Pressure Relief / Pressure Sustaining Valve

In Pressure Relief Valves or pressure sustaining valve, the pilot senses the upstream pressure through a connection to the valve inlet. The control valve and pilot remain closed until the inlet pressure exceeds the pilot setting. The pressure sustaining valve opens rapidly to relieve damaging over-pressure and closes smoothly at an adjustable speed, when the pressure valve returns below the set-point. The upstream pressure is limited to the pilot set-point