| 摘要 |
PROBLEM TO BE SOLVED: To provide a butterfly valve having excellent reliability and capable of suppressing the progress speed of abrasion of components without causing the defective operation of a disk-like valve element even if a fluid flowing inside is a slurry including grains of iron powder or the like. SOLUTION: A seat ring 3 inserted into the casing 2 of the butterfly valve 1 comprises an outflow side ring 31 inserted from the outflow side of the fluid and an inflow side ring 32 inserted from the inflow side of the fluid. A hardened padding layer is formed on the whole face of each of the inner peripheral faces of the rings 31 and 32, and predetermined gaps are formed between the rings 31 and 32 and the peripheral edge section of the disk-like valve element 4. O-rings 7 are inserted into O-ring grooves provided on a rotation side shaft 51 and a support side shaft 52 of the disk-like valve element 4 to prevent the leak of the fluid reaching the O-ring grooves through gap closing rings closing the gaps between a shaft hole 21 and the rotation side shaft 51 and between a shaft hole 22 and the support side shaft 52.
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