These provide access to the central bore of the well underneath most of the heavy valves which should have closed off the flow of oil, but for some reason did not.
这些为连接在许多沉重的真空阀下的钻井中心的钻孔提供了条件。这些真空阀本应该阻止石油的外泄，但出于某种原因没有做到这一点。
Some NDT methods for surface defects, mainly cracks, on the rotor central bore of steam turbine and generator are introduced, and the features are compared and analyzed.
介绍了目前常用的几种检验汽轮机、发电机转子中心孔内表面缺陷（主要是裂纹）的无损检测手段，并对各自的特点进行了分析比较。
Tool shanks and draw-in must have a central through bore.
刀柄和引入轴必带一个穿过钻孔的中心点。
Tool shanks and draw-in must have a central through bore.
刀柄和引入轴必带一个穿过钻孔的中心点。
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