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As a valve with an important protection function, the safety valve is widely applied to various pressure vessels and piping systems, and can automatically sense and open when the pressurized container (system) reaches the upper limit of the specified pressure. , Excess media is discharged from the pressurized container (system), and can be automatically closed after discharge is completed to ensure that the pressure vessel can be operated within a safe and reliable pressure range to avoid major safety accidents. The normal operation of the safety valve not only relates to the normal and safe use of pressure vessels such as boilers, but also directly relates to the safety of life and property of the people. Therefore, a high degree of attention must be paid to the common failures of the boiler safety valve and the timely elimination and elimination thereof. In the following, the author analyzes and discusses the common faults of the boiler safety valve in the daily operation and the related exclusion methods. 1. The reasons for the low pressure return failure of the safety valve and the solutions:
The low back pressure will cause a large amount of medium to be discharged over time, resulting in unnecessary energy loss. The reason is that the amount of steam discharged on the spring pulse safety valve is large. After this type of impulse safety valve is opened, the medium is continuously discharged. The safety valve body or the front and back force of the impulse safety valve continues to rise due to the lack of the medium discharge of the main safety valve. Therefore, the steam in the pulse tube continues to flow along the gas header in the steam drum to the impulse safety valve to maintain the impulse safety valve action. On the other hand, this type of impulse safety valve operates the sealing surface of the impulse safety valve. After recombination to form a kinetic energy pressure zone, the valve core is raised, so that the impulse safety valve continues to be discharged, the greater the steam discharge amount, the greater the safety upward force acting on the valve core, and the smaller the impulse safety valve is, the easier it is to return to the seat. . The method to eliminate this kind of failure at this time is to close the throttle valve to reduce the flow of media out of the impulse safety valve and reduce the pressure in the kinetic pressure zone so that the impulse safety valve can be returned to seat. The second factor that causes the low back seat pressure is that the clearance between the valve plug and the guide bush is not suitable, and the clearance is small. When the impulse safety valve is seated, the high pressure pressure area is instantly throttled and the valve core is formed. Raise, delay the return time, eliminate this fault is to carefully check the size of the spool also guide the sleeve, with the gap is too small, reduce the valve cover directly or valve flap diameter or increase the valve flap and guide The radial clearance between the sleeves increases the flow area of ​​the part so that the flow path of the steam is not diverted, and the local pressure forms a high kinetic energy pressure area.
2. Safety Valve Leakage Valve leakage is one of the most common failures in boiler safety valve faults. It mainly refers to the leakage of the valve between the valve disc and the seat seal that exceeds the allowable level under normal working pressure.
The cause of the failure and its solution:
1 Dirt on the sealing surface. Use a lifting wrench to open the valve a few times to wash away the dirt; 2 damage to the sealing surface. According to the degree of damage, it should be repaired by grinding or grinding after turning. After the repair, the flatness of the sealing surface should be ensured, and its smoothness should not be less than 10; 3 The concentricity of the parts is destroyed due to improper assembly or pipeline load. Should be re-assembled or excluded from the pipeline additional load; 4 valve opening pressure is too close to the normal pressure of the device, so that the sealing surface than the pressure is low. When the valve is vibrated or the medium pressure fluctuates, it is more likely to leak. The opening pressure shall be properly adjusted according to the equipment strength conditions; 5 The relaxation of the spring will reduce the setting pressure and cause the valve to leak. May be due to high temperature or corrosion and other reasons, should be taken to replace the spring, or even change the valve and other measures. If it is caused by improper adjustment, just tighten the adjusting screw properly.
3. Safety valve flutter The vibration phenomenon of the safety valve during the discharge process is called flutter of the safety valve. The occurrence of fluttering phenomenon can easily cause metal fatigue and degrade the mechanical performance of the safety valve, causing severe equipment. Hidden danger.
The cause of the failure and its solution:
The reasons for chatter vibration are mainly the following aspects: On the one hand, improper use of the valve, and the exhaust capacity of the selected valve are too large. The elimination method is to make the rated discharge capacity of the selected valve as close as possible to the necessary emission of the device. On the other hand, because the diameter of the inlet pipe is too small, smaller than the inlet diameter of the valve, or the resistance of the inlet pipe is too large, the elimination method is that when the valve is installed, the inner diameter of the inlet pipe is not smaller than the inlet diameter of the valve or the inlet pipe is reduced. Resistance, excessive discharge pipe resistance, excessive back pressure caused by discharge is also a factor that causes valve chatter, and can be solved by reducing the resistance of the discharge pipe.
4. Leakage at the joint surface of the valve body The leakage at the joint surface of the valve body mainly refers to the leakage phenomenon at the joint surface between the upper and lower valve bodies.
The cause of the failure and its solution:
One is that the tightness of bolts on the joint surface is not enough or tight, resulting in poor sealing of the joint surface. The elimination method is to adjust the tightness of the bolts. When tightly tightening the bolts, it must be carried out diagonally. It is best to measure the gaps at the tight edges and tighten the bolts until they are tight, and make the gaps at the joint surfaces. Consistent. The second is that the toothed seals on the valve body joint surface do not meet the standards. For example, toothed seals have slight groove marks in the radial direction, poor parallelism, and defects such as sharp teeth or over-slopes can cause seal failure. So that the valve body surface leakage. The quality of a good spare part can be shut off during inspection and the use of a standard toothed seal can avoid this phenomenon. Third, the flatness of the joint surface of the valve body is too bad or it is sealed by hard impurities, causing the seal to fail. For the case that the joint surface of the valve body leaks due to the poor flatness of the joint surface of the valve body, the method of elimination is to re-grind the joint surface of the valve until it meets the quality standards. As the impurities are trapped and cause the seal to fail, carefully clean the joint surface during valve assembly to prevent impurities from falling.
5 Relief of safety valve delay The main performance is that the time for delaying the return of the main safety valve after the impulse safety valve is seated is too large.
The cause of the failure and its solution:
The main reasons for this failure are the following two aspects. On the one hand, the amount of steam leakage in the piston chamber of the main safety valve, although the impulse safety valve is seated back, but the pressure in the pipeline and the steam in the piston chamber is still very high, and the force pushing the piston downward is still very large. As a result, the main safety valve returned slowly. The method to eliminate this kind of failure is mainly solved by opening the opening of the throttle valve and increasing the throttle aperture. The opening of the throttle valve and the increase of the throttle hole will quickly discharge the steam left in the pulse tube. Therefore, the pressure in the piston is reduced, and the thrust acting on the piston is reduced rapidly, and the valve core is rapidly returned to the upward force of the steam medium in the steam header and the upward force of the main safety valve. seat. On the other hand, the reason is that the friction force between the moving parts and the fixed parts of the main safety valve is too large to cause the main safety valve to return slowly. The solution to this problem is to match the clearance between the moving parts of the main safety valve and the fixed parts. Console standard range.
Conclusion:
The boiler safety valve is one of the most important safety accessories for ensuring the safe operation of the boiler. Whether it can be opened accurately and reliably is of great significance to the safe operation of the boiler. In this article, the author discusses the common failures of boiler safety valves and proposes relevant solutions from the aspects of leakage of safety valves, low pressure of safety valve seat return, leakage of valve body joint surface, delay of safety valve seat return, and safety valve chatter. . (Finish)
Boiler Safety Valve Common Faults and Solutions - Shenzhen Euro Valve Analysis
The boiler safety valve is one of the most important safety accessories for ensuring the safe operation of the boiler. Whether it can be opened accurately and reliably is of great significance to the safe operation of the boiler. In this article, the author analyzes and discusses the common faults of the boiler safety valve in the daily operation and the related exclusion methods. This article is reproduced and shared by Shanghai Wuyue Pump & Valve Manufacturing Co., Ltd. Shanghai Wuyue is a professional safety valve manufacturer. It mainly produces various kinds of spring-type safety valves and pilot-operated safety valves, and provides related product technical support for life units.