(1) The main process parameters of the grid include grid pitch, grid flow velocity and head loss. The grid pitch is the distance between two adjacent grid bars. A grid with a grid pitch greater than 40mm is a thick grid, a grid with a grid pitch of 20-40mm is a medium grid, and a grid with a grid pitch less than 20mm is a fine grid.

 (2) The grid velocity refers to the speed at which sewage flows through grid bars and grid channels. The flow velocity across the grid should not be too high, otherwise the soft debris that should have been intercepted may be washed over. If the flow velocity across the grid is too small, the larger sand particles in the sewage may be deposited in the channel in front of the grid.

 (3) The head loss of sewage across the grid refers to the water level difference before and after the grid, which is related to the velocity of the grid. If the water head loss across the grid increases, it means that the flow velocity across the grid increases. At this time, it is possible that the amount of water that crosses the grid increases, or it is more likely that the grid is partially blocked and needs to be cleaned in time. The reduction in head loss across the gate indicates that the flow velocity across the gate is reduced, and measures should be taken to prevent sand accumulation in the channel in front of the gate.

(1) The grille is divided into two types: artificial grille and mechanical grille. In order to avoid the poisoning of pollutants to the human body, reduce the labor intensity of workers, improve work efficiency and realize automatic control, mechanical grille should be used as much as possible. When the sewage contains oil and other volatile combustible gases, the power unit of the mechanical grille should have explosion-proof facilities.

(2) The specific form and material of the grille should be determined according to the characteristics of sewage water quality, such as the level of pH and the size of solids.

(3) Large-scale sewage treatment plants generally need to set up two grids and one screen. The grid spacing should be determined according to factors such as the type of sewage, the flow rate, the type and size of representative debris, and it can meet the requirements of the pump structure. Requirements, while meeting the requirements of subsequent water treatment structures and equipment. The first pass uses coarse grating (50-100mm) or middle grating (20-4omm), the second uses middle grating or fine grating (4-10mm), and the third is a screen (<4mm).

(4) The cross-sectional shapes of commonly used grid bars include five types: a square with a side length of 20mm, a circle with a diameter of 20mm, a rectangle with a diameter of 10mm×50mm, a rectangle with a half-round head on one side 10mm×50mm, and a rectangle with a half-round head on both sides 1omm×50mm. The circular grid has good hydraulic conditions and low water flow resistance, but it has poor rigidity and is easily deformed by external forces. Therefore, it is best to use a rectangular section when there is no special need.

(5) The grille is generally installed at the head of the treatment process or at the water inlet of the pumping station. It is located in the throat. To ensure safety, there must be a spare unit or other means to ensure that the grille can be overhauled without stopping the water.

(6) In order to protect the power equipment, the mechanical grille is generally installed in a well-ventilated grille room. Large and medium-sized grilles should be equipped with lifting equipment to facilitate equipment maintenance and daily removal of grille slag.