Gas filled metal O Ring for high temperature and moderate pressure applications. OGI for internal pressure and OGE for external pressure.
Spring-energised metal O Ring for Internal pressure (OSI) and (OSE) for external pressure are designed for extreme low leakage at moderate pressures.
Non-vented rings (OI & OE) are designed for lower pressure ranges. The perfectly closed O Ring design avoids ingress of the media into the seal. Moderate load, moderate pressure capability.
Metal seals are used in a wide variety of applications in aerospace. Specially the turbine engine section. Since the temperature in engine crosses the limits of elastomeric seals the only optimum solution is metal seals. For high temperature applications exotic materials like hastealloy, Haynes, Inconel and Eligiloy can be used.