PURPOSE: To reduce the resistance of tidal current and the variation of dynamic pressure, by upsetting inward the jointing part of a steel pipe used for a leg or a riser pipe and providing an external pressure seal at the external face to eliminate discontinuous parts on the external face.
CONSTITUTION: The inside of a joint of a steel pipe is upset (thickened) and a tapered male screw is formed at one end thereof and a tapered female screw is formed at the other end thereof to make equal the external diameter of the joint to the external diameter of the steel pipe. The seal (b) is positioned at the external face of the pipe. An inverse shoulder is formed at the fitting face of a pin A with a male screw and a box B with a female screw. A difference of the tapered angles on the seal faces of the pin side and the box side is formed so as to give a uniform surface pressure distribution in the shoulder. In this way, discontinuous parts on the external face are eliminated to reduce the tidal resistance and lessen the influence of bending stresses due to waves and prevent plastic deformation and scorching on the seal face. Accordingly, a steel pipe joint excellent in the external pressure-resistance can be obtained.
OKAMURA KUNIHIKO
MIMAKI TOSHITARO
Next Patent: VIBRATIONLESS AND NOISELESS COMPACTING SAND PILE PREPARATION WORK