The Sealing Mechanism of Gaskets And Main Leakage Factors
The Sealing Mechanism of Gaskets And The Main Factors Affecting Flange Gasket Leakage
Sealing mechanism of gaskets
Firstly, connect the two parts of the flange connection together with bolts, then pre-tighten the bolts and apply force to the gasket through the flange compression surface, causing the gasket to undergo elastic or plastic deformation and fill the flange compression surface, achieving a sealing effect. The sealing effect of flanges is closely related to the performance of gaskets and bolt pre-tightening force. It is also affected by external environmental factors. The main factors that affect sealing include several categories.
1. Operating conditions
Operating conditions refer to the external conditions and environment related to the entire flange connection system, such as operating pressure, operating temperature, medium properties, etc. When the operating temperature is too high, the viscosity of the medium will decrease. Accordingly, the permeability will increase, and the leakage situation will worsen. Under high temperature, flanges, gaskets, and bolts may experience creep and stress relaxation, which can damage the sealing performance.
Compared to metal gaskets, temperature has a greater impact on non-metallic gaskets. Excessive temperature often leads to deterioration and accelerated aging of non-metallic gaskets, causing serious consequences such as reduced rebound or even burning.
2. Pre-tightening force of bolts
Increasing the pre-tightening force of the bolt can enhance the sealing performance of the gasket, but when the pre-tightening force of the bolt is too large, it usually leads to a decrease in the elasticity of the gasket or even damage. The magnitude of bolt pre-tightening force is usually related to the coefficient m of the gasket and the minimum clamping force y value. In addition, an inappropriate bolt tightening sequence can also cause the gasket to bend or wrap.
3. Design the overall coefficient m and minimum compression force y value
The gasket coefficient m and the minimum clamping force y value are two very important parameters in the design of pressure vessel flange seals. The selection of m and y values usually requires reference to the standard GB 150-2001 "Pressure Vessels".
In the past, the industry believed that the values of m and y were only related to the material, structure, and thickness of the gasket. However, relevant studies have shown that the values of m and y are also related to factors such as the sealing surface of the flange, the width of the gasket, the operating environment, the characteristics of the medium inside the pressure vessel, and the roughness of the clamping surface, and there is also a certain internal relationship between them.
4. Gasket types
According to different materials, gaskets can be divided into non-metal gaskets, metal gaskets, and metal and non-metal combination gaskets. Different materials of gaskets are suitable for different operating temperatures and pressures. According to their different cross-sectional forms, gaskets can be divided into corrugated gaskets, flat gaskets, serrated gaskets, elliptical gaskets, and octagonal gaskets.
The cross-sectional form of gaskets needs to be selected according to specific mining and operating conditions. Metal non-metal composite gaskets combine the advantages of both metal and non-metal gaskets, making them suitable for applications with higher temperatures and pressures. When selecting gaskets, various factors need to be considered comprehensively. Choosing unsuitable materials often leads to gasket failure during operation, resulting in leakage.
5. Compression surface forms
In addition to the above factors, it is also necessary to consider the installation position of the gasket and the impact of the surrounding environment on the gasket, that is, to consider the influence of the flange connection surface form and the roughness of the compression surface. The commonly used forms of compression surfaces mainly include protruding surfaces, concave convex surfaces, mortise and tenon surfaces, and trapezoidal groove surfaces. The different forms of compression surfaces have different effects on the gasket. For example, gaskets with concave and convex surfaces are easier to align and less likely to be blown out.
6. Chemical corrosion
Pressure vessels are often used in various special working environments, such as corrosive media. If the material of the gasket is not selected properly, when the gasket or sealing surface comes into contact with the medium, the gasket will be corroded, causing device leakage.
Sealing mechanism of gaskets
Firstly, connect the two parts of the flange connection together with bolts, then pre-tighten the bolts and apply force to the gasket through the flange compression surface, causing the gasket to undergo elastic or plastic deformation and fill the flange compression surface, achieving a sealing effect. The sealing effect of flanges is closely related to the performance of gaskets and bolt pre-tightening force. It is also affected by external environmental factors. The main factors that affect sealing include several categories.
1. Operating conditions
Operating conditions refer to the external conditions and environment related to the entire flange connection system, such as operating pressure, operating temperature, medium properties, etc. When the operating temperature is too high, the viscosity of the medium will decrease. Accordingly, the permeability will increase, and the leakage situation will worsen. Under high temperature, flanges, gaskets, and bolts may experience creep and stress relaxation, which can damage the sealing performance.
Compared to metal gaskets, temperature has a greater impact on non-metallic gaskets. Excessive temperature often leads to deterioration and accelerated aging of non-metallic gaskets, causing serious consequences such as reduced rebound or even burning.
2. Pre-tightening force of bolts
Increasing the pre-tightening force of the bolt can enhance the sealing performance of the gasket, but when the pre-tightening force of the bolt is too large, it usually leads to a decrease in the elasticity of the gasket or even damage. The magnitude of bolt pre-tightening force is usually related to the coefficient m of the gasket and the minimum clamping force y value. In addition, an inappropriate bolt tightening sequence can also cause the gasket to bend or wrap.
3. Design the overall coefficient m and minimum compression force y value
The gasket coefficient m and the minimum clamping force y value are two very important parameters in the design of pressure vessel flange seals. The selection of m and y values usually requires reference to the standard GB 150-2001 "Pressure Vessels".
In the past, the industry believed that the values of m and y were only related to the material, structure, and thickness of the gasket. However, relevant studies have shown that the values of m and y are also related to factors such as the sealing surface of the flange, the width of the gasket, the operating environment, the characteristics of the medium inside the pressure vessel, and the roughness of the clamping surface, and there is also a certain internal relationship between them.
4. Gasket types
According to different materials, gaskets can be divided into non-metal gaskets, metal gaskets, and metal and non-metal combination gaskets. Different materials of gaskets are suitable for different operating temperatures and pressures. According to their different cross-sectional forms, gaskets can be divided into corrugated gaskets, flat gaskets, serrated gaskets, elliptical gaskets, and octagonal gaskets.
The cross-sectional form of gaskets needs to be selected according to specific mining and operating conditions. Metal non-metal composite gaskets combine the advantages of both metal and non-metal gaskets, making them suitable for applications with higher temperatures and pressures. When selecting gaskets, various factors need to be considered comprehensively. Choosing unsuitable materials often leads to gasket failure during operation, resulting in leakage.
5. Compression surface forms
In addition to the above factors, it is also necessary to consider the installation position of the gasket and the impact of the surrounding environment on the gasket, that is, to consider the influence of the flange connection surface form and the roughness of the compression surface. The commonly used forms of compression surfaces mainly include protruding surfaces, concave convex surfaces, mortise and tenon surfaces, and trapezoidal groove surfaces. The different forms of compression surfaces have different effects on the gasket. For example, gaskets with concave and convex surfaces are easier to align and less likely to be blown out.
6. Chemical corrosion
Pressure vessels are often used in various special working environments, such as corrosive media. If the material of the gasket is not selected properly, when the gasket or sealing surface comes into contact with the medium, the gasket will be corroded, causing device leakage.
