The purpose of the multistage orifice plate is to reduce the aperture at the proper place of the pipe. As the liquid flows through the orifice, the velocity of the orifice will either become thinner or shrink. The small cross section of the flow velocity appears downstream of the actual lock, which is called the shrinkage section. At the contractive section, the pressure at the contractive section decreases with the increase of velocity. Expanded into a larger area, when the flow rate, pressure increase, but the downstream pressure is not fully restored to the upstream pressure, there is a large internal turbulence and the result of energy consumables, if contracted flow section of the pressure corresponding to PVC liquid temperature of saturated steam pressure under the pv, in velocity gas escaping steam and dissolved in the water, steam and gas mixture of small bubbles, the lower the pressure, the more bubbles. When the pressure difference between front and rear of the pipeline is large, it is usually adopted to increase the orifice of throttling. The principle is as follows: when the fluid flows in the pipeline, the pressure of the fluid decreases and the energy is lost due to the local resistance of the orifice. This phenomenon is called throttling phenomenon in thermodynamics. This method is simpler than using the control valve, but it must be chosen properly, otherwise, the liquid is easy to produce air turbidity phenomenon, affecting the safe operation of the pipeline.