Spiral wound gaskets, while highly effective for demanding applications, present several disadvantages including susceptibility to damage during improper installation, higher cost, and specific material compatibility concerns.
Key Disadvantages of Spiral Wound Gaskets
Despite their excellent sealing capabilities across various temperature and pressure conditions, spiral wound gaskets have specific drawbacks that need consideration:
Installation Complexity and Risk of Damage
One significant challenge with spiral wound gaskets lies in their installation. They require precise compression to achieve an effective seal. If not installed correctly, several issues can arise:
- Protrusion and Leakage: During installation, improper compression or misalignment can cause a spiral wound gasket to protrude beyond the intended sealing gap. This protrusion can lead to physical breakage of the gasket or, more commonly, result in leaks as the sealing element is not properly contained or compressed.
- Over-compression: Applying too much torque can crush the winding or filler material, leading to a loss of resilience and premature gasket failure.
- Buckling or Collapse: Uneven tightening or excessive force can cause the windings to buckle or collapse, compromising the gasket's structural integrity and sealing performance. Proper torque control procedures and trained personnel are crucial for successful installation.
Higher Cost
Compared to more basic gasket types like full-face or ring gaskets made from non-metallic sheets, spiral wound gaskets are considerably more expensive. Their manufacturing process is complex, involving the winding of metallic strips and filler materials, which drives up production costs. The specialized materials used (e.g., various stainless steels, Inconel, graphite, PTFE) also contribute to their higher price point.
Material Compatibility and Corrosion
While spiral wound gaskets offer a wide range of material options for their metallic windings and filler materials, careful selection is critical.
- Chemical Attack: If the chosen filler or winding material is not compatible with the fluid being sealed, it can degrade, swell, or corrode, leading to gasket failure and leaks.
- Galvanic Corrosion: When dissimilar metals are used in the gasket (e.g., winding and inner/outer rings) or in contact with the flange, and exposed to an electrolyte (like certain fluids), galvanic corrosion can occur. This electrochemical reaction can prematurely degrade the gasket's metallic components.
Potential for Creep and Relaxation
Although spiral wound gaskets are designed to resist creep (permanent deformation under sustained mechanical stress) and relaxation (loss of sealing force over time), these phenomena can still occur, especially under high temperatures or in long-term applications. This can lead to a gradual reduction in sealing effectiveness, potentially necessitating re-tightening or replacement.
Handling and Storage Requirements
Spiral wound gaskets are relatively delicate before installation. They must be handled carefully to prevent bending, twisting, or damaging the windings or filler material. Improper storage, such as stacking them unevenly or exposing them to harsh environments, can lead to deformation or degradation, rendering them unusable before they even reach the flange.
Practical Considerations and Mitigation
To minimize the disadvantages of spiral wound gaskets, several practices are recommended:
- Installer Training: Ensure personnel are properly trained in gasket handling, flange preparation, and precise bolt tightening procedures, including proper torque sequence and values.
- Material Selection: Always specify the correct winding and filler materials based on the fluid, temperature, and pressure of the application to ensure chemical compatibility and corrosion resistance.
- Quality Control: Purchase gaskets from reputable manufacturers to ensure consistent quality and adherence to specifications.
- Storage Best Practices: Store gaskets in a clean, dry, and flat environment away from extreme temperatures and physical damage.
Disadvantage | Description | Potential Consequence |
---|---|---|
Installation Difficulty | Requires precise torque and alignment; improper installation can lead to protrusion, buckling, or over-compression, especially when the gasket protrudes beyond the sealing gap. | Leakage, premature gasket failure |
Higher Cost | More expensive to manufacture due to complex winding processes and specialized materials (e.g., high-performance alloys, specialized fillers). | Increased operational expenses |
Material Incompatibility | Incorrect selection of winding or filler materials can lead to chemical degradation, swelling, or galvanic corrosion when exposed to aggressive media or dissimilar flange materials. | Gasket degradation, seal failure |
Creep/Relaxation | While designed for resilience, some materials can exhibit creep (permanent deformation) or stress relaxation (loss of sealing force) over time, particularly under sustained high temperature and pressure, potentially leading to a gradual loss of seal. | Long-term leakage, reduced lifespan |
Fragility Before Install | Susceptible to damage from mishandling, bending, or improper storage prior to installation, which can compromise their integrity and sealing ability. | Pre-installation failure |