DTH eccentric overburden casing drilling system 178
Working Principle of Drill: 1.When start drilling , the reamer swings out and reams the pilot-hole wide enough for the casing tube to slide down behind the drill bit assembly. 2.When the required depth is reached, rotation is reversed carefully, whereupon the reamer swings in. Allowing the drill bit assembly to be pulled up through the casing.
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