"Butt Welding Techniques" for Second-hand Drill Pipes: Reduce Wear And Improve Drilling Accuracy

Due to long-term use, second-hand drill pipes are prone to wear and deformation at the joints. If the butt connection operation is not standardized, it will not only accelerate the wear of the drill pipe but also affect the verticality and depth accuracy of the borehole. Mastering scientific docking skills is the key to ensuring the stable operation of rotary drilling RIGS. The following is a detailed explanation from six practical operation dimensions.

1. Joint cleaning treatment: Before butt connection, use a high-pressure air gun to remove the dirt and oil stains inside and outside the joint. If there is rust, it can be ground with a wire brush to avoid impurities getting stuck and causing seal failure. Residual impurities will accelerate the wear of the joint and may also cause mud leakage, affecting the quality of hole formation.

2. Coaxiality calibration: Lift the upper and lower drill pipes to the same axis. By adjusting the luffing cylinder of the drilling rig, ensure that the flange surfaces of the joints are parallel and aligned, with a deviation controlled within 2mm, to prevent additional torque during butt connection. Excessive coaxiality deviation can cause the drill pipe to bend and the borehole to shift.

3. Bolt tightening sequence: Install the connecting bolts by diagonal cross tightening. First, pre-tighten all bolts to 50% torque, then gradually tighten them in a clockwise direction to the rated torque (usually 200-300N · m) to avoid flange deformation caused by unilateral force. Uneven tightening of bolts can easily cause loose joints and mud leakage.

4. Inspection and replacement of sealing parts: Before each connection, check whether the sealing ring of the joint has cracks or aging. If the elasticity of the sealing part decreases, it should be replaced immediately. After replacement, apply grease to the surface of the sealing ring to enhance the sealing performance. Seal failure will lead to the loss of mud in the hole, affecting the suspension effect of the construction waste.

5. Relay control: When starting the rotary mechanism of the drilling rig, apply the relay force slowly. Stop the rotation only after the joint is fully in contact to avoid damaging the tooth surface of the joint due to sudden impact. The strength of the second-hand drill pipe joint has decreased. Violent connection is prone to cause the tooth surface to crack and fail to transmit force normally.

6. Post-docking test run: After the docking is completed, conduct a 3-5 minute low-speed test drill to observe if there is any abnormal vibration or noise in the drill pipe, and at the same time check if the mud circulation is smooth. Only after confirming that there are no problems can the normal operation state be entered. Trial operation can promptly identify potential connection hazards and prevent drill pipe breakage during construction.

In conclusion, the quality of the connection of second-hand drill pipes directly determines the construction efficiency and safety. By applying six key techniques including cleaning the joints, calibrating coaxiality, standardizing the tightening of bolts, inspecting seals, controlling the coupling force and conducting trial runs, the wear of drill pipes can be effectively reduced and the drilling accuracy can be improved. Adhering to standardized connection operations for a long time can extend the service life of second-hand drill pipes, reduce equipment maintenance costs, and ensure the stability of rotary drilling rig construction.