November 13, 2025
Industrial systems operating under extreme temperatures and pressures require sealing materials engineered for long-term structural stability, chemical resistance, and reliable bolt load retention. Flexible graphite and metallic (or semi-metallic) gaskets are two of the primary solutions evaluated for these demanding environments. Each material class provides unique mechanical and thermal advantages that make it more suitable for specific operating conditions.
This technical guide outlines the performance characteristics, engineering criteria, and application factors used to determine the appropriate gasket type.
Understanding Flexible Graphite Gaskets
Flexible graphite is produced by expanding crystalline graphite into a highly compressible, chemically resistant sheet. The material preserves its mechanical performance at elevated temperatures and maintains sealing integrity despite thermal cycling.
Key Advantages:
- Exceptional temperature resistance (typically up to ~450°C in oxidizing environments)
- Excellent chemical compatibility, including acids, solvents, hydrocarbons, and steam
- Low creep relaxation, supporting long-term bolt load retention
- High conformability, allowing it to seal uneven flange surfaces or damaged sealing faces
Where Flexible Graphite Performs Best:
- Steam distribution systems
- Refining and petrochemical processing
- High-temperature exhaust and emissions handling
- Flange connections that require excellent recovery and resiliency
Limitations:
Flexible graphite alone may lack the structural strength required for extreme pressures. For these conditions, composite designs should be considered. One example is spiral wound gaskets with graphite filler.
Understanding Metallic and Semi-Metallic Gaskets
Metallic and semi-metallic gaskets (such as spiral wound, kammprofile, and ring-type joints) incorporate metals such as stainless steel, Inconel®, or Monel® to deliver high structural integrity under pressure and mechanical load.
Key Advantages:
- Performs reliably under very high system pressures.
- Remains stable at elevated temperatures.
- Provides excellent blowout resistance, including during rapid pressure changes.
- Offers configurability in winding profiles, rib designs, and facing materials.
Where Metallic Gaskets Perform Best:
- High-pressure steam systems
- Oil and gas production systems
- Chemical reactors operating at elevated temperatures
- Heat exchangers and compressor flanges
Limitations:
Metallic gaskets generally require precise flange alignment, high bolt loads, and controlled surface finishes. Their lower conformability makes them less suitable for imperfect or damaged sealing surfaces unless additional facing materials are used.
Application-Based Material Selection
| Operating Condition | Recommended Material | Technical Rationale |
|---|---|---|
| High temperature with moderate pressure | Flexible Graphite | Provides chemical and thermal stability with sufficient resilience. |
| Very high or cyclic pressure | Metallic / Semi-Metallic | Maintains structural integrity and blowout resistance. |
| Older or damaged flange surfaces | Flexible Graphite | Conforms to irregularities and compensates for surface degradation. |
| Critical emissions control | Metallic with Graphite Filler | Combines recovery, tightness reliability, and mechanical strength. |
Durlon® Gasket Material Solutions
- Durlon® Flexible Graphite Gaskets: Suitable for a wide range of industrial thermal environments.
- Durlon® Spiral Wound and Kammprofile Gaskets: Designed for high-pressure/temperature flange sealing in demanding industries.
Conclusion
Choosing between flexible graphite and metallic gaskets depends on the combination of temperature, pressure, system cycling, flange condition, bolt load availability, and chemical environment. Understanding these parameters ensures reliable, leak-free service life and reduces the risk of premature gasket failure or unplanned downtime.
If you require support selecting the correct gasket for a specific application, our sealing professionals are available to help. Contact us today.