| 摘要 |
A gate valve [10] is disclosed having a primary [300, 302] and secondary [316] seal on the upstream and downstream sides of the gate [15], wherein the gate [15] forms a seal with the seat [300] which is activated mechanically [320] and is fluid powered, and wherein a resilient seal [316a] is moved toward the gate [15] by mechanical actuation [31 ] to form a fluid powered secondary fluid-tight seal with the gate [15].
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