculation of the gate opening and closing force, which includes the gate leaf self-weight, walking frictional resistance, counterweight or water column pressure, lifting force, and suction force. All these forces except for the self-weight are related to the water pressure the gate withstands, and the water pressure varies with the movement of the gate leaf. Therefore, the load of the opening and closing machine fluctuates continuously, with a large variation and uneven distribution. For instance, when the gate falls to close, the load on the flexible components of the opening and closing machine may drop to zero, meaning the gravitational force of the gate and its accessories is not enough to overcome the frictional resistance, and it is necessary to add counterweight or use rigid rods to apply closing force and push the gate down. Sometimes, during the lifting process of the gate, a jam may occur due to unforeseen reasons, and the maximum load may exceed the originally designed rated load.