Upper and lower bushings are standard for smooth valve operation.

上部和下部衬套符合流畅平稳轻松操作阀门的标准要求。

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Open the upper sea inlet valve and close the lower one.

打开高位海底阀，关闭低位海底阀。

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Open the upper sea inlet valve and close the lower one.

打开高位海底阀，关闭低位海底阀。

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