The pressure relief valve is a mechanical safety device that is automatically triggered when irregular pressure conditions occur inside the silo. The valve is made of 4 elements: protection cap, overpressure disc, depression disc and 3 adjustment springs. If the setting remains within the limits, the three springs will keep the two discs hermetically closed. On the contrary, when there is a pressure increase inside the silo, the overpressure disc lifts up to let out the air in excess; when the pressure decreases, the depression disc opens, allowing the external air to enter and reset the initial pressure inside the silo.