A correctly installed orifice plate should have the constriction facing the direction of the fluid. The fluid contracts locally at the throttling center, increasing the flow rate and reducing the static pressure, so a static pressure difference is generated before and after the orifice plate, and this pressure difference has a certain functional relationship with the flow aperture.
When the orifice plate is installed upside down, the degree of contraction of the fluid when flowing through the orifice plate and the speed when flowing through the rear end of the orifice plate are both less than when it is installed in the right position.
The distance between the flow neck and the orifice plate is farther than when it is installed in the right position, which makes the pressure behind the orifice plate larger, resulting in a decrease in the static pressure difference before and after the orifice plate, and the measured flow value is reduced, affecting the accuracy of the flow measurement.
