Subsea gate valves installed at depths exceeding 10,000 ft require ROV-operable stems with hyperbaric-qualified seal packages. External seawater pressure acts on the stem, so dynamic seals must resist implosion while maintaining internal pressure containment. Die-formed graphite packing with Inconel anti-extrusion rings is the standard solution, qualified to 15,000 psi internal and 5,... https://globalsealstech.com/product-category/oil-gas-seals/api-6a-gate-valve-seals/