Drill pipe specification and appearance quality

　　(1) the internal and external surfaces of oil drilling pipe and joint shall be free of cracks, folds, rolled folds, delaminations, hairlines and scabs. These defects shall be completely removed, and the wall thickness shall not exceed the negative deviation of diameter after removal.

　　(2) there shall be no serious protrusion on the surface of the thickened part of the oil drilling pipe and the place where it transits to the nominal wall thickness.

　　(3) if the length of API Drill Tube and Pipe for Down The Hole Dril is 8m and 12m without joint, the joint will not be supplied at the time of delivery. Each 6m long drilling pipe shall be screwed with a joint.

　　(4) the thread surface of oil drilling pipe and joint shall be smooth and free of burr, tear and other defects sufficient to interrupt the thread and affect the strength and tight connection.

　　(5) according to Yb / t5052-93 steel pipe for geological drilling, there are clear requirements for the outer diameter of drill pipe, wall thickness and the outer diameter, inner diameter, thickening length, transition length and thread length of the thickened part, and there are strict regulations for the threads of drill pipe and its coupling.

　　(6) the internal and external surfaces of geological drill pipe and coupling shall be free of cracks, folds, folds, delaminations, hairlines and scabs. The depth shall not exceed the allowable tolerance of outer diameter and wall thickness, and the defects such as slight concave convex surface and longitudinal straight path are allowed to exist.