| 摘要 |
<p>A protection system for a pipeline comprises a hydraulically actuated valve operable to switchably prevent a flow of fluid from a first section of the pipeline to a second section of the pipeline, a hydraulic fluid source for supplying hydraulic fluid to said hydraulically actuated valve to enable actuation thereof, a vent for venting hydraulic fluid from the hydraulically actuated valve, the hydraulically actuated valve being connected to the vent via a differential pressure valve to control venting of the hydraulically actuated valve, a pressure transfer barrier with a first port connected to the first section of the pipeline and a second port connected to said differential pressure valve, said differential pressure valve being supplied with hydraulic fluid at a reference pressure. If the pressure of fluid in the first section of pipeline exceeds the reference pressure of the hydraulic fluid supplied to the differential pressure valve, the differential pressure valve is caused to be in an open state, thereby causing the hydraulic pressure in the hydraulically actuated valve to be released via the vent. The protection system is of particular application to sub-sea hydrocarbon extraction wells. Referring now to Figure 2, a thin-walled section of pipeline 1 is connected to a thick-walled section of pipeline 2 via a hydraulically actuated valve comprising HIPPS valve 3 and failsafe hydraulic thin-walled section of pipeline 1 is connected to a thick-walled section actuator 4. As before, a directional control valve 5 located in a sub-sea control module 6 is used to allow control of the HIPPS valve for purposes other than pressure protection, such as shutting down the production output. The hydraulic actuator 4 is fed hydraulic fluid, typically waterglycol rather than oil, via DCV 5 and umbilical 8 from hydraulic power unit 7, located above the sea surface. The pipeline 2 from the well tree is connected to a pressure transfer barrier 12. This device is shown in sectioned view, and comprises a sealed cylinder with a sliding piston 13 inside which is sealed to the wall of the cylinder. The other side of pressure transfer barrier 12 is filled with hydraulic fluid and is connected to a control port of a pilotless, dual, toggle-action differential pressure operated valve system 14. Valve system 14 comprises two differential pressure valves 16 and 17, connected together so that when one valve is caused to be in a closed state, the other is caused to be in an open state, and vice versa. The other control port of valve system 14 is fed with a reference hydraulic pressure, the pressure being set as required by regulator 15, from the HPU 7 and through umbilical 8. Valve 17 is connected between actuator 4 and a vent via hydraulic feeds 18. Valve 16 is connected between actuator 4 and DCV 5 via hydraulic feeds 19.</p> |
