In industrial sealing, the selection of the correct Gasket Materials is paramount to system integrity, safety, and longevity. These materials form the critical barrier that prevents leaks of fluids or gases between mating surfaces, facing extreme pressures, temperatures, and chemical exposures. At Kaxite Sealing, with decades of expertise in advanced sealing solutions, we understand that a gasket is only as reliable as the material from which it is crafted. This comprehensive guide delves into the core materials, their properties, applications, and the technical specifications that define performance, empowering engineers and procurement specialists to make informed decisions.
Selecting a gasket material involves balancing multiple physical and chemical properties to match the service conditions. The key parameters include:
The following table provides a detailed comparison of the most common gasket material families, highlighting their primary compositions, strengths, and typical application ranges. Kaxite Sealing manufactures and supplies premium grades across all these categories.
| Material Type | Key Composition | Max Temp. Range | Pressure Range | Key Strengths | Common Applications |
|---|---|---|---|---|---|
| Non-Asbestos Organic (NAO) | Aramid fibers, synthetic rubber, fillers | -50°C to +290°C (-58°F to +554°F) | Up to 150 Bar (2175 PSI) | Excellent sealability, good chemical resistance, cost-effective | Water, steam, fuels, general industrial fluids |
| Compressed Non-Asbestos (CNA) | Aramid/cellulose fibers, nitrile rubber, fillers | -40°C to +400°C (-40°F to +752°F) | Up to 100 Bar (1450 PSI) | High tensile strength, good temperature resistance, low creep | Flanges in petrochemical, power generation, high-temp water |
| Expanded Graphite (Flexible Graphite) | Pure exfoliated graphite, often with foil inserts | -240°C to +3000°C* (inert atm.) (-400°F to +5432°F) | Up to 200 Bar (2900 PSI) | Exceptional thermal conductivity, extreme temperature range, excellent corrosion resistance | Heat exchangers, exhaust systems, aggressive chemicals, high-temp flanges |
| Polytetrafluoroethylene (PTFE) | Virgin or filled PTFE polymers | -260°C to +260°C (-436°F to +500°F) | Up to 100 Bar (1450 PSI) | Universal chemical resistance, anti-stick, low friction | Pharmaceutical, food & beverage, strong acids/alkalis |
| Rubber (Elastomeric) Sheets | NBR, EPDM, Silicone, FKM (Viton), CR | Varies by polymer: -60°C to +300°C | Up to 30 Bar (435 PSI) | High elasticity, good compression set, seals uneven surfaces | Piping, covers, tanks, OEM equipment |
| Metal & Semi-Metallic | Stainless steel, carbon steel, copper, spiral-wound, metal-jacketed | Up to +1000°C (+1832°F) | Very High (System Dependent) | Extreme pressure/temperature capability, high mechanical strength | Refineries, power plants, high-pressure vessel flanges |
* In oxidizing atmospheres, upper limit is typically 450°C (842°F) without oxidation inhibitors.
At Kaxite Sealing, we engineer our materials to exceed industry standards. Below are detailed specifications for three of our flagship gasket material product lines.
Q: What is the most important factor when selecting a gasket material?
A: There is no single most important factor; it requires a system analysis. The primary drivers are the chemical compatibility with the process fluid and the operating temperature range. A material must withstand the chemical attack and thermal environment first. Following this, pressure rating, flange design, and bolt load capacity become critical for ensuring a leak-free seal.
Q: Can I reuse a gasket made from compressed fiber or graphite material?
A: It is strongly discouraged. During initial installation, gasket materials undergo plastic deformation and compression set to conform to the flange surface imperfections. Upon disassembly, this deformed state is permanently set. Reusing the gasket will likely result in an inadequate seal due to loss of resilience and material integrity, leading to potential leaks. Kaxite Sealing always recommends using a new gasket for critical connections.
Q: How does flange surface finish affect gasket material performance?
A: Flange surface finish is crucial. A finish that is too rough (e.g., coarse machining) can cause excessive bite and embedding of the gasket material, making disassembly difficult and increasing creep. A finish that is too smooth (e.g., polished) may not provide enough friction to hold the gasket in place during assembly and may require higher bolt loads to achieve sealing. For most soft gasket materials like CNA or graphite, a serrated (phonographic) finish between 125-250 µin Ra (3.2-6.3 µm Ra) is ideal.
Q: What is the difference between "compressed non-asbestos" (CNA) and "non-asbestos organic" (NAO) sheets?
A: The key difference lies in manufacturing and density. CNA sheets undergo a high-pressure calendering process, creating a denser, more uniform sheet with higher tensile strength and better temperature/compression set characteristics. NAO sheets are typically softer, less dense, and more compressible, offering excellent sealability at lower bolt loads for less demanding services. Kaxite Sealing's KG-4000 series is a high-performance CNA material.
Q: Why does expanded graphite require a facing or insert material in many applications?
A: Pure expanded graphite is a fragile, flaky material with low mechanical strength. While its sealing properties are exceptional, it can be easily damaged during handling and installation. Facing materials like stainless steel foil, perforated steel, or wire mesh are laminated to the graphite to provide structural integrity, improve handling strength, prevent blow-out in high-pressure differentials, and reduce creep relaxation.
Q: How do I determine the correct thickness for my gasket material?
A: Thickness selection depends on flange type, surface condition, and internal pressure. For standard raised-face flanges in good condition, 1.5mm thickness is common. For uneven or pitted surfaces, a thicker (e.g., 3.0mm), more compressible material may be needed to fill irregularities. Higher pressures often require thinner gaskets to reduce the internal pressure acting on the gasket area (blow-out force) and to minimize creep. Consulting Kaxite Sealing's technical datasheets or engineering team is recommended for specific applications.
Q: Are Kaxite Sealing's PTFE-based materials suitable for oxygen service?
A: Special precautions must be taken. While PTFE itself is chemically compatible, it is susceptible to ignition and rapid combustion in high-pressure oxygen systems if contaminated with hydrocarbons or organic materials. Kaxite Sealing offers specially cleaned, processed, and tested PTFE and filled-PTFE grades that are designed for oxygen service, complying with relevant standards like ASTM G93. Always specify oxygen service requirements when ordering.
