When the drill pipe reaches critical speeds, the drill pipe vibrates, often resulting in bending, excessive wear, rapid damage and fatigue damage.
Tension failure usually occurs when pulling stuck drill pipe. When the tensile force exceeds the yield point, “neck” deformation occurs in the thinnest local or smallest cross-section of the drill pipe wall. If the lifting force exceeds the previous limit strength, the drill pipe will be broken. Tensile damage usually occurs in the upper part of the drill pipe.
Fatigue damage is the most common type of drill pipe damage.
There are two basic types of fatigue damage
At present, the main cause of drill pipe fatigue damage is the cyclic stress when the drill pipe rotates in the curved hole. Fatigue damage can occur even if the drill collar is thick enough in a bent hole.
When the drill pipe is bent, the corresponding position of the drill pipe will generate periodic stress due to repeated stretching and compression due to each rotation of the drill pipe.
The imperfect appearance of drill pipe, whether machining or metallurgical process, can greatly affect the fatigue limit of drill pipe, and the degree of influence depends on the position, orientation, shape and quantity of drill pipe. If the cuts are located on the drill pipe where they are not primarily stressed, there is little effect on fatigue damage. However, if the notch is within 50 cm of the joint, it will become the center of fatigue damage.
Website:https://www.dth-drilling.com
Email:[email protected]
