풋 밸브를 이용한 DTH 해머 성능에 관한 연구

Abstract

Drilling equipment that is used in various fields such as mining, construction, and energy industries, has drawn increasing attention due to recent advancement of such industries. Drilling methods that are currently used in industrial areas have adopted several types such as, top hammer, DTH (Down-The-Hole) hammer, and rotary method. Among those, the DTH method has been widely used because it allows more economical drilling compared to other drilling methods. As a key of a DTH hammer, the valve which is placed between a piston and bit, normally works with a face-to-face contact. We designed and tested a DTH hammer with a novel valve where the outer surface of piston contacts with an inner surface of a hammer (or foot valve) in order to improve a performance of a DTH, which is originally proposed by Falcon Inc. A lab-scale DTH hammer adopted with the foot valve with a pressure up to 10 bar, was designed and tested in order to analyze impact frequency, average velocity and impact energy with input pressure. It is shown that the impact frequency when hammering is higher than that of previous study at relatively low inlet pressure, which means that the use of the foot valve at the present study requires low input energy. Moreover, this study shows that an impact frequency of the proposed DTH hammer is 2 to 5 times higher than that of previous DTH hammers which adopts direct face-to-face contact. We also scrupulously obtained a pressure distribution inside a piston when the foot valve works with opening and closing to better understand unsteadiness of pressure in DTH hammer. We believe that the present study provides design rules of a DTH hammer adopted with a foot valve for the industrial drilling fields.