| 摘要 |
In oil wells which utilize a reciprocating pump installed in a tubing string, an apparatus is disclosed which has the preferred form of a pair of telescoped tubular members threaded into the pump just above the lower end where sanding locks the pump. The two are telescoped together and are pinned by a shear pin. When it is time to pull the pump, if there is undue resistance to its removal from the tubing string, the shear pin will shear, releasing the two for telescoping movement. The innermost sleeve has a protruding shoulder limiting its upward travel. When the telescoping movement occurs, a set of slots is exposed. The slots open to the interior, and sand accumulated around the tool under pressure of a column of liquid standing thereabove washes down through the slots and out of the way. If no sanding occurs, the shear pin is not sheared and the two telescoped members maintain their original position.
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