Segmental orifice plate is suitable for waste water treatment, chemical water treatment and water treatment systems. It should be installed in a horizontal line, and cannot be used in vertical pipe. If the flow contains solid particles, the segment should be in lower part, if there is a gas in a liquid precipitation, the segment should be placed on. Before welding the pressure pipe, the drill on the pressure-tapping tube should be taken first, its diameter is the same as the diameter of pressure-tapping hole on the flange. The pressure-tapping hole on the flange is aligned with the pressure-tapping hole on the pipe. When the throttle device is connected with the pipe, the non-verticality between the end face and the pipe axis at the welding place shall not be greater than 1°. After welding, the internal welding seam shall be processed to make it smooth and free from welding splashes and slag.