The safety valve is a safety protection valve and an automatic pressure relief valve. Its opening and closing parts are normally closed under the action of external force. When the pressure of the medium in the equipment or pipeline rises and exceeds the specified safety value, it will automatically open, By discharging a rated amount of fluid to the outside of the system to prevent the pressure of the medium in the pipeline or equipment from exceeding the specified safe value. When the pressure returns to normal, the valve will be closed again to prevent the medium from continuing to flow out.
(1) According to the opening height of the safety valve disc
1: Micro-lift safety valve (micro-lift opening stroke height: ≤0.05d0 (minimum discharge throat diameter)
2: Full-lift safety valve (opening height of full-lift safety valve is ≤0.25d0 (minimum discharge throat diameter)
(2) According to the structure of the safety valve
1: Pendant type
2: Leverage
3: Spring type (safety valve that uses the force of a compression spring to balance the pressure of the disc and seal it, commonly used in gas transmission stations)
4: Pilot type (pulse type) It designs the main valve and the auxiliary valve together and drives the main valve to act through the pulse action of the auxiliary valve. This structure is usually used in large-diameter, large-displacement, and high-pressure systems. It designs the main valve and the auxiliary valve together, through the pulse action of the auxiliary valve.
(3) According to the structure of the valve body
1: Closed safety valve (closed safety valve means that the discharged medium does not leak, and all drains along with the outlet to the designated place, generally used in toxic and corrosive media.)
2: Non-closed safety valve (For air and steam safety valves, non-closed safety valves are mostly used.)
(4) According to the medium used
1: Safety valve for steam (usually represented by A48Y type)
2: Safety valve for air and other gases (usually represented by type A42Y)
3: Safety valve for liquids (usually represented by A41H type)
(5) According to the nominal pressure
1: Low-pressure safety valve: safety valve with nominal pressure PN≤1.6Mpa
2: Medium pressure safety valve: a safety valve with a nominal pressure of PN2.5-6.4Mpa
3: High-pressure safety valve: a safety valve with a nominal pressure of PN10.0-80.0Mpa
4: Ultra-high pressure safety valve: a safety valve with a nominal pressure of PN>100Mpa
(6) According to the applicable temperature
1: Ultra-low temperature safety valve: t≤-100℃ safety valve
2: Cryogenic safety valve: －100℃<－40℃ safety valve.
3: Normal temperature safety valve: -40℃<t≤120℃ safety valve
4: Medium temperature safety valve: 120℃<t≤450℃ safety valve
5: High-temperature safety valve: t>450℃ safety valve
(7) According to the connection method
1: The flange is connected to the safety valve. The safety valve inlet and pipeline connect the flange form, and the outlet form is flexible.
2: Threaded connection safety valve. The safety valve inlet and the pipe are connected with threads, and the outlet form is flexible.
3: Welding and connecting the safety valve. The safety valve inlet and the pipe are connected with threads, and the outlet form is flexible.
(8) Classification according to the principle of action
1: Direct-acting safety valve. A safety valve that directly relies on the force generated by the medium pressure to overcome the mechanical load acting on the valve disc to open the valve.
2: Pilot-operated safety valve. Composed of the main valve and a pilot valve, it is a safety valve that is driven or controlled by the medium discharged from the pilot valve.
3: Safety method with the supplementary load. Before the inlet pressure reaches the opening pressure, there is always an additional force to enhance the seal, and the additional force is a safety valve that can be reliably released when the valve opening pressure is reached.
(9) According to the classification of the sealing pair
1: Cemented carbide to cemented carbide sealing pair. Suitable for high temperature and high-pressure occasions, especially high temperature and high pressure superheated steam.
2: 2Cr13 to 2Cr13r sealing pair. Used in saturated steam and superheated steam on general occasions, or on containers or pipes with other media whose temperature is lower than 450℃.
3: The sealing surface of the valve seat is 2Cr13, and the sealing surface of the disc is hard alloy. It is used for high-pressure steam and other media that have a relatively large flow rate and are likely to cause scouring of the sealing surface.
4: The sealing surface of the valve seat is made of alloy steel, and the sealing surface of the disc is made of PTFE. It is suitable for oil or natural gas medium, where the sealing requirements are strict, but the working temperature is lower than 150℃.
5: The sealing pair is austenitic stainless steel. The valve body and bonnet of this kind of safety valve are mostly austenitic stainless steel, which is used in occasions where the medium contains corrosive components such as acid and alkali.
(10) Classification with or without back pressure balance mechanism
1: Backpressure balanced safety valve. A safety valve that uses bellows, pistons, or diaphragms to balance the effects of backpressure to balance the effects of the back pressure on the upper and lower sides of the disc before the valve is opened.
2: Conventional security method. Safety valve without original back pressure balance.
