The cast steel flap door product is divided into round flap door and square flap door. The flap door is suitable for various pipelines and water channels in water supply and drainage and sewage treatment projects for overflow and check, and can also be used as various vertical shaft covers. It is only used for circular water outlet structures with unidirectional water flow. The flap door has the function of opening and closing in the forward and reverse directions of the flow channel. The counterweight flap door utilizes the balancing effect of the counterweight to automatically open or close the door leaf under the action of water flow, or to open or close the door leaf with a slight external force; The float type flap door uses the buoyancy of the door leaf in water to open or close the door leaf under the action of water flow.1. The advantages and disadvantages of the counterweight door；
1) Simple construction and reliable operation;
2) The opening of the door requires the use of balanced weights;
3) When the door leaf is closed, the impact force is strong and the door seat is easily damaged.
2. Advantages and disadvantages of floating box doors;
1) The door seat structure is the same as the counterweight flap door, and the door leaf is a sealed cavity structure with a specific gravity of 1.2-1.5;
2) No need to hang and configure counterweights;
3) The impact force is small when the door is closed.