With a safety valve is a safety valve, opening and closing parts of its normally closed by the external force in the state, when a device or medium pressure inside the pipe increases, exceeds the set value automatically open, through the medium outside the system to prevent discharge medium pressure piping or equipment exceeds the specified value. Safety valves are automatic valves, mainly used for boilers, pressure vessels and piping, control pressure does not exceed the value of personal safety and equipment operation play an important protective role. 
 Valve structure are two major categories: spring and lever. Spring-loaded valve and valve seat is sealed by a spring force. Lever is the force by the lever and hammer. With the large capacity needs, but also a pulse-type safety valve, also known as pilot safety valve, safety valve and auxiliary valve from the main component. When the pipeline pressure exceeds the pressure within the medium value, the auxiliary valve is first opened, the media along the catheter into the main valve and main valve open, so that increased media pressure to reduce. 
 Emissions depends on the valve seat diameter and height of the valve opening can also be divided into two types: low lift-style open seat height diameter (1 / 15) - (1 / 20), all start-style is (1 / 3) ~ (1 / 4). 
 In addition, with different requirements, there are closed and not closed. Closed that the media does not exhaust leak, all along the discharge of the export regulations, generally used for toxic and corrosive media. Closed or not generally used for non-toxic non-corrosive media. 
 Shanghai Tang Yang valve safety valve products: (K) AF46Y pilot safety valve, safety valve 900 Series DIN, A21F spring loaded low lift type safety valve external thread, A28H spring safety valve, A28W-10T Copper safety valve, A37H, A43H double spring-loaded safety valve, A38Y double spring-loaded safety valve, A41H (Y) Closed spring loaded low lift safety valve, A41Y-160 spring loaded low lift type high pressure safety valve closed, A41Y-320 type Closed spring loaded low lift high-pressure safety valve, A42Y-1000-type high pressure safety valve full-Kai, A42Y closed valve spring full-Kai, A42Y closed high-pressure safety valve spring full-Kai, A44Y, A48Y dedicated boiler safety valve, A44Y Wrench spring safety valve, A47H (Y) with spring loaded low lift type safety valve wrench, A48Y with a wrench spring safety valve, A49H-4 the main valve, A49H main high temperature and pressure safety valve, A49Y-10 medium temperature and pressure impulse safety device, A49Y spring safety valve (pulse), A61Y-320P spring loaded low lift type safety valve, AH42F liquefied petroleum gas safety valve, AHN42F-P18 parallel safe return valve, AQ series air compressor safety valve, AY42H safety overflow valve, GA49H pulse valve, SANA42F built-in safety valve, SFA72W-10P vacuum safety valve, WA42Y bellows balanced safety valve, YA40Y with radiator spring safety valve, YFA72W vacuum safety valve, Single-lever safety valve, pressure relief valve spring loaded low lift closed, spring loaded low lift type safety valve