Regarding the thickness of the sealing gasket
Thread Content
This post was last edited by Xin Ruifangxiao on 2025-6-10 at 13:07. Click the blue text to follow us. Different thickness options can have a significant impact on the performance of gaskets, yet the ASME B16.21 standard does not provide any guidelines regarding the selection of thicknesses for non-metallic gaskets. So how do you choose the appropriate gasket thickness? What are the advantages of gaskets of different thicknesses? 1. What are the advantages of thin gaskets? a. The higher resistance to ejection is due to the smaller surface area in contact with internal pressure. Because the thicker the gasket, the greater the surface area of the gasket in contact with the internal pressure, which results in a higher blowing force; b. the leakage rate is also lower. All gasket materials are permeable to some extent, allowing the medium to pass through the body of the gasket. Thicker gaskets create larger pathways for penetration, while thin gaskets have a smaller surface area in contact with internal pressure, resulting in a lower leakage rate. c. Since thinner gaskets have lower creep relaxation properties, fasteners maintain their torque better. Thicker gaskets result in greater creep relaxation, which means that throughout the service life of the flange connection, the user may need to retighten the bolts to maintain sufficient compressive load on the gaskets. d. Lower cost. The thinner the gasket of the same size, the lower the cost. 2. Is it true that the thinner the gasket, the better? The answer is certainly no, because in some cases, thicker gaskets are indeed needed. For example, in some low-pressure, full-flat large-diameter flanges that do not have enough bolts, the limited number of bolts results in a limited degree of compression of the gaskets; as a result, the gaps between the bolts are barely compressed or not compressed at all. Thin gaskets do not have sufficient compression to compensate for severely damaged flange surfaces, whereas thick gaskets, with their greater initial thickness, experience more compression, making them particularly suitable for flanges that are severely damaged or warped. 3. What factors affect gasket thickness? The thickness of metal and semimetal gaskets generally does not change the gasket pressure and temperature (PT) ratings. Non-metallic (soft) gaskets, the thickness of which can be selected based on the flange material or flange conditions. The type of gasket material and the allowable compressive load also affect the thickness of the gasket required to seal a specific flange connection. 4. Factors in selecting gaskets? a. Temperature: It primarily affects the physical, chemical, and mechanical properties of the gasket. b. Pressure: This includes operating pressure, design pressure, service pressure, and test pressure. c. Medium: The medium (fluid) can be gas or liquid; it can range from hot to cold, with pH levels varying from high to low, from corrosive to neutral, from flammable to non-flammable, as well as all types of media in between. It mainly affects the physical, chemical, and mechanical properties of the gasket. d. Dimensions: The dimensions of the sealing interface don’t impose many restrictions on the selection of gaskets, but they do influence the choice of material. e. Application: The specific location where it is used in the equipment, its intended purpose, etc. For example, whether it is used in a tower as an access hatch, an inlet, an outlet, or for heat exchange; the number of times each part opens and closes also affects the selection of the gasket. Modify/Remove
When selecting the appropriate gasket thickness, we need to take multiple factors into consideration. Below are answers to the various aspects of your question: 1. The advantages of thin gaskets include: – High resistance to blowing out: Thin gaskets have a smaller surface area in contact with internal pressure, resulting in less force being exerted on them. - Low leakage rate: Thin gaskets reduce the pathways for medium penetration due to their low material thickness. - Low creep relaxation: Thin gaskets exhibit better creep resistance, which helps maintain the torque of fasteners. - Lower cost: Less material is used, resulting in relatively low costs. 2. Thinner gaskets are not necessarily better. In certain special cases, thicker gaskets may be required. For example: when the flange surfaces are uneven or severely damaged, thick gaskets can provide more compression to compensate for such unevenness. - Flanges with a small number of bolts may not be able to provide sufficient compression for thin gaskets. 3. Factors affecting the selection of gasket thickness include: - The type and physical properties of the gasket material. - The compressive load to be withstood. - Material and conditions of the flange. 4. The factors involved in selecting gaskets include: - Temperature: It is necessary to consider the highest and lowest temperatures that the gasket can withstand. - Pressure: Working pressure, design pressure, and other factors all influence the selection of gasket material and thickness. - Medium: The chemical properties and state of the fluid (such as gaseous, liquid, or corrosive) influence the selection of gasket material. - Size: The size of the flange affects the size of the gasket, which in turn may influence the choice of material. - Applications: Based on the specific requirements of the gasket’s installation location, such as the frequency of opening and closing, as well as whether it is easy to replace. In summary, when selecting the gasket thickness, it is necessary to determine it based on the actual operating conditions and the environment to which the gasket will be exposed. Choosing the most appropriate gasket thickness pragmatically will help ensure the sealing performance and durability of the connection. .
I’ve learned that it’s difficult to explain the issue of gasket thickness; often, people try to solve leakage problems by using thicker gaskets； Is the above content based on standards, or is it an analysis done independently?
Thicker gaskets result in greater creep relaxation, which means that throughout the service life of the flange connection, it will take more time to retighten the connections and replace the gaskets. When selecting the type and thickness of gasket material, we need to carefully consider all the variables related to the application conditions. However, sometimes the defects in the flanges or bolts cannot be completely compensated for by gaskets; proper installation of the flange connection system is also very important. We specialize in expanded polytetrafluoroethylene sealing materials. If you have any needs, feel free to contact us at 19141369821; the WeChat ID is the same
Personally, I think thick gaskets are slightly better in practical applications. Some units have been in operation for a long time (over ten years), and due to inadequate maintenance of flanges, pipelines, and insulation, corrosion of varying degrees has occurred. Furthermore, the flanges purchased may not all meet the specifications, and the company hires cheap construction teams for inspection and maintenance; the skill levels of these teams vary. Using thicker gaskets provides a better margin for error. We usually choose gaskets that are 4.5 thick. Additionally, the width of the gasket specified in the standards is a bit narrow; we use custom-made gaskets to achieve a wider seal. By the way, the device pressure is not very high, below 4.0 MPa.