(57) A hydraulic safety valve manifold system for providing positive opening and closing
of a surface-controlled, sub-surface safety valve in a subsea well, including a shut-off
valve which prevents leakage of well fluids to the outside environment if a leak should
occur in the safety valve or in hydraulic lines which are connected to the hydraulic
actuator of the safety valve. A hydraulic control line is connected to the safety
valve actuator through a normally closed shut-off valve, and this line is also connected
to the actuator of the shut-off valve to hold both the shut-off valve and the safety
valve open when the line is pressurized. The hydraulic line is also connected to an
actuator of a variable volume accumulator to empty the accumulator when the line is
pressurized. When pressure in the hydraulic line is relieved the shut-off valve closes
and the accumulator accepts fluid from the hydraulic actuator of the safety valve
to insure that the safety valve closes.
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