What are the rules for the thread of the casing pipe?

International requirements for the threads of casing pipe when a pair of inner and outer cones are fitted to each other, only the allowance of the end face is satisfied, and the axial displacement can be used to complete the interference at the connecting surface. And can be used to improve the processing quality of the connecting area, increase the axial force to add the touch area at the touch area and pressure, and then get more tight ring pressure touch area. The larger the area of the touch area, the less likely the leakage path is, and the more reliable the sealing function is. The thread of casing pipe is a special taper sealing method with thread groove - taper pipe thread seal.
    
When the tapered pipe thread meets, only the face allowance (close distance) is satisfied, and the preload in the sealing surface can be easily obtained by screwing the thread and causing the axial displacement. After reviewing the taper sealing method, when the inner and outer taper threads are matched with each other, a continuous and discontinuous annular pressure touch area must be formed at the connecting surface in order to maintain the seal.

In the thread cone of the casing pipe, the area of the conical helicoidal surface is increased due to the presence of the thread, resulting in a maze-like labyrinth in which the pressure medium is difficult to pass through. This is advantageous for sealing, but it also increases various touch errors on the threaded touch surface, which adds the ability to leak. This requires that the various elements of the taper thread should be as accurate as possible during drawing and production. And in the course of the application of tightening force during the use of its internal and external thread tightly screwed on a certain amount of interference, so that the screw teeth kneading, stretching, twists and turns and other messy deformation, to compensate for the shortcomings between the touch surface, Block the gaps on the touch surface and block the leak path.