| 摘要 |
A tubing hanger has an exterior surface and carries a seal arranged inwardly of this surface. The seal has two sealing portions and, when the hanger is located in a wellhead, the seal is engaged by an activating device operated by a piston to force one sealing portion into engagement with the tubing hanger and the other portion into engagement with the wellhead. The movement of the piston can be reversed to break the seals.
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