| 摘要 |
PROBLEM TO BE SOLVED: To provide a valve applicable to a fluid containing slurry and foreign matter with a simple structure, usable at a high flow speed, and having the structure without partly applying unreasonable stress, while a noise is suppressed by decreasing cavitation generated in a flow contracted part of the butterfly valve. SOLUTION: A main unit internal diameter on the back flow side just behind a valve seat is provided with a partially enlarged part 34 having enlarged sectional shape formed into a symmetrical shape relating to the center so as to suppress a noise and cavitation generated from a valve element. Enlarged dimension Dy of the partially enlarged part 34 is formed 1.3 times or more a pipe internal diameter D, and length X1 of an enlarged part 33 is 0.5 times or more the pipe internal diameter D just after a valve seat part.
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