| 摘要 |
An apparatus is described for providing a visual display of the presence or absence of a change from the normal to the abnormal in the condition of a pipeline, for example an adverse change in the current supply to the pipeline for cathodic corrosion control purposes. In a preferred form, the apparatus consists of a transparent weatherproof housing within which is mounted two sets of vanes, one set being immovable and the other set being mounted on a rotatable central shaft which is linked to the instrument monitoring the condition of the pipeline. The vanes are painted in distinctive colors so that in the normal position, a single color or distinctive pattern can be seen by a distant observer as an indication that all is well. Upon an adverse change in condition, the central shaft is rotated so as to move the movable vanes to another position where a different color or color pattern is displayed, thus indicating the occurrence of the adverse change to the distant observer.
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