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The Complete Knowledge of Valve Sealing! Sealing Principle and Influencing Factors

Views: 344     Author: Site Editor     Publish Time: 2020-06-22      Origin: Site

With the rapid development of science and technology and the continuous improvement of production technology and product structure, the stainless steel valve has rapidly developed into the major type of valves. Also, there are many types of other valves such as gate valve, globe valve, check valve, ball valve, butterfly valve, water check valve, forged steel valve, knife gate valve and so on.


stainless steel gate valves manufacturers


Principle of Valve Sealing


The sealing of valve is to prevent leakage, so the principle of valve sealing is also from the principle of preventing leakage. There are many types of valves, but the basic function of them is the same. They are all designed to connect or shut off the flow of media. Therefore, the sealing problem of the valve is very prominent.


To ensure that the valve can intercept the flow well and that no leakage occurs, it is necessary to ensure that the valve is intact. There are many reasons for valve leakage, including unreasonable design of structure, defective surface for sealing, loosening of some parts, inadequate cooperation between body and bonnet of the valve and so. All these problems may lead to insufficient sealing of the valve.  Therefore, the technology of valve sealing is an important technology related to valve performance and quality, which requires systematic and in-depth research.


From its creation to the modern times, the sealing technology of valve has also experienced great development. So far, the technology of valve sealing has been mainly reflected in two major aspects, namely static sealing and dynamic sealing.


rubber sealing butterfly valve


Influencing Factors of Valve Sealing

The size of valve is also a major factor affecting the performance of valve sealing.


For small-sized valves, the annular section between the stem and the inner wall should be small. However, in some cases, small section is not necessarily good, because it will limit the choice of elements for sealing. The annular section of small-sized valves is usually only 125, which makes it difficult to install sealing elements with strong materials and so on.


There are also problems for large-sized valves. Large-sized valve may cause excessive load on the valve stem and other parts of the valve. When the valve vibrates, the force generated may be too large for sealing elements. The difference in temperature between different parts of large valves is also significant, which may cause structural deformation.


For most types of valves, the ideal ratio of the size for stuffing box is that the height of the cavity is approximately three to five times long as the diameter of the the cross-section. If it is a rotary valve with right angle which has low requirements in sealing, it can be effectively sealed even if the stuffing box is shallow. If the stuffing box is too deep, it first means that the sealing components are easy to consolidate, resulting in loss of sealing stress. It will finally cause leakage. Secondly, in the valve which has a deep box for stuffing, the friction on the valve stem is high, which may become an obstacle in some applications.

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