Recently, a customer called to report a dangerous situation where their rotary drilling rig was deviating during piling, significantly hindering their work. We promptly informed our technical staff, and based on their explanation, we've compiled this article to share our insights on this issue:#nov drilling rigs#
Drilling deviations caused by operation are not only due to the operator's skill but also significantly influenced by the geological formation. Reasons include: blindly applying pressure leading to rig jacking, improper selection of drilling tools, failure to properly correct deviations, and excessively high drilling speeds. Deviating holes are prone to occur in certain geological formations. Uneven distribution of geological mechanical strength is a major cause of deviating holes. Such accidents can occur in inclined rock formations, limestone cave formations, boulder and boulder formations, hard rock formations, formations with alternating soft and hard surfaces, and pebble formations. Other contributing factors include: the drill bit connector not being centered in the cylinder; improper drill tooth arrangement causing unbalanced forces during drilling; excessively large cylinder taper; and internal structural constraints (such as unlocking mechanisms, connecting shafts, or inclined plates) leading to soil accumulation. Diagnosis: In cases of borehole deviation caused by drilling tools, the tools are inevitably under unbalanced stress. Corrections include adjusting the barrel wall and guide cone position, repositioning the drill teeth, increasing the gauge of the drill bit, and minimizing the taper. When starting drilling in boulders or rocky formations, begin with a tubular drill, strictly prohibiting pressurization, floating drilling, or drilling with the drill rod suspended. Gradually increase pressure only after the drill bit has penetrated a certain distance into the full-section of the rock. Use auger bits with caution. Use pulsed pressurization in hard rock formations, strictly prohibiting excessive pressure or prolonged duration in a single drilling operation, and prohibiting prolonged rig lifting. Release pressure promptly after pressurization, and never advance too far or too deep while the rig is lifted.
If mud is found on the drill rod keyway after lifting the drill, or if there is resistance during lifting or lowering, it indicates borehole deviation. In this case, adjust the slewing of the upper rig and the mast cylinder (adjusting the mast's Y-coordinate) to center the drill rod in the hole and drill, then perform multiple idle runs to clean the hole at the deviation point. =#nov drilling rigs#
Rotary drilling rig mast deviation: Due to equipment, debugging, or operator error, the automatic mast adjustment function of some drilling rigs may not guarantee the verticality of the mast, resulting in a slight deviation. During construction, uneven settlement of the chassis caused by drilling rig vibration and hydraulic cylinder depressurization can also cause the mast to deviate from its original vertical position. Using surrounding vertical objects (buildings) as reference points, a preliminary assessment of the mast can be made by removing the drill bit and observing the gap between the drill rod and the keyway bar of the power head from directly below. The gap can be determined by checking if the three keyway bars are equal to the three sets of gaps of the power head. Manually rotating the drill rod square head will also help. If the mast is vertical, the drill rod is not subject to lateral constraint, and the rotational resistance is small. If the rotational resistance is large, the mast is likely deviated (assuming the drill rod is intact). Solution: Check the hydraulic cylinder and calibrate the mast. Reset the automatic mast adjustment function and prevent the mast from becoming vertical before construction due to ground subsidence or hydraulic cylinder depressurization during construction.
When drilling in formations with varying hardness, the drill bit is prone to misalignment or deviation during the first 10-500px of each bucket's advance. In this case, minimize the applied pressure. Gradually increase the pressure only after the depth exceeds the height of the drill teeth and the bottom of the drill string. ④ For formations prone to borehole deviation, use straight-tube, extended, and heightened drill bits, avoiding the use of tapered drill bits.
Therefore, there are many possibilities for this problem. We must understand this issue and not rush into it. By correctly checking each step, we can find the cause and properly improve the equipment.#nov drilling rigs#
