Abstract:In the drilling process of DTH drill rig, frequent connecting and unloading are needed as drill pipe keeps moving forward. The traditional connecting and unloading procedures are manually controlled by pushing forward and rotating the knob. The operations are complicated and require a lot of labor. With the development of PLC controlled technology, the aforesaid process may be ideally completed by proportional connecting and unloading (which is by combining electrical and hydraulic technologies). By contrast, proportional connecting and unloading are highly automatic and reduce the labor intensity of operators, which are worth promoting.