The function of the multi-stage orifice plate is that the pore size becomes smaller in the proper place of the pipe, and when the liquid flows through the orifice, the flow rate is reduced or the shrinkage is reduced. A small cross-section of the flow rate appears downstream of the actual port of the lock, called a flow cross section. At the reduced flow section, the flow velocity increases with the reduction of the pressure in the flow section. When the flow rate to expand into a larger area, rate of decline, the increase of pressure, but the downstream pressure will not fully recover to the upstream pressure, this is a large internal turbulent energy and consumables results, if the pressure PVC shrinkage section down to liquid saturated steam under pressure corresponding to the temperature below PV, there is a steam flow dissolved in water and gas, mixed gas and steam to form small bubbles, the lower the pressure, the more bubbles. The pipe before and after the pressure is high, often used to increase the throttle plate, the principle is that the fluid flow in the pipeline, because of local resistance plate, so that the fluid pressure decreases, the energy loss, this phenomenon is called throttling phenomenon in thermodynamics. This method is simpler than the use of regulating valve, but must be chosen properly, otherwise, the liquid is prone to produce gas turbidity phenomenon, affecting the safe operation of the pipeline