The section of mechanical fine screens has four shapes: square, circular, rectangular and rectangular with semi-circle. When choosing the grid, considering the good hydraulic condition of the circular section, the flow resistance is small, but the stiffness is poor, so the grid with rectangular section is usually used.

In order to prevent the gap clogging during the use of mechanical fine screens, the flow rate of sewage through the gap should not be less than 0.8-1.0m/s. In order to prevent the phenomenon of backwater blocking in the water surface of the channel in front of the grille, it is better to set the expansion angle of the connection between the channel in front of the grille and the channel in front of the grille at 20 degrees.

In the design of mechanical fine screens, the gap width of fine screens is not fixed. The gap width of the grille varies with the field data. According to the requirement of general hydraulic turbine for clearance of trash rack, the optimum width of mechanical grille is 3-5 cm. This width is used as the gap width of the intake grille.

The main function of mechanical grille equipment in small hydropower stations is to discharge ice, so as to solve the freezing danger in winter operation of diversion type small hydropower stations in alpine areas. In small hydropower stations, we generally adopt the principle of "positive ice discharge, lateral water intake" in the layout of mechanical grilles. This arrangement has special requirements for small hydropower stations. In order to ensure the normal operation of this project, the pressure forebay of a hydropower station must have sufficient discharge of ice.www.khnwatertreatment.com