In the light of the phenomena of well blowing, well kick and leak during well servicing, a bottom hole switch for reservoir protection, that is closed and opened radially, is developed. 针对修井作业中的井喷、井涌和井漏现象,研制了一种径向开启的保护油层井底开关。
Light, durable, cheap to manufacture and simple to maintain, the rifle creates a deadly spray of bullets without much of a kick. 该突击步枪质量轻、耐用、制造成本低且易于维护,轻易就能发射出一连串致命的子弹,而且后座力不大。