The Impact of Gasket Dimensions on Sealing Performance

In industrial production, gaskets, as sealing elements, are widely used in various pipe and flange connections. Their dimensional parameters have a crucial impact on sealing performance. This article will delve into the mechanisms by which gasket thickness, width, inner diameter, outer diameter, and other dimensional factors affect sealing performance. It will also explore how to select gasket dimensions reasonably based on actual working conditions to ensure the safe and reliable operation of sealing systems.

Gasket thickness is one of the key factors affecting sealing performance. Under the same clamping load and medium pressure conditions, as the gasket thickness increases, the leakage rate will gradually decrease. This is because a thicker gasket has a greater compression and rebound capacity under the same axial load. When the initial sealing conditions are met, a thicker gasket, with its larger elastic reserve, can better compensate for the relative separation between sealing surfaces caused by medium pressure. It also maintains a higher residual clamping stress on the gasket surface, thereby effectively reducing the leakage rate.

However, this does not mean that the thicker the gasket, the better the sealing performance. Different gasket thicknesses require different conditions to establish initial sealing. The end face of the gasket is under triaxial compressive stress due to frictional forces, resulting in higher material deformation resistance. In contrast, the central part of the gasket, less affected by the ends, has relatively lower deformation resistance. Under the same pre-tightening load, the central part of the gasket is more likely to undergo plastic deformation than the surface. Establishing an initial sealing surface becomes more difficult in this case. Therefore, once the gasket thickness reaches a certain value, the sealing performance will not only fail to improve further but may even deteriorate. Moreover, the thicker the gasket, the larger the cross-sectional area for permeation leakage, and the higher the permeation leakage rate will be.

Gasket width also has a significant impact on the leakage rate. Within a certain range, as the gasket width increases, the leakage rate will increase linearly. This is because the leakage resistance within the effective width of the gasket is proportional to the length of the leakage path (which is proportional to the gasket width). However, a wider gasket is not always better. The larger the gasket surface area, the greater the bolt force required to generate the same clamping stress on the gasket. If the bolt force is insufficient, it will not ensure adequate clamping force between the gasket and the sealing surface, thereby affecting the sealing effect.

The inner diameter, outer diameter, and other related dimensional parameters of the gasket play an indispensable role in sealing performance. The rational selection of these parameters can ensure a tight fit between the gasket and components such as flanges, thereby achieving good sealing results. We will now explore the specific impacts of these dimensional parameters in detail.

The inner diameter of the gasket must not be less than the thickness of the selected gasket material to avoid material tearing or defects during production. For example, if you choose a 3.00 mm thick fluororubber as the gasket material, the minimum inner diameter of the gasket should be 3 mm. The size of the inner diameter directly affects the sealing performance and service life of the gasket. An inner diameter that is too large or too small can lead to poor sealing or material damage.

The outer diameter is another important dimensional parameter of the gasket. We possess a variety of advanced production technologies that enable us to custom-manufacture larger-sized gaskets according to specific customer specifications. When selecting the outer diameter of the gasket, it is necessary to ensure that it corresponds to the flange sealing surface, and the gasket's outer diameter is usually 1 - 2 millimeters larger than the sealing surface to ensure complete sealing. For example, if the diameter of the flange sealing surface is 100 mm, the outer diameter of the gasket should be chosen as 101 - 102 mm.

Flange size refers to the gasket flange width, which is the difference between the outer diameter (OD) and the inner diameter (ID) at the narrowest point. The gasket flange width must not be less than the thickness of the gasket material. For example, if you choose a fluororubber thickness of 5.00 mm and an inner diameter of 5.00 mm, the outer diameter must be at least 15.00 mm (material thickness plus inner diameter). The rational selection of flange size is crucial for ensuring the seal between the gasket and the flange.

The pitch circle diameter (PCD) refers to the diameter of the center circle of the bolt holes on the gasket. The PCD must not exceed the outer diameter (OD) of the gasket or be less than the inner diameter (ID), and there should be sufficient material on both sides of the PCD holes, with a thickness equal to or greater than the material thickness selected. For example, if you choose a fluororubber thickness of 6.00 mm, a PCD hole diameter of 4.00 mm, and an inner diameter of 6.00 mm, then the PCD should be marked as 22 mm, the outer diameter should be 38 mm (minimum production threshold), and the flange width should be 16 mm. To ensure that the gasket can be cut, the flange size (outer diameter minus inner diameter) should be equal to the minimum value of the PCD hole diameter plus twice the material thickness selected. Once the PCD is considered, the measurement [A] must leave space for the material thickness [C] on both sides of the PCD hole diameter.

In practical applications, selecting the appropriate gasket dimensions requires a comprehensive consideration of various factors, including the nature of the medium, pressure, temperature, flange size, and sealing requirements. The following are some suggestions for reasonably selecting gasket dimensions.

Different media have different requirements for gasket materials and dimensions. For example, for highly corrosive media, gasket materials with good corrosion resistance should be chosen, and the gasket thickness should be appropriately increased to enhance sealing performance. For high-temperature media, gaskets with good heat resistance should be selected, and the elastic recovery capability of the gasket at high temperatures should be considered.

Under high-pressure or high-temperature conditions, the sealing performance of the gasket is more challenging. In such cases, gaskets with appropriate thickness and width should be chosen, and the gasket material should be capable of withstanding the corresponding pressure and temperature. For example, in high-pressure steam pipelines, thicker metal wound gaskets should be selected, and the inner and outer diameters of the gasket should be closely matched with the flange sealing surface.

The dimensions of the gasket should match the flange size. The inner diameter of the gasket should be the same as or slightly larger than the flange inner diameter, and the outer diameter should be 1 - 2 millimeters larger than the flange sealing surface. Additionally, the pitch circle diameter (PCD) should be selected based on the bolt hole distribution of the flange to ensure a tight fit between the gasket and the flange, achieving good sealing results.

When selecting gasket dimensions, relevant standards and specifications, such as ISO, DIN, ANSI, and other international or industry standards, should be followed. These standards and specifications provide clear guidance and references for gasket dimension selection, ensuring the safety and reliability of the gasket.

The dimensions of gaskets have a crucial impact on sealing performance. Variations in gasket thickness, width, inner diameter, outer diameter, and other dimensional parameters all affect the sealing effect. When selecting a gasket, it is necessary to consider the actual working conditions and sealing requirements comprehensively, taking into account factors such as medium characteristics, pressure, temperature, and flange size to reasonably select the gasket dimensions. By reasonably selecting gasket dimensions, the safety and reliability of the sealing system can be effectively improved, ensuring the smooth progress of industrial production. At the same time, following relevant standards and specifications is also an important guarantee for the correct selection of gasket dimensions.

Q1: How do I determine the appropriate thickness for a gasket?

A1: The appropriate thickness of a gasket depends on several factors, including the nature of the medium, the operating pressure and temperature, and the flange design. Thicker gaskets generally provide better sealing performance under higher pressures and temperatures, but they can also lead to increased leakage if not properly compressed. It is important to balance these factors and refer to industry standards such as ISO, DIN, or ANSI for specific recommendations.

Q2: What is the impact of gasket width on sealing performance?

A2: Gasket width significantly affects the leakage rate. Within a certain range, increasing the gasket width can increase the leakage rate linearly because the leakage resistance is proportional to the length of the leakage path. However, wider gaskets require more bolt force to achieve the same clamping stress, and insufficient bolt force can lead to poor sealing. Therefore, it is crucial to select an optimal width that balances leakage resistance and clamping requirements.

Q3: Why is the inner diameter of a gasket important?

A3: The inner diameter (ID) of a gasket is crucial for preventing material tearing or defects during production and ensuring proper sealing. The ID should not be less than the thickness of the gasket material. An ID that is too large or too small can lead to poor sealing or material damage. It is important to select an ID that matches the flange design and the specific application requirements.