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Reasons and solutions for the difficulty of disassembling the horizontal directional drill pipe
Mar 15, 2019

During the back-drilling and reaming process of the large-tonnage horizontal directional drilling rig, the drill pipe is often difficult to disassemble and the construction period is delayed. To this end, we analyzed the reasons why the drill pipe is difficult to disassemble and summed up a feasible solution.
Through the drilling machine approaching, guiding drilling, to the tracking process of the back-drilling and reaming, the reason why the drill pipe is difficult to disassemble is that the drill pipe connecting thread is abnormally damaged, and the reason for the abnormal damage of the drill pipe connecting thread is mainly three aspects. As described below.
(1) There is a deviation in the angle of the drill pipe into the soil
In the preparatory stage, due to the failure of the operator to adjust the angle of the drill frame in a timely and accurate manner, the angle between the rig body and the drill pipe is deviated, resulting in the front and rear vise bodies being different from the clamped pipe. During the drilling and returning of the drilling rig, the connecting thread of the drill pipe is abnormally stressed, causing abnormal damage to the connecting thread. The deviation between the drilling rig and the drill pipe into the soil is shown in Figure 1.
(2) The drilling speed is too fast
During the construction process, the drilling speed of the drilling rig is too fast, the drilling rod rotation pressure is increased to 18 MPa, the drill rod rotation torque is increased to 80000 N×m, and the maximum rotating torque of the 140 type drill pipe is exceeded (65000 N×m). , causing abnormal damage to the drill pipe connection thread.
(3) There is a problem with the quality of the drill pipe
Drill pipe connection thread damage deformation, inspection of the difficult to remove the drill pipe at the construction site, found that the connection thread of these drill pipe has been damaged, deformation, indicating that the drill pipe connection thread strength is not enough.
Solution
(1) Reasonable use of drill pipe
When a large-tonnage directional drilling rig is equipped with a drill pipe, the drill pipe should be reasonably selected according to the soil condition, and the rotary torque of the drill pipe should be strictly controlled. For example, the Type 140 drill pipe allows a maximum rotational torque of 65000 N × m, and the Type 168 drill pipe allows the use of a maximum rotational torque of 80,000 N × m.
(2) Correctly operate the rig
During the pipeline drilling/retracting construction process of the drilling rig, the propulsion speed of the power head should be appropriately slowed to ensure that the rotating pressure is ≤12MPa and the rotating torque is ≤60000N×m during the construction process. At the same time, the training of the rig operator should be strengthened to avoid the lack of understanding of the drilling rig and construction geological conditions by the operator, resulting in excessive rotation torque of the rig, resulting in damage and deformation of the drill pipe connecting thread.
(3) Drill pipe removal method
When disassembling the drill pipe, first use a vise for conventional disassembly. After clamping the 2~4 drill pipes, the vise should check whether the tiger teeth are worn. If it is worn, the tiger teeth should be replaced in time.
When the drill pipe is particularly difficult to disassemble, that is, when the vise clamps the drill pipe more than 2 times and the skin of the drill pipe clamping portion is excessively worn, the disassembly should be stopped, and the clamping force of the vise is increased by the inner pad tiger block method. Alternatively, the oxygen acetylene flame may be used to bake the threaded joint of the drill pipe, or the hammer may be used to vibrate the threaded joint of the drill pipe.
Drill rod female end cutting triangle mouth
If the above method is used, the drill pipe can not be dismantled, and only the cutting pressure release method can be adopted. The specific method is as follows: the gas drill is used to cut the inner end of the drill pipe to cut a triangular incision to release the tightening force, and the drill pipe can be disassembled. Down, as shown in Figure 3. Due to the high cost of the drill pipe, the cutting pressure relief method can make the drilled pipe difficult to repair, so this method should be used with caution.crawler-mounted-drilling-rig-machine-for-sale20251122627