| 摘要 |
A specially designed valve is incorporated in the pumping tube of an oil well pump secured to the lower end of an oil well pipe string. In pumping the well, oil is drawn up through the pumping tube and oil pipe string to the surface. The check valve is arranged to be actuated from the surface of the well in response to lowering the sucker rods for operating the pump beyond the normal amplitude limits to thereby place into communication the oil in the pumping tube and pipe string with the annulus of the well between the well casing and exterior walls of the pumping tube pipe string thereby equalizing the hydrostatic pressure and permitting pulling of the well pipe for pump servicing or other operations.
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