| 摘要 |
A ball valve is provided especially for use between adjacent sections of a pipe line conducting an inflammable fluid and comprises a valve housing, a valve ball (2) in the housing and having a through passage, a trunnion in the housing projecting into a first socket in the ball, and a control shaft projecting into and drivingly engaging a second socket in the ball diametrally opposed to the first socket. A pair of annular valve seat members (4) spaced axially of the pipe line carry sealing rings (8), spring means (9) urging the seat members towards the ball. Each seat member at its end adjacent the spring means has a frusto-conical portion (11) which tapers from a shoulder (12) on the seat member towards the end face (4A) of the latter. A graphite ring (13) is fitted between the frusto-conical portion and the adjacent peripheral wall of the housing and a first spacer ring (14) is located between the graphite ring and the shoulder. Furthermore, an annular pressure plate (15) is located between the end face of the seal member and the spring means and is abutted by the latter and has an annular lip (15A) abutting the graphite ring. Additionally, a second spacer ring (16) is provided between the end face of the seat member and the pressure plates. In the event of fire in the pipe line, the sealing ring and spacer rings disintegrate so that the spring means pushes the seat member. |
