Guide to the Selection of PTFE Packing

In the industrial sector, the choice of sealing materials is of vital importance, as it directly affects the operational efficiency, safety, and service life of equipment. Polytetrafluoroethylene (PTFE) packing, as a high-performance sealing material, is widely used in various fields such as machinery, electronics, and chemicals. However, with the vast array of PTFE packing products available on the market, selecting the appropriate type and specification has become a challenging task for many users. This article will provide a detailed guide on how to select PTFE packing, helping you choose the best sealing protector for your equipment.

PTFE packing comes in various types, and depending on different application scenarios and performance requirements, the following common products can be selected:

Split Fiber PTFE Packing: Made through a special splitting process, it offers good flexibility and sealing performance, making it suitable for sealing general-purpose equipment.

High Water-Based Packing: Containing a high proportion of water-based lubricants, it is designed for high-temperature, high-pressure, and high-humidity environments, effectively preventing leaks.

The widespread application of PTFE packing is due to its outstanding performance characteristics:

Sealing Performance: It effectively prevents the leakage of liquids and gases, providing reliable sealing effects.

Oil Retention: It can store an appropriate amount of lubricating oil, reducing the amount of lubricant used while maintaining the lubrication effect of the equipment.

Shock Absorption: It has good shock-absorbing properties, capable of absorbing vibrations during equipment operation, thereby extending the equipment's lifespan.

Sound Insulation: It can effectively isolate noise, reducing noise pollution during equipment operation.

Thermal Insulation: It has good thermal insulation properties, helping to maintain a stable internal temperature of the equipment.

Anti-static: It prevents the accumulation of static electricity, avoiding safety issues caused by static discharge.

When selecting PTFE packing, multiple factors need to be considered to ensure that the chosen product meets the sealing requirements of the equipment. Here are several key points for selection:

The specific gravity (grams per cubic centimeter) of PTFE packing significantly affects its performance. If the specific gravity is too high, the packing will lose its elasticity, leading to reduced sealing performance; if it is too low, the packing will lose its wear resistance and become prone to wear. Therefore, selecting an appropriate specific gravity is crucial. Generally, packing with a specific gravity between 0.5 and 1.5 grams per cubic centimeter can balance elasticity and wear resistance, making it suitable for most application scenarios.

The thickness and diameter of the packing also affect its performance. Thicker packing provides better sealing effects but may increase installation difficulty and equipment operating resistance; thinner packing is more flexible and suitable for space-limited applications. Users can select the appropriate thickness and diameter based on specific application requirements. For example, in high-pressure, high-temperature environments, it is recommended to choose thicker packing; in small equipment or precision instruments, thinner packing may be more appropriate.

Currently, PTFE packing is divided into two main categories: special grade and general grade. Special grade packing, made from higher-quality raw materials and advanced manufacturing processes, offers superior performance and longer service life; general grade packing provides a balance between performance and price, suitable for applications with less stringent sealing requirements. Users can select the appropriate grade based on the importance of the equipment and its operating environment. If the equipment operates under extreme conditions, such as high temperature, high pressure, or strong corrosive environments, special grade packing is recommended; if the operating conditions are relatively mild, general grade packing can meet the needs.

The technical requirements for PTFE packing mainly include tensile strength, elongation, and capillary action. Packing with high tensile strength can withstand greater pressure and is less likely to deform; packing with high elongation has better flexibility, allowing it to adapt to the thermal expansion and contraction of equipment; packing with low capillary action can reduce the penetration of lubricants, maintaining the sealing effect. Users can select packing that meets the technical requirements based on the specific needs of the equipment. For example, in high-speed rotating equipment, packing with high tensile strength and elongation is required; in applications where the cleanliness of lubricants needs to be maintained, packing with low capillary action should be chosen.

When ordering PTFE packing, users need to provide detailed specification information based on the specific requirements of the equipment, including category naming code, thickness, length, and width. If colored packing is required, the color requirements should also be specified. For example, a user needs to order high water-based packing for chemical equipment with the category code "HSP-001," a thickness of 5 millimeters, a width of 10 millimeters, and a length of 100 meters, and the packing should be dyed blue. When placing the order, users should clearly provide these specification requirements to ensure that the purchased product meets the actual needs.

The weaving technology of PTFE packing significantly affects its performance. Good weaving technology can enhance the sealing effect and service life of the packing. Here are several key points of weaving technology:

Weaving density is a key factor affecting the performance of packing. Tight and orderly weaving can improve the wear resistance and compressive strength of the packing, reducing the possibility of leaks. Generally, the higher the weaving density, the better the performance of the packing. However, increasing weaving density can also reduce the flexibility of the packing, so a balance between performance and flexibility needs to be found. In most application scenarios, it is recommended to choose packing with a higher weaving density to ensure sealing effects.

The number of spindles and tracks of the weaving machine also affects the quality of the packing. Machines with more spindles can make the packing weaving tighter, improving its durability; machines with more tracks can make the outer surface of the packing smoother and flatter, thereby improving sealing efficiency and reducing clamping force. For example, packing produced on a four-track machine has a smoother and flatter outer surface than that produced on a three-track machine. However, in some small-sized packing, using a four-track machine may not be appropriate due to its high cost and complex operation. Therefore, users should select the appropriate weaving machine based on the size and application requirements of the packing.

The cross-sectional shape of PTFE packing is usually square, rectangular, or circular. Different shapes are suitable for different sealing chambers. For example, square and rectangular packing is suitable for rectangular sealing chambers, while circular packing is suitable for circular sealing chambers. Users should select the appropriate packing shape based on the shape of the equipment's sealing chamber to ensure sealing effects.

PTFE packing has many unique performance advantages, making it perform well in various industrial applications:

Flexibility and Adjustability: PTFE packing has good flexibility and adjustability, allowing it to closely fit with the shaft and stuffing box, providing excellent sealing effects.

Corrosion Resistance: PTFE material has excellent corrosion resistance, capable of withstanding the erosion of most chemicals and solvents, making it suitable for various harsh chemical environments.

Self-lubrication: PTFE packing has good self-lubrication properties, reducing friction and wear, and extending the service life of equipment.

Non-stick: PTFE material has extremely low surface tension and does not adhere to any substances, preventing media from depositing on the packing surface and maintaining sealing effects.

Mechanical Toughness: Even at extremely low temperatures (such as -196°C), PTFE packing can still maintain a certain elongation rate and has good mechanical toughness.

Chemical Inertness: PTFE material shows inertness to most chemicals and solvents, capable of withstanding strong acids, strong bases, water, and various organic solvents.

Low Friction Coefficient: PTFE is one of the materials with the lowest friction coefficients among solid materials, effectively reducing friction and wear during equipment operation.

Physiological Inertness: PTFE material has physiological inertness, and as artificial blood vessels and organs, it can be implanted in the human body for a long time without adverse reactions, making it suitable for food, medical, and other industries with high hygiene requirements.

As a high-performance sealing material, PTFE packing is widely used in various industrial fields. Selecting the appropriate PTFE packing requires a comprehensive consideration of application scenarios, performance requirements, weaving technology, installation, and maintenance. Through the introduction of this article, it is believed that you have a clearer understanding of how to select PTFE packing. In practical applications, it is recommended that users select the appropriate grade, specification, and technical requirements of packing based on the specific needs of the equipment and strictly follow the installation and maintenance requirements to ensure the sealing performance and service life of the equipment.

With its outstanding performance and wide range of applications, PTFE packing has become one of the preferred materials in the industrial sealing field. It is hoped that this article can help you choose the most suitable sealing protector for your equipment, ensuring the normal operation and safe production of the equipment.