1.The drill pipe is a key component of the drilling rig. Therefore, the drill pipe must be selected according to the drilling capacity parameters and drilling diameter of the drilling rig. The drilling depth can be determined according to the empirical ratio of D/d=4.5.
2.It is necessary to know the main parameters of the drill pipe, that is, the torque. We know that the torque transmitted by the drill pipe is transmitted by the engagement of the key and the keyway. It is impossible for them to be processed due to machining accuracy, material properties, welding quality, etc. It is ideal to divide the torque evenly on each key. It is impossible for each contact key to uniformly contact the force. Therefore, the long key is often partially broken and broken. When selecting the design torque of the drill pipe, it must be selected to be larger than the drill. Design torque.
3.Select geological drill pipe according to feed pressureThe rig's feed pressure is also the main external force of the drill pipe. When selecting the drill pipe, it is important to consider the design tolerance of the key, especially the tight drill pipe. The main consideration is the innermost minimum drill pipe diameter and wall thickness. Not only the anti-torque section modulus is the smallest, but also its flexural section modulus is small. The force of the drill pipe in the hole is very complicated, and the tension and compression are simultaneously applied. The synthetic stress during the drilling may exceed the fatigue limit of the drill pipe. However, we can't just consider the strength of the drill pipe from the outside. In fact, the working state and nature of the drill pipe in the hole are unstable conditions, so the instability should also be considered when checking the bending strength.
4. Actually select the type of drill pipe in combination with the construction environment.The types of drill pipe are divided into two types: friction resistance and fixed type. Which type of drill pipe is selected is mainly based on the ground conditions. Generally, the ground layer, such as soil layer, sand layer, gravel layer, and silt geological layer, is selected as friction-resistant drill pipe. Gravel stones, boulders, hard slabs and hard rock layers should be selected for fixed drill pipes, while fixed drill pipes are also suitable for general formations. It is best for qualified companies or private companies to purchase two types of drill pipes.
5, consider the weight of the geological drill pipeWhen selecting the drill pipe, it must also be considered whether the maximum tension of the main hoist in the lifting system is equal to the weight of the drill pipe, and the weight of the drill pipe is compatible with the weight of the drill slag, because the weight of the drill pipe in the lifting weight accounts for about 50% to 60% of the lifting weight. Special mention here is the sudden braking during the lifting process of the drill pipe and the inertial force that starts to rise from the borehole. The inertial force may account for 30 to 40% of the lifting weight. The direction of the force and the direction of the lifting weight. Consistent, so there must be sufficient consideration for the choice of the weight of the drill pipe.
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