| 摘要 |
<p>The body of the valve includes an annular shoulder adjacent an annular seat; and an annular collar of incombustible corrosion resistant, nongalling material is specifically mounted on the shoulder. The collar includes a 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 is provided with prestressed regions normally situating the lip portion proximate the body shoulder and in position wherein the lip portion will not interface with the movable valve element. Upon thermal relief of the stresses, the collar reacts to dispose the lip portion into sealing engagements with the valve elements.</p> |
