| 摘要 |
<p>A wellhead safety valve control system for opening and closing subsurface and surface safety valves in a predetermined sequence and certain components used with such control system. Dump valves in both latching and non-latching configurations are utilised within the control system. Embodiments of the dump valve mag incorporate a time delay feature to ensure the subsurface safety valve is closed after a desired time period following the closure of the surface safety valve in the event of flowline anomalies. Provision is made for independent closure of the surface safety valve without closure of the subsurface safety valve.</p> |
