| 摘要 |
<p>A flow control screen having a fluid flow path between the interior of a base pipe and a filter medium. A valve assembly, including a piston body, a valve plug and a ball retainer having an opening, is disposed within the fluid flow path. The piston body has an internal seat and a collet assembly that is radially outwardly constrained by the ball retainer in a first operating position to retain the valve plug therein and radially outwardly unconstrained by the ball retainer in a second operating position. Reverse flow is initially prevented as internal differential pressure seats the valve plug on the internal seat and causes the piston body to shift to the second operating position upon reaching a predetermined threshold. Thereafter, external differential pressure causes the valve plug to be expelled from the valve assembly through the opening of the ball retainer, thereby no longer preventing reverse flow.</p> |
