| 摘要 |
PROBLEM TO BE SOLVED: To provide a closed valve state holding device for an emergency shutoff valve through which water soiled by a foreign matter mixed at the time of repairing a damaged point, etc., never enters a reservoir tank by mistake even when an abnormal situation of damage, etc., takes place upstream from a setting position of the emergency shutoff valve on a distributing main pipe. SOLUTION: A closed valve state of a valve body 14 is detected by switching on a limit switch 26, and this valve closed state detection signal is input to a control means 27. The control means 27 outputs a valve closing signal to a closed valve state holding valve 25 in accordance with input of the valve closed state detection signal and closes the relative closed valve state holding valve 25. Consequently, even when hydraulic pressure of a distributing main pipe 1 recovers to a value exceeding a working set value after completion of repair of the damaged point of the distribution main pipe 1, this pressure never works on a piston 14A in a pressure chamber 16 as pilot pressure. Consequently, it is possible to hold the closed valve state of the valve body 14.
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