GEM-VALVE RETRIEVABLE WIRELESS
SURFACE-CONTROLLED SUBSURFACE
SAFETY VALVE
■ The GEM-Valve safety valve is an
electromagnetic, surface-controlled
subsurface safety valve, which uses
the proven **self-equalizing flapper valve
design, for securing wells containing
a damaged or nonexistent control line.

Спасибо!

Baker Hughes’ self-equalizing, surface-controlled subsurface safety valves (SCSSVs) ensure more cost-effective operations than completions using a nonequalizing valve. Equalizing pressure enables you to place a well on production much sooner after a system test or emergency shutdown.
A subsurface safety valve must be pressure-equalized above and below the flapper before opening. The self-equalizing mechanism allows shut-in pressure below the valve to be vented to the tubing above the flapper.
Я бы сказал, конструкция клапана позволяет выравнивать давление через дроссельную заслонку... Имхо.