A ball valve, especially for use between adjacent sections of a pipe line conducting an inflammable fluid, said ball valve comprising a valve housing a valve ball in said housing and having a through-passage,Ball Valves a trunnion in said housing projecting into a first socket in said ball, a control shaft projecting into and drivingly engaging a second socket in said ball diametrally opposed to said first socket, Ball Valvesa pair of annular valve seat members made of metal and spaced axially of the pipe line, and spring means urging said seat members into sealing engagement with the ball; in which a heat-sensitive bush is provided between said trunnion and the peripheral wall of said first socket and between said control shaft and the peripheral wall of said second socket, BALL VALVESand said spring means presses against heat-sensitive material; whereby, in the event of fire or excessive heat reaching a ball valve in a pipe line, and the valve is turned to its closed position, said bushes disintegrate, and said heat-sensitive material disintegrates so that the valve seat members are no longer spring urged, and the ball moves axially of the pipe line, under pressure of the fluid in the pipe line, and pushes the downstream valve seat member into sealing contact with the valve housing.

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