The whole valve is a security valve, its opening and closing parts of the external force is normally closed state, the media pressure when the equipment or piping, open automatically when you exceed the specified value, emissions of media outside the system to prevent medium pressure piping or equipment exceeds the set value. The safety valves are automatic valves used in boilers, pressure vessels and piping, control pressure does not exceed the specified value, play an important protective effect on personal safety and equipment operation. 
 The valve structure has two categories: spring and leveraged. Spring-loaded valves and valve seat seal by a spring force. Leveraged by the force of the lever and hammer. With the large capacity needs, have a pulse valve, also known as pilot safety valve, the main valve and auxiliary valve. When the pipe medium pressure exceeds the set pressure value, the auxiliary valve first opens, the media along the catheter into the main valve and main valve to open, the increased media pressure is reduced. 
 Safety valve emissions determines the opening height, diameter and valve seat can be divided into two types: inching opening height of the seat inner diameter (1/15) - (1/20), full-Kai (1/3) ~ (1/4). 
 In addition, with the different application requirements, closed and not closed. Closed-discharge media is not compromised, all along the required exit discharge, generally used for toxic and corrosive media. Not closed in general for non-toxic or non-corrosive media.