In industrial applications, the use of gaskets is very common, and they play a key role in ensuring equipment sealing. However, many people often feel confused when choosing gasket thickness, because there is no simple answer to this question. This article will explore in depth how to choose the appropriate gasket thickness based on different application scenarios, helping you make more informed decisions in practical work.
The main function of a gasket is to fill the gap between flanges and prevent fluid leakage. Gasket thickness directly affects its compressibility, sealing performance, and service life. Choosing an inappropriate gasket thickness may lead to seal failure or even cause safety accidents. Therefore, when selecting gasket thickness, it is necessary to consider multiple factors comprehensively, including flange type, operating pressure, operating temperature, media characteristics, and flange flatness.
Because gasket thickness selection involves many complex factors, we strongly recommend consulting with application engineers when unsure how to choose. Application engineers, with their rich experience and professional knowledge, can provide the most suitable advice based on specific application scenarios. They can evaluate the condition of the flange, operating conditions, and gasket material characteristics to determine the optimal gasket thickness.
As gasket application engineers, we generally recommend using the thinnest gasket possible. Thin gaskets have many advantages, including higher blowout resistance, lower leakage rates, better bolt torque retention, and lower cost. However, in certain specific situations, thicker gaskets may be required. Next, we will discuss these situations in detail.
In discussing gasket thickness selection, we have learned that thin gaskets have advantages in many applications. However, in certain specific cases, choosing a thicker gasket may be more appropriate. We will now explore these situations in detail.
In low-pressure, large-diameter flange applications, gaskets with a thickness of 3.2 mm are common and acceptable. These flanges usually do not have enough bolts, mainly because the internal pressure is not high, and the design does not require many bolts to maintain the seal. The limited number of bolts means limited gasket compression. If the flange is relatively thin, the flange may deform after bolt tightening, resulting in very small or no compression between bolts. In this case, a thin gasket cannot provide enough compression to compensate for flange unevenness.
Additionally, in very low-load areas, such as angle iron flanges, it is difficult to provide sufficient flange thickness to maintain flatness and the stress required for sealing a thin gasket. The internal pressure of these flanges is usually low, so even thicker gaskets do not pose a high blowout risk. The large bolt spacing results in very small compression load between two bolts. In this case, thin gaskets cannot adapt well to bent flanges, while thicker gaskets can fill these gaps better.
When there is no internal pressure, using thicker gaskets has no obvious adverse effects or disadvantages, because the gasket will not be blown out. In this situation, a thick gasket can better adapt to flange unevenness and provide better sealing performance.
For flanges designed for higher pressure, the situation is completely different. These flanges are usually thicker, and when bolts are tightened, they can maintain flatness, which can reach 0.1 mm. In this case, the advice of “the thinner, the better” is appropriate. The advantages of thin gaskets include:
Due to the smaller surface area exposed to internal pressure, thin gaskets have higher blowout resistance. This means that in high-pressure environments, thin gaskets are less likely to be blown out by internal pressure, ensuring reliable sealing.
Similarly, due to the smaller surface area exposed to internal pressure, thin gaskets have a lower leakage rate. This helps reduce fluid leakage and improve system safety.
Thinner gaskets have lower creep relaxation, which means better bolt torque retention. Over long-term use, thin gaskets can maintain compression load better, reducing the risk of seal failure caused by creep relaxation.
Thin gaskets themselves are also less expensive, helping to reduce overall maintenance and replacement costs.
Although thick gaskets are necessary in some cases, they also have potential issues. First, thick gaskets have higher creep relaxation. This means that during the entire service cycle of the flange connection, users may need to retighten bolts to maintain sufficient compression load on the gasket. Second, thick gaskets bring greater blowout force. Because the surface area of the gasket exposed to internal pressure increases, this produces a greater total force trying to push the gasket out of the flange, i.e., blowout force. Finally, since all gasket materials are permeable to some extent, the medium can penetrate the gasket body. Thick gaskets create larger permeation paths, so the leakage rate is higher.
However, it should be noted that if the gasket is too thin and cannot compensate for flange defects, the medium may leak through the flange gap instead of the gasket body, and the leakage rate may be higher than that of thick gaskets. Therefore, when selecting gasket thickness, a balance must be struck, taking into account flange flatness while ensuring gasket sealing performance.
In certain special situations, extremely specific gasket thickness may be required. For example, when using tongue-and-groove or recessed flat-face flange structures, the gasket must fill the entire space, and the gasket is compressed before metal-to-metal contact occurs between the flanges. In this case, the compressed gasket thickness after loading must be calculated and must be greater than the gap formed after flange contact. For example, if the groove depth is 3.2 mm and the tongue height is 0.6 mm, the compressed gasket thickness must exceed 2.6 mm; otherwise, the flange will contact before the gasket is fully compressed.
In addition, the type of gasket material and the allowable compression load also affect the gasket thickness for sealing specific flange connections. Under ASTM F36 standard testing, gaskets with higher compressibility do not require the same thickness as those with lower compressibility, because a more easily compressed gasket does not need to be as thick to adapt to flange defects.
To ensure sealing performance and reliability of flange connections, we recommend the following best practices.
Use High-Quality Flanges: High-quality flanges can provide better flatness and strength, reducing reliance on thick gaskets. When designing and purchasing flanges, select high-quality products that meet standards.
Maintain Good Flange Surface Condition: Regularly inspect and maintain flange surfaces to ensure flatness and cleanliness. If flange surfaces are damaged or warped, repair or replace them promptly.
Choose the Appropriate Gasket Material: Select gasket materials based on specific application scenarios and operating conditions. Different materials have different performance characteristics, and the most suitable material should be chosen accordingly.
Choose Gasket Thickness Reasonably: When selecting gasket thickness, consider flange type, operating pressure, temperature, media characteristics, and flange flatness comprehensively. Prefer thin gaskets whenever possible, but choose appropriate thick gaskets when necessary.
Collaborate with Professional Engineers: When unsure how to select gasket thickness, consult application engineers. They can provide the most suitable advice based on the specific application scenario, ensuring sealing performance and reliability of flange connections.
Choosing the appropriate gasket thickness is a complex issue that requires comprehensive consideration of multiple factors. In general, we recommend using thin gaskets whenever possible, as they have many advantages, including higher blowout resistance, lower leakage rate, better bolt torque retention, and lower cost. However, in certain specific situations, such as low-pressure, large-diameter flanges or cases without internal pressure, thicker gaskets may be needed. Additionally, in special situations, extremely specific gasket thickness may be required. When selecting gasket thickness, it is essential to communicate with application engineers to ensure the most suitable choice, thereby ensuring the sealing performance and reliability of flange connections.
By following the above recommendations, you can make wiser decisions in practical work, ensuring safe operation and efficient maintenance of equipment. Remember, choosing the right gasket thickness is crucial for ensuring flange sealing performance and should not be overlooked.