How to adjust the hammer pressure of a down-the-hole hammer drill bit?
Adjustment through the drilling rig control system
Hydraulic system adjustment: Many down-the-hole drills use hydraulic drive to provide hammer pressure. In this case, the hammer pressure can be changed by adjusting the pressure regulating valve of the hydraulic system. The hydraulic system usually has a pressure control knob or handle, and the construction personnel can increase or decrease the pressure by turning the knob clockwise or counterclockwise according to the hardness of the rock. For example, when drilling into harder granite, turning the pressure regulating knob in the direction of increasing pressure allows the hydraulic system to provide higher pressure to the hammer down-the-hole drill bit. This adjustment method can accurately control the pressure and can be adjusted in real time according to the actual drilling situation.
Electronic control system (if any): Some advanced down-the-hole drills are equipped with electronic control systems. Preset pressure parameters can be entered or selected through the electronic display and buttons on the drilling rig operation panel. The electronic control system automatically adjusts the hydraulic system or other power system according to the input instructions to achieve the set hammer pressure. This method is more accurate and convenient, and can store the best pressure parameter settings under different geological conditions for quick call under similar working conditions.
Changing the counterweight or booster (for some drilling rigs)
Adding counterweights: Some simple down-the-hole drills adjust the hammer pressure by adding counter weights. The weight of the counterweight can directly affect the pressure exerted by the drill bit on the rock. When drilling hard rock, counterweights can be added to appropriate parts of the drilling rig (such as the mast or chassis). For example, when encountering quartzite with a higher hardness, adding a certain weight (such as 50-100 kg) of counterweights to the mast of the drilling rig allows the drill bit to hammer the rock with greater pressure. However, this method is relatively rough, and adding counterweights may have a certain hammer on the stability and maneuverability of the drilling rig.
Adjusting the parameters of the booster: Some drilling rigs are equipped with special boosters, such as spring or hydraulic boosters. By adjusting the parameters of these boosters, such as the preload of the spring or the pressure of the hydraulic booster, the hammer pressure of the drill bit can be changed. For example, for a spring-type booster, the preload of the spring can be changed by tightening or loosening the adjustment nut of the spring, thereby increasing or decreasing the hammer pressure of the drill bit. This method requires a certain understanding of the structure of the booster of the drilling rig, and attention should be paid to safety during the adjustment process to avoid equipment failure or personal injury due to sudden changes in pressure.
Adjustment in combination with drilling speed and slag discharge
Observe the drilling speed: If the drill bit drills too fast in the rock, it may mean that the hammer pressure is too large. At this time, the pressure can be appropriately reduced to avoid excessive wear of the drill bit and damage to the hole wall. On the contrary, if the drilling speed is too slow, it may be that the pressure is insufficient and the pressure needs to be increased. For example, when drilling medium-hard rock (such as limestone), if the drilling speed of the drill bit exceeds the normal range per minute (such as more than 30 cm/min), the hammer pressure can be appropriately reduced to observe whether the drilling speed returns to a reasonable range (such as 10-20 cm/min).
Pay attention to the slag discharge: The slag discharge is also an important reference factor for adjusting the hammer pressure. If the slag discharge is smooth and the rock cuttings particle size is moderate, it means that the hammer pressure is relatively appropriate. However, if slag removal is difficult and the rock cuttings are in powder or large pieces, it may be caused by too high or too low pressure. For example, when the pressure is too high, the rock may be over-crushed, resulting in a large amount of powdery rock cuttings, which can easily clog the borehole. In this case, the pressure needs to be reduced; when the pressure is too low, the rock is not fully crushed, resulting in large pieces of rock cuttings, which will also affect slag removal, and the pressure needs to be appropriately increased.
