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How to Use the DTH Hammer and Drill Bit Reasonably?
Oct 18, 2018

How to Use the DTH Hammer and Drill Bit Reasonably?



DTH Hammer With Foot Valve


  (1) The speed of the DTH Hammer During Drilling

  The rotational speed of the down-the-hole hammer, the main role of the submerged hole impactor during the drilling process is to rotate the bit alloy through a certain angle for the next impact on the rock. There are many descriptions of some of the domestic data on the speed of the downhole impactor. However, according to our experience, when impacting hard rock, the impact of the drill bit tooth (the outermost ring alloy tooth) is 1/3~1/2. We have also proved through a large number of experiments that the speed of the downhole impactor affects the drilling speed of the rock. Too fast or too slow has an impact on the drilling efficiency. The drilling speed of the DTH Hammer can be determined by the following formula: n=fd/(∏D) n------- DTH Hammer speed (r/min) f--------DTH Impactor impact frequency (times/minute) d--------Drill bit tooth alloy diameter (mm) ∏-----piule ratio (3.14) D--------Drilling diameter (mm The rotational speed of the down-the-hole impactor is not only related to the impactor frequency, the diameter of the drilled hole, the diameter of the bit-toothed alloy, but also has a great relationship with the nature of the rock. The life and cost of the drill bit during the drilling operation is for every user. Very concerned, then how to improve the life of the drill bit has to be discussed, and reasonable speed selection can not only improve the drilling speed, but also improve the life of the drill and reduce the cost of use. Since the drilling speed is related to many factors, whether it is pressure, rock hardness, DTH impactor frequency, or the shape and size of the bit alloy teeth, we also correct it according to the actual situation when drilling the rock. For the well construction, the general speed is 10~30 r/min.

 

 (2) Axial Pressure During Drilling

  The main purpose of the axial pressure (drilling pressure) when drilling the downhole impactor is to overcome the reaction force during the impact, so that the bit alloy is in close contact with the rock at the bottom of the hole. It is related to the type of downhole impactor, the hardness of the rock, and the pressure that the air compressor provides to the downhole impactor. Each type of downhole impactor has its own axial pressure range. As the diameter of the hole increases, the axial pressure increases. As the pressure increases, the axial pressure increases. As the hardness of the rock increases. The axial pressure increases. However, in general, we recommend applying a shaft pressure of 6Kg to 14.6Kg per millimeter of borehole diameter. For example, using the SPM360 downhole impactor with the SPM360-152 drill bit requires a shaft pressure of 6 Kg X152 = 912 Kg when drilling a 152 mm diameter hole at a pressure of less than 1.7 MPa. However, when the hardness of the rock is hard, we need to increase the axial pressure properly, which can be determined by observing the actual use of the drill. But when we carry out deep hole construction, we must consider the weight of the drill, so the actual axial pressure we get should be: Actual axial pressure = theoretical axial pressure - drill pipe weight - DTH impactor weight - drill weight test shows Reasonable axial pressure can improve drilling efficiency and blindly increase axial pressure, which not only can not improve the impact efficiency, but also aggravate the wear of the drill bit. Therefore, the reasonable choice of axial pressure must consider the following factors: 1. Type of down-the-hole impactor and diameter of borehole 2. Physical and mechanical properties of rock, mainly rock hardness 3. Air compressor provides pressure and volume of down-the-hole Hammer

  

(3) Torque During Drilling

  The torque required to drill a downhole impactor is primarily provided by the rig, primarily to enable the downhole impactor to achieve the desired rotation during construction. Generally, the required rotational torque per millimeter of borehole diameter is 1.06 N·M, but considering other factors in the bore, we recommend a torque of about 2.7 N·M per millimeter (mm) of borehole diameter. At the same time, as the drilling depth increases, the torque also needs to increase; the hardness of the rock becomes harder and the torque needs to be increased, so we are drilling: 1. Drilling diameter 2, drilling depth 3, rock formation by the above analysis The "three elements" of the downhole impactor and the drill bit are the speed, the shaft pressure and the torque. Reasonable selection of drilling three factors during the drilling process can effectively improve drilling efficiency and reduce the cost of use.


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