| 摘要 |
A blowout preventer (BOP) is provided in which one of the BOP rams is forme d with an extended central bore sealing section to seal across the central bor e in a central bore closing position when the polish rod is not present. The ram bores of t he BOP are sized to accommodate this extended central bore sealing section in any of th e open, sealing or central bore closing positions. The front ends of the BOP rams ma y be adapted to carry elastomeric or thermoplastic seals to seal against the poli sh rod or against each other. The central bore seals for the extended central bore sealing section may be formed with elastomeric or thermoplastic seals. In the case o f thermoplastic seals, the rams and ram bores are adapted to ensure that the thermoplastic seals are compressed outwardly, to seal the ram bores, or are lifted upwardly, to seal the central bore.
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