Suppliers of High-Performance Semi-Metallic Gaskets

Introduction to Semi-Metallic Gaskets

Semi-metallic gaskets represent a critical advancement in sealing technology, engineered to bridge the gap between the robustness of solid metal gaskets and the conformability of soft, non-metallic seals. At Kaxite Sealing, we specialize in the design and manufacture of high-performance semi-metallic gaskets that deliver unparalleled reliability in the most demanding industrial environments. These gaskets are composite structures, combining metallic and non-metallic materials to create a seal that offers superior mechanical strength, excellent thermal resistance, and exceptional adaptability to flange surfaces and operating conditions. They are the preferred choice for applications where standard rubber or fiber gaskets would fail, and where full metal gaskets are too expensive or difficult to install.

The core principle behind a semi-metallic gasket is its hybrid construction. The metallic components, often in the form of a corrugated, wound, or jacketed core, provide the structural integrity and spring-like recovery needed to maintain a seal under fluctuating pressures and temperatures. The non-metallic filler or facing material, such as flexible graphite, PTFE, or ceramic fibers, fills the micro-imperfections on the flange faces, ensuring a tight, leak-proof barrier. This synergy allows Kaxite Sealing semi-metallic gaskets to perform reliably in refineries, chemical processing plants, power generation facilities, and offshore oil & gas installations, sealing everything from steam and hydrocarbons to aggressive acids and alkalis.

Key Product Parameters and Specifications

Understanding the detailed parameters of semi-metallic gaskets is essential for proper selection and application success. Kaxite Sealing provides comprehensive data for each gasket type to ensure engineers and procurement specialists can make informed decisions.

Material Composition & Construction

The performance characteristics are directly determined by the materials used. Below is a breakdown of common components.

• Metallic Core/Winding Strip: Provides strength and resilience. Common materials include:
  • 304/316 Stainless Steel: For general corrosion resistance.
  • Inconel 600/625: For high-temperature and severe corrosive service.
  • Monel 400: For excellent resistance to sulfuric and hydrofluoric acids.
  • Titanium: For chloride environments and high strength-to-weight ratio.
  • Carbon Steel: For non-corrosive, high-pressure applications.
• Filler/Facing Material: Provides the primary sealing layer.
  • Flexible Graphite (Grafoil®): Superior thermal conductivity, excellent chemical resistance (except strong oxidizers), and wide temperature range (-400°F to 3000°F in inert atmospheres).
  • PTFE (Teflon®): Outstanding chemical inertness, low friction, and good flexibility. Temperature range typically -320°F to 500°F.
  • Mica/Graphite Composites: Excellent for high-temperature fire-safe applications.
  • Ceramic Fiber: For extreme high-temperature environments.
• Inner & Outer Rings: Often included for additional compression control, blow-out prevention, and handling stability.

Performance Data Table

The following table compares key performance metrics across standard Kaxite Sealing semi-metallic gasket types under typical test conditions.

Physical & Mechanical Properties

• Density: Varies by type; Spiral Wound gaskets typically range from 90 to 120 lbs/ft³, affecting sealing force and recovery.
• Compressibility: The percentage reduction in thickness under a specific load (e.g., ASTM F36). Kaxite Sealing gaskets are engineered for optimal compressibility (15-25% for wound gaskets) to seal effectively without over-stressing bolts.
• Recovery: The ability to return to its original thickness after compression, crucial for maintaining seal during thermal cycles. Our designs target high recovery percentages (>40%).
• Sealing Stress (y-stress): The minimum seating stress required on the gasket face to initiate a seal. This is a critical design parameter for bolt load calculations.
• Blow-out Resistance: The ability to withstand internal pressure differentials without being extruded from the flange gap.

Frequently Asked Questions (FAQ) About Semi-Metallic Gaskets

Selection & Application

Q: How do I choose between a spiral wound, metal jacketed, and a camprofile gasket?

A: The choice depends on service conditions and flange type. Spiral wound gaskets (especially with flexible graphite) offer the best combination of resilience, sealing performance, and cost-effectiveness for a wide range of pressures and temperatures, making them the most versatile. They are ideal for raised face (RF) flanges. Metal jacketed gaskets are used for high-pressure containment, often in tongue-and-groove or male-female flanges. Camprofile and Kammprofile gaskets, with their solid metal core and soft facing, excel in severe cyclic service, high temperatures, and on flanges with slight irregularities or large diameters. Kaxite Sealing engineers can provide detailed selection guidance based on your specific P/T ratings, media, and flange specifications.

Q: Can semi-metallic gaskets be used for low-pressure or vacuum service?

A: Absolutely. In fact, spiral wound gaskets with V-shaped metallic windings are highly recommended for vacuum service. The winding structure creates a labyrinth seal path, and the spring-back action helps maintain tightness even at very low pressures. It is critical to select the correct density and filler material (often graphite) and ensure proper flange surface finish and flatness.

Q: What is the importance of the inner and outer ring on a spiral wound gasket?

A: The rings serve multiple purposes. The outer ring (centering ring) provides radial location, centers the gasket in the bolt circle for easy installation, and acts as a compression stop to prevent over-compression and crushing of the winding. The inner ring prevents inward buckling or erosion of the winding by the process flow, which is crucial for gaseous or high-velocity media. For Kaxite Sealing gaskets, we recommend inner rings for pipe sizes above 4" or for services with potential for erosion/corrosion.

Installation & Performance

Q: What is the recommended flange surface finish for semi-metallic gaskets?

A: A proper flange surface is vital. For spiral wound and camprofile gaskets with graphite filler, a serrated finish (e.g., 125-250 µin Ra, 30-55 grooves per inch spiral or concentric) is ideal. This provides "bite" for the soft filler without causing excessive wear. A smooth finish can lead to slippage, while a rough finish may damage the filler. For PTFE-filled gaskets, a smoother finish (63-125 µin Ra) is often sufficient. Always consult Kaxite Sealing or relevant standards like ASME B16.20.

Q: How do I determine the correct bolt torque for a semi-metallic gasket?

A: Bolt torque must achieve the required gasket seating stress (y-stress) without exceeding the yield strength of the bolts or flanges. This calculation involves the gasket's seating stress value, effective sealing area, number and size of bolts, and friction coefficients. Using a standardized procedure like ASME PCC-1 or the EN 1591 methodology is essential. Kaxite Sealing provides gasket stress data sheets and can assist with bolt load calculations to ensure a leak-free, safe joint.

Q: Are semi-metallic gaskets reusable?

A: Semi-metallic gaskets are generally designed for single use. During installation, the metallic winding deforms plastically and elastically, and the filler material compresses to conform to the flange. After disassembly, the gasket will not return to its original uncompressed state, and its sealing performance cannot be guaranteed for a second service cycle. Reuse can lead to leakage. Kaxite Sealing always recommends replacing the gasket during any maintenance disassembly.

Material & Compatibility

Q: What are the limitations of flexible graphite as a filler material?

A: Flexible graphite has outstanding properties but is susceptible to oxidation in air at temperatures above 750°F (400°C). In such oxidizing atmospheres, the graphite can slowly degrade. For high-temperature oxidizing service, alternative fillers like mica/graphite composites or ceramic fibers should be selected. Additionally, graphite is not recommended for use with strong oxidizing agents like hot concentrated nitric acid or sulfuric acid above certain concentrations.

Q: Why would I choose a PTFE-filled gasket over a graphite-filled one?

A: Choose PTFE when your primary concern is extreme chemical resistance to a broad spectrum of aggressive chemicals (acids, bases, solvents) at moderate temperatures. PTFE is also FDA-compliant for food and pharmaceutical applications and provides a contaminant-free seal. However, it has a lower temperature ceiling than graphite, is more prone to cold flow (creep) under sustained load, and typically requires higher seating stresses. Graphite is preferred for higher temperatures, better thermal conductivity, and generally lower seating stress requirements.

Q: Can Kaxite Sealing provide gaskets for special alloy requirements?

A: Yes, our manufacturing capabilities extend to a wide array of exotic and specialty alloys. We can fabricate semi-metallic gaskets using Hastelloy, Incoloy, Tantalum, Zirconium, and other alloys to meet specific corrosion resistance needs in challenging environments like sour gas service, deep-sea applications, or concentrated chemical processing. Contact our technical team with your material specifications.