| 摘要 |
PROBLEM TO BE SOLVED: To provide an orifice valve capable of eliminating the necessity for removing it from a pipe, allowing a worker to visually confirm clogging and deposit of foreign matters, and allowing the worker to perform a cleaning work for removing the clogging and deposit of foreign matters. SOLUTION: An inspection window 11 is opened on the upstream side of a position where a movable plate 3 is arranged in a valve box 1, and the inspection window 11 is liquid-tightly, attachably and detachably blocked by a valve box inside visual confirmation cover 12 provided with a first seal member 12A, a transparent plate 12B, a second seal member 12C, and a fixed frame 12D. The clogging and deposit of foreign matters are visually confirmed by seeing them through the transparent plate 12B. Moreover, when the clogging and deposit of foreign matters whose are confirmed, cleaning is performed by removing the valve box inside a visual confirmation cover 12 and inserting a cleaning tool through the opened inspection window 11.
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