Engineering Application of Changeable Wash-pipe Assembly with Large Diameters of 140 mm

A large rescue borehole construction using air reverse circulation technology on Shanxi Jincheng Coal Group was did on May of 2015, inner boreholes of main shaft and washpipe assembly of truck-mounted drilling rig top-drive power head were blocked frequently. On the basis of introduction of process of air reverse circulation drilling technology, the inner borehole blocking reason was found, a changeable wash-pipe assembly with diameter of 140 mm was proposed. During the design process, a rotary seal among four packings and wash-pipe in lower packing box was specially considered, a changeable module on goose neck was designed, use-cost was lowered. Engineering application results show that the application of replaceable punching tube assembly with large diameter of 140 mm and slag discharge pipeline makes the slag discharge smoothly in the process of air reverse circulation drilling of the cluster drill hammer, the drilling efficiency is improved, and the labor intensity of the workers is greatly reduced.