| 摘要 |
Blowout preventers each having at least one movable bonnet and an operating cylinder therewith which are movable together relative to a piston in the cylinder for exposing a ram mounted inwardly of the bonnet to effect the removal of the ram, wherein the preventer has detent or resistance means between the piston and an extension of the body to resist movement of the piston, the piston rod, and the ram connected therewith when fluid pressure is applied in the operating cylinder outwardly of the piston for thereby effecting an opening outward movement of the bonnet to the ram-exposed position.
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