Safety valve knowledge Description: (safetyvalve) To prevent the boilers, pressure vessels and other equipment or pipeline damage due to over-pressure valve. When the body fluid pressure reaches slightly higher than the normal working pressure of a specified value (ie, the valve opening pressure), the safety valve automatically open, part of the fluid discharge, the pressure drop. When the pressure drops slightly below the normal operating pressure (ie, the valve seat back pressure), the safety valve automatically shut down to stop the discharge of fluid and keep the seal. The role of safety valve is to prevent the pipeline or device in the media pressure exceeds the prescribed value, so as to achieve the purpose of security. Safety valve is a kind of safety protection valve, its opening and closing parts are normally closed under the external force. When the medium pressure in the equipment or pipeline rises and exceeds the specified value, it will be automatically turned on. The medium is discharged to the outside of the system Medium pressure in pipe or equipment exceeds specified value. Safety valves are automatic valves, mainly for boilers, pressure vessels and pipes, the control pressure does not exceed the specified value, the personal safety and equipment plays an important protective role. Press the safety valve flap opening height can be divided into micro-Kai-type safety valve and full-valve safety valve, micro-open safety valve opening stroke height: ≤ 0.05d0 (minimum discharge throat caliber); full-Kai safety valve open Height ≤ 0.25d0 (minimum discharge throat caliber). Safety valve according to the structure of the points, should be divided into vertical hammer, lever type, spring type and pilot type (pulse type); According to the valve body structure can be divided into closed and not closed two. Closed safety valve that is not excluded from the media, all along the exit to the designated location, generally used in toxic and corrosive media. For air and steam safety valve, multi-use non-enclosed safety valve. For the selection of safety valve products, the actual seal pressure should be determined. For spring-loaded safety valves, springs with several working pressure ratings within a nominal pressure (PN) range should be specified when ordering, in addition to indicating the safety valve model, name, medium, and temperature , Otherwise according to the maximum sealing pressure supply. Safety valve selection principle: 1. Steam boiler safety valve, the general choice of open all-spring-type safety valve; 2. Liquid medium safety valve, the general choice of micro-spring-type safety valve; 3. Air or other gas medium with safety valve , The general selection of fully enclosed spring-loaded safety valve; 4. liquefied petroleum gas tanker car or liquefied petroleum gas tanker truck safety valve, the general use of Kai-type built-in safety valve; 5. Oil well export safety valve, the general choice of pilot Type safety valve; 6. High-pressure bypass safety valve for steam power generation equipment, generally use the pilot safety valve with dual functions of safety and control; 7. Safety valve with lifting wrench should be used when required to regularly open the test valve. When the medium pressure reaches more than 75% of the cracking pressure, use a lifting wrench to slightly lift the valve flap from the valve seat to check the safety valve opening. 8. If the medium temperature is high, Temperature, the general when the closed safety valve temperature exceeds 300 ℃ and open safety valve temperature exceeds 350 ℃, should be used with a safety valve with a radiator; 9. If the safety valve outlet back pressure is changing, the amount of change over Corrugated pipe safety valve should be used when the pressure is 10%; 10. If the medium is corrosive, the bellows safety valve should be used to prevent important parts from failure due to medium corrosion. Safety valve installation and maintenance should note the following: 1, all kinds of safety valves should be mounted vertically. 2, safety valve outlet should be no resistance, to avoid the phenomenon of compression. 3, safety valve should be specially tested before installation, and check its official seal. 4, the use of the safety valve should be regularly checked. Safety valve classification: safety valve for its different purposes, the structure of many types, but generally classified as follows (1) by the use of media points: steam safety valve (usually A48Y-type representative) of air and other gases (Usually A41H type represented) (2) Press the nominal pressure points: Low-pressure safety valve: PN ≤ 1.6MPa nominal pressure safety valve pressure relief valve: nominal Pressure PN2.5-6.4Mpa safety valve High pressure safety valve: Nominal pressure PN10.0-80.0Mpa safety valve Extra high pressure safety valve: Nominal pressure PN> 100Mpa safety valve (3) According to the applicable temperature points: Cryogenic safety valve: Safety valve with t≤-100 ℃ Low-temperature safety valve: -100 ℃ Normal temperature safety valve: -40 ℃ Medium-temperature safety valve: 120 ℃ High-temperature safety valve: t> 450 ℃ safety valve In particular, to point out that given the domestic spring The actual situation, when the safety valve for more than 350 ℃ working conditions, most of the use of the radiator or the valve cover made of flower basket, so that the spring can better heat dissipation, so that the spring has always been able to work below 350 ℃ To ensure that its stiffness constant, thus ensuring proper and open the back seat and other performance requirements of the safety valve. (4) According to the connection points: Flange connected safety valve. Safety valve inlet and pipe connection flange form, the export form of flexible. Screw thread safety valve. Safety valve inlet and pipe connections thread, the export form of flexible. Welded safety valve. Safety valve inlet and pipe connections thread, the export form of flexible. (5) according to the structural form According to the structural features or the maximum open valve flap height and seat diameter ratio (h / d), safety can generally be divided into the following categories: Lever hammer safety valve. Spring-loaded safety valve. Utilize the force of a compression spring to balance the disc pressure and make it a hermetically sealed safety valve. See, for example, A42Y16C safety valve. Pulse safety valve. Pulse safety valve, also known as pilot-operated safety valve. It is the main valve and auxiliary valve design together, through the auxiliary valve pulse driven main valve action. This structure is usually used for large diameter, large displacement and high pressure system. Pulsed safety valve type WFXD. Micro-Kai safety valve. Valve opening height of the seat diameter of 1/40 ∽ 1/20, such as A27W-10T, A47H-16C safety valve. Full Kai safety valve. Such as A47H-16C-type safety valve. Valve opening height of the valve seat diameter of 1/4. Fully enclosed safety valve. Such as A47H-16C-type safety valve. Semi-closed safety valve. Such as A48Y-16C safety valve. Open safety valve. (A48Y-16C safety valve is also open) pilot-operated safety valve. Such as WFXD-type safety valve. (6) According to the classification of the sealing pair Carbide pairs of carbide seal. For high temperature and pressure of the occasion, especially the high temperature and pressure of superheated steam. 2Cr13 pair 2Cr13r seal pair. Used in general occasions, saturated steam and superheated steam, or other media at temperatures below 450 ℃ containers or pipes.
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