| 摘要 |
<p>Priese Case 217 FIRE RESISTANT SEAT FOR BUTTERFLY AND BALL VALVES The invention contemplates a flow control valve that provides emergency sealing action upon inadvertent, thermally induced failure of the primary seal. The body of the valve includes an annular shoulder that is disposed adjacent an annular seat; and an annular collar of substantially incombustible corrosion resistant, nongalling material is specifically mounted on the shoulder, the collar including a first portion hermetically connected to the shoulder and a second, lip like portion free to move with respect to the shoulder and normally spaced from the selectively positionable valve element. This collar and more specifically the lip portion thereof is provided with prestressed regions normally situating the lip portion proximate the body shoulder and in position wherein said lip portion will not interface with the movable valve element. Upon thermal relief of the stresses stored in such regions, the collar reacts to dispose the second, or lip portion into sealing engagement with the valve element when in the flow aperture closing position. This stress relief is permanent, such that upon subsequent cooling of the valve, the collar lip portion will remain in sealing engagement with the valve element, thereby preventing leakage, even though the primary seal may have been destroyed by the thermal event.</p> |
