Performance Metallic Seals

Metallic seals offer excellent solutions to many very difficult sealing applications. In principle, metal seals can be applied in a manner similar to standard O-rings and seals (e.g., MIL-G-5514, AS4716). In many cases, metal seals can replace elastomer or Teflon (PTFE)-based seals using the existing cavities.

Selecting the correct metal seal for a particular application requires more care than for a comparable rubber or PTFE seal. Typical characteristics of each seal profile are given on the reverse. APS will be pleased to analyze your particular application and make a recommendation. Considerations for a successful design include:

Fits: Unlike elastomer and most PTFE seals, metallic seals are manufactured to exacting dimensions with tight tolerances, and the fit into the cavity is more critical. They cannot be stretched over rods or into shaped grooves and therefore, must be designed and manufactured to fit with proper shape and clearances.

Loads: Loads required to compress metal seals are greater than those for elastomer and PTFE seals. APS can analyze the loads of a particular design to assist you in hardware design and bolt loading.

Springback (or resiliency): This is the degree to which a seal will recover from the compressed state. Generally, the larger the free height, the more resilient the seal. Seals with greater springback will continue to seal as flange surfaces separate during pressure and temperature excursions.

Pressure Capability: Metal seals can seal from high vacuum to 50,000 psi.

Leak Tightness: Metal seals are capable of achieving very tight leak rates, which depend upon a combination of factors, including flange surface roughness, lay direction, seal design, coatings, plating and the amount of compression. Unlike rubber O-rings, a metal seal's leak tightness diminishes when overcompressed.

Temperature Capability: Metal seals are capable of operating at temperatures of -50° to 870°C (-60° to 1600°F), depending upon the seal and plating materials.

Chemical Resistance: APS metal seals are constructed of corrosive-resistant alloys. Many materials meet NACE MR-01-075 requirements. Consult with APS's engineering department for materials recommendations for extreme applications.

Analysis: Metallic seals are generally used in extreme applications where the performance of conventional elastomeric or polymeric seals is unacceptable. APS Technology has extensive capability in analyzing the behavior of the seal and the system. Structural, thermal and vibration analyses are performed using ANSYS and NASTRAN Finite Element Analysis programs.

O-RING	Pressures 1,000 psi nonvented 5,000 - 25,000 vented Temperature 480°C (900°F) (321 stainless) Load Moderate Springback Low Applications For rigid, stable connections Lowest-cost metal seal
C-RING	Pressures 8,000 - 25,000 psi 50,000 psi special designs Temperature -50° to 870°C (-60° to 1600°F) Load Moderate Springback Medium Applications Stable connections, minor separation permissible Highest temperature rating
C-LIM	Pressures 8,000 - 25,000 psi Temperature -50° to 650°C (-60° to 1200°F) Load High Springback Low Applications Used as high-performance compression (crush) seal
SLS	Pressures 5,000 - 22,000 psi 35,000 psi special designs Temperature -50° to 650°C (-60° to 1200°F) Load High Springback Medium Applications Most tolerant seal for surface imperfections, waviness High vacuum capable
E-RING	Pressures 5,000 psi Temperature -50° to 870°C (-60° to 1600°F) Load Low Springback High Applications Hot air ducts, gas turbine engines, valve seats, turbochargers