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专门为反循环取样钻进设计的BULROC-6型中空式潜孔锤，在钻进中能使岩屑通过钻头与锤体的中心孔返到地面。这种中空式潜孔锤能有效地避免用普通潜孔锤进行反循环钻进时所造成的混样问题。岩心钻探成本昂贵，且在破碎地层中钻进时，岩心采取率极低，因而岩心钻探往往无法应用。所以，在不要求采取岩心的部位，就可通过双壁钻杆连续反循环钻进采取样品。在坚硬地层中可用三牙轮钻头或潜孔锤钻进，在软地层可采用硬质合金凿刀钻头。
The BULROC-6 hollow downhole hammer, designed for reverse circulation sampling drilling, enables cuttings to pass back to the ground through the center hole of the bit and hammer during drilling. This hollow hammer can effectively avoid the use of ordinary DTH hammer reverse drilling caused by the mixing problem. Core drilling is expensive and when it is drilled in a fractured formation, core drilling rates are so low that core drilling can often not be applied. Therefore, the sample can be taken from a continuous reverse circulation drilling of a double-wall drill pipe without requiring the core to be taken. In hard formations can be used tricone bit or down-hole hammer drilling, soft ground can be carbide bit bit.