Selection of supporting equipment for down-the-hole drilling tools
The size of the down-the-hole hammer mainly depends on the drill hole diameter and rock type. For blast holes, the hole diameter range of down-the-hole drilling is from 89mm to 252mm. For holes smaller than 89mm, the top hammer type is mainly used, and for holes larger than 252mm, the rotary drilling method is commonly used.
Generally speaking, the minimum hole diameter that a down-the-hole hammer can apply to is its nominal size, which means that the minimum hole diameter that a 4-inch hammer can apply to is a 4-inch hole diameter. Generally speaking, in this case, there is enough annular space between the hammer and the hole wall, and between the drill pipe and the hole wall for slag discharge.
The maximum drill bit size is the hammer size plus 1 inch. For example, the maximum drill bit size for a 4-inch hammer is 5 inches.
The closer the outer diameter of the drill pipe and the outer diameter of the hammer is, the better, which can ensure better slag discharge and also reduce the possibility of drill sticking.
From the processing technology of drill pipe (drill pipe), the surface finish and dimensional accuracy of cold-drawn pipes are better than those of hot-rolled pipes. Good surface finish means that the surface of the steel pipe is not prone to peeling, and the metal debris caused by peeling will reduce the service life of the hammer. In addition, it would be better if friction welding is used to connect the threads and the main body of the drill pipe, which can increase the strength of the drill pipe. At the same time, if the heat treatment of the threaded part is done well, the reliability and strength of the thread can be increased, making the connecting rod more durable. Smooth, improving work efficiency and overall piercing speed.
