Is there anything special about the selection of silicone gaskets?

In the daily inspection process, the sealed pressure-bearing devices such as boilers, pressure vessels, and pressure pipes are inseparable from silicone gaskets. However, most companies lack professional knowledge in the selection and application of silicone gaskets. Relying on experience to choose will inevitably produce some misunderstandings. As a result, the phenomenon of running, popping, dripping and leaking is not uncommon, causing a lot of waste to the unit, and even causing serious accidents due to the failure of the silicone gasket. This kind of situation is mainly caused by problems in the selection and assembly of the silicone gasket. . In view of the above situation, it is necessary to make a more specific introduction to the selection of silicone gaskets.

1. The function, mechanism and factors affecting sealing of silicone gasket

The role of the silicone gasket is to prevent the leakage of the sealed medium, and the form of leakage can be divided into two types: interface leakage and penetration leakage. The cause of interface leakage is usually due to the relaxation of the pressing force between the sealing surfaces, the aging, deformation, corrosion, wear or burning of the sealing surfaces, and the existence of mechanical vibration under working conditions. The penetration and leakage are related to the material type, manufacturing method, nature of the sealed medium, working pressure, temperature and other factors of the silicone gasket.

Theoretically, it is impossible to achieve complete contact between the sealing surfaces even with silicone gaskets, so that there are no microscopic channels or gaps. Although these channels are extremely narrow, they are still small relative to the molecular volume of the fluid medium. Large enough, so it is impossible for the fluid to be completely blocked at the edge of the sealed surface, there will always be part of the fluid entering between the sealing contact surfaces, and complex hydrodynamic and thermodynamic processes will be generated in it. It is generally believed that after the fluid enters the extremely fine and irregular gaps between the sealing surfaces, resistance loss will occur during its flow to consume its energy, and at the same time, a static boundary layer will be generated on the walls of these gaps, so that the tiny The channel becomes narrower or even completely blocked, so that the fluid entering the sealing surface cannot continue to flow, thereby achieving sealing.

The factors that affect the seal mainly include the following conditions: the surface condition of the sealing surface; the contact width of the sealing surface; the nature of the fluid; the temperature of the fluid; the material of the silicone gasket; Influence (mainly the vibration of the system, the deformation of the connecting parts, the offset of the installation position, etc.). If the seal is reliable, the above factors must be carefully considered, and the quality and selection of silicone gaskets are also crucial.

Second, the selection of silicone gasket

Factors to be considered in the selection of silicone gaskets:

1. The nature of the fluid, that is, the physical and chemical properties of the fluid medium in contact with, whether it will react with the gasket.

2. The pressure of the fluid, that is, the pressure state of the fluid medium, whether it is positive pressure or negative pressure, the maximum working pressure, and whether there is pressure pulsation and other factors.

3. The temperature of the fluid, that is, the temperature 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.

After understanding the above situation in detail, you can refer to the technical performance data of the relevant silicone gaskets, and choose the silicone gaskets suitable for the working conditions of the sealing part.

3. Assembly of silicone gasket

The assembly of silicone gaskets is a key factor in practical applications. Generally, the requirements for assembly are as follows.

1. The surface of the silicone gasket and the sealing surface of the flange should be clean.

2. On the basis of accurately grasping the size of the flange sealing surface, use special tools to cut the silicone gasket material, and it is strictly forbidden to obtain the silicone gasket by knocking on the edge of the flange.

3. The outer diameter of the silicone gasket is slightly smaller than the flange sealing surface, and the inner diameter is slightly larger than the flange sealing surface. The difference is generally twice the thickness of the silicone gasket.

4. Before pre-tightening the silicone gasket, use a torque wrench to control the compression force of the bolts under the condition of knowing the specific pressure value of the pre-tightening seal of the gasket, so as not to cause the pre-tightening force to be too large or too small, resulting in Seal failure.

5. When pre-tightening the silicone gasket, in order to make the gasket evenly stressed, it should be pre-tightened diagonally and sequentially. The pre-tightening value cannot be reached at one time. Generally, the pre-tightening value is reached after 2 to 3 cycles.

6. When changing the silicone gasket, the nature of the medium should be considered, especially for flammable and explosive media, and safety tools must be used.

Four. Conclusion

In order to make the seal reliable and durable, considering the safety and efficiency of the unit, and eliminating waste, the selection of silicone gaskets is an aspect that needs to be carefully considered when enterprises install, repair, and renovate.




About silicone foam, please check the details:
https://www.siliconefoam.net/product-extra-soft-cellular-silicone-iota-bf-1000-.html