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A spiral wound gasket (SWG) is a semi-metallic gasket designed for high-temperature and high-pressure sealing applications. It consists of a metal winding (usually stainless steel or special alloys) and a filler material (graphite, PTFE, or mica). The combination provides both flexibility and resilience, making SWGs suitable for critical flanged joints in pipelines, refineries, petrochemicals, power plants, and process industries.
Construction
- Winding Strip:
- Formed from a thin strip of metal (SS304, SS316, Inconel, Monel, Hastelloy, etc.).
- Wound in a spiral with a non-metallic filler.
- Filler Material:
- Common: Graphite (high temperature), PTFE (chemical resistance), Mica (extreme heat).
- Centering Ring (Outer Ring):
- Carbon steel or stainless steel.
- Provides correct gasket positioning on the flange.
- Inner Ring (Optional):
- Stainless steel or alloy.
- Prevents inward buckling, protects from corrosion and heat erosion.
Types of Spiral Wound Gaskets
- Basic Type (Wound Only): No inner/outer ring, used in tongue & groove flanges.
- With Outer Ring (Type CG): Provides centering and protection.
- With Inner Ring (Type CGI): Provides internal support and prevents buckling.
- With Both Inner & Outer Rings: For severe services.
Material Options
- Metal Strip: SS304, SS316, SS321, SS347, Monel, Inconel, Hastelloy, Titanium.
- Filler: Flexible Graphite, PTFE, Mica, Ceramic.
- Rings: Carbon steel, SS304, SS316, other alloys depending on service.
Technical Specifications
- Pressure Class: ASME 150 to 2500
- Temperature Range:
- Graphite filler: –200°C to +550°C
- PTFE filler: –200°C to +260°C
- Mica filler: up to +1000°C (with suitable alloys)
- Standards: ASME B16.20, BS 3381, DIN, API 601, EN 1514-2
- Sizes: ½" to 60" (ASME standard), custom sizes available
Applications
- Refineries & Petrochemicals
- Power Plants (Steam, Gas, Nuclear)
- Chemical Processing Units
- Heat Exchangers, Pumps, Compressors, Valves
- High-pressure & high-temperature piping systems
Advantages
- Excellent sealing at high pressure & temperature.
- Resilient – can accommodate flange surface irregularities.
- Long service life under fluctuating conditions.
- Compatible with a wide range of fluids and gases.
Selection Guidelines
- Choose filler based on operating temperature and chemical compatibility.
- Select metal winding based on corrosion/temperature resistance.
- Decide inner/outer rings based on flange type and service conditions.