| 摘要 |
A flow control screen having a flow path between the interior of a base pipe and a filter medium. A valve assembly, including a valve plug, a ball retainer and a piston body with a collet assembly is disposed within the flow path in an opening of a housing disposed about the base pipe. The collet assembly is radially outwardly constrained by a radially reduced section of the opening in a first position preventing entry of the valve plug therein and radially outwardly unconstrained by the radially reduced section in a second position. Reverse flow is initially prevented as internal differential pressure seats the valve plug on a seat of the opening and causes the piston body to shift to the second position upon reaching a predetermined threshold. Thereafter, external differential pressure causes the valve plug to enter the piston body and contact the ball retainer, thereby allowing reverse flow.
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