| 摘要 |
<p>A gate valve [10] has a secondary seal, wherein the gate [15] forms a metal to metal seal with the seat [29], and wherein a resilient seal (36a) is moved toward the gate [15] in a closed position to form a secondary fluid- tight seal with the gate [15]. A cam arrangement [31, 34] for backing off the secondary seal is provided in order to prevent wear of the secondary seal upon opening of the gate and also to reduce the gate [15] drag caused by the secondary seal. A spring 40 is provided for loading the seal against the gate. <IMAGE></p> |
