A Guide to the Selection and Application of PTFE Gaskets

In the industrial sector, the sealability of piping systems is of utmost importance. Gaskets, as the key components of sealing, play a crucial role in ensuring the reliability and safety of the system. PTFE gaskets, known for their unique properties, are widely used in various complex working conditions. This article will provide a detailed introduction to the selection points and relevant performance parameters of PTFE gaskets, helping readers to better understand and use this high-performance sealing material.

PTFE is a high-performance engineering plastic renowned for its excellent corrosion resistance, high-temperature resistance, and low coefficient of friction. PTFE gaskets are sealing elements made from PTFE material and are extensively used in flanged connections of pipes, valves, pumps, heat exchangers, and other equipment. The main features of PTFE gaskets include:

Corrosion Resistance: PTFE can resist the erosion of almost all chemical media, including strong acids, strong bases, and organic solvents.

High-Temperature Resistance: PTFE has an extremely wide operating temperature range, maintaining stable performance between -200℃ and 260℃.

Low Coefficient of Friction: PTFE has an extremely low coefficient of friction, which makes it perform well in dynamic sealing applications.

Good Electrical Insulation: PTFE is an excellent electrical insulating material, suitable for sealing in electronic and electrical equipment.

Next, let's delve into the performance parameters of PTFE gaskets. These parameters are important criteria for evaluating whether a gasket is suitable for specific working conditions. Understanding these parameters can help you more accurately select the appropriate gasket to ensure its reliability and safety in practical applications.

The operating temperature range of PTFE gaskets is -200℃ to 260℃. In practical applications, the appropriate temperature range should be selected based on specific working conditions. For example, if the working temperature exceeds 200℃, special attention should be paid to the performance changes of the gasket, as PTFE may soften at high temperatures, affecting the sealing effect.

PTFE gaskets are suitable for low-pressure to medium-pressure conditions. Generally, PTFE gaskets are not recommended for high-pressure steam pipelines because they may be ruptured under high-temperature and high-pressure conditions. For steam pipelines, when the temperature exceeds 180℃ or the pressure reaches 10 kilograms, other types of gaskets, such as asbestos rubber gaskets, should be used.

By adjusting the tension of the wound steel belt, the density (hardness) of the PTFE gasket can be changed. This adjustment can provide more suitable sealing performance according to different application requirements. For example, in areas where higher sealing pressure is required, a gasket with higher density can be selected.

PTFE has extremely high chemical stability and can resist the erosion of almost all chemical media. This makes PTFE gaskets perform well when handling corrosive media, effectively preventing leakage and corrosion.

Selection is a key step to ensure the sealing effect. Only with the correct selection can the advantages of PTFE gaskets be fully utilized to meet the sealing requirements under different working conditions. The following are the selection points for PTFE gaskets to help you make wise choices in practical applications.

Normal Temperature and Low Pressure: Under normal temperature and low-pressure conditions, it is recommended to use non-metallic soft sealing gaskets. These gaskets have good flexibility and sealing performance, which can adapt to slight unevenness of the flange surface.

Medium Pressure and High Temperature: When the working environment is at medium pressure and high temperature, a combination of metallic and non-metallic sealing gaskets or metallic gaskets should be selected. Metallic gaskets have higher strength and high-temperature resistance, capable of withstanding greater pressure and temperature changes.

Large Temperature and Pressure Fluctuations: In such cases, it is recommended to use gaskets with good elasticity or self-tightening sealing gaskets. These gaskets can automatically adjust the sealing pressure to adapt to temperature and pressure fluctuations, ensuring the reliability of the seal.

Low Temperature, Corrosive Media, or Vacuum Conditions: For low-temperature, corrosive media, or vacuum environments, PTFE gaskets with special properties should be selected. PTFE gaskets perform well under these extreme conditions, effectively preventing leakage.

Corrosive Media: PTFE gaskets are an ideal choice for handling corrosive media. Due to their excellent chemical corrosion resistance, PTFE gaskets can resist the erosion of most chemical media, ensuring long-term stable sealing.

Non-Corrosive Media: For non-corrosive media, such as general steam pipelines, asbestos rubber gaskets can be considered. These gaskets are cost-effective and can provide good sealing effects when the temperature and pressure conditions are met. However, if higher sealing performance or use under extreme conditions is required, PTFE gaskets are still a better choice.

Flange Type: The type of flange has an important impact on the selection of gaskets. For example, flat face flanges and raised face flanges require different types of gaskets. Flat face flanges usually require thicker gaskets, while raised face flanges need thinner gaskets to ensure sealing effectiveness.

Surface Roughness: The surface roughness of the flange has a significant impact on the sealing effect. For non-soft gaskets, such as metallic gaskets, when the surface roughness of the flange is high, leakage is likely to occur. This is because the spiral grooves formed by machining tool marks cannot be completely blocked by the gasket, resulting in leakage under pressure. Soft PTFE gaskets have lower requirements for the smoothness of the flange surface because they can deform and block the machining tool marks to prevent leakage. However, an overly smooth flange surface is not conducive to the sealing of PTFE gaskets, as it reduces the resistance to interface leakage.

Compression and Resilience: Gaskets should have good compression and resilience to adapt to temperature and pressure fluctuations. This helps maintain the reliability of the seal and prevents leakage even when the working conditions change.

Malleability: Gaskets need to have good malleability to fit well with the flange sealing surface. This not only helps improve the sealing effect but also reduces the risk of leakage due to uneven flange surfaces.

Safety: For piping systems conveying toxic chemicals or flammable liquids, the safety of the gasket is crucial. Gaskets that meet relevant safety standards should be selected to ensure their safe and reliable operation within the maximum working pressure and temperature range.

Machining and Installation: The machining performance of the gasket should be good, and it should be easy to install and tighten. In addition, the gasket should not adhere to the flange sealing surface to facilitate disassembly and maintenance.

Next, we will enter the practical operation stage, that is, how to select the appropriate PTFE gasket according to the specific application scenario. The correct selection of gaskets can not only ensure the sealing effect but also extend the service life of the equipment and reduce maintenance costs.

Determine the structure type of the PTFE gasket according to the pressure of the sealing chamber. For example, for high-pressure conditions, a balanced gasket may be required to reduce the impact of pressure on the sealing surface. For low-pressure conditions, a non-balanced gasket may be sufficient.

The working speed also affects the selection of gaskets. If the equipment operates at high-speed rotation, rotating or hydrodynamic gaskets should be selected. These gaskets can maintain stable sealing performance during high-speed rotation, preventing leakage.

Temperature and the properties of the fluid are important factors in selecting gaskets. For high-temperature or low-temperature conditions, gaskets with corresponding temperature adaptability should be selected. At the same time, according to the corrosiveness of the fluid, suitable friction pairs and auxiliary sealing materials should be chosen. In addition, mechanical seal cycle protection systems such as lubrication, flushing, insulation, and cooling should be considered to ensure the long-term stable operation of the gasket.

The size of the installation space also affects the selection of gaskets. If the space is limited, multi-spring or wave spring gaskets should be selected, which can provide good sealing performance in a smaller space. At the same time, according to the installation position, internal or external gaskets should be chosen.

The correct selection of PTFE gaskets is the key to ensuring the sealing performance of piping systems. When selecting, a comprehensive consideration of multiple factors such as working pressure, temperature, corrosiveness of the medium, flange type, and surface roughness is required. PTFE gaskets, with their excellent corrosion resistance, high-temperature resistance, and good sealing performance, are widely used in various industries. By reasonably selecting the type and parameters of the gasket, the reliability and safety of the system can be effectively improved, the risk of leakage can be reduced, and the long-term stable operation of the equipment can be ensured.

In practical applications, it is recommended to cooperate with professional gasket manufacturers or suppliers to obtain more detailed technical support and selection suggestions. By gaining a deep understanding of the various performance and application scopes of PTFE gaskets, users can better select gaskets suitable for their working conditions, thereby achieving efficient and safe sealing effects.