Graphite gaskets are categorized based on their construction and application requirements. Here are the common types:
1. Solid Graphite Gaskets: Made entirely from flexible graphite sheets, Suitable for applications requiring high chemical resistance and thermal stability.
2. Metal-Reinforced Graphite Gaskets: Incorporating metal components to enhance mechanical strength, including
Hooked Carbon Steel Reinforced: Carbon steel sheet sandwiched between graphite layers.
Stainless Steel Reinforced: Stainless steel (304 or 316L) sheet adhered to graphite layers.
3. Composite Graphite Gaskets
Combine graphite with other materials to improve performance.
Common forms:
Basic Type: Simple graphite gasket without additional reinforcement.
Inner-Edge Wrapped: Graphite gasket with an inner edge wrapped in stainless steel.
Outer-Edge Wrapped: Graphite gasket with an outer edge wrapped in stainless steel.
Fully Wrapped: Graphite gasket with both inner and outer edges wrapped in stainless steel.
4. Specialty Graphite Gaskets
Designed for specific applications or environments.
Examples:
High-Temperature Applications: Graphite gaskets suitable for extreme temperatures.
Chemical-Resistant Applications: Graphite gaskets with enhanced resistance to specific chemicals.
Excellent Thermal Resistance: Flexible graphite maintains its physical properties across an extensive temperature range, from -270°C in cryogenic conditions to 3650°C in non-oxidizing atmospheres. It can also be used up to approximately 450°C in air.
Superior Chemical Resistance: Flexible graphite is highly resistant to corrosion, withstanding almost all inorganic and organic media. The only exceptions are strong oxidizing agents such as aqua regia, concentrated nitric acid, concentrated sulfuric acid, and high-temperature chromates, permanganates, and ferric chloride.
Good Self-Lubrication: Like natural graphite, flexible graphite has a layered structure that allows for easy sliding under external forces. This results in excellent lubrication properties, low friction coefficients, and good wear-reducing characteristics.
High Resilience: When there is radial runout due to manufacturing or installation eccentricities in shafts or sleeves, flexible graphite gaskets can still provide sufficient flexibility. Even if cracks occur in the graphite, the gasket can maintain a tight seal and prevent leakage.
Low Flange Requirements: Flexible graphite gaskets do not require highly polished flange surfaces. They can achieve effective sealing with relatively low pre-tensioning forces. Additionally, their ease of cutting makes them a cost-effective and practical choice for sealing applications.
Graphite gaskets are made from graphite materials and are widely used in industrial production due to their excellent corrosion resistance, thermal stability, electromagnetic radiation resistance, low friction coefficient, self-lubrication, and elasticity. Here are some specific application scenarios.
Petrochemical Industry: Used in various chemical equipment, pipelines, and valves to form seals, preventing medium leakage and ensuring the safety and stability of equipment and processes.
Power Industry: Applied in the sealing of generators, transformers, and electric motors, effectively preventing electrical leakage.
Metallurgical Industry: Suitable for environments with high temperatures and strong corrosive gases and liquids, such as sealing in blast furnace gas pipelines.
Marine Industry: Used in the sealing of ship pipelines and valves, preventing medium leakage and seawater ingress.
Aerospace Industry: Utilized in the sealing of aircraft and rocket components, offering good high-temperature and oxidation resistance.
Automotive Industry: Applied in the sealing of engines, transmissions, and other components, providing excellent oil and high-temperature resistance.
Construction Industry: Used in the sealing of building water supply and drainage pipelines, HVAC pipelines, and other connections, offering good leak prevention and sound insulation.
Let's delve into the differences between PTFE (polytetrafluoroethylene) and graphite fillers by examining their composition, attributes, applications, and benefits.
Graphite: Graphite is an inorganic form of pure carbon. Graphite filler is a black, braided sealant made entirely of carbon. It can be combined with other elements or PTFE to enhance its functionality.
PTFE: PTFE, commonly known as Teflon, is a white synthetic polymer created by polymerizing tetrafluoroethylene. Teflon yarn can be lubricated to create flexible packing with superior performance.
Graphite: High-quality graphite yarns are woven together to form graphite fillers. These fillers have a very low coefficient of friction and can conduct heat. Graphite is also a good thermal conductor.
PTFE: PTFE is a high-strength resin with a low coefficient of friction. It is highly resistant to corrosion from chemicals, acids, and gases. Teflon, a variant of PTFE, is widely used in non-stick cookware and as an insulating material for electrical applications. PTFE fillers are strong and have excellent lubricating properties.
Graphite: Graphite packing is ideal for agitators, valves, and shafts that handle chemicals and acids. It is also used in high-pressure, high-speed, and high-temperature applications.
PTFE: Expanded graphite packing is used in steam turbines and high-temperature valves. Teflon boards are used to handle fuel gas, mineral oil, synthetic oil, steam water, and sewage. PTFE fillers are used in industrial plants to manage corrosive substances and oxidants, except for molten alkali metals. PTFE packing is suitable for pharmaceutical, food, aerospace, and electrical industries. Teflon enveloped gaskets are used for handling highly active substances in industrial settings.
Graphite: Expanded graphite filler is an excellent alternative to asbestos filler. It offers simplified installation and quick maintenance.
PTFE: PTFE filler has a long shelf life due to its low coefficient of friction. Multi-yarn PTFE filler can be designed to meet FDA requirements for food and medicine applications.
Combined Benefits: Graphite filler can be treated with PTFE to enhance its properties, such as preventing color contamination and improving stability. Both graphite and PTFE fillers are cost-effective due to their durability and low maintenance needs.
