Xiangtan Q‐Type Automatic Hydraulic Flap Gate

The automatic operation of Xiangtan Q‐type gate is based on hydraulic pressure only. As the upstream water rises above the top of gate, the gate opens automatically to safeguard the banks against flood. As the water level drops below the normal water level, the gate begins to close for retaining water. Hence it allows unmanned operation and requires neither lifter nor electric power supply. Q‐type gate is different from the conventional automatic hydraulic gates. There is no floating body as balancing weight. The gate arm is a simple rectangular plate turning along the surface of bearing that is also a simple elliptical plate made of common steel. Owing to simplicity in structure, the cost of work is lower and skillful maintenance is unnecessary. Q‐type gate can operate in free out flow or in submerged flow. Its discharge coefficient is analogous too, even larger than that of broad crest weir and its capacity to remove flood debris is better. Since 1980, a group of Q‐type gates have been installed on weirs and have operated safely for 5–8 years without any damage. In this paper the functions of Q‐type gate and the design of its key parts will be introduced.