Other designs have a circular cutout in the middle that corresponds to the diameter of the pipe in the hole to seal the well when pipe is in the hole.

其它类型的设计则在中间有一个圆形的剪切块，使其适合井眼内管柱的直径以便当管柱位于井眼内时能够密封井眼。

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Large-diameter hydraulic cylinders, normally retracted, force the two halves of the cover together in the middle to seal the wellbore.

大直径的液压缸，通常是收缩，迫使闸板的两半一起向中间运动去密封井眼。

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Have resolved the leakage problem through improving quality of seal face, adding diameter of O-ring and other measures.

通过提高密封表面的质量、增加O型圈的直径等措施，解决了渗漏问题。

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