During the daily inspection process, sealing gaskets are indispensable in sealed and pressurized devices such as boilers, pressure vessels, and pressure pipelines. However, most enterprises lack professional knowledge in the selection and application scope of sealing gaskets and merely rely on experience to make the selection. This inevitably leads to some misunderstandings. As a result, phenomena such as leakage, overflow, dripping, and spilling are common, causing a lot of waste for the organization and even resulting in serious accidents due to the failure of the sealing gaskets. The main reason for these situations is problems in the selection and assembly of sealing gaskets. In view of the above circumstances, it is necessary to provide a more specific introduction to the selection of sealing gaskets. 
I. The Function, Mechanism and Factors Affecting Sealing of Sealing Gaskets
The function of sealing gaskets is to prevent the leakage of the sealed medium. The forms of leakage can be divided into interface leakage and penetration leakage. The causes of interface leakage are usually due to the relaxation of the compressive force between the sealing surfaces, aging, deformation, corrosion, wear or burn of the sealing surfaces, or mechanical vibration during operation, etc. Penetration leakage is related to the material type of the sealing gasket, the manufacturing method, the nature of the sealed medium, as well as the working pressure and temperature.
Theoretically, even if a sealing gasket is used, it is impossible to achieve complete contact between the sealing surfaces, eliminating any microscopic channels or gaps. Although these channels are extremely narrow, they are still large enough relative to the molecular volume of the fluid medium. Therefore, it is impossible to completely prevent the fluid from entering the edge of the sealing surfaces. Some fluid will always enter the gap between the sealing surfaces and undergo complex fluid mechanics and thermodynamics processes. Generally, it is believed that after the fluid enters the extremely fine and irregular gaps, it will generate resistance loss during its flow, consuming its energy, and at the same time, a stationary boundary layer will be generated on the walls of these gaps, making the tiny channels narrower or even completely closed, preventing the fluid from continuing to flow into the sealing surfaces, thus achieving sealing.
The main factors affecting sealing include the following situations: the surface condition of the sealing surfaces; the contact width of the sealing surfaces; the nature of the fluid; the temperature of the fluid; the material of the sealing gasket; the preload applied to the sealing surfaces; the influence of external factors (mainly the vibration of the system, the deformation of the connecting parts, the offset of the installation position, etc.). To ensure reliable sealing, these factors must be carefully considered, and the quality and selection of the sealing gasket are also crucial. 
II. Selection of Sealing Gaskets for Suzhou Rubber Products
The selection of sealing gaskets requires the consideration of the following factors:
1. The properties of the fluid, including the physical and chemical properties of the fluid medium in contact, and whether they will react with the gasket.
2. The pressure of the fluid, including 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, etc.
3. The temperature of the fluid, including the temperature condition of the fluid medium and whether there are temperature changes during operation.
4. The type of flange, including the shape, size, and condition of the sealing surface of the flange.

After a detailed understanding of the above situations, relevant technical performance data of sealing gaskets can be consulted to select the appropriate sealing gasket for the working conditions of the sealing part.

III. Assembly of Sealing Gaskets
The assembly of sealing gaskets is a key factor in practical applications. Generally, the requirements for assembly include the following aspects:
1. The surface of the sealing gasket and the sealing surface of the flange should be clean.
2. Based on an accurate understanding of the size of the flange sealing surface, use special tools to cut the sealing gasket material. It is strictly prohibited to obtain the sealing gasket by hitting the edge of the flange.
3. The outer diameter of the sealing gasket is slightly smaller than the sealing surface of the flange, and the inner diameter is slightly larger. The difference is generally twice the thickness of the sealing gasket.
4. Before pre-tightening the sealing gasket, in the case of knowing the pre-tightening sealing ratio pressure value of the gasket, use a torque measuring force wrench to control the bolt compression force to avoid excessive or insufficient pre-tightening force, which may lead to sealing failure.
5. During pre-tightening of the sealing gasket, to ensure uniform force on the gasket, use diagonal sequential pre-tightening. It is not allowed to reach the pre-tightening value at once. Generally, it is necessary to cycle 2-3 times to reach the pre-tightening value.
6. When replacing the sealing gasket, consider the nature of the medium, especially for flammable and explosive media, use safety tools. 4. Conclusion
In order to ensure reliable and long-lasting sealing, considering factors such as safety, efficiency and waste prevention, the selection of sealing gaskets is an aspect that enterprises need to carefully consider during installation, repair and renovation.