When the steam pressure under the valve disc of the internally threaded spring sealed safety valve exceeds the clamping force of the spring, the valve disc is pushed open. After the valve disc is opened, the discharged steam acts on the valve disc clamping ring due to the rebound of the regulating ring, causing the valve to quickly open. As the valve disc moves upward, steam impacts the upper regulating ring, causing the exhaust direction to tend vertically downward. The reaction force generated by the exhaust pushes the valve disc upward and maintains it at a sufficient lifting height within a certain pressure range. With the opening of the safety valve, steam is continuously discharged, and the steam pressure in the system gradually decreases. At this point, the force of the spring will overcome the steam pressure acting on the valve disc and the reactive force of the exhaust, thereby closing the safety valve. Closed type means that the discharged medium does not leak out and is completely discharged along the designated outlet. It is generally used for toxic and corrosive media. Non enclosed type is generally used for non-toxic or non corrosive media.