| 摘要 |
<p>A surface controlled subsurface safety valve ("SCSSV") assembly has primary and secondary valves, typically an upper and lower flapper valve. Only one of the valves is in service at a time. In the event that the primary valve is compromised, and therefore leaks, the SCSSV is shifted (via wireline or other means) to place the primary valve out of service and the secondary valve in service. The SCSSV may have more than two flappers, thereby providing multiple secondary valves, with only one valve in operation at any one time.</p> |
