| 摘要 |
PROBLEM TO BE SOLVED: To provide a seat ring structure of a valve casing provided concurrently with flexibility and rigidity. SOLUTION: A cylindrical valve casing seat 13 is concentrically arranged to the flow path axial center in the inside of a valve casing 12 which is brought into pressure contact with a valve casing O-ring 14a, 14b arranged in an annular groove 15, formed in an inner surface of the valve casing 12, thick parts 13a, 13b which form an external diameter coming into pressure contact with the O-rings 14a, 14b are formed in both end parts of the valve casing seat 13, and between both the thick parts 13a, 13b, thin part 13c is formed a forming an external diameter not coming into pressure contact with the valve casing O-rings 14a, 14b.
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