Leakages of Valves

Leakages of Valves


Valves play an indispensable key role in oil and gas storage and transportation. Valve leakage is one of the common problems to be seen. If measures cannot be taken as soon as possible to deal with the problem, serious consequences will arise. Leakages of valves include internal and external leakages. If external leakage occurs, the sound of airflow can be heard. If internal leakage happens, it is not easy to detect, which can easily lead to safety hazards. The main factors of valve leakage are analyzed in this article. Understands the harm to production and the environment, and starts from the situation of petrochemical production. Analyze the mechanical energy of valve detection, and put forward targeted suggestions for valve leakage detection in petrochemical production.
 
Analysis of valve leakages
In the process of carrying out actual production research, the most important problem caused by valve leakage is quality. Since valve leakage mainly includes internal leakage and external leakage, the internal leakage and external leakage of valves are generally caused by the failure of the sealing pair of the valve. Valve external leakage refers to the fluid coming from the outside of the valve, while internal leakage refers to the leakage caused by the poor sealing of the valve. After the valve is closed, some fluid still flows inside the pipeline. Although there are differences between the two leakages, it is related to the quality of the valve and the application of the valve. Under normal circumstances, the adverse consequences caused by external leakage are more serious than internal leakage. In production, once the valve leaks, it will lead to a serious waste of energy and raw materials, and even pollute the environment, leading to poisoning, explosion or fire, which will endanger life, and cause serious damage to the environment and national economic losses.
 
External leakages of valves
External leakage often exists in the valve body, stuffing box, valve stem and valve body connecting part. Most of the valve body leakage is caused by casting, which can easily lead to the formation of blow holes and induce casting defects. There will be a blow hole in the valve body, which can easily cause the occurrence of leakages of media. The general situation is small leakage, which can be found by means of hydrostatic tests. Most of the reasons for valve stem leakage are the material selection or lack of rationality of the valve stem design, which leads to the valve stem being stuck at a certain position, which leads to the failure of the valve to close normally and affects the tightness of the valve closing, harming the production equipment and the surrounding environment. 
 
The stuffing box is mainly composed of stuffing compactors, packing pads, packing and stuffing boxes. The stuffing box needs to exist on the bonnet or valve body, and its main function is to contain the packing. A packing pad is placed at the bottom of the stuffing box, which acts as a packing support. The packing includes molding packing and soft sealing packing. The elastic material is the raw material for the molding packing. It mainly uses turning processing and compression molding to make the annular sealing ring. The molding packing has a more compact structure, better sealing performance, and adaptability. The main causes of leakage in stuffing box are loose packing glands, lack of tightness of seals, packing types or quality that do not meet requirements, packing aging, and valve stem wear and other factors. Leakages of valve connecting parts refer to the sealing between the bonnet and the valve body. 
 
Causes of valve internal leakages
The isolation of the medium is mainly realized by the surface sealing of the valve seat and the position of the valve core. The loss of the sealing effect of the valve seat and the sealing effect of the valve core will lead to internal leakage of the valve. The reason is that there are existing problems in the valve manufacturing process and design, which can easily lead to the lack of tightness of the valve seal, and induce leakage of media, most of which are small leakage. In the process of making valves, transporting valves, inspecting valves, installing valves and applying valves, the sealing surface of the valve is seriously damaged and its sealing performance is affected. Even if the leakage is small, it is easy to cause a lot of leakages. The existence of solid impurities can easily harm the closing of the valve, leading to the occurrence of leakages of media. This leakage can be little, and if it is serious, there may also be great.
 
A comprehensive study of the valve leakage factors can conclude that leakages are easily formed in the manufacture, design and transportation of valves. Reliability control research should be carried out by relying on effective inspection methods in the early stage. In the process of valve installation and application, leakages are easily formed, mainly due to damage to the seal of the valve stem stuffing box or the flange seal at the valve connection part, which leads to the loss of the effectiveness of the sealing surface of the valve seat and induces the formation of external leakage or internal leakage. According to the statistical results, 4/5 of the valve leakages are mostly caused by damage to the sealing surface. In petrochemical production, because the internal leakage is not easy to detect, there are often accidents such as medium pollution, poisoning or fire.