| 摘要 |
A fire-safe butterfly valve (FIG. 2) provides bi-directional sealing. In normal duties a polymeric seal provides forward and reverse sealing against the edge of the valve disc, the polymeric seal being resiliently loaded in the axial direction of the valve by a resilient metal ring. The metal ring provides a bi-directional seal with the disc edge in the event of destruction of the polymeric seal by fire. The metal ring in transverse cross-section consists of an arm having a curved radially inner end presenting a convex surface for engagement with the disc edge. For fluid pressure acting from the smaller diameter side of the disc, in the burnt out condition, the curvature of the radially inner end of the metal ring gives rise to an increased sealing force with the disc edge as the disc moves in response to the fluid pressure and the ring inner end remains in rolling contact with the disc edge. |
