拦污格栅Dirt blocking grid，设在进水口前，用于拦阻水流挟带的水草、漂木等杂物（一般称污物）的框栅式结构制作标准参考图集90s503。
The dirt blocking grid is composed of a frame, a transverse partition board and a bar strip (see figure, which is supported on the wall of the concrete pier, and is generally made of steel. The distance depends on the size of dirt, how much and the application requirements. The spacing of the grid used for the hydropower station depends on the type and size of the water turbine to ensure that the dirt in the grid is not stuck in the flow passage of the turbine. Discharge tunnel and drain hole generally no trash grille, such as hole diameter or diameter is small, and the wood more need to set when the grid spacing should be increased. The load to the grid, in addition to the dead weight, mainly dirt blocking, before and after the gate due to the water level difference between the formation of water load, generally by 2 ~ 4m head. The gate size depends on the surface of the trash rack and allow a gate gate over flow velocity. In order to reduce the head loss and facilitate cleaning, the flow rate is not more than 1.0m/s. The grid can be made into a fixed or capable of lifting.
Dirt blocking grid trash grille, is arranged on the water inlet, for arresting flow with water, floating wood and other debris (generally called dirt) box gate type structure.
Trash grille in the plane can be arranged in a straight line or a zigzag semicircle, the facade can be vertical or inclined, depending on the nature and flow with how much dirt, use requirements and clean-up decisions. High head Bahou hydropower station vertical semicircular water inlet used; intake, hydraulic tunnel and water pipelines with straight line.
Deep water inlet grille height and water level of the reservoir trash and cleaning mode. For the need for frequent cleaning, the top elevation can be slightly higher than the flood control limit water level (see reservoir characteristic value); the need for regular cleaning, it should be higher than the highest water level required to clean up. High trash grille, can be made into several sections, each section size can be determined according to the lifting capacity.
In the cold area of winter, the need to take measures to stop the sewage grid. The commonly used methods are: the low voltage (50V) current to the trash grille, using resistance heating metal structure itself to antifreeze, the method is simple, but the power consumption is large; in the gate before the surface, the higher the temperature of reservoir water to the surface of compressed air, maintain no sewage gate before and after freezing range, this method is mainly used in large reservoir.
Dirt cleaning can be used for manual or cleaning machine. Manual cleaning application depth is shallow, generally not more than 5m. When the rack is located in deep water, multi- purpose cleaning machine in cleaning; if necessary, can also set up two sewage interception grille, need decontamination, first standby trash grille in gate slot, and then work to clean up trash grille hanging out.