502减压持压阀

型号  520 减压持压阀
综合减压阀和泄压阀的功能
维持用户端管道的压力；当管道压力超过设定值时，阀门自动打开，把多余的压力释放到下游；当管道压力低于设定值时，阀门关闭；
维持较低的出口压力，不管进口压力和流量如何变化；
 

The Model 520 Combination Pressure Reducing and Pressure Sustaining Valve
automatically performs two independent functions. It maintains a constant downstream pressure, regardless of fluctuating demand and sustains the upstream pressure to a pre-determined minimum.The pressure reducing control responds to slight variations in downstream pressure and immediately repositions the main valve to maintain the desired downstream pressure. The pressure sustaining control is normally held open by the upstream pressure,but modulates should the pressure drop to the control set point.This, in turn, modulates the main valve to sustain the desired upstream pressure.