| 摘要 |
<p>A safety valve for use in a hydrocarbon production tube comprises a valve member which is opened by a piston tube displaceable as a result of the intake of hydraulic fluid into an operating chamber therefor, and a tubular receptacle for receiving an auxiliary safety valve recoverable by means of a cable. The receptacle is longitudinally displaceable between inactive and active positions and is engaged telescopically with the piston tube in a sealed manner to define, with the piston tube, the operating chamber. The receptacle is normally retained in its inactive position by shearable elements, but after the elements have been sheared, descends to its active position simultaneously driving the piston tube to its lower position to open the valve member.</p> |
