| 摘要 |
A gas isolation valve which is capable of maintaining a reliable seal even if exposed to a fire. In one arrangement a ball valve is sealed by O-rings (5, 7), the ball valve being in the form of a housing, a ball (3) located within the housing, and a spindle (4) engaging the ball through an opening in the housing wall. The spindle (4) and ball (3) are interengaged by mating dovetail formations. One of the sealing O-rings may be associated with an annular member (12) which is spring (14) biased towards the ball (3), the annular member (3) being arranged such that in the absence of the O-ring it is biased against the ball (3) and forms a seal between the ball and the valve housing. The ball valve may be used in association with a heat activated isolation valve in which a valve member is mounted on a spring biased over centre mechanism extending across the interior of the valve housing. A bimetallic strip (26, 27) extends adjacent the over centre mechanism, the bimetallic strip being arranged to move the valve member to a valve closed position if the temperature exceeds a predetermined limit. |
