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Analysis Of Causes And Treatment Methods Of Safety Valve Leakage
Dec 06, 2018

Analysis of Causes and Treatment Methods of Safety Valve Leakage

Under the normal working pressure of the equipment, leakage exceeds the allowable degree at the sealing surface of the valve disc and the valve seat, and leakage of the safety valve not only causes media loss. In addition, the continuous leakage of the medium will also damage the hard sealing material. However, the sealing surface of the commonly used safety valve is made of metal material to metal material. Although it is intended to be smooth and smooth, it should be done under the condition of medium pressure. It is also very difficult to never miss. Therefore, for a safety valve whose working medium is steam, if the leak is not visible to the naked eye at the specified pressure value, the sealing performance is considered to be acceptable. There are three main reasons for the leakage of the valve:

In one case, the dirt impurities fall on the sealing surface, and the sealing surface is padded, causing a gap between the valve core and the valve seat, so that the valve leaks. The way to eliminate this kind of failure is to remove the dirt and impurities that fall to the sealing surface. Generally, when the boiler is ready to be shut down, the safety door running test is first carried out. If it is found that the leak is stopped, the disassembly and repair are carried out. After the furnace was tested, the safety door leak was found. It is estimated that this situation is caused by the fact that it can be cooled after 20 minutes of running and then ruddered again to flush the sealing surface.

Another situation is damage to the sealing surface. The main reasons for the damage of the sealing surface are as follows: First, the sealing surface material is poor. For example, in the main safety door of No. 3-9 furnace, due to years of maintenance, the sealing surface of the main safety valve spool and the valve seat has been generally studied very low, so that the hardness of the sealing surface is also greatly reduced, thereby causing a decrease in sealing performance, eliminating this The best way to do this is to turn the original sealing surface down and then re-surge the welding according to the drawings to improve the surface hardness of the sealing surface. Note that the processing quality must be guaranteed during the processing. For example, cracks such as cracks and trachoma on the sealing surface must be turned and reworked. Newly processed spool seats must meet the drawing requirements. At present, the effect of the valve sealing surface of YST103 universal steel electrode surfacing welding is better. Second, the quality of the inspection is poor, and the valve seat is not up to the quality standard. The method to eliminate the failure is to repair the sealing surface by grinding or turning after grinding according to the degree of damage. 

Another cause of leakage of the safety valve is due to improper assembly or improper size of the part. During the assembly process, the valve seat is not completely aligned or the joint surface is transparent, or the sealing surface of the valve seat is too wide to seal. The elimination method is to check the size and uniformity of the matching clearance around the valve core, to ensure that the top hole of the valve core and the sealing surface are the same degree, and it is not allowed to lift the valve core to check the gap of each part; the width of the sealing surface is appropriately reduced according to the drawings to achieve effective sealing. .