| 摘要 |
<p>A control valve apparatus adapted to be positioned within a subsea blowout preventer stack for controlling the flow of fluid from an offshore well includes a control unit releasably latched to a valve body having tandem, normally closed valve assemblies, the upper valve assembly including a flapper valve element and the lower valve assembly including a ball valve element. The control unit has hydraulically operable mechanisms adapted to open the valve elements in response to pressurization of control lines extending upwardly to the surface, and to assist in closure of the ball valve element to effect cutting of wireline or cable extending into the well in case of emergency.</p> |
