... drilling performance is fit for specification of API Spec 4F,7K,8A, Oil Rig Type and Basic Parameters of SY/T5609-1999 1. Motorized ... operation as driving manner; the hoister takes the structure of sealed chain for driving, hydraulic disc for breaking, hoister and drill ... in parallel operation as driving manner; the hoister adopts sealed chain driving structure, the main brake adopts disc breaking or ...