Expanded graphite gaskets, often termed flexible graphite gaskets, are high-performance sealing solutions engineered from exfoliated graphite. This process involves treating natural flake graphite with acid and heat, causing it to expand or "exfoliate" into a low-density, vermiform structure. This unique material is then calendered into sheets without the need for binders, possessing exceptional natural properties. These gaskets are renowned for their superior thermal conductivity, chemical inertness, and excellent sealing capabilities under a wide range of temperatures and pressures. They are a preferred choice in demanding applications across industries like chemical processing, power generation, oil & gas, and refining, where reliability is non-negotiable.
At Kaxite Sealing, we specialize in the manufacturing and supply of high-integrity expanded graphite gaskets. With decades of expertise in advanced sealing technology, we understand the critical role a gasket plays in system safety, efficiency, and uptime. Our products are crafted from the highest purity graphite, subjected to rigorous quality control at every production stage. We don't just supply gaskets; we provide engineered sealing solutions backed by technical support, custom fabrication capabilities, and a commitment to meeting the most stringent international standards. When you specify Kaxite Sealing, you choose uncompromising quality and performance.
Our expanded graphite gaskets are designed to excel in the most challenging environments. Below is a detailed breakdown of their core features and technical parameters.
| Parameter | Specification / Value | Test Standard |
|---|---|---|
| Density Range | 0.9 - 1.15 g/cm³ (Typical 1.1 g/cm³) | ASTM F1315 |
| Tensile Strength | ≥ 4.5 MPa (650 psi) | ASTM F152 |
| Recovery | ≥ 40% | ASTM F36 |
| Compressibility | 15 - 40% at 69 MPa (10,000 psi) | ASTM F36 |
| Stress Relaxation | ≤ 15% | ASTM F38 |
| Thermal Conductivity | 80 - 150 W/m·K (in-plane) | ASTM E1461 |
| pH Value | 5 - 7 (Neutral) | ASTM E70 |
| Sulfur Content | ≤ 500 ppm | ASTM D4239 | Chloride Content | ≤ 50 ppm | ASTM D4208 |
The versatility of expanded graphite gaskets makes them indispensable across numerous sectors:
Q: Can expanded graphite gaskets be used in oxidizing atmospheres at high temperatures?
A: While expanded graphite has excellent inherent temperature resistance, prolonged exposure to strong oxidizing atmospheres (like air or oxygen-rich streams) above approximately 450°C (842°F) can lead to gradual oxidation and material loss. For such applications, we recommend specific high-temperature grades or alternative materials like PTFE or ceramic fibers. Consulting with Kaxite Sealing engineers is crucial for material selection in high-temperature oxidizing services.
Q: How do I handle and store expanded graphite gaskets properly?
A: Expanded graphite is somewhat fragile and can be damaged by bending or creasing. Always handle with care. Store gaskets in a clean, dry, and flat environment, away from direct sunlight, moisture, and chemicals. Do not stack heavy objects on them. For spiral wound or metal-reinforced gaskets, ensure they are packaged to prevent deformation of the metal winding or core.
Q: Are there any media compatibility issues with expanded graphite?
A: Expanded graphite is highly chemically inert. However, it is not recommended for use with strong oxidizing agents like concentrated nitric acid, sulfuric acid above 98%, or bromine at elevated temperatures. It is also generally not suitable for molten alkali metals. Always consult Kaxite Sealing's chemical resistance chart or our technical team for specific media compatibility.
Q: What is the significance of low chloride and sulfur content in graphite gaskets?
A: Low chloride and sulfur content (often specified as <50 ppm Cl, <500 ppm S) is critical for applications involving austenitic stainless steels (e.g., 304, 316) to prevent stress corrosion cracking (SCC). In the presence of moisture and stress, chlorides can concentrate and initiate cracks. Our high-purity grades are certified for such sensitive applications in nuclear, aerospace, and fine chemical industries.
Q: Can I reuse an expanded graphite gasket after disassembly?
A: It is strongly discouraged to reuse any flat gasket, including expanded graphite gaskets. Upon initial compression, the material flows to conform to the flange faces. During disassembly, it can be torn, compressed unevenly, or contaminated. Reusing it compromises the seal integrity and significantly increases the risk of leakage. Always install a new Kaxite Sealing gasket for a guaranteed leak-free connection.
Q: What flange surface finish is recommended for expanded graphite gaskets?
A> A serrated or phonographic (spiral) finish is ideal, typically in the range of 125 to 250 µin Ra (3.2 to 6.3 µm Ra). This provides enough "tooth" for the graphite to grip into without allowing excessive extrusion. Excessively rough finishes can cause high seating stress and material loss, while mirror-finish flanges may not allow sufficient grip. The flange must be clean, dry, and free of old gasket material, pitting, or scratches.
Q: How does Kaxite Sealing ensure the quality of its expanded graphite gaskets?
A> Quality is integral to our manufacturing process. We start with sourcing high-purity raw graphite. Our production is monitored with Statistical Process Control (SPC). Every batch of material is tested for key properties like density, tensile strength, compressibility, recovery, and chemical composition (S, Cl). Finished gaskets are inspected for dimensional accuracy per customer drawings and relevant standards (ASME, DIN, EN, JIS). We provide material test reports (MTRs) and certificates of conformity (C of C) with each shipment.
