| 摘要 |
PROBLEM TO BE SOLVED: To reduce initial cost, suppress running cost required for an opening display to a substantial '0', adopt an opening display device, regardless of the presence or absence of a power source equipment and manual/electric operations and thereby expand a use range by eliminating a complicated action that a supervisor moves up to an installation location of a valve each occasion when confirming an opening of a valve element, simplifying a structure and unnecessitating the power source equipment. SOLUTION: An opening cam 1 rotating at the same time as a valve rod 3 is provided and a tip part of a piston rod 14 is normally abutted on the cam surface 12 by energizing of a spring 17 within a cylinder 16. In a cylinder rear chamber 16A, oil 19 colored in red is filled. The cylinder rear chamber 16A communicates with the inside of a transparent and bottomed display tube 23 of an opening indicator 22 installed at a remote location via an oil take-out port 20 and a piping 21 connected to this oil take-out port 20 and opening of a valve element 1 is confirmed by visual observation of an oil level inside the display tube 23.
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