循环接头在工作时在工具管柱的上段打开通向环形空间的通路，于是能够建立较大的循环流量。

When operated, the circulation sub allows a higher circulation rate to be established by opening a path to the annulus in the top section of the tool string.

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螺钉和螺母装配工具。双头开口扳手双头环形扳手和组合扳手。最大头部宽度。

Assembly tools for screws and nuts - double - headed open - ended wrenches, double - headed ring wrenches and combination wrenches - maximum widths of heads.

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螺钉和螺母装配工具。双头开口扳手双头环形扳手和组合扳手。最大头部宽度。

Assembly tool for screws and nuts - open - end double - head engineers wrenches, double - head box wrenches and combination wrenches - maximum outside dimensions of heads.

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