Abstract: Pneumatic DTH drilling has the advantage of high efficiency,it is a major consideration for the construction of ground emergency rescue drill,CBM wells and water wells.The disadvantage is that in the process of drilling,out of the orifice will appear a lot of dust.The function of orifice sealing device is to realize the orifice sealing and purification,and direct the dust away from the orifice oriented sediment pool.The design of orifice sealing device was introduced,and the design was optimized by CFD analysis.At last,field test was carried out to prove that the orifice sealing device completely meets the need of pneumatic DTH hammer drilling.

Key words: Pneumatic DTH drilling, Orifice sealing device, CFD analysis, Optimum design