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Common failures of boiler safety valve
Safety valve is a very important protection valve, widely used in various pressure vessels and piping systems, when the pressure in the pressure system exceeds the specified value, it can automatically open, the excess media to the atmosphere Go, to ensure the safe operation of pressure vessels and piping systems to prevent accidents, and when the system pressure back to the working pressure or slightly lower than the working pressure can automatically shut down. Safety valve work is directly related to the reliability of equipment and personal safety, it must be given attention. First, the valve leakage Under the normal working pressure of the device, the valve flap and valve seat sealing surface occurred more than the allowable degree of leakage, leakage of the safety valve will not only lead to loss of media. In addition, the continuous leakage of media will make the hard sealing material is damaged, but the sealing surface of the commonly used safety valve is a metal material on the metal material, although strive to be smooth and smooth, but in the case of media pressure To the absolute leak is also very difficult. Therefore, the working medium is a steam safety valve, at the specified pressure value, if the naked eye at the exit can not see the leak, it is considered the sealing performance is acceptable. Second, the valve body surface leakage refers to the junction between the upper and lower valve leakage phenomenon, resulting in leakage of the main reasons for the following aspects: First, the joint surface of the screw force is not enough or tight bias, resulting in a combination of surface The sealing surface is not good. Second, the valve body with the tooth surface seal does not meet the standards. Third, the flatness of the valve body with poor or hard padded impurities caused by seal failure. Third, the impulse safety valve does not move after the main safety valve action This phenomenon is often referred to as the main safety valve refused to move. Main safety valve refuse to move on the operation of the boiler hazards is very large, is a major hidden danger to equipment, seriously affecting the safe operation of equipment, once the pressure in the operation of the media and pipeline pressure exceeds the rated value, the Lord Safety valve does not move, so that equipment over-pressure operation can easily cause equipment damage and major accidents. Fourth, the impulse safety valve seat back after the main safety valve delay back seat too long This failure occurs mainly in the following two aspects: On the one hand, the main relief valve piston chamber leak steam size, although the impulse safety valve back Seat, but there is still pressure in the pipeline and the steam in the piston chamber is still high, pushing the piston downward force is still large, resulting in slow back seat main safety valve. The way to eliminate this kind of failure is mainly solved by opening the large throttle opening and increasing the throttle aperture. The large opening of the throttle valve and the increase of the throttle aperture allow the steam remaining in the pulse tube to be drained rapidly , Thereby reducing the pressure inside the piston, so that the downward thrust on the piston quickly reduce the thrust in the steam turbine steam accumulator up thrust and the main safety valve spring pull up rapidly under its own back seat. On the other hand, the main safety valve is the friction between the moving parts and fixed parts can also cause the main relief valve seat back slowly, to solve this problem is the main safety valve moving parts and fixed parts with the gap Control within the standard range. Fifth, the safety valve seat back pressure is low Relief valve back seat low pressure on the boiler's economic operation has a great harm, back seat pressure is too low will cause a large number of media time-out emissions, resulting in unnecessary energy loss. This failure occurred in 200MW units used in the A49H-type spring pulse safety valve, the analysis of the reasons are mainly caused by the following factors: First, spring pulse relief valve on the steam discharge, this form of impulse After the safety valve is opened, the medium is continuously discharged to promote the action of the main safety valve.