| 摘要 |
<p>A check valve (80) for gas lift applications can be attached externally to a side pocket mandrel (30) or can be a gas lift valve used in the mandrel. The valve has a seat (100) with a non-elastomeric element and a metal element. A biasing element resiliently biases the non-elastomeric element to provide resiliency to the seal produced. A metal dart (66) moves in the bore relative to the seat and allows or prevents flow through the valve body. When exposed to a first differential pressure, the dart (66) engages the non-elastomeric element resiliently biased by the biasing element. When exposed to a greater differential pressure, the dart (66) engages the metal element (140), which can be part of the valve in the bore.
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