Substantiation of dth air drill hammer parameters for penetration rate adjustment using air flow

Abstract

One of the critical process flows in open pit mining is blasthole drilling using self-propelling equipment. Roller-bit drilling rigs enjoy wide application in surface mining. It is of the current concern to increase penetration rate of drilling with such drilling rigs, especially in structurally complex rock mass. The most effective tool to this end is a DTH air drill hammer which allows adjustability of penetration rate, reduction in probability of roller-bit jamming and intensification of removal of chippings. The authors review alternative modifications of roller-bit drilling rigs with intensification of rotary drilling by means of applying impact loads to roller bit. The theoretical research determines the ultimate impact force of a DTH air drill hammer such that the penetration rate of rotary drilling increases at the preserved durability of roller bit. The re-designed air drill hammer with adjustable air damper enables optimized treatment of well bottom by roller bit owing to variation in the compressed air jet intensity and in the tool impact energy. It is expected to manufacture and test a pilot DTH air drill hammer for roller-bit drilling rigs in an open pit mine in the northwest of the country. The experimental research of penetration rate versus impact load proves feasibility of a substantial increase in the penetration rate with the increasing energy of impact generated by DTH air drill hammers. It is required to take into account an essential decrease in the roller bit durability as function of the impact energy in this case. It seems to be important to obtain experimental relationships or families of graphs of roller bit durability and impact energy at different characteristics of rocks and using the three-mass piston–pin–tool system. Wide introduction of drilling rigs SBSH-250 equipped with DTH air drill hammers with adjustable air dampers can essentially increase drilling performance and decrease drilling cost.