In the daily inspection process, the boilers, pressure vessels, pressure pipes and other sealed pressure devices cannot be separated from the silicone gasket, but because most companies lack professional knowledge in the selection and scope of application of the silicone gasket, they only rely on experience to choose, which will inevitably produce some misunderstandings. So that running, taking, dripping, leakage phenomenon is common, causing a lot of waste to the unit, and even due to the failure of the silicone gasket caused serious accidents, this kind of situation is mainly due to the selection of silicone gasket and assembly problems, caused by. In view of the above situation, it is necessary to make a more specific introduction to the selection of silicone gaskets.
First, the role of silicone gasket, mechanism, factors affecting sealing
The role of the silicone gasket is to prevent the leakage of the sealed medium, and the form of leakage can be divided into interface leakage and penetration leakage. The reason of interface leakage is usually due to the relaxation of the pressing force between the sealing surface, the aging, deformation, corrosion, wear or burn of the sealing surface and the mechanical vibration in the working state. The penetration leakage is related to the material type of silicone gasket, the manufacturing method, the nature of the sealed medium, and the working pressure, temperature and other factors.
In theory, even if the silicone gasket is used, it is impossible to achieve complete contact between the sealing surface, so that there is no microscopic channel or gap, although these channels are extremely small, but relative to the molecular volume of the fluid medium is still large enough, so that the fluid is completely blocked at the edge of the sealing surface is impossible. There will always be a part of the fluid entering between the sealed contact surfaces, and there will be complex hydrodynamic and thermodynamic processes. It is generally believed that after the fluid enters the extremely fine and irregular gap between the sealing surface, it will produce resistance loss in the flow process to consume its energy, and at the same time, a static boundary layer will be generated on the wall of these gaps, thus making the small channel become more narrow or even completely blocked, so that the fluid entering the sealing surface can not continue to flow, so as to achieve sealing.
There are several factors affecting the sealing: the surface condition of the sealing surface; The contact width of the sealing surface; The properties of the fluid; The temperature of the fluid; Material of silicone gasket; The preload force applied on the sealing surface; The influence of other external conditions (mainly the vibration of the system, the deformation of the connector, the installation position deviation, etc.). If the seal is reliable, these factors must be seriously considered, and the quality and selection of silicone gaskets are also crucial.
Second, the selection of silicone gasket
Factors to consider in the selection of silicone gaskets:
1. The properties of the fluid, that is, the physical and chemical properties of the fluid medium in contact, will react with the gasket.
2. The pressure of the fluid, that is, the pressure state of the fluid medium, is positive or negative pressure, the maximum working pressure, and whether there are pressure fluctuations and other factors.
3. The temperature of the fluid, that is, the temperature condition of the fluid medium, and whether there is a temperature change during operation. 4. Flange type, that is, flange shape, size, sealing surface condition, etc.
In the case of detailed understanding of the above, you can consult the technical performance information of the relevant silicone gasket, from which to choose the silicone gasket suitable for the working conditions of the sealing part.