Abstract: An engagement section of a holder is engaged with a metal gasket, the gasket is received in a tubular section, and the tubular section is fitted in a step of a connection pipe. Another connection pipe is placed close to and facing the connection pipe that holds the gasket through the holder, and a center ring is installed surrounding the outer peripheries of the flanges. While a trapezoidal section having slopes which define both sides is inserted into a groove, center ring segments are closed to form a ring shape. A bolt which penetrates through a cutout of a segment is screwed into a threaded hole of the segment. The screwing of the bolt causes the amount of insertion of the trapezoidal section, which has slopes which define both sides, into the groove to be increased. As a result, the distance between flanges is reduced and the contact pressure of projections against both sides of the gasket is increased.

Abstract: Engagement section 7a of holder 7 is engaged with a metal gasket 6, gasket 6 is received in tubular section 7b, and tubular section 7b is fitted in step 5a of connection pipe 1a. Then, another connection pipe 1b is placed close to and facing connection pipe 1a that holds gasket 6 through holder 7, and center ring 9 is installed surrounding the outer peripheries of flanges 2a, 2b. Subsequently, while a trapezoidal section having slopes 3a, 3b which define both sides is inserted into groove 14, segments 10a-10c are closed to form a ring shape. Bolt 11 which penetrates through cutout 12 of segment 10a is screwed into threaded hole 13 of segment 10c. The screwing of the bolt causes the amount of insertion of the trapezoidal section, which has slopes 3a, 3b which define both sides, into groove 14 to be increased. As a result, the distance between flanges 2a, 2b is reduced and the contact pressure of projections 4a, 4b against both sides of gasket 6 is increased.