Spring-energized seals use Inconel or Elgiloy springs inside U-shaped PTFE or PEEK jackets. They maintain contact pressure even after elastomer degradation. In HPHT/RGD service, they provide secondary metal-to-metal sealing capability. Standard in tubing hangers and subsea connectors where zero leakage after multiple decompressions is mandatory. https://globalsealstech.com/oil-gas-seals/