1) The single impact power of a pneumatic drill is large, generally up to tens of kilograms or more than a hundred kilograms, which is more than ten times-dozens of times the single impact energy of the current hydraulic impactor. Therefore, from the perspective of rock crushing, the gas drill is mainly based on impact crushing rock, and the rotation only changes the location of impact crushed rock, and at the same time plays the role of auxiliary rock crushing. Therefore, the drilling efficiency depends to a large extent on the performance and quality of the down-the-hole hammer.
(2) Due to the low air density during gas drilling, the pressure of the gas column in the full-hole section is much smaller than that of the liquid column, which improves the multi-directional pressure state of the rock at the bottom of the hole, which is conducive to breaking the rock and improving the drilling efficiency; But on the other hand, it requires a high flow rate to purge the bottom of the hole. Generally, it is required that the speed of the upward return air in the outer annular gap of the drill pipe must be 10-15m/s, and the hydraulic impactor of the water drill has a liquid flow when drilling. The up-return speed is only 0.8-1.2m/s, and the annulus flow velocity during small-diameter diamond rotary drilling is mostly 1m/s. Therefore, when drilling with a pneumatic DTH water well drilling rig, there is less rock powder at the bottom of the hole, which reduces repeated fragmentation of rock powder, and its drilling efficiency can be doubled.
The down-the-hole hammer of the air drill uses compressed air as the motive medium when drilling. After the high-pressure air passes through the impactor, the pressure around the bit is suddenly reduced, and heat is absorbed, which is very beneficial to increase the life of the bit.
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