The Sealing Forms and Principles of Power Station Valves

With the continuous progress of science and technology and the rapid development of the social economy, all walks of life in China have also faced new opportunities and new challenges. The power station system has also faced new changes and improvements. As a vital part of the power station system, the power station valve is an important fluid control device, which has a very important impact on the operation of the entire power station system. Therefore, we must attach great importance to the quality of the power station valve. Usually, in the operation of the power station, many accidents in the power station are caused by the leakage of the valve. It can be seen that it is of great significance to improve the sealing performance of the valve. In order to further ensure the safety of the power station, it is necessary to improve the quality of the power station valves and improve their leakages. The sealing principle and form of the power station valve are analyzed and introduced in detail, and some of its existing problems are expounded, hoping to provide some reference.
 
The advent of the era of science and technology has accelerated the pace of scientific and technological development, and if the power station system wants to achieve long-term progress and stable development, it is bound to keep pace with the times, constantly transform and improve to ensure the stable operation of its power station system. When it comes to stable development, we must first ensure the safety of the power station and ensure its quality. Safety is closely related to the valve of the power station, and its sealing performance has a crucial impact on the valve. Tightness puts forward higher requirements and higher challenges. Its sealing cannot be guaranteed, and leakage will naturally occur, which will affect the stable operation of the equipment, and even cause worse consequences. Internal leakage and external leakage are the main forms of valve leakage, and internal leakage usually occurs on the contact surface between the valve seat and the closing member. External leakage occurs more frequently in the stuffing box, where the flange gasket is connected. The following article will conduct a specific analysis of the sealing form of the power station valve.
 
1. The sealing of the power station valve
There are two types of sealing forms for power station valves, that is, contact sealing and non-contact sealing. Contact sealing refers to the sealing surfaces closely related to each other to eliminate the gap, such as sealing surfaces of seats, packing and flange sealing. These reserved assembly clearances eliminate the need for sealing force to seal against the sealing surface of a hermetically sealed non-contact seal. Dynamic seals and static seals are divided according to the relative movement of the contact pair. Contact types and non-contact types are referred to as dynamic seals. The Polymer elastic material is the main material for its elastic seal. To reduce or completely remove the gap, it is necessary to skillfully use the elastic-plastic deformation compensation of the sealing material. The structure is not complicated; the size is relatively compact. The product has high quality and low price, and the sealing is good. However, the disadvantage is that there is a certain partiality in the operating temperature range, and the service life needs to be improved. At present, the service life is short, and it can only be applied to seals with low parameters. These non-elastic materials such as metal or graphite are used to manufacture non-elastomeric sealing surfaces, and a small amount of elastic deformation and wear compensation mechanism is applied to seal. This requires it to have high machining accuracy. Although the price is relatively high, its temperature range is much wider and its service life is longer. Contrary to the above, it is widely used in sealing with high parameters.
 
2. The sealing principle of the power station valve
The following is a further discussion on the sealing principle of power station valves. The main task of sealing the valve is to prevent leakages. The reasons for leakages of valves come from many aspects, mainly including the gap of the sealing pair and the pressure difference on both sides of the sealing pair. The main reason that affects the sealing of power station valves is the gap in the sealing pair. Therefore, the principle of the sealing of the power station valve is mainly to use various methods to reduce its leakage. The waviness of the distance between the wave crests, and the small roughness scattered on the wave surface is the composition of the valve surface of the power station. If the problem of leakage can be reduced or avoided, the sealing of the power station valve can be further improved. Ideally, the gap between the sealing surfaces should be smaller than the diameter of the fluid molecules, but there are often some problems in practice; it is difficult to achieve this ideal requirement, that is to say, even though the surface structure metal of the power station valve is very finely polished, its roughness is still not as expected, and it is 30 times higher than the diameter of water molecules. Through theoretical support and practical experience accumulation, it can be known that the measures to improve the fineness of the sealing surface cannot effectively affect the sealing of the valve. By increasing the specific pressure, the micro-profile peaks on the sealing surface are flattened and plastically deformed to ensure that the gap becomes smaller, and finally achieve the sealing effect on the fluid.