| 摘要 |
<p>In a butterfly valve, comprising a valve disk pivotally mounted for movement between a closed position, in which the disk prevents the passage of fluid along a passageway, and an open position, in which the passage of fluid is allowed, an annular seal is provided to seal between the periphery of the disk and the wall of the passageway, provided by a valve housing, when the disk is in its closed position. The seal comprises two deformable sealing members, of P.C.T.F.E., mounted to seal against fluid flow in either direction along the passageway. A rigid former or rigid support ring is mounted between the sealing members to provide support therefor, and to act as a back-up seal in case fire should destroy the primary sealing members. In order that the former can be effective as a seal, it is clamped between the valve housing and a clamping ring independently of the fire-destructible primary sealing members. In the event of a fire, the former remains securely clamped upon destruction of the sealing members, and the valve disk can be moved into engagement with the former to effect a seal.</p> |
