Keywords: Petrochemical enterprises; Valve; Leakage; Reasons; Countermeasures Foreword In petrochemical enterprises to carry out various production activities when the need to use certain refining equipment, of which the valve is an indispensable one of the important components. In order to complete the production activities, companies need to use a large number of different types of valves. However, the actual use of the valve, by a variety of reasons, can easily lead to the emergence of a variety of leaks. The emergence of valve leakage will lead to a large number of products and raw materials, such as waste, causing some environmental pollution, and even lead to a variety of accidents. To this end, the positive reasons for the leakage of the valve to summarize and find feasible measures to ensure the safety of petrochemical production activities carried out is essential.
1 Petrochemical enterprises related to the reasons for the leakage valve 1.1 The causes of leakage Leakage of petrochemical enterprises can be roughly divided into two reasons for leakage and internal leakage. Among them, the leakage, including stem leakage and leakage of valve body connections and stuffing box leakage. Stem leakage occurs because the stem design or improper material selection, resulting in the production process stem stuck stuck phenomenon. Resulting in the valve can not be shut down properly or can not be closed tightly, resulting in media leakage. Leakage of the valve body connection is due to poor sealing between the valve body and the bonnet, resulting in the appearance of leakage . The connection part will use a certain gasket, the corresponding gasket in the material or size does not meet the requirements, or appear improperly fastened bolts, etc., will lead to the valve body connection additional load is too large and so on, resulting in There is a leak in the connection area. The stuffing box includes stuffing boxes and packing. If there is loose packing gland, the packing is not tight and the valve stem is worn, it will cause the leakage of the packing at the packing.
1.2 The reasons for leakage In addition to the above reasons for leakage, the valve leakage also involves a variety of reasons for internal leakage. Leakage due to lax valve closure due to internal leakage, leakage occurred mostly in the valve seat sealing surface. Analysis of the causes of internal leakage, on the one hand, and the valve design and manufacturing process should be the relationship between. If the valve design and manufacture is not scientific and reasonable, it can easily lead to lax valve seal, leading to media leakage. Or subject to certain factors, the valve plate or sealing surface deformation will occur, resulting in poor sealing, on the other hand, the valve manufacturing, transportation or installation process may have different degrees of the valve sealing surface Damage, thereby affecting its sealing line, leading to the emergence of leakage.
2 to reduce valve leakage countermeasures 2.1 Stem leakage response In different types of valves, the stem is one of the most important parts of the force. Taking into account the peculiarities of daily production activities of petrochemical enterprises, the stem material used needs to have good corrosion resistance, strength and toughness. In addition, in the practical application process, the stem surface is often strengthened to some extent to better improve the wear resistance and corrosion resistance of the stem surface . In order to ensure the sealing of the valve and reduce the occurrence of leakage during the production process, the valve stem material used needs to be properly selected. At present, martensitic stainless steel is the more applied stem material. However, martensitic stainless steel does not have the ideal crevice corrosion resistance, subject to a certain degree of acidity, the stem surface prone to some passivation, leading to local corrosion. To this end, to ensure the sealing of the valve, you can choose to use highly resistant crevice corrosive austenitic-ferritic duplex stainless steel, thereby enhancing the stem of the crevice corrosion resistance, to avoid leakage at the stem, thus reducing Valve leakage caused by the emergence of the situation.
2.2 Leakage at the valve body connection To the valve body connection, a reasonable seal is to be made. In actual application, we can choose to use different types of gaskets, including concave and convex flat gaskets or tongue and groove flat gaskets, in combination with the actual situation. In addition, in recent years, "O" ring seal technology has also been widely used in production activities. In the use of "O" ring is the process, you can get the ideal radial extrusion deformation. As a result, a rational sealing effect can be obtained without axial loading. In addition, for low-pressure small-diameter valve, the valve body is generally used to connect the internal thread to reduce the weight of the valve body and the size of the structure. For the sealing element at the junction, a flat gasket or "O" ring seal can be used to achieve the desired sealing effect.
2.3 Stuffing Box Leakage The poor packing of the valve stuffing box is also an important cause of leakage. In the stuffing box sealed, most of the past choose to use soft packing seal. In this mode, the choice of using the packing gland axial pressure to achieve the desired sealing effect. Under this pressure, a certain radial contact stress will be generated between the valve stem and the packing, and between the packing and the side wall of the stuffing box, so as to obtain the ideal sealing effect. Therefore, the axial force of the gland must be quite large, resulting in an increase in the wear of the corresponding soft sealing packing. To this end, in order to ensure the sealing effect, you need to carry out regular inspection gland bolts, tighten often, or in time to replace the packing. In addition, the choice of different packing seals and packing seal combination of applications to improve the reliability of the valve to ensure the sealing of the valve and extend the service life of the valve.
2.4 optimization and selection For a variety of valve design and manufacturing process caused by the valve leakage problems, but also the need for a reasonable valve optimization selection, in order to better reduce the emergence of various leaks. In the choice of the valve form, we should pay attention to the actual needs of the day-to-day production and the requirements of the process conditions, to conduct a comprehensive optimization . Should pay attention to the construction and practical experience, to ensure that the valve used in addition to meet the requirements of the relevant process, design specifications. In addition, full consideration should be given to the specific circumstances, to make it as much as possible with the operating conditions to match, to maximize the use of the request. In the choice of different types of valves, pay attention to combine the corrosiveness of different media and temperature, comprehensive consideration, and then use the valve manufacturing materials targeted selection. In addition, you also need to combine the working point of the process requirements, the valve core and valve body material selection.
3 Conclusion In short, the petrochemical companies in a variety of valves for the process, a variety of reasons may lead to the emergence of valve leaks, including stuffing box leaks and a variety of internal leakage causes. To this end, for enterprises, the daily use of different valves, but also for different causes of leakage, combined with the actual production needs, such as the rational selection and process design, in order to better reduce valve leakage The emergence of. Improve production efficiency and ensure production safety.
References  Zou Bing, Ding Dewu, Zhu Shengjie, et al.Study on detection of sealing point leakage in petrochemical enterprises [J] .Proceedings of Safety Science and Technology in China, 2011,07 (12): 192-196.
 Zheng Daoli. Analysis of petrochemical plant valve sealing principle and cause of leakage [J]. China Chemical Industry Trade, 2015, (34): 234-234.
ZHAO Bing, JIA Zhao-di, LI Wei, et al.Study on acoustic emission characteristics of valves in gas pipelines [J] .Proceedings of Safety Science in China, 2015, (7): 30-35.
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