Pressure responsive safety system for fluid lines

摘要

An electro-pneumatic or electro-hydraulic safety system for shutting in a well or the like in the event of unusual pressure conditions in the production line of the well. The safety system includes a pressure transducer (30) which senses the flowline pressure and provides a corresponding electrical signal to a digital controller (34). When the signal applied to the controller is outside of a preset range defined between low and high settings of the controller, a control circuit deenergizes a solenoid valve which bleeds fluid from a fluid actuator in order to close a surface safety valve (10). Once the safety valve has closed, the controller is latched out of service and must be manually reset before the safety valve can be opened. For protection of a subsurface safety valve (155), the safety system provides a time delay between opening of the subsurface valve and opening of the surface valve and also between closing of the surface valve and closing of the subsurface valve.