Pressure responsive safety system for fluid lines

A safety system for closing a fluid flowline when the fluid pressure therein is outside of a predetermined pressure range defined between a preselected low pressure level and a preselected high pressure level, said safety system comprising:

• a safety valve for the flowline having an open position wherein the flowline is open and a closed position wherein the flowline is closed;
• a fluid actuator connected with said safety valve and operable to maintain the valve in its open position when fluid pressure is applied to the actuator, said actuator having means for moving the safety valve to its closed position upon bleeding of fluid from the actuator;
• a source of fluid under pressure for applying pressurized fluid to said actuator;
• a solenoid valve connected between said source and actuator to control the flow of fluid therebetween, said solenoid valve having an energized condition wherein fluid flow from said source to said actuator is permitted and a deenergized condition wherein said actuator is bled of fluid to move the safety valve to the closed position;
• means for sensing the fluid pressure in said flowline;
• electrical control means for maintaining said solenoid valve in the energized condition when the pressure sensed by said sensing means is within said predetermined pressure range, said control means being operable to maintain said solenoid valve in the deenergized condition when the pressure sensed by said sensing means is outside of said predetermined pressure range;
• means for preventing said solenoid valve from returning to the energized condition after having been in the deenergized condition;
• and
• manually operated reset means for resetting said solenoid valve in the energized condition from the deenergized condition to override said preventing means.

In a safety system for a fluid flowline having a safety valve movable between open and closed positions to respectively open and close the flowline, the improvement comprising:

• control means including an electrical control circuit having a high relay and a low relay arranged in series, said control circuit being completed when both relays are in a closed position and being interrupted when either relay is in an open position;
• a pressure sensor connected with the flowline to sense the fluid pressure therein, said pressure sensor applying to said control means a signal indicative of the sensed fluid pressure;
• means for maintaining the low relay in the closed position when the signal applied to said control means is above a preselected low level corresponding to a low pressure level in the flowline, and for moving the low relay to the open position when said signal is below said preselected low level;
• means for maintaining the high relay in the closed position when the signal applied to said control means is below a preselected high level corresponding to a high pressure level in the flowline, and for moving the high relay to the open position when said signal is above said preselected high level;
• means for releasably latching said low and high relays in the open position when moved thereto, thereby preventing said control circuit from being completed following interruption thereof;
• actuator means for maintaining the safety valve in its open position when said control circuit is completed and for moving the safety valve to its closed position when said control circuit is interrupted;
• and
• manually operated reset means for unlatching said relays from the open position to override said releasable latching means.

A pressure responsive safety system for a fluid flowline extending partially within a well bore and having a downstream portion extending out of the well bore, said safety system comprising:

• a surface safety valve mounted to said downstream portion of the flowline at a location out of the well bore, said surface safety valve being movable between open and closed positions relative to the flowline;
• an actuator for said surface safety valve having an activated condition wherein the surface safety valve is maintained in the open position and a deactivated condition wherein the surface safety valve is maintained in the closed position;
• a subsurface safety valve mounted to the flowline at a location within the well bore, said subsurface valve being movable between open and closed positions relative to the flowline;
• an actuator for said subsurface safety valve having an activated condition wherein the subsurface valve is maintained in the open position and a deactivated condition wherein the subsurface valve is maintained in the closed position;
• means for sensing the pressure in said flowline and providing a signal indicative of the sensed pressure;
• electrical control means having preselected low and high settings corresponding to respective low and high pressure levels in the flowline, said control means receiving the signal from said sensing means and detecting when said signal is within a predetermined range defined between said low and high settings;
• means for maintaining said actuator for the surface safety valve in the activated condition when the signal detected by said control means is within said predetermined range and for effecting the deactivated condition of said surface safety valve actuator when said signal is outside of said predetermined range;
• manually operable shutdown means for effecting the deactivated condition of said surface safety valve actuator and said subsurface safety valve actuator independently of said control means, thereby effecting movement of said surface and subsurface valves to the closed positions;
• and
• means providing a time delay between movement of said surface safety valve to the closed position and movement of said subsurface safety valve to the closed position.

A pressure responsive safety system for a fluid flowline extending partially within a well bore and having a downstream portion extending out of the well bore, said safety system comprising:

• a surface safety valve mounted to said downstream portion of the flowline at a location out of the well bore, said surface safety valve being movable between open and closed positions relative to the flowline;
• an actuator for said surface safety valve having an activated condition wherein the surface safety valve is maintained in the open position and a deactivated condition wherein the surface safety valve is maintained in the closed position;
• a subsurface safety valve mounted to the flowline at a location within the well bore, said subsurface valve being movable between open and closed positions relative to the flowline;
• an actuator for said subsurface safety valve having an activated condition wherein the subsurface valve is maintained in the open position and a deactivated condition wherein the subsurface valve is maintained in the closed position;
• means for sensing the pressure in said flowline and providing an electric signal indicative of the sensed pressure;
• electrical control means having preselected low and high settings corresponding to respective low and high pressure levels in the flowline, said control means receiving the electric signal from said sensing means and detecting when said signal is within a predetermined range defined between the low and high settings;
• and
• means for maintaining each actuator in the activated condition thereof when the signal detected by said control means is within said predetermined range and for effecting the deactivated condition of each actuator when said signal is outside of said predetermined range.