Medium Wind Pressure Air Drilling Technique and Equipments in Soft Coal Seam

It is difficult to drill bedding long borehole for gas extraction in soft coal seam.The available drilling technology and equipments with the problems of shallow borehole depth and lower hole-forming ratio can't meet the demand of gas efficient extraction.Therefore,the medium wind pressure air drilling technique for soft coal seam was developed,which included compound exhausting slag technique with compressed air and helix drilling rod,multistage dust collection technique and protecting hole technique with screen liner.The application results showed that the average borehole depth generally increased by one time,the drilling efficiency was enhanced about 35 percent,and the hole-forming ratio reached 70% after using pressure air drilling technology and equipment under the same construction conditions,which provided a reliable technology and equipment support for the construction of gas extraction borehole in soft coal seam.