| 摘要 |
An apparatus (2) for indicating passage of a pig in a pipeline is disclosed. The apparatus comprises a trigger (26) adapted to protrude into a bore of a pipeline and to engage a pig passing along the pipeline, and a body (8) adapted to be mounted to an aperture (6) in a wall of the pipeline. A first actuator member (40) is adapted to move relative to the body as a result of a pig passing along the pipeline engaging the trigger, and a second actuator member (58) is adapted to move relative to the body as a result of magnetic attraction between the first and second actuator members. A flag (72) is actuated by movement of the second actuator member relative to the body to provide a visible indication of engagement of the pig in the pipeline with the trigger.
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