1. The characteristic of the sleeve trapezoidal thread: the angle of the sleeve of the trapezoidal thread is 13°. The two side angles are not equal, the front side angle is 10°, and the rear side angle is 3°. The taper of the thread is divided into 1:16 and 1:12 according to the specifications of the bushing.
2. The sealing mechanism of the sleeve-biased thread. After the sleeve-biased threads are connected to each other, the 30 and 100 sides of the outer and inner threads are closely fitted together. The pressure is sealed between the surface and the surface under the action of a certain axial force, and the main seal is formed by the thread. In addition, due to design requirements, a gap of up to 0.51 mm is allowed between the crest and the bottom of the thread, and the metal particles contained in the thread grease create a bridging action within the gap to form a grease seal.
3, the tensile performance of the sleeve partial thread, the casing string is transferred to the upper casing thread by the thread connection at the lower casing weight, and compressive stress is generated on the side of each thread, and the axial component of the compressive stress Constant equal to the casing weight load. Since the two side angles of the trapezoidal thread are not equal, the tensile load carrying capacity of the 30 flank is greater than the tensile load carrying capacity of the 100 flank, which is close to the tensile strength of the tubular body, and is the tensile bearing surface of the trapezoidal thread.
4. The casing trapezoidal thread has the ability of Kangda axial tensile load or compressive load compared with the casing round thread.