| 摘要 |
The blow-out preventer takes the form of a four-way fitting arranged to be substituted for the conventional three-way fitting in a pumping well head between the pipe string and upper stuffing box. The four-way fitting includes a spring-biased ball which will be ejected to the central portion of the fitting should the polished rod break or otherwise be ejected, the resulting oil flow urging the ball against the under entrance portion of the stuffing box to block oil flow until such time as the normal Radigan valve can be closed.
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